Groundwater resource assessment within del monte farm, Thika area, Kiambu county Kenya

Z.N. Kuriaa,* A. Mbuguab T.W. Githinjic

a. Technical University of Kenya, Department of Geoscience and Environment, 48231-00100, Nairobi, Kenya.

b. Regional Centre on Groundwater Resources, P.O Box 41156-00100 Nairobi, Kenya.

c. University of Nairobi, Department of Earth and Climate Science. P.O. Box 30197, 00100 Nairobi Kenya

  Groundwater resource potential is assessed for Delmonte Farm Ltd. covering an area 9,051 hectares, situated in Thika area, Kiambu County.  The farm comprises of 5 smaller farm divisions namely: Anglo, Chui, Gatuanyaga, Muka Mukuu and Kayata. At present, the Del Monte Farm requires 195,500 m3/day to irrigate the entire farm assuming an overhead irrigation at a rate of 1litre/sec/hectare for 6 hours regime in day. However, the actual daily water requirements fall way below these figures because farming is carried out at different times in different fields. Therefore, water requirement varies from one field to another. Currently, bulk of water supply is from small Dams located within the farm along rivers that cross the farm. These dams have always provided sufficient water for irrigation and factory purposes. However, due to prolonged drought the river stages are very low and dams depend largely on the flash floods, which have not been experienced over a long period of time. The Client thus intends to drill borehole (s), for immediate emergency supply purposes. On a long-term basis, the boreholes will be operated as a stand-by source in times of insufficient supply from the surface abstractions

  Groundwater potential for The Delmonte Farms was determined using spatial analysis in a GIS platform. The data input included gridded vectors maps of rainfall, slope angles, geology and transmissivity. The combination of the four datasets indicated low - moderate - high groundwater potential zones: a zone of high groundwater potential covers the entire Anglo farm (except to the south) and increases in the western direction. A moderate potential zone covers the corridor between western farm (Anglo) and eastern farms (Gatunyaga and Chui) running a north south direction, while zone of low potential covering the Chui and Gatuanyaga Farm. The potential yields from the above zones are as follows: Low potential (0-8 m3/hr); Moderate potential (8-20 m3/hr); and high potential is above 20 m3/hr.

Additionally, four resistivity profiles were performed across the farms Anglo, Chui and Gatuanyaga in NW-SW direction. Profile 1, on the southern end indicated a corridor of the moderate resistivity sandwiched between high resistivities. To the further north along Profile 2, the western high resistive margin was not encountered. However, along profile 3 much of the eastern part indicated an encroaching Precambrian Basement inlier. The north part of the Anglo indicated a probe within the aquifer. This finding attest to the fact that groundwater potential increases from south to north and from east to west with high groundwater potential on the north western part of the Anglo farm.

Geologically, the western part of study area is covered by approximately 270 to 300 metres of Tertiary volcanic rocks (tuffs and lavas), which form a thick blanket over massive gneisses of the Precambrian Basement System. Stratigraphically, the formations underlying the site form the lower (i.e. oldest) part of the so-called Nairobi Volcanics. The dominant formations are Upper Athi Series and associated sediments and tuff layers (indicative depth: 0 - 50 m bgl), Simbara Series (50 - 130 m bgl), Kapiti Phonolites (130 - 210 m bgl), and basal volcanic sediments underlying the Kapiti (210 - 240 m bgl). However, on the eastern end Precambrian rocks form huge and massive outcrops.

The available data indicates that shallow water strikes often occur between 20 and 60 metres, within the Upper Athi Series. In some cases, the static water level drops below these aquifers: this indicates that they are perched, and rather insignificant. The average main water strike occurs at 86 mbgl, within the Simbara Series (100-130 mbgl). Subsequent water strikes occur between 120 and 210 m within the Kapiti Phonolites (> 200 m bgl). The majority of the boreholes draw most of their water from the SimbaraSeries, while the deeper ones also abstract from the Kapiti Phonolites.

The dominant recharge mechanism is regional groundwater drainage from the humid volcanic uplands west and northwest of the study area. This flow is supplemented with only little replenishment from infiltrating rainfall: the effective local recharge is in the order of 50 mm/year. Within the valley floors, there will be additional (indirect) recharge from surface water leakage and underflow below the floodplain.

The study recommends that a detailed borehole site investigation be carried out covering the zone of high groundwater potential in order to the optimise location of high yielding boreholes. The study should largely cover Anglo and Muka Mukuu Farms.

Emergency interventions for drought adaptation in rural areas of the Limpopo Province (South Africa)

Nebo JOVANOVIC

  Climate change and the increased frequency of drought have made it urgent to implement interventions in support of water supply, especially in rural areas of South Africa that do not have access to tap water. In this research and development program conducted in Greater Giyani Municipality, adaptation interventions consisted in the installation of solar-powered groundwater pumping systems that make use of renewable energy suitable to off-grid power supply in remote areas and cheaper than conventional energy sources based on fossil fuels. The sources of water are groundwater and non-perennial river sand alluvium, which are historically under-utilized in the Limpopo Province. Nine pilot sites phased in over three years were established based on a previous feasibility assessment. Performance of solar-powered groundwater pumping systems is assessed based on the following measurable indicators: number of people supplied with drinking water, water use volumes, water quality, biophysical and economic water productivity, water use efficiency, power supply, durability of equipment and groundwater levels. The communities were trained in the operation and maintenance of solar-powered groundwater pumping systems and agricultural water skills.  Communities were equipped to monitor power supply, groundwater abstraction, groundwater levels and water quality. Declines in groundwater static levels varied from site to site. Water source qualities made it imperative to install small water treatment systems, especially for domestic use, due to elevated concentrations of NO3- recorded in the proximity of villages, and occasionally elevated total organic carbon, salinity and heavy metals. The newly installed solar-powered groundwater pumping systems resulted in substantial savings in energy costs. It is envisaged that the practical drought adaptation interventions accomplished in this project will impact directly >5,000 community members, they will alleviate poverty and improve water utilization, community resilience and economic growth of local and women-led enterprises. However, monitoring in the long term will be essential to assess the sustainability and durability of the system.

High-Resolution Flood Modelling in Different Data Availability Context

Qiuhua Liang1, 2, Huili Chen2, Xiaodong Ming3, Lin Lin1

1School of Water Conservancy and Transportation, Zhengzhou University, Zhengzhou, PR China.

2School of Architecture, Building and Civil Engineering, Loughborough University, England, UK.

3Ping An Property and Casualty Insurance Company, Shenzhen, China.

Flooding is the most wide-spread natural hazard affecting millions of people and their properties in all countries or regions across the world. The risk of flooding is expected to rise due to climate change and unsustainable socio-economic development. Modelling has become an indispensable tool to facilitate flood risk assessment and management. With the rapid development of high-performance computing technologies, large-scale high-resolution flood simulation that involves millions of computational nodes has now become feasible. However, high-resolution data that is necessary to support such applications is not always available, especially in the low- and middle-income countries.

This work introduces the High-Performance Integrated hydrodynamic Modelling System (HiPIMS) and its application to predict flooding in cities of different level of data availability. HiPIMS is a hydrodynamic model that solves the full two-dimensional shallow water equations (SWEs) using a shock-capturing Godunov-type finite volume numerical method. It is therefore suitable for simulating different types of flooding processes, including the dramatic hydrodynamics induced by a dam break. In order to substantially improve its computational efficiency for large-scale high-resolution simulations, HiPIMS is specifically developed to harness the great computational power of GPUs to achieve high-performance computing.

The first application involves using HiPIMS to reproduce a flash flood hit Newcastle upon Tyne, UK in late June 2012, where high-resolution digital elevation model (DEM) and rainfall data are available. HiPIMS is then further applied to simulate a mega flood disaster that killed more than 300 people in July 2021 in the City of Zhengzhou, China. In the second application, high-resolution data is not available and different techniques are used to improve the quality of data from multiple sources to produce satisfactory results. In both applications, the simulation results are consistent with the crowd-source information collected from the public.

Identification of compound flood potential in China's coastal areas

Xiaohong Chen, Lele Zhang

1 School of Civil Engineering, Sun Yat-Sen University

  A method for identifying compound events in different scenarios is proposed, and a quantification method for compound flood danger (possible occurrence of compound flood events) is developed using the Copula concept. Taking 14 coastal provinces and cities in China as an example, the driving mechanism of compound floods is sorted out. Return periods of compound events and correlations among flood drivers were used to quantify compound flood danger. The potential for compound flooding was comprehensively evaluated with the potential compound effects extracting from three kinds of driving elements. Using the typhoon disaster loss database, the disaster losses of typhoon compound events under different scenarios were calculated. Based on typhoon track data, the nested Archimedean-Copula model was used to simulate the temporal and spatial distribution of typhoon compound event intensity. A risk assessment model is constructed to assess the compound flood risk in China's coastal areas.

  It was found that different definitions of compound events and sampling methods resulted in different compound risks. On the whole, the compound flood risk in the southern coastal provinces is higher than that in the northern provinces, with the highest frequency of compound events from July to September. In addition, the compound risk in some areas is on the rise, and the compound events caused by typhoons are more significant. The results show that different typhoon paths will cause compound floods of different scenarios in different regions. The number of typhoon compound events shows a distribution pattern of more in the south and less in the north. The rainfall brought by typhoons is the main reason for the loss of compound event disasters.

Total dissolved solids risk assessment and optimization scheme of managed aquifer recharge projects in a karst area of northern China

Weiping Wang1, Jinchao Li1, Shisong Qu1

1 School of Water Conservancy and Environment，University of Jinan

  Jinan, China, is famous for its springs. However, societal and economic development over the past decades has detrimentally altered the natural water cycle in the spring area. Managed aquifer recharge (MAR) is an effective measure to ensure the normal gushing of springs, though balancing water resource utilisation, ecological effects, and water quality risks is not always easy to implement. This study focused on the potential effects of MAR projects that divert water from mul-tiple local surface water sites, e.g., the Yellow River and South-to-North Water Diversion (SNWD) Project. A numerical simulation model for the entire spring area was built using MODFLOW and MT3DMS. The SNWD Project diverts water with relatively high total dissolved solids (TDS) to the Yufu River, which consequently recharges groundwater and poses a potential risk to the down- stream karst water in the Jinan Spring area. Different simulation scenarios were set, and the results showed that the 90% recovery ratio scheme yields the highest TDS reduction efficiency as well as the largest karst water extraction volume. In addition, the water table remains stable as a whole. The benefits of the designed scheme are multifold, including improving water quality up to Standard III groundwater quality and meeting the water needs of the economy. The study provides a novel method of addressing the groundwater quality risks posed by artificial recharge.

Water-induced landslides in China

Qiang xu

State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, Chengdu University of Technology, Chengdu, China, 610059

  Water-induced landslides are increasingly common in China. Since 1860, global temperatures have continued to rise. The climate warming has triggered a redistribution of global water resources. Due to the turbulent weather, rapid melting of ice and snow, heavy rainfall and other extreme weather events occur frequently, causing more and more geological disasters. Based on the research of water-induced landslides in the past 20 years, this paper divides China's water-induced landslides into four main types, snowmelt-induced landslides, rainfall-induced landslides, irrigation-induced landslides, and reservoir-water-induced landslides. (1) Snowmelt-induced landslides are mainly distributed on the Qinghai-Xizang Plateau, which defined as landslides related to the melting of ice or snow, such as ice or snow avalanches, glacier lake breaches, and landslides caused by meltwater. (2) Rainfall-induced landslides are mainly distributed in the southwest of China. Water has a pushing effect on slopes, also has a softening and muddying effect on rock. According to immersion tests, water will reduce the shear strength of rock by 50-80%. Especially in the red layer area, which is composed of interbedded red mudstone and sandstone with a stratigraphic dip angle of less than 10° and a near-horizontal stratum, many landslides have been caused by historical extreme rainfall. (3) Irrigation-induced landslides are mainly distributed in the Loess Plateau. For example, more than 140 landslides have occurred in Heifangtai. Since 1968, agricultural irrigation has raised the groundwater level in the area by 20 m, saturating the landslide base and inducing static liquefaction landslides. (4) Reservoir-water-induced landslides are mainly distributed on the reservoir bank slopes of major reservoirs. In addition to small collapses caused by wave erosion, large-scale landslides on the reservoir bank are often affected by suspended load shedding and dynamic water pressure effects. When the water level rises, the anti-sliding force of the slope foot is reduced due to the water buoyancy force. When the water level drops sharply, the hydraulic gradient increases, and the seepage pressure will reduce the slope stability. With global climate warming and the resultant melting of ice and snow, these four types of water-induced landslides will occur not only in China, but also in other parts of the world, which needs to focus on in the future.

Simulation of the response processes of flash flood warning and improvement of its effectiveness

Ruikang Zhang, Dedi Liu

State Key Laboratory of Water Resources Engineering and Management, Wuhan University, Wuhan, China

* Correspondence to Dedi Liu: dediliu@whu.edu.cn

  Flash flood disaster is one of the deadliest natural disasters, and flash flood warning is taken as an effective means to prevent flash flood disasters. The effectiveness of flash flood warnings directly depends on the response processes of the population to flash flood warnings, including receiving warnings, understanding warnings, believing warnings, perceiving risks, and implementing evacuation. If the response level of the population to flash flood warnings is low, the warnings are difficult to stimulate corresponding effective evacuation, and the effectiveness of the warnings is hindered, even if the warnings are reliable and issued with sufficient lead time. Optimizing the issuing of flash flood warnings is an important way to improve the response level of the population to flash flood warnings. To optimize the issuing of flash flood warnings, it is necessary to identify the threshold of issuing flash flood warnings, thereby determining whether they will be issued or not. If it is decided to issue the flash flood warnings, it is necessary to determine the times of issuing the flash flood warnings. Therefore, to address three key issues: "how to simulate warning responses, whether to issue flash flood warnings, and how to issue flash flood warnings", this thesis simulates the response processes to flash flood warnings and identifies the times of issuing flash flood warnings. The study consists of four parts: identification of factors influencing the flash flood warning evacuation intention, development of an agent-based model (ABM) for the response processes to flash flood warnings, and proposal of identification methods for the threshold and the times of issuing flash flood warnings. The study can help enhance the understanding of the mechanism of flash flood warning response processes, and improve the response level of the population to flash flood warnings, and thus improve the effectiveness of flash flood warnings.

Satellite-based analysis of soil moisture change in Zhang-Cheng area, China

Jin Xiaomei, Zheng Jintao

China University of Geosciences (Beijing), Beijing, China

jinxm@cugb.edu.cn

  A regional approach was presented in this paper for the spatiotemporally distributed assessment of soil moisture change in a semi-arid area, China. To achieve this, the recent trends (from year 2001 to 2021) of soil moisture in Zhang-Cheng area were assessed using a combination of remote sensing and GLDAS data.

  As an important ecological barrier of Beijing City, the Zhang-Cheng area is located in north part of Hebei Province which covers a surface area about 76,276.8 km2. The area has a typical temperate continental climate with annual precipitation of 430 mm and most precipitation is concentrated in the summer season from June to September. The annual air temperature is 10°C and the winters are cold and windy. The pattern of land cover is as follows: 32.4% farmlands, 35.3% forest, 26.2% grassland, 1.4% water bodies, 3.5% urban area and 1.2% bare soil.

MOD13A1 and MOD11A1 data from 2001 to 2021 formed the core datasets and the Temperature Vegetation Dryness Index (TVDI) was employed as the main method for mapping spatial distribution of soil moisture in Zhang-Cheng area. The Mann-Kendall non-parametric test was used to discuss the time series trends of soil moisture in this research. Furthermore, 10 impact factors related climate, vegetation, topography and soil property were selected in geodetector to explain the variation of soil moisture in Zhang-Cheng area.

  The results revealed that the soil moisture is generally frustrating increased during the period of 2001 to 2021 and the annual average TVDI is varied between 0.52 and 0.67. The maximum data is observed in 2018 while the minimum value is happened in 2004. Spatially, the soil moisture is relative higher in the east part and the highest soil moisture is mostly clustered in forest land. When we look at the spatial distribution of the trends, the soil moisture of 83.1% of the study area has increasing trend and the decreasing trend is only concentrated in the urban areas which is located in the west part of Zhang-Cheng area. Moreover, the Hurst result indicated that the soil moisture in most areas will be sustained increasing trend in the future except the southeast part. The soil moisture estimated from remote sensing data was validated in July to August, 2021 and the result are in good agreement with the field measurements for both two surface layers (0-10 cm, 10-20 cm) and the R between their correlations are 0.78 and 0.69, respectively. The variation of soil moisture is caused by combination effects and among them the vegetation cover is the dominant impact factor. According to the analysis of geodetector, vegetation cover, precipitation, elevation, slope and clay content have positive effects on soil moisture change while the air temperature and sand content have negative impacts.

Transport of Am (III) in the vadose zone sediments

Qiulan Zhang (qlzhang919@cugb.edu.cn）

China university of Geosciences, Beijing

  Am(ⅠⅠⅠ) in the natural environment is considered immobile due to its very low solubility, strong adsorption, and high affinity to solid surfaces. We investigated the individual and co-transport behaviors of Am(ⅠⅠⅠ) and natural colloids through the vadose zone sediments under the influence of pH, ionic strength, flow velocity, Am(ⅠⅠⅠ) concentration and natural colloids concentration. It was found that Am(ⅠⅠⅠ) individual transport did not construct significant breakthrough due to its strong adsorption properties. In the co-transport system of Am(ⅠⅠⅠ) and natural colloids, the elution or retention of Am(ⅠⅠⅠ) depends almost entirely on the stability of the colloids. DLVO theoretical calculations reveal that a decrease in pH and an increase in ionic strength lead to a drop in electrostatic repulsion, and the natural colloids tend to be dispersed and stabilized. In addition , the increase of flow velocity and colloids concentration will lead to greater breakthrough of natural colloids. The results of this study provide new insights into the behavior of natural colloids carrying the radionuclide Am(ⅠⅠⅠ) into aquifers through the vadose zone sediments.

Variations in groundwater seepage fields within the landslide with complex structures following the reservoir water level fluctuation and their effects on the landslide reactivation — A case study in the Three Gorge reservoir of China

Baoping Wen, Jiasong Xiang

School of water Resource and Environment, China University of Geosciences (Beijing), No. 29, Xueyuan Rd., Haidian district, Beijng 100083

E-mail: wenbp@cugb.edu.cn

  It has long been recognized that variation in groundwater seepage fields within slopes and consequent seepage forces is one of the major causes leading to landslides, particularly those in the reservoir areas following reservoir water level fluctuations. The Three Gorge reservoir is one of the largest in the world. Since its impoundment in June of 2003 and during its operation, more than 600 landslides occurred, including the reactivated old landslides. The Chaiwan landslide is one of the reactivated old landslides. This landslide is characterized by its complex structure of three layers of materials along with three slip zones. The three layers are distinction in their properties, particularly their permeabilities. The top layer is the least permeable, and the bottom layer is the most permeable. Shortly after the reservoir operation, the landslide reactivated slowly. Field monitoring disclosed that the significant displacements of the landslide was along the slip zone beneath the top layer during the reservoir water level rising period and along the slip zone beneath the middle layer during the water level drawdown period. Its displacement was greater during the reservoir water level drawdown period than that during the water level rising period. This gave rise to a speculation that the landslide reactivation may be mainly related to variations in the groundwater seepage fields and consequent seepage forces following the reservoir water level fluctuations. To verify this speculation, a series of numerical simulation were conducted using FEFLOW and FLAC3D.

  The simulation results revealed that variations in the groundwater seepage fields following the reservoir water level fluctuations and consequent seepage forces within the landslide were layer specific due to their differences in permeability. During the reservoir water level rising period, an uplift groundwater seepage filed was within the bottom layer (the most permeable layer) along with a noticeable uplift force to the middle layer, while an inward groundwater seepage filed was within the top layer (the least permeable layer) together with a substantial inward seepage force to the layer. The upper lift force thus facilitated displacement of the landslide along the slip zone beneath the middle layer, whereas the inward seepage force restrained the displacement along the slip zone beneath the top layer. During the reservoir water level drawdown period, an outward groundwater seepage fields occurred within each layer, and a significant outward seepage force was produced within the top layer. The outward seepage force within the top layer therefore led to displacement of the landslide along the slip zone beneath the top layer. Additionally, the simulation also revealed that the outward seepage force within the top layer during the water level drawdown period was greater than the uplift force within the bottom layer during the water level rising period, hence leading to greater displacement of the landslide during the water level drawdown period than that during the water level drawdown period. The results of this study not only verified that the speculation assumed but also demonstrate control of the permeabilities of landslide materials on landslide occurrence.

Effects of the operation of large dams on floods and sediment transport in downstream river channels – case of the Yellow River of China

He-Qing Huang

School of Geography and Information Engineering

China University of Geosciences (Wuhan), Wuhan, China

(Email: huangheqing@cug.edu.cn)

  Over the last several decades, numerous reservoirs have been built up across the world, significantly enhancing the level of water resources utilization and yet causing considerable changes in floods and sediment transport in the downstream river channels. The Yellow River of China has been carrying an extremely large sediment load, and long-term sediment deposition has made the lower reach a perched river, with the riverbed being around 10m higher than the ground. With the construction of Sanmenxia Dam in 1960, Liujiaxia Dam in 1968, Longyangxia Dam in 1985 and Xiaolangdi Dam in 1999, significant changes occurred in the variations of flow and sediment load in the Lower Yellow River in the different periods of dam operation, affecting significantly the magnitude and frequency of floods and sediment transport. Our detailed study shows that during large overbank floods, the bankfull channel is subject to significant erosion when the sediment transport coefficient (ratio of sediment concentration of flow to flow discharge) is less than 0.034, while the main and secondary floodplains both accumulate sediment. During small overbank floods, in contrast, the bankfull channel is subject to erosion when the sediment transport coefficient is less than 0.028, while the amount of sediment deposited in the secondary floodplain is closely associated only with the sediment concentration of flow. During non-overbank floods, the bankfull channel is subject to erosion only when the sediment concentration of flow is less than 50 kgm-3. Consequently, the riverbed of the Lower Yellow River has been incising since 2000, while sharp bends occurred more frequently, yielding new problems in preventing flooding disasters.

Natural attenuation mechanism of hexavalent chromium in a wetland

Jia Zhang, Honghan Chen, Huanzhen Zhang, Jingjie Chang

Key Laboratory of Groundwater Conservation of MWR, China University of Geosciences, Beijing 100083, China

  Natural wetland has great retention effect on Cr(VI) migration due to its abiotic and biotic reduction abilities, however, the zoning characteristics of dominating reduction mechanism along Cr(VI) pollution plume in wetland is still unclear. In this study, a Cr(VI) contaminated natural wetland was explored to investigate the distributions of Cr and Fe in groundwater and sediment, and their relationship with microorganisms according to metagenomics, aiming to reveal the natural attenuation mechanism of Cr(VI) from the perspective of zoning characteristics of abiotic and biotic effects. The wetland was divided into contaminated zone, transition zone and uncontaminated zone according to the contamination states of groundwater and sediment. At the upstream of contaminated zone, Cr(VI) concentration in groundwater was as high as 26.7 mg L-1, which has significant inhibition effect on microbial growth, and thus chemical reduction of Cr(VI) by natural organic matters (NOMs) dominated in this area, leading to the increasing of H/C and O/C ratios of NOMs because of the oxidation of aromatic moieties. At the downstream of contaminated zone, Cr(VI) concentration in groundwater decreased to less than 4.46 mg L-1 resulting from dilution and attenuation, but the microbial community was altered substantially, chromate resistant bacteria with ChrA, ChrR, NemA and AzoR genes were enriched, such as Sphingomonas, Mesorhizobium and Comamonadaceae, and thus the direct microbial reduction of Cr(VI) dominated in this area. While at the transition zone, which is located at the front edge of the pollution plume, Cr(VI) could only reached in this area intermittently, and the microbial community remained similar to that of the uncontaminated zone, dominated by Chloroflexi and Acidobateria phylum with dissimilatory ferric iron reduction capacity, and thus Cr(VI) was indirectly reduced by Fe2+ intermediately in this area.

  In addition, humic substances and iron minerals are crucial components of soils and sediments, playing significant roles in the chemical detoxification and fixation of Cr(VI) in underground environments. However, in natural environments, they often do not exist in their individual forms, but rather form humic substance-iron mineral complexes, especially in natural wetlands. Our study explores the synergistic/antagonistic effects of humic acid-ferrihydrite/magnetite complexes of different formation patterns on the adsorption and reduction processes of Cr(VI). On one hand, it quantifies the impact of the C/Fe ratio on the retardation of Cr(VI) by humic substance-iron mineral complexes, thereby avoiding overestimation or underestimation of the actual roles of natural humic substances and iron minerals in the underground migration and transformation of Cr(VI) pollutants. Moreover, considering the substantial differences in molecular structures and functional group compositions of humic substances from different sources, as well as the complexities in the migration and transformation of Cr(VI) in natural environments, the project delves into the influence of humic substance sources on the migration and transformation processes of Cr(VI), as well as the study of self-purification processes of Cr(VI) in natural wetlands. Ultimately, it establishes a quantitative relationship between humic substance sources and the retardation effect on Cr(VI), proposing a levelling-banding mechanism for the self-purification of Cr(VI) in natural wetlands. The study findings provide a theoretical basis for accurately predicting and assessing the migration and transformation processes of Cr(VI) in the vadose zone, as well as for proposing environmentally friendly and efficient chromium pollution control and remediation technologies.

Hydrogeochemical fingerprint, driving forces and spatial availability of groundwater in a coastal plain, Southeast China

Yasong Li1,2,3

1. Fujian Provincial Key Laboratory of Water Cycling and Eco-Geological Processes, Xiamen 361021, China

2. Institute of Hydrogeology and Environmental Geology, Chinese Academy of Geological Science, Shijiazhuang 050061, China

3. IAH, China National Chapter

  Groundwater is a critical water source and was investigated from a coastal plain of southern China to reveal its hydrochemical constrains on water supply from phreatic aquifers of humid regions. Groundwater is dominantly fresh but with a relatively large TDS variation of 59-5,800 mg/L. Groundwater chemical composition is complex and presents variable hydrochemical facies from HCO3-Ca to Cl Na type. Nitrogen and trace elements in groundwater exceed the desirable drinking limits and may pose health risks to all populations through oral pathways. Nitrogen and Mn are the dominant health threats. Groundwater has a large variation of integrated water quality with the EWQI in the range of 11–1179, but is predominantly (84.78%) excellent to medium quality and suitable for domestic usages. The piedmonts are the ideal areas for groundwater exploitation as groundwater presenting good to poor quality trend from the piedmont downstream-wards. Groundwater hydrochemistry is naturally governed by rock-water interactions, and sporadically regulated by evaporation. Agricultural practices and sporadic municipal sewages input nitrogen and major chemicals into groundwater and result in salinity and quality deterioration. Groundwater exceeding F, I, Fe and Mn are derived from geogenic sources. Both anthropogenic and geogenic toxic substances should be concerned in long-terms groundwater supply.

Identification of Typical Antibiotics and List of Priority-controlled Antibiotics in Various Environmental Compartments in China

Fei Liu1, Fuyang Huang2, Guangcai Wang1

1. Key Laboratory of Groundwater Conservation of MWR, China University of Geosciences, Beijing 100083, China

2. International Technology Cooperation Base of Sichuan Low-cost Wastewater Treatment Technology, Southwest University of Science and Technology, Mianyang, Sichuan 621010, China

  Since the advent of penicillin in 1920s, antibiotics have been widely used to prevent and treat diseases pertaining to humans and livestock. Due to the enormous usage, the low metabolic rate in vivo, and the multiple transfer pathways from sources to receptors, antibiotics have been widely detected in the environmental compartments. Based on the standards of quality control and quality assurance in the original text, this study screened out 172 statistically significant publications in the past ten years and established a database of antibiotic residues in China's environmental compartments by summarizing the 172 publications. This study explored the overall residual levels of antibiotics and the transfer pathways of antibiotics between various environmental compartments and constructed an identification method of priority-controlled antibiotics; and this method was applied and verified in a typical karst underground river system. The main results obtained are as follows:

  (1) The established database of antibiotic residues in China's environmental compartments contained approximately 15,000 concentration values of 110 antibiotics and covered 8 environmental compartments and 7 major basins. The results showed that a total of 105 antibiotics were detected and the median concentration ranges of antibiotics in aqueous phase and solid phase were 2.9−156 ng/L and 2.1−39 μg/kg, respectively. The median concentrations of antibiotics in sources were 1.9−54 times higher than that in receptors.

  (2) Hierarchical clustering based on antibiotic concentration (Euclidean Distance and Ward Method) identified that tetracycline, oxytetracycline, chlortetracycline, ofloxacin, enrofloxacin, norfloxacin and ciprofloxacin were the typical antibiotics coexisting in aqueous phase and solid phase of the environment in China. Hierarchical clustering based on antibiotic detection patterns (Asymmetric Binary and Ward Method) revealed the two main transfer pathways from sources to receptors were from animal wastewater/WWTPs effluent to surface water/sediment, and from animal manure/WWTPs sludge to soil/groundwater, respectively.

  (3) Combining with the status of antibiotic pollution, an identification method of priority-controlled antibiotics based on detections, concentrations, and physical and chemical properties of antibiotics (persistence, bioaccumulation, and toxicity) was constructed. The priority ranking of 105 antibiotics was established, and 26 antibiotics were identified as the priority-controlled antibiotics in China's environmental compartments. These priority-controlled antibiotics were mainly veterinary antibiotics, and the average proportion of veterinary use was 83%. Therefore, controlling the usage of antibiotics used for animals in China is a necessary measure to reduce environmental pollution of antibiotics in the future.

  (4) Based on the monitoring data during several years in the typical karst underground river system, 11 priority-controlled antibiotics were identified by the identification method of priority-controlled antibiotics. 73% of the priority-controlled antibiotics in the typical karst underground river system was consistent with the list of priority-controlled antibiotics in China's environmental compartments, which verified the reliability of the priority-controlled antibiotic list established in this study.

  This study systematically assessed the levels of antibiotic residues in environmental compartments in China and clarified the main transfer pathways of antibiotics from sources to environmental media. The established list of priority-controlled antibiotics provides theoretical and methodological support for the precise control of antibiotic environmental pollution in various environmental media in the future and contributes to formulate relevant regulations for antibiotic monitoring and usage control.

Study on catalytic degradation of sulfamethoxazole in groundwater by Ce/N@BC materials based on phytometallurgical strategy

Jiang Yu, Yuanxiao Jin, Jie Yu, SiweiDeng, Zhi Huang, Yinying Jiang, Weiwei Zhu

Department of Environmental Science and Engineering, College of Architecture and Environment, Sichuan University, Chengdu, 610065, China

Email: yujianggz@163.com

  A novel carbon catalyst was created based on plant metallurgy strategy for organic pollutants removal. Plants rich in CeO2-NPs  in  water  were  used  as  carbon  precursors  and pyrolyzed with urea to obtain Ce/N co-doped carbon catalysts. They were used in the degradation of sulfamethoxazole (SMX) by active peroxymonosulfate (PMS). The results showed that the Ce/N @BC/PMS system achieved a 94.5% degradation of SMX in 40 minutes at a rate constant of 0.0602cm-1. The activation center of PMS is widely dispersed Ce oxide nanocrystals, and CeO2 -NPs promote the formation of oxygen centered PFR with enhanced catalytic ability and longer half-life. In addition, N-doping facilitates the transfer of π-electrons within the sp2 carbon of biochar, increasing active sites and thus improving PMS activation efficiency. The degradation process was contributed to by both radical and non-radical activation mechanisms. Major factors included 1O2 and direct electron transfer, with  O2•- serving  as  1O2’s  precursor.  Further, DFT calculations, LC-MS and toxicological analyses were used to reveal the degradation pathway of pollutants and the toxicity changes throughout the entire degradation process. It was found that the degradation of SMX effectively reduced ecological toxicity, and the toxicity values of most intermediates have been reduced.

Evaluation and attribution of trends in compound dry-hot events for major river basins in China

Tongtiegang Zhao and Xiaohong Chen

Sun Yat-sen University, Guangzhou, China

  Concurrent compound dry and hot events (CDHEs) amplified more damange on the ecosystems and human society than individual extremes. Under climate change, compound dry and hot events become more frequent on a global scale. This paper proposes a mathematical method to quantitatively attribute changes of CDHEs to changes of precipitation, change in temperature and change in the dependence between precipitation and temperature. The attribution is achieved by formulating the total differential equation of the return period of CDHEs among Meta-gaussian model. A case study of China is devised based on monthly precipitation and temperature data during the period from 1921 to 2020 for 80 major river basins. It is found that temperature is the main driving factor of increases in CDHEs for 49 major river basins in China, except for the upper and middle reaches of the Yangtze River. In West China, precipitation changes drove the increase in CDHEs in 18 river basins (23%), particularly in parts of North Xinjiang, Qinghai and Gansu. On the other hand, dependence between precipitation and temperature dominated changes of CDHEs in 13 river basins (16%) of China with other factors, including parts of South China, East China and Northwestern China. Furthermore, changes in both the mean and spread of precipitation and temperature can also contribute to changes in CDHEs.

Regulation of water supply system under saltwater stress in coastal city

Xinjun Tu1,2,3, Haiou Wu1,2,3, Xiaohong Chen1,2,3

1 Center of Water Resources and Environment, School of Civil Engineering, Sun Yat-sen University, Guangzhou 510275, China.

2 Center of Water Security Engineering and Technology in Southern China of Guangdong, Guangzhou 510275, China.

3 Guangdong Laboratory of Southern Ocean Science and Engineering, Zhuhai 519000, China.

  Salt-tide invasion in the dry season seriously threatens freshwater availability in a tidal river area. Freshwater availability is associated intensely with natural factors and human activities. Therefore, an improved framework, i.e. regulation by avoiding saltwater withdrawal (RASW), which developed relationships among saltwater intrusion, upstream streamflow and local water supply, was established. The RASW contains three phases, i.e. estuary salinity-exceedance simulation, upstream streamflow distribution design, and local water supply optimization, which was applied in Zhuhai-Macao water supply system of the Guangdong-Hong Kong-Macao Great Bay Area, China. Results demonstrate that a hybrid data-driven method coupling wavelet transform and random forest was more accurate for the salinity-exceedance simulation. By coupling the wavelet machine learning model and the hydrodynamic simulation model, time windows for avoiding saltwater withdrawal were finely identified. Critical upstream streamflow for various scenarios of water demand in the dry season were identified. Upstream streamflow processes in the dry season by multiple copula functions were simulated, designed and regulated. Impacts on water supply security in the estuary city from upstream streamflow processes were presented. By a multi-objective non-dominated genetic algorithm, optimization scheduling rules of joint water supply of rivers and reservoirs considering different time scales of long-term (ten-day) and short-term (daily) were developed. The proposed framework facilitates integrated decision-making for water supply security in coastal area.

Urban hydrometeorological modelling towards climate-resilient and low-carbon cities

Jiyun Song

School of Water Resources and Hydropower Engineering, Wuhan University

  Rapid global urbanization and the associated landscape modifications have led to numerous environmental problems, such as urban heat island, urban moisture island, urban rainfall island, urban water security, and excessive carbon emission. Urban land surface processes are much more complicated as compared to natural ones due to land use land cover changes with modified geometric and hydrothermal properties, complex turbulence field, spatial heterogeneity, as well as anthropogenic heat, moisture, and carbon sources. The modified urban surface processes will be further reflected in the overlying atmospheric dynamics, with significant impacts on local, regional, and even global climate, which will in turn influence the management and utilisation of urban energy and water resources. To better tackle the challenges of urban environmental changes, more climate-resilient and low-carbon city strategies are urgently needed, such as the implementation of blue-green infrastructure and energy-efficient building design, as well as the development of high-precision urban risk prediction and early warning systems, etc. In this presentation, I will briefly introduce the physical mechanisms of water and heat exchange between the complex urban surface and the atmosphere, and then discuss the impacts of urban morphology, urban blue-green infrastructure, energy-efficient architectural design, and human activities on urban hydrometeorology, energy consumption, and carbon emissions. Besides, I will discuss low-carbon adaptive strategies for cities under different climatic and geographical conditions. Our study will help deepen our insights into the fundamental physics of urban land–atmosphere interactions and provide useful guidance for smarter urban planning under challenges of climate change and continuous rapid urbanization.

Adsorption of Coxsackievirus in Sediments: Influencing Factors, Kinetics, and Isotherm Modeling

Xiaoying Zhang, Mengyu Li, Tianshan Lan, Weiheng Su, Zhenxue Dai

College of Construction Engineering, Jilin University, Changchun 130026, China

  Drinking groundwater contamination by pathogenic viruses represents a serious risk to worldwide public health, particularly for enteric viruses, which exhibit high prevalence and occurrence during outbreaks. Understanding how enteric viruses adsorb in groundwater is essential to protecting human health and ensuring the sustainable use of water resources. The adsorption properties of Coxsackievirus A16 (CA16), a common gastrointestinal virus that spreads through groundwater, were investigated in this work. A typical batch equilibrium approach was used to investigate CA16 adsorption and factors that influence it. In a laboratory recognized nationally as a biosafety level 2 facility, stringent research protocols were followed to guarantee compliance with experimental standards. The variables that were investigated included the size of the sediment particles, the starting concentration of the virus, temperature, pH level, and humic acid content. The findings showed that the CA16 virus was more strongly attracted to finer sediment particles and that its adsorption increased as the size of the sediment particle decreased. Furthermore, it was discovered that higher temperatures improved the CA16 virus’s ability to bind to sediment particles. The pH of the aqueous environment has a significant effect on the effectiveness of virus adsorption; higher effectiveness was seen in acidic environments. Furthermore, it was found that the presence of humic acid decreased the ability of clay to adsorb CA16, suggesting that humic acid has a detrimental influence on clay’s ability to adsorb viruses. The examination of kinetic models demonstrated that, in every scenario examined, the adsorption process of CA16 adhered to the pseudo-second-order kinetics model. Additionally, the Langmuir and Freundlich isotherm models were used to assess the equilibrium data that were collected in this investigation. The outcomes amply proved that the most accurate representation of the adsorption equilibrium was given by the Langmuir isotherm model. The study offered a solid scientific foundation for treating groundwater and creating plans to stop the spread of viruses.

Carbon emission reduction of reclaimed water substitution for Inter-basin water transfer for sustainability of water supply in valley urban area

Nian Ma1,2, Yongxin XU1

1. Faculty of Natural Science, University of the Western Cape, Cape Town 7535, South Africa;

2.International Engineering Consulting (China) Co. Ltd., Chongqing 401121, China；

  Urbanization simultaneously faces the dual pressures of water resources shortage and environment impact. The use of multiple water sources can offer solutions to alleviate these pressures. Inter-basin water transfer(IBWT) can address the conflicts between demand and supply of urban water resources for cities with local water shortages, thus which has been widely adopted in the world. While water obtained from transfer over long distance is of good quality, this process of water transfer is not only expensive but also with high carbon emissions. Reclaimed water use(RWU) seems an effective way to address the problems. In the present study, a valley urban region in Chongqing, Southwest China, was taken as a case to explore effect of the carbon emission reduction of RWU substituting IBWT water. Accumulation method accounting for carbon intensities at various stages was used to calculate carbon emissions for each scenario. The result shows that the operational carbon emission intensities of IBWT and RWU are 0.7447KgCO2/m3 and 0.1880KgCO2/m3, respectively, which means that the RWU substitution reduces carbon emissions by 0.5567KgCO2/m3 or 75%. The study further reveals the mechanism of carbon emission reduction, that is to save energy consumption by the use of reclaimed water without long-distance transport and lifting of water over huge elevation drop. This paper also discusses the substitution effect and environmental impact of three scenarios of reclaimed water use on IBWT, namely urban miscellaneous water(UMW), river flow recharge(RFR) and agricultural irrigation(AGI). Estimation of the carbon emission reduction of reclaimed water use was based at the planned scale, and the maximum potential of reclaimed water utilization was predicted. Finally, the paper puts forward an improved strategy for identifying and prioritizing the factors affecting the utilization of reclaimed water and the effect of carbon emission reduction, leading to the formation of robust legal, institutional, managerial frameworks and the establishment of multi-disciplinary and cross-sectoral cooperation mechanism.

Risk Reduction through Sustainable Water Management in Developing Countries

Ms. Wacuka Cynthia Nyambura

Hydrometeorologist - RCGW  Email: wacukacynthia11@gmail.com/cynthia.wacuka@rcgw.go.ke

Corresponding Authors: Agnes W. MbuguaEmail: mbuguaagne@yahoo.co.uk

Patrick Murunga Email: patrickmurunga@gmail.com

  Availability of source water is one of the basic prerequisites for taking up any Managed Aquifer Recharge (MAR) structure. Similarly, realizing full potential for MAR necessitates among others undertaking hydrological investigations to determine the feasibility for an MAR exercise. The study considered runoff as the main water source for MAR for Tiwi aquifer. Thus, runoff from the nearby two watersheds namely Kongo/Mwachema and Pemba-Shimbo were quantified to establish the available water for MAR. The Soil Conservation Service Curve Number (SCS-CN) method was employed. The method made use of 2020-2022 daily rainfall, FAO soil and 2022 land use datasets as the main inputs and runoff was calculated for monthly, seasonal, and annual timescales.

  The analysis resulted to curve numbers of values 40.38- Kongo and 61.12-Pemba-Shimbo with little runoff occuring. A further analysis of the data to establish percentage of rainfall that was converted to runoff resulted to 1.2% (2020), 1.3% (2021) and 0.04% (2022) for Pemba-Shimbo. For Kongo, conversion was observed for 2020 (0.1%) only. This study period was however later found to represent a drought period in the area. Longer historical dataset of ten years, or more was suggested to establish the average amount of excess water that has been available in the past as well eliminate biases from multiyear climate cycles.

  In conclusion, little to no excess rainfall occurred during the study period inferring that much of the rainfall infiltrated to the ground and little was left to contribute to direct runoff. The study also revealed that steady supply of the water will be impacted by the climate variability among other competing water use needs, resulting to its sporadic and seasonal availability. However, the findings inform the amount available for MAR in Tiwi aquifer and the need to consider both the wet and dry years

Updating the Conceptual Model of the Nairobi Aquifer System

Sarah Mutua1 – corresponding author (sarah.mutua@tukenya.ac.ke) Dr. Agnes Mbugua2

Hibrahim Otieno Nyakach3 Dr. Samson Oiro4 

1 Technical University of Kenya

2 Regional Centre on on Groundwater Resources Education Training & Research of Kenya

3 Nairobi City County Government

4 Water Resources Authority of Kenya

  The resilience of groundwater to climate change effects has made it an emerging important water source globally. In Nairobi city for example, the Nairobi aquifer system (NAS) has become a key complementary source of water supply in new property development projects. NAS is one of the most studied aquifers in Kenya and is reported to have important water quality issues like high fluorides. Further, the piezometric levels of the various aquifers are reported to be declining at an alarming rate pointing to a possible groundwater mining case. Despite this, there is no known one stop shop for updated NAS quality and quantity data. The unsuspecting population is left to speculate, unaware of the public health issues lurking beneath. This study, which is an initiative of multiple stakeholders, aims to contribute towards creation of a NAS database by creating an updated timeline of NAS water quality and quantity dynamics. Specifically, the study seeks to identify the key aquifers and the evolution of their piezometric/potentiometric levels over their recorded history. Further, to explore solute and/or contaminant transport, the spatio-temporal variability of the water quality within the aquifer systems will be determined. The study is utilizing groundwater data from borehole completion records and stored by the Water Resources Authority (WRA) of Kenya and the Regional Center on Groundwater Resources Education Training & Research (RCGW) of Kenya. Aquifer elevation and piezometric maps (from different periods) will be developed. Updated water quality maps as well as piper diagrams from different periods, for all the aquifers will also be developed.

Rogue waves in three wave resonance and long wave-short wave resonance models

Qing Pan

Department of Mechanical Engineering, University of Hong Kong, Pokfulam, Hong Kong

Email: upanqing@connect.hku.hk

  Rogue waves are unexpected, large amplitude waves arise from tranquil sea surface. Crossing sea states have been suggested as one possible formation mechanism of rogue wave, which is characterized by free surface waves with two or more spectral peaks propagating at oblique angles to one another. Here the triad in stratified fluid and long wave-short wave resonance in layered fluid have been applied to model the crossing sea states condition, focusing on the modulation instability and breather formation, which are crucial factors contributing to rogue wave generation. It is demonstrated that modulation instability will be enhanced compared to single waves. There is a preferred inclination of oblique wave propagation for a maximum growth rate, suggesting the occurrence of rogue waves. By deepening the understanding of these complex wave propagation configurations in fluid mechanics, we can enhance maritime safety and develop strategies to mitigate the risks associated with crossing sea states.

Evaluation of impacts of climate change on groundwater in Ewaso Ngiro-Lagh Dera basin, Kenya

Githinji Tabitha Wambui 1, Dindi Edwin Wandumbi 1, Kuria Zacharia Njuguna2, Olago Daniel Ochieng1

1Department Earth and Climate Sciences, University of Nairobi

2 Department of Geoscience and the Environment, Technical University Kenya

Correspondence to: tgithinji@uonbi.ac.ke

  Ewaso Ngiro-Lagh Dera Basin, Kenya, is a water-stressed, arid region of Kenya that heavily relies on groundwater as the primary water source. Hence, proper utilization and management of groundwater resources are paramount. Climate Change escalates the water resource scarcity in the basin as evidenced by prolonged droughts. This study aimed to evaluate the impact of climate change and future abstraction on groundwater quantity in the Ewaso Ngiro Lagh Dera basin. The methodology involved the utilization of an integrated hydrological model integration (SWAT-MODFLOW) to simulate surface water and groundwater resources, an ensemble of ten Global Circulation Models (GCMs) under three shared socio-economic pathway (SSP) emission scenarios. Three SSPs were considered; these are SSP1- 2.6, SSP2-4.5, and SSP5-8.5 for 2015-2100.  Results show an increase in annual rainfall in all the SSPs. That is a projected increase from the baseline period to 24.5%, 28.8%, and 41.1% for SSP1- 2.6, SSP2-4.5 and SSP5-8.5 respectively. The annual minimum temperature is projected to increase by 1.4°C, 1.2°C, and 4.4°C whereas the annual maximum temperature is expected to rise by 1.3°C, 2.4°C, and 3.7°C, for SSP1- 2.6, SSP2-4.5 and SSP5-8.5 respectively. The future increase in rainfall will be experienced for a short period, resulting in little infiltration and percolation into the ground. Increased temperature will lead to increased evapotranspiration and subsequent decreased water recharge across all SSPs. Further, the projected increase in yearly population by 2% will lead to increased groundwater abstraction and an overall decrease in groundwater levels. The information on the future groundwater quantity is vital to decision-makers for strategic management and sustainable utilization of the resources.

The Development Kuznets Curve and Household Water Security

Feng Mao

School for Cross-faculty Studies, University of Warwick, United Kingdom

  Achieving water security is not merely about ensuring sufficient and safe water supply, but also about its equitable distribution among populations. The dynamics of water security inequality, especially in low- and middle-income nations, remain underexplored, posing a challenge to sustainable development efforts. This study delves into the disparities in water security, examining data from 7,603 households spread over 28 sites in 22 countries, including on 8 sites in 6 African countries: Bahir Dar (Ethiopia), Accra (Ghana), Lilongwe (Malawi), Lagos (Nigeria), Morogoro and Singida (Tanzania), and Arua and Kampala (Uganda). Our findings reveal an inverted-U shaped relationship between site water security and inequality of household water security. This pattern indicates that with the growth in water security, inequality initially widens before narrowing down. Our findings introduce the concept of the Development Kuznets Curve in the context of water security, offering valuable insights for enhancing equitable water distribution and fostering sustainable development.

Potential success in the artificial groundwater recharge of the Nairobi Aquifer System: A review

Japhet Rugendo KANOTI

  This paper explores innovative and safe ways of replenishing Nairobi Aquifer System through a review of existing sustainable groundwater practises in other parts of the world. We review and provide an overall approach to quantify and identify suitable recharge sites and evaluate challenging recharge water quality and other issues encountered during managed groundwater recharge projects. Due to rapid expansion of the Nairobi city and the population increase, domestic water currently supplied to the city is not enough and therefore drilling boreholes for groundwater supply is the short term solution adapted by the property owners and other institutions. However, there is a noted reduction in borehole productivity that is attributed to over-pumping, and a reduction in natural groundwater recharge due to an increase in built-up areas, increased surface run-off, climate variability and an increase in the number boreholes in the recent past. The Nairobi aquifer system require urgent human interventions for its sustainability. Through harvesting of ever increasing storm-runoff water and domestic waste water, the city can succeed in revitalizing the endangered aquifer through managed aquifer recharge. However, the development of successful artificial groundwater recharge system require in-depth assessment of the quality of the recharge waters and their likely impacts on the quality of revamped groundwater. The residual contaminants in domestic waste water and surface-runoff water can have adverse impacts on groundwater quality and aquifer health. Chemical, microbial and other characteristics of the recharge water should be determined to ensure compatibility so as to protect the health of the aquifer and the quality of groundwater after recharge. Particular attention should be given to potential water quality and aquifer characteristic changes attributable to artificial recharge for sustenance of the aquifer.

Application of the stable isotopes and MixSIAR model to identify nitrate sources in Mihe River, Eastern China

Yuyu Liu

  Nitrate pollution of water bodies is a widespread global environmental problem. The Mihe River Basin, which is at risk of eutrophication, was chosen as the study region, and 44 surface water samples were collected there in August 2022 (wet season) and March 2023 (dry season). Using multi-isotope techniques along with water chemistry characterization, land use and Bayesian stable isotope mixing modelling (MixSIAR), the source and pollutant contribution of NO3- in the surface water of the Mihe River were examined. The results showed that NO3- content varied significantly among different land uses. Sample sites within the Industrial Area (IA), High Urbanisation Area (UA) and Agricultural Area (AA) had higher NO3--N concentrations. Water chemistry analyses and nitrogen and oxygen isotope double-labelling plots indicated that manure and sewage (MS), and soil organic nitrogen (SON) were the main mixed sources of NO3-. In the Mihe River, nitrification dominates the nitrogen transformation process; denitrification plays a minor role. According to the MixSIAR model, soil organic nitrogen (SON), manure and sewage (MS) are the primary contributors of the NO3- in surface water. Soil organic nitrogen (SON) was the largest contributor of nitrate in the Low Urbanisation Area (LA), Agricultural Area (AA), and High Urbanisation Area (UA) during the period of abundance, while manure and sewage (MS) was the largest contributor in the Industrial Area (IA). Manure and sewage (MS) during dry periods were the largest contributors of nitrate throughout the watershed. The results of the research can provide scientific references for NO3- pollution control and surface water resource management in watersheds.

Keep the Flow: Citizen science for sustainable use of water resources

Jacqueline Goldin

Department of Earth Sciences, University of the Western Cape, Robert Sobukwe Road, Bellville 7435, South Africa.

jaquigoldin@gmail.com

  This paper addresses the transformative and emancipatory potential of citizen science not only concerning its role in groundwater management and sustainable utilization of water resources, but also regarding its contribution to enhanced and sustainable well-being and improved stakeholder engagement.  Our work is in the Hout Catchment region of the Limpopo province in South Africa where living conditions vary greatly but all share a vulnerable dependency on the dwindling availability of water. We propose that the interaction between human water systems and its contextual social dimensions with regard to diversity and historically shaped structures of power, has had serious impacts on the ability to tackle challenges of sustainable water management. In our project, citizen scientists markedly expand data collection and analysis at a faction of the cost of traditional scientific endeavour.  Keep the Flow is not simply about effectively using measurement instruments but also about practices of authentic learning through innovative methodologies that were used to communicate with citizens about science and with scientists about social transformation and well-being. Citizen science has been defined as a multi-stakeholder process that aims at increasing democratization of science and policy, scientific citizenship, public engagement, transparency, equity, inclusiveness and justice. Our own definition is simpler: citizen science takes science out of laboratories and libraries and into real life.

Human-induced intensification of terrestrial water cycle in dry regions of the globe

Yansong Guan1,2, Xihui Gu1,3,4,5,6,7.8

1. Department of Atmospheric Science, School of Environmental Studies, China University of Geosciences, Wuhan 430074, China;

2. Department of Computer Science and Technology, School of Computer Science, China University of Geosciences, Wuhan 430074, China;

3. Key Laboratory of Meteorological Disaster Ministry of Education & Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science & Technology, Nanjing 210044, China;

4. Institute of Arid Meteorology, China Meteorological Administration, Lanzhou 730020, China;

5. Key Lab of Basin Water Resource and Eco-environmental Science in Hubei Province, Wuhan 430010, China;

6. The National Key Laboratory of Water Disaster Prevention, Nanjing Hydraulic Research Institute, Nanjing 210029, China;

7. Hubei Key Laboratory of Yangtze Catchment Environmental Aquatic Science, Wuhan 430074, China;

8. Centre for Severe Weather and Climate and Hydro-geological Hazards, Wuhan 430074, China.

  Anthropogenic climate change (ACC) strengthens the global terrestrial water cycle (TWC) through increases in annual total precipitation (PRCPTOT) over global land. While the increase in the average global terrestrial PRCPTOT has been attributed to ACC, it is unclear whether this is equally true in dry and wet regions, given the difference in PRCPTOT changes between the two climatic regions. Here, we show the increase in PRCPTOT in dry regions is twice as fast as in wet regions of the globe during 1961–2018 in both observations and simulations. This faster increase is projected to grow with future warming, with an intensified human-induced TWC in the driest regions of the globe. We show this phenomenon can be explained by the faster warming and precipitation response rates as well as the stronger moisture transport in dry regions under ACC. Quantitative detection and attribution results show that the global increase in PRCPTOT can no longer be attributed to ACC if dry regions are excluded. From 1961 to 2018, the observed PRCPTOT increased by 5.63%~7.39% (2.44%~2.80%) over dry (wet) regions, and as much as 89% (as little as 5%) can be attributed to ACC. The faster ACC-induced TWC in dry regions is likely to have both beneficial and detrimental effects on dry regions of the globe, simultaneously alleviating water scarcity while increasing the risk of major flooding.

Understanding the occurrence, pathways, and human health risks of contaminants of emerging concern (CECs) in groundwater – a South African case study

N. Kalebaila

Water Research Commission, 18 Hilden Road, Lynnwood, Pretoria , 0081, South Africa

Email address: nonhlanhlak@wrc.org.za

  As a water-scarce country, groundwater is acknowledged as an integral part of South Africa’s water resources mix, crucial for ensuring water security and resilience in the face of increasing demand and variability in supply. However, the introduction of diverse Contaminants of Emerging Concern (CECs) into groundwater systems via both natural recharge and anthropogenic activities poses significant threats to water quality and human health. Despite this, there remains a scarcity of studies on the occurrence and impacts of CECs in South African groundwater. This paper presents a synthesis of recent research funded by the Water Research Commission, which has documented the presence of various CECs, including pharmaceuticals, brominated flame retardants (BFRs), microplastics, and per- and polyfluoroalkyl substances (PFAS), in groundwater sources across the country.   Notably, antiretroviral   drugs, brominated flame retardants, and   microplastics   have   been   detected   at concentrations of concern.

  Antiretroviral drugs, such as, Stavudine, Nevirapine, Tenofovir, Nelfinavir and Saquinavir have been detected groundwater sources in South Africa in concentrations ranging from 03 to 5.3 ng/L. Amongst BFR compounds, the highest concentrations were reported for polybrominated diphenyl ethers (BDE), with concentrations of up to 9.4 ng/g (dry weight) detected in leachate sediments, and up to 2.5 ng/L in leachate water samples. Similarly, BDEs were also detected in groundwater samples. Microplastics counts of up to 0.2889 fragments and fibres per Litre of groundwater have been reported in South Africa. For PFAS, compounds such as FOET, PFAS, PFBA, PFOA, LPFOS, 8:2 FTS and PFHxS showed the highest concentrations (up to 1400 ng/L) in groundwater.

  To better understand the sources and transport mechanisms of these CECs, a preliminary principal component analysis (PCA) was conducted. Results suggest that CECs primarily enter groundwater through leachates and natural recharge processes. However, it's important to note that PCA alone may not provide a comprehensive understanding of CEC behaviour, warranting further investigation using complementary analytical and modelling approaches. Moreover, an assessment of human health risks associated with CEC-contaminated groundwater  revealed the   potential  for  enhanced  toxicity, persistence, and mobility due to the synergistic effects of individual contaminants.

  These findings underscore the urgent need to revise groundwater quality regulatory frameworks to incorporate contaminants of emerging concern, and promote the adoption of adaptive management practices to ensure the safe recharge of groundwater through both natural and artificial processes. In conclusion, comprehensive understanding of the sources, levels, pathways, and compound risks of CECs is essential for safeguarding groundwater quality and ensuring the sustainable use of this vital resource.  Continued research, collaboration, and innovation is important to address emerging challenges and protect groundwater ecosystems for present and future generations.

Global flood projection and socioeconomic implications under a physics-constrained deep learning framework

Jiabo Yin

Wuhan University

  As the planet warms, the frequency and severity of weather-related hazards such as floods are intensifying, posing substantial threats to communities around the globe. Rising flood peaks and volumes can claim lives, damage infrastructure, and compromise access to essential services. However, the physical mechanisms behind global flood evolution are still uncertain, and their implications for socioeconomic systems remain unclear. In this study, we leverage a supervised machine learning technique to identify the dominant factors influencing daily streamflow. We then propose a physics-constrained cascade model chain which assimilates water and heat transport processes to project bivariate risk (i.e. flood peak and volume together), along with its socioeconomic consequences. To achieve this, we drive a hybrid deep learning-hydrological model with bias-corrected outputs from twenty global climate models (GCMs) under four shared socioeconomic pathways (SSPs). Our results project considerable increases in flood risk under the medium to high-end emission scenario (SSP3-7.0) over most catchments of the globe. The median future joint return period decreases from 50 years to around 27.6 years, with 186 trillion dollars and 4 billion people exposed. Downwelling shortwave radiation is identified as the dominant factor driving changes in daily streamflow, accelerating both terrestrial evapotranspiration and snowmelt. As future scenarios project enhanced radiation levels along with an increase in precipitation extremes, a heightened risk of widespread flooding is foreseen. This study aims to provide valuable insights for policymakers developing strategies to mitigate the risks associated with river flooding under climate change.

Integrated flood risk management on reduce sedimentation, course stabilization and spare-course planning in Yellow River Delta

Huang Bo

College of Water Resources and Environment, University of Jinan

Stu_huangb@ujn.edu.cn

  The Yellow River Delta is the youngest land of China originated since 1855. Thereafter, the river channel shifted and swayed naturally due to great silt sedimentation, which cause frequent flooding and great impacts on local industry, agriculture and resident lives. High silt concentration and sedimentation are the major problems and core reasons for the rising flood risk in Delta region, which lead to river bed rising, end reaches extending, swaying and channel diversion in the end.

  The paper focus on integrated analysis and feasible measures on flood risk management in delta area. The first is the main problems, which are instability of the river course and channel sedimentation and riverbed rising. Then is the analysis of the problems, including water-sediment relationship, sedimentation and water-silt decrease. For the fundamental measures to decrease flood risk in delta are sediment reduction in reservoir, sediment conservation in middle reaches and measures for course stabilization and spare-course planning. The paper gives a comprehensive analysis on water and sediments relationship, evolution process of end reaches, and presents possible solutions on flood risk management in Yellow River Delta.

Study on the Impact of Climate Change on Hydrological Processes and Water Environment of Three Gorges Reservoir Basin

Hong Peng 1, Wang Yue2, Wanshun Zhang2,3, Yidian Sun2

1 School of Water Conservancy and Hydropower Engineering, Wuhan University, Wuhan 430072, China；

2 School of Resource and Environmental Sciences, Wuhan University, Wuhan 430079, China；

3 School of Water Resources and Hydropower, State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan 430072, China

  As the important ecological security barrier, the strategic reserve of water resources and the ecological function area of the Yangtze River basin, the Three Gorges Reservoir area (TGRA) boasts a unique and extremely important strategic position in the ecological environment protection of the Yangtze River basin. The structure, composition and water cycle of the regional ecosystem will be altered by global climate change. The prediction of future climate and water environment trends in the basin can provide a scientific basis for disaster prevention and control, resource allocation and ecological protection in the basin. Taking the TGRA as the study area, we constructed an integrated air-ground-water model to realize the accurate simulation of climate change and water environment processes in the basin, and predicted the spatial and temporal trends of climate and water environment processes in the Three Gorges Reservoir Basin for the period of 2023-2033 based on the two future scenarios, the RCP4.5 (medium-emission scenario) and the RCP8.5 (high-emission scenario, and the response mechanisms of water environment elements to climate change were revealed. Laying a theoretical foundation for effective water resource management programs under climate change for basin management, and to promote the environmental and socio-economic sustainability of the Three Gorges Reservoir Basin.

Research on Re-development And Utilization Of Hydropower under the new energy system

Shichun Gao

School of Water Resources and Hydropower Engineering, Wuhan University, China

Email: scgao@whu.edu.cn

  In response to construct a low-carbon and efficient new modern energy system, China is vigorously developing renewable energy. The volatility and randomness of new energy bring risks to the power system, and the power grid needs flexible and controllable hydropower for regulation. Under the condition that the conventional hydropower development is basically completed, it is of great significance to carry out the secondary development of hydropower, that is, to expand the installed capacity of the power station and install pumped storage units.

  The Three Gorges Reservoir assumes the task of flood control safety in the middle and lower reaches of the Yangtze River. Due to the prominent contradiction between flood control and profit, Severe drought in the Yangtze River in 2022 has greatly affected the reservoir filling rate at the end of the flood season, and then affected the power generation efficiency during the dry season, bringing a certain impact to the power supply system. In order to analyze the impact of different end-flood reservoir storage, that is, "water storage", on the power generation in dry season, and reveal the relationship between "water storage" and wind power, photovoltaic, hydropower, this paper takes the actual operation of the Three Gorges Power Station from 2022 to 2023 as an example to make a comparative analysis. Relevant analysis shows that the power generation will increase by 4.882 billion kW·h in 2023 during the dry season. Among them, the storage capacity of reservoirs at the end of flood season accounts for about 64%, and the increased power generation due to the increase of power generation head accounts for about 36%. "Water energy storage" can be obtained by relying on natural runoff, or it can store excess wind power and photovoltaic power in the grid through pumped storage. Therefore, renewable energy and "water energy storage" unified planning and scheduling, has great efficiency potential

Impact of land use and climate change on water environment in the middle and lower reaches of Hanjiang River

Wanshun Zhang1,3, Zhang yue1, Hong Peng2, Xiao Zhang1

1 School of Resource and Environmental Sciences, Wuhan University, Wuhan 430079, China；

2 School of Water Conservancy and Hydropower Engineering, Wuhan University, Wuhan 430072, China；

3 School of Water Resources and Hydropower, State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan 430072, China

  The middle and lower reaches of the Han River are strongly affected by human activities such as the South-to-North Water Diversion Middle Route Project and the construction of cascade reservoirs. The combined resource development and utilization rate is as high as 47%. Under global climate change, water environment problems are becoming increasingly complex. Land surface model, hydrodynamic model, water quality model and reservoir model adjustment were used to construct a variation-hydrodynamic-coupled model of the middle and lower reaches of the Han River to study the impact of basin engineering adjustments on the water environment in the middle and lower reaches of the Han River, and significantly change the drainage water resources of the underlying surface of the basin. Drawing on spatiotemporal measurements reveals the changing characteristics of river hydrological quality under the operation of cascade reservoirs, analyzes the influence of water conservancy project operating mechanisms, climate change and river basin land use/cover changes on basin hydrological quality, and further provides information for the realization of sustainable river basin management. Scientific basis.

Rising rainfall intensity induces spatially divergent hydrological changes within a large river basin

Yiping Wu1, Xiaowei Yin1, Guoyi Zhou2

1 Institute of Global Environmental Change, Department of Earth & Environmental Science, Xi’an Jiaotong University, Xi’an, Shaanxi Province, 710049, P. R. China.

2 Institute of Ecology, School of Applied Meteorology, Nanjing University of Information Science and Technology, Nanjing 210044, P. R. China

rocky.ypwu@gmail.com

  Occurrences of droughts or floods are usually attributed to precipitation anomalies (deficit or surplus) that may become more frequent and severe under continued global warming. Concurring large-scale droughts in the Southwest and floods in the Southeast of China in recent decades have attracted considerable attention, but the causes and interrelations of drought and flooding are not well understood. Here, we examined the spatiotemporal changes of key hydrometeorological variables and investigated the mechansim of soil dryness and wetness during 54 years (1965–2018) across a representative mega-watershed in South China—the West River Basin (353,120 km2). Rainfall showed a significant increase in intensity, with an upward trend ranging from 0.01 to 0.04 mm d-1 across the watershed over time, in spite of no significant change in the amount. The spatiotemporal analyses demonstrated that drought index declined with a rate up to –0.05 y-1 locally (an average rate of –0.02 y-1) in the upstream; whereas it rose with a rate up to 0.15 y-1 locally (an average rate of 0.004 y-1) for downstream. Also, the decrease in soil water (up to –2.0 mm y-1 locally) and water yield (up to –4.8 mm y-1 locally) in the upstream and their increases for downstream, together with a pronounced decrease of baseflow (up to –3.2 mm y-1) in the upstream, further confirmed the severe drying upstream versus the wetting downstream. This mechansim—temporal change of rainfall could cause spatially divergent hydrological changes—was further proved using scenario design and process modeling at different scales (e.g., slope land, hydrological response unit, subbasin and upstream/downstream). Our study highlights the simultaneous occurrence and interrelation of increased droughts and flooding due to rainfall intensification across a basin, illustrating increasing vulnerability in terms of water and food security under current climate change.

Water Transfer Conflict Resolution Using Game Theory under Climate Changes and Human Impacts

Yu Li, Xiang Fu*, Zhipeng Fan

State Key Laboratory of Water Resources Engineering And Management, Wuhan University, Wuhan, China 430072

*Corresponding author. xfu@whu.edu.cn

  Water transfer projects between basins are critical for managing water resources but can lead to conflicts due to varying needs and availability of water. This fuzzy water conflict could be exacerbated by shifts in precipitation patterns and increased evaporation rates in future climates. This research addresses these challenges by proposing a game theory-based approach to resolve water transfer conflicts under changing climatic conditions and human influences. We develop an integrated framework using the open-source Spatial Processes in Hydrology (SPHY) model, focusing on four interconnected basins in China. By incorporating future climate scenarios from CMIP6 General Circulation Models (GCMs) and optimizing human interventions, our framework projects the water availability, consumption and reservoir operations to provide data reference for water transfer projects. Furthermore, our approach incorporates optimization of water resources usage and decision makers' preferences for regional equity and tradeoffs among multiple water agents. This holistic framework provides valuable insights for sustainable water management and decision-making in inter-basin water transfer projects, addressing conflicts and ensuring efficient reallocation of water resources.

Research on Short-term Inflow Forecasting Method for Cascade Hydropower Stations in Data-scarce Regions

Longqing Zhao1, Xueshan Ai 1,2,3 , Xuanyu Shi1, Fengshuo LIU1, Yangxi YU

1. School of Water Resources and Hydropower Engineering, Wuhan University, Wuhan 430072,China；

2. State Key Laboratory of Water Resources Engineering and Management, Wuhan University, Wuhan 430072,China；

3. Hubei Key Laboratory of Water System Science for Sponge City Construction, Wuhan University, Wuhan 430072, China

  The calculation of inflow is one of the most fundamental tasks in reservoir operation. In the scheduling of cascade hydropower stations in river basins, the leading power station is affected by upstream inflow, while other stations are not only influenced by the outflow of their upstream reservoirs but also by the inflow from the adjacent watershed areas, where few hydrological stations are available. To carry out the inflow forecasting for cascade hydropower stations in data-scarce regions, this paper proposes an hourly-scale inflow forecasting method for cascade hydropower stations that comprehensively considers the influencing factors of watershed confluence. The inflow forecasting is divided into two parts: the inflow of the leading reservoir and the inflow between cascade power stations. Based on the theory of water balance, Muskingum routing method, and the laws of watershed runoff generation and confluence, historical matching methods are used for forecasting the inflow of the leading reservoir. Meanwhile, correction coefficients are introduced to process the runoff sequences in the cascade power station intervals to compensate for the lack of data on watershed confluence, thereby enabling the inflow forecasting for all cascade hydropower stations. Practical applications in the middle and lower reaches of the Hongshui River Basin have shown that the Nash-Sutcliffe Efficiency (NSE) of the confluence results calculated by the Muskingum method and the corrected inflow sequences during the evolution of the main stream flow are both above 0.9. The NSE of the comprehensive forecasted inflow sequences for all cascade power stations and the measured inflow sequences are all above 0.8. The results indicate that this method has a high accuracy in inflow forecasting and can provide a reference for the inflow forecasting of reservoirs in short-term and real-time scheduling of cascade reservoir groups.

The removal behavior of PPCPs pollutants by suspended sediments from the Yellow River, China

Wei Zhang1,2,3, Quantao Cui1, Qiting Zuo2,3,4*

1 School of Ecology and Environment, Zhengzhou University, 100 Kexue Avenue, Zhengzhou 450001, PR China;

2 Henan International Joint Laboratory of Water Cycle Simulation and Environmental Protection, Zhengzhou 450001, PR China

3 Yellow River Institute for Ecological Protection and Regional Coordination Development, Zhengzhou University, 100 Kexue Avenue, Zhengzhou, Henan 450001, PR China

4 School of Water Conservancy Engineering, Zhengzhou University, 100 Kexue Avenue, Zhengzhou, Henan 450001, PR China

E-mail: zuoqt@zzu.edu.cn

  Although previous studies have proven that sediments could act as an important transport vector of antibiotic pollutants, the crucial impact of suspended sediments (SS) on the migration and fate of antibiotics in water bodies remains unclear. This study systematically investigated the performance and potential mechanism of removal of PPCPs pollutants by SS from the Yellow River. The physisorption (pore filling, hydrogen bonding) and chemisorption (π-π interaction, surface complexation, and electrostatic interaction) activities would contribute to the adsorption of PPCPs by SS. Furthermore, the contribution of different mineral components (SiO2, Fe2O3, and Al2O3) of SS on PPCPs adsorption was also investigated. What’s more, the SS could efficiently activate PMS to remove PPCPs pollutants from water environment in the peroxymonosulfate (PMS) solution (without any other catalysts). This study provides new insights into the removal mechanism and migration of PPCPs pollutants in rivers with high SS content.

Chemical compositions evolution of groundwater and its risk assessment in an intensive agricultural region in South Africa

Oluwadimimu P Akinpelu1, Muthukumar Perumal1, Rakesh R. Gantayat1, Vetrimurugan Elumalai

Department of Hydrology, University of Zululand, Kwa Dlangezwa, 3886, South Africa.

*Corresponding author: Email: ElumalaiV@unizulu.ac.za; Tel: (+ 27) 35-902 6404

Presenter(s): Prof. ELUMALAI, Vetrimurugan (University of Zululand)

  The Luvuvhu catchment in Limpopo, South Africa, is part of the vast Limpopo River system, extending into Mozambique. Originating in the Soutpansberg Mountains, the Luvuvhu River and its tributaries, like the Mutshindudi and Mutale rivers, are crucial for farming and domestic water use. Despite agricultural activities, it faces anthropogenic pressures and contains geothermal springs. Groundwater assessment spanning over 2 years on this catchment revealed the acidic to alkaline nature of water, with dominant hydro-chemical facies of Ca-Mg-Cl and Ca-HCO3. Despite agricultural activities, groundwater remained suitable for drinking. Irrigation analysis showed overall suitability but magnesium hazard in some areas. Groundwater chemistry results from natural processes like weathering and human inputs such as irrigation and sewage. Major ions such as Na. K. Mg. Ca and Cl are predominantly geogenic whereas NO3, NH3 and F are attributed by agricultural activities and wastewater infiltration whereas increased metal leaching was observed in proximity to deforested areas. Source apportionment model indicated high of P, Co, Cd, B and Ag in agricultural soil. Soil derived from mafic igneous rocks such as Basalt rich in serpentine along with geothermal spring interaction during soil pedogenesis were major contributors of metals like Cr, B, Co, Zn, Ni, Mn and Fe. Agricultural enrichment of metals is mainly responsible for higher levels of contamination whereas metal accumulation in basaltic soil poses higher ecological risk in the catchment with a toxicity probability of more than 76%. Source based probabilistic human health assessment using Monte Carlo simulation (MCS) in soil predicted high non-carcinogenic (NCR) and carcinogenic risk (CR) in 55 and 90% of the scenarios for children. Such risk was mainly attributed by geothermal sources (>40%) in case of NCR through Co, Cr and Cd whereas 76% contribution in CR found associated with basaltic soil accumulation of Ni and Cr. On the other hand, groundwater was found free of any health risk for both adults and children. The findings suggest that prevention efforts should prioritize addressing trace metals, with soil contamination posing a significant threat in the basin due to accumulation.

Geochemical tracing of stray gas detected in abandoned wells and associated shallow aquifers from the Karoo Basin, South Africa

Murendeni Mugivhi1*, Thokozani Kanyerere2, Yongxin Xu2

1. Petroleum Agency of South Africa, Heron Place, Heron Cl, Century City, Cape Town, 7441, South Africa, MugivhiM@petroleumagencysa.com;

2. Department of Earth Science, University of the Western Cape, Cape Town, South Africa, tkanyerere@uwc.ac.za; yxu@uwc.ac.za.

  Interest in exploiting Karoo Basin shale gas to eluviate the current demand of energy supply in South Africa has led to background investigations of stray gas leakage from abandoned wells and possible contamination of shallow aquifers before large-scale shale gas extraction. The aim is to document baseline dataset that will benchmark the state of the Karoo Basin prior to shale gas extraction and serve as reference for regulators to monitor the extraction process during and after the operation to determine whether there is any contamination to pristine aquifer. Lack of this dataset will compromise assurance of monitoring compliance. To document this dataset dissolved gas and water samples were collected from deep wells (2490 to 3500 meters below land surface (mbls)) and shallow groundwater boreholes (5 to 169 mbls) throughout the Karoo Basin using GT5000 gas analyzer and a bailor. Samples were analyzed at Stratum Isotech for hydrocarbon molecular and isotopic compositions, isotopic compositions of water, strontium, sulfate, inorganic carbon, and radioactive elements, and concentrations of cations, anions, metals, nutrients, and carbon-14. Compared to other regions in the Karoo Basin with indication of meteoric water source, groundwater samples from Ceres had much more positive 13C of dissolved inorganic carbon and a lack of carbon-14, indicating a greater presence of older water and carbonate dissolution, samples from this region also had higher 87Sr/86Sr ratios indicating water-rock interactions with volcanic.  Of the 50 wells sampled in this study, 11 of them had significant dissolved hydrocarbon concentrations for isotopic analyses (ranging from 0.41 to 16 mg/l of CH4; 0.003 to 0.58mg/l of C2H6 and 0.0016 to 0.019mg/l of C3H8). Isotopic analysis revealed microbial gas via fermentation, microbial gas via carbon dioxide reduction, thermogenic gas, and geothermal gas as evidence of heavier 13C-CH4 values and isotopic reversals (when the 13C is heavier in methane compared to ethane). Observed geothermal gas is associated with the intrusion of dolerite dykes and sills bringing high heat through organic-rich rocks and/or already present thermogenic gas that then caused isotopic reversals. Abandoned wells are leaking deep geothermal gas indicating improper abandonment, but their associated shallow aquifers show no evidence of gas cross-contamination, except for one groundwater borehole situated 7km away from an abandoned well in Murraysburg which showed evidence of geothermal gas contamination. Bearing the distance between the borehole and the well, and higher gas salinization in groundwater borehole of 16mg/l compared to 11mg/l of abandoned wells suggests that the leakage could either be natural through a dolerite intrusion or a fault. In Graaff-Reinet, a groundwater borehole situated 1km away from an abandoned well tested the presence of thermogenic gas with salinization of 13mg/l indicating potential linkage. Tested microbial gas in shallow aquifers indicate shallow gas not leaked through abandoned wells. Generally, abandoned wells are not conduits for gas leakage into shallow aquifer, except in Graaff-Reinet. It is therefore recommended that shale gas extraction be allowed with a 1km setback of development from abandoned wells.