Long-term Water Resources Management Research Articles

Evaluation of hydrological responses to climate change in the Gibe Gojeb catchment, southwestern Ethiopia

ABSTRACT The expected influences of climate alteration on hydrological responses in the Gibe Gojeb catchment, southwestern Ethiopia, were evaluated using the Soil and Water Assessment Tool (SWAT) model and regional climate models (RCMs). This study emphasizes the evaluation of the climate change impact on hydrological responses. The RCM data were downloaded from CORDEX-Africa. Power transformation and delta change methods were used for bias correction of precipitation and temperature, respectively. The calibration and validation of the SWAT model showed good agreement, and climate change impact was simulated. Accordingly, precipitation, soil water content, percolation, water yield, and groundwater are projected to decrease by 28.18, 7.5, 9.1, 5.4, and 9.2%, respectively, under RCP4.5 in the future (2021–2050). Besides, surface runoff and potential and actual evapotranspiration are projected to increase by 17.4, 11.32, and 5.06%, respectively. Soil water content, percolation, water yield, and precipitation are projected to decrease by 10.51, 5.63, 2.76, and 21.57%, respectively, under RCP8.5 in the future. Rain-fed crop production and hydropower generation in the catchment would be vulnerable to the effects of climate change. The results help to develop effective adaptation measures to reduce the impacts of climate change and draft long-term water resource management plans in the Gibe Gojeb catchment.

Empowering Farmers to Enhance Water Use Efficiency: Innovative Practices in SSPC

The Sardar Sarovar project, featuring a gravity dam on the Narmada River in Gujarat, stands as one of the largest in terms of concrete volume globally. This study investigates the project's extensive canal network and its impact on agricultural productivity in the command area. Covering a vast expanse across multiple states, the project's irrigation allocation and water management strategies are examined. Special attention is given to addressing soil degradation issues, particularly salinity, and implementing farmer-centered interventions to enhance water use efficiency. Methodologies include land rejuvenation efforts, reclamation of salt-affected land, participatory irrigation management, and promoting improved agricultural practices. Results indicate successful mitigation of soil degradation and increased crop yields through strategic interventions like cotton-castor relay cropping which has demonstrated a 1.5-fold increase in income compared to sole cropping. Intercropping with isabgul/ajwain, and implementing deficit irrigation have resulted in a substantial 43% increase in overall yield, particularly in cumin cultivation. Farmers have also embraced innovative water-saving techniques, such as alternative furrow irrigation and strategic timing of irrigation during critical growth stages, resulting in water savings of 30-35%. However, challenges remain in achieving widespread adoption of participatory irrigation management practices. The study concludes with insights into the necessity of sustained social engineering efforts and community engagement for long-term water resource management and agricultural sustainability in the project area.

Exploring potential trade-offs in outdoor water use reductions and urban tree ecosystem services during an extreme drought in Southern California

In Southern California cities, urban trees play a vital role in alleviating heat waves through shade provision and evaporative cooling. Trees in arid to semi-arid regions may rely on irrigation, which is often the first municipal water use to be restricted during drought, causing further drought stress. Finding a balance between efficient water use and maintaining tree health will be crucial for long-term urban forestry and water resources management, as climate change will increase drought and extreme heat events. This study aimed to quantify how urban tree water and carbon fluxes are affected by irrigation reductions, and how that relationship changes with tree species and temperature. We used an ecohydrologic model that mechanistically simulates water, carbon, and energy cycling, parameterized for 5 common tree species in a semi-arid urban area. We simulated a range of irrigation reductions based on average outdoor water use data from the city for a recent extreme drought as well as with warmer temperatures. We then analyzed the response of model outcomes of plant carbon fluxes, leaf area index (LAI), and water use. Results show that reducing irrigation up to 25%, a comparable amount as the California state mandate in 2014, has minimal effects on tree primary productivity and water use efficiency. We found that transpiration was linearly related to irrigation input, which could lead to a short-term loss of evaporative cooling with irrigation reductions during drought. However, primary productivity and LAI had a nonlinear response to irrigation, indicating shade provision could be maintained throughout drought with partial irrigation reductions. Results varied across tree species, with some species showing greater sensitivity of productivity to both irrigation reductions and potentially warmer droughts. These results have implications for water resources management before and during drought, and for urban tree climate adaptation to future drought.

Impact of climate change on Kupang River flow and hydrological extremes in Greater Pekalongan, Indonesia

Located downstream the Kupang Catchment in Indonesia, Pekalongan faces significant land subsidence issues, leading to severe coastal flooding. This study aimed to assess the impact of climate change on future flow regimes and hydrological extremes to inform long-term water resources management strategies for the Kupang Catchment. Utilizing precipitation and air temperature data from general circulation models in the Coupled Model Intercomparison Project 6 (CMIP6) and employing bias correction techniques, the Soil and Water Assessment Tool (SWAT) hydrological model was employed to analyze climate-induced changes in hydrological fluxes, specifically streamflow. Results indicated a consistent increase in monthly streamflow during the wet season, with a substantial rise of 22.8%, alongside a slight decrease of 18.0% during the dry season. Moreover, both the frequency and severity of extremely low and high flows were projected to intensify by approximately 50% and 70%, respectively, for a 20-year return period, suggesting heightened flood and drought risks in the future. The observed declining trend in low flow, by up to 11%, indicated the potential for long-term groundwater depletion exacerbating the threat of land subsidence and coastal flooding, especially in areas with inadequate surface water management policies and infrastructure.

Assessing water and energy fluxes in a regional hydrosystem: case study of the Seine basin

While it is well accepted that climate change and growing water needs affect long-term sustainable water resources management, performing accurate simulations of water cycle and energy balance dynamics at regional scale remains a challenging task.

A study of land use changes and its impacts on flood inundation in the Konkoure River Basin, Republic of Guinea.

Due to rising land development, mitigating the negative effects of land use change is becoming a problem. Understanding how land development affects flood inundation is critical for long-term water resource management. This study evaluates the land use change in the Konkoure River Basin and its impact on flood inundation. The land use changes were assessed using Landsat image (level 1) in August 2006 and August 2021. In addition, we used GIS and remote sensing applications to assess the degree of changes that took place in the Konkoure watershed. According to the findings, 32.16% of the total area became built-up areas, and 35.51% was converted to other land uses in Konkoure watershed. Konkoure's most significant change is that 29.50% of forest area transformed into built-up areas and other land uses. The rainfall-runoff-inundation model (RRI) based inundation of the Konkoure River Basin was compared to the MODIS extent between 31 August 2006 and 30 August 2021 flood events. Flood inundation variations in the Konkoure watershed were studied in terms of inundation area, peak inundation depth, runoff volume, and the infiltration rate. As a result, the flood inundation area increased from 139.98 to 198.72 km2 and the infiltration rate decrease from 7 to 5mm/h. Moreover, we used flow duration curves (FDCs) to fully comprehend the streamflow processes. The result indicates that the Konkoure watershed has experienced flooding partly due to land use change.

Groundwater Sustainability Assessment against the Population Growth Modelling in Bima City, Indonesia

Most of Indonesia’s population lives in areas with volcanic–alluvium geological characteristics. Based on the national hydrogeological map of the Indonesian Geological Agency, areas with volcanic–alluvium geological conditions have high groundwater potential and potential for groundwater damage. This study aims to test the resilience of groundwater areas with volcanic–alluvial characteristics to population growth. The MODFLOW groundwater model was built based on the site’s volcanic and alluvial geological conditions. This groundwater model was tested against pumping scenarios based on population water demand in 2011–2020 and then predicted population growth until 2030. The result shows that groundwater resilience in volcanic–alluvium locations has different characteristics based on lithology and population density characteristics. Urban areas that are mostly located in alluvium areas tend to have a linear groundwater decline pattern but have the sharpest groundwater decline gradient. In contrast, suburban areas in the alluvium-to-volcanic transition area initially experience exponential groundwater decline but change to linear, while rural areas located in volcanic areas that become the main development target have exponential groundwater decline characteristics. To counteract the continuous depletion of groundwater, researchers conducted a scenario for optimizing surface water use. Based on the results of the scenario, a 60% reduction in groundwater use is sufficient to stop continuous groundwater depletion. The results of this study can be used as a recommendation for long-term water resources management targets for volcanic and alluvium areas that are being targeted for development.

Evaluating Non-Stationarity in Precipitation Intensity-Duration-Frequency Curves for the Dallas–Fort Worth Metroplex, Texas, USA

Extreme precipitation has become more frequent and intense with time and space. Infrastructure design tools such as Intensity-Duration-Frequency (IDF) curves still rely on historical precipitation and stationary assumptions, risking current and future urban infrastructure. This study developed IDF curves by incorporating non-stationarity trends in precipitation annual maximum series (AMS) for Dallas–Fort Worth, the fourth-largest metropolitan region in the United States. A Pro-NEVA tool was used to develop non-stationary IDF curves, taking historical precipitation AMS for seven stations that showed a non-stationary trend with time as a covariate. Four statistical indices—the Akaike Information Criterion (AIC), Bayesian Information Criterion (BIC), Root Mean Square Error (RMSE), and Nash–Sutcliffe Efficiency (NSE)—were used as the model goodness of fit evaluation. The lower AIC, BIC, and RMSE values and higher NSE values for non-stationary models indicated a better performance compared to the stationary models. Compared to the traditional stationary assumption, the non-stationary IDF curves showed an increase (up to 75%) in the 24 h precipitation intensity for the 100-year return period. Using the climate change adaptive non-stationary IDF tool for the DFW metroplex and similar urban regions could enable decision makers to make climate-informed choices about infrastructure investments, emergency preparedness measures, and long-term urban development and water resource management planning.

Delay-aware karst spring discharge prediction

As an essential component of the hydrological cycle at both regional and global scales, karst aquifers store large amounts of water, serving as the main source of fresh water supply in many areas. Karst springs provide a natural drainage pathway for karst groundwater systems to participate in the hydrological cycle. Accurate prediction of karst spring discharge is of great value to the long-term planning and management of karst water resources. The mainstream methods proposed have achieved high prediction accuracy by introducing deep learning technology. However, these methods ignore the delay time of spring water discharge to water supply or drainage, so there is still room for improvement in prediction accuracy. To address this issue, this paper proposes a delay-aware spring discharge prediction (DSDP) framework that introduces the delay time to predict spring discharge. Specifically, the framework consists of three modules, including a time calibration module, a variation estimation module and a discharge prediction module. The time calibration module identifies the delay time of spring discharge to each element to calibrate the observations. And the variation estimation module utilizes a neural network to infer spring discharge variations. Finally, the discharge prediction module predicts spring discharge with derived discharge variations. This study validates the performance of the proposed method by using spring discharge data from Jinci Spring, a typical karst spring in China. The experimental results show that the proposed method outperforms baselines, with significant decreases in both MAE and RSM. The study will provide evidence for the precise management of Jinci Spring, and provide a methodological reference for the discharge prediction of other springs.

Evaluation of Methods for Estimating Long-Term Flow Fluctuations Using Frequency Characteristics from Wavelet Analysis

This study was aimed at exploring different indices to quantify flow fluctuations and calculate long-term flow indicators (L-FFI). Three approaches were considered to calculate the indicators: Method (1)—calculate the annual index and then average it; Method (2)—average the annual flow characteristics and then calculate the index; and Method (3)—calculate the index considering all available data. Wavelet analysis was performed to evaluate the derived L-FFI. The evaluation index was based on the period corresponding to the highest spectral power from the wavelet transformation of seasonally differenced data. Strong and negative positive correlations were observed between the L-FFI and the high- and low-flow variations, respectively. The correlation coefficient (R) between L-FFIs and the frequency with maximum global wavelet power showed that Method (2) consistently yielded the most reliable results across various facets, having a determination coefficient of 0.73 (R2) on average. In the regionalization analysis using the Ward method, it was consistently observed that the two largest dams (the Chungju Dam and the Uiam Dam) were significantly differentiated from the other dams. Furthermore, Method (2) showed the most similar characteristics to the clustering of the wavelet features. The outcomes are expected to facilitate long-term water resource management.

Unravelling Relationships between In Vivo Effects on Plants and Detected Pesticide Mixtures in Freshwaters of a South-European Agro-Ecosystem

The multiple benefits agriculture provides to society depend on the long-term sustainable management of water resources, including the preservation of a good ecological and good chemical status of the water bodies. Presently, this good chemical status has not been reached in the majority of European river basins. Implemented monitoring strategies are targeted to identify the presence and magnitude of the ecological impacts that come from mixtures of chemicals but fail to give information on the causes of the ecosystem disruptions. This work aims to contribute to assessing the quality of surface waters used for irrigation in the LGVFX agricultural area (Central Portugal) by applying non-conventional in vivo phytotoxicity tests on three primary producers, a monocotyledon (Sorghum saccharatum) and two dicotyledons (Lepidium sativum and Sinapsis alba), complemented by chemical screening and mixture-risk modelling with component-based methods (summation of risk quotients) based on the classic concept of concentration addition (CA). Although inhibition percentages of the phytotoxicity parameter germination and root and shoot growth may be related to the presence of mixtures of pesticides, it was not possible to establish the fingerprinting of the detected compounds with the observed biological effects, mostly due to the large gap of ecotoxicological data on terrestrial plants exposed to contaminated water. In addition, pesticides can interact within the plant, leading to antagonism and synergism phenomena.

Simulating Groundwater Potential Zones in Mountainous Indian Himalayas—A Case Study of Himachal Pradesh

Groundwater resources are increasingly important as the main supply of fresh water for household, industrial, and agricultural activities. However, overuse and depletion of these resources can lead to water scarcity and resource deterioration. Therefore, assessing groundwater availability is essential for sustainable water management. This study aims to identify potential groundwater zones in the Bilaspur district of Himachal Pradesh using the Multi Influencing Factor (MIF) technique, a modern decision-making method widely used in various sectors. Geospatial models were integrated with the MIF technique to evaluate prospective groundwater areas. Grid layouts of all underground water influencing variables were given a predetermined score and weight in this decision-making strategy. The potential groundwater areas were then statistically assessed using graded data maps of slope, lithology, land-use, lineament, aspect, elevation, soil, drainage, geomorphology, and rainfall. These maps were converted into raster data using the raster converter tool in ArcGIS software, utilizing Survey of India toposheets, SRTM DEM data, and Resourcesat-2A satellite imageries. The prospective groundwater zones obtained were classified into five categories: nil–very low, covering 0.34% of the total area; very low–low (51.64%); low–moderate (4.92%); moderate–high (18%) and high–very high (25%). Scholars and policymakers can collaborate to develop systematic exploration plans for future developments and implement preservative and protective strategies by identifying groundwater recharge zones to reduce groundwater levels. This study provides valuable insights for long-term planning and management of water resources in the region.

Regional significance of historical trends and step changes in Australian streamflow

Abstract. The Hydrologic Reference Stations is a network of 467 high-quality streamflow gauging stations across Australia that is developed and maintained by the Bureau of Meteorology as part of an ongoing responsibility under the Water Act 2007. The main objectives of the service are to observe and detect climate-driven changes in observed streamflow and to provide a quality-controlled dataset for research. We investigate trends and step changes in streamflow across Australia in data from all 467 streamflow gauging stations. Data from 30 to 69 years in duration ending in February 2019 were examined. We analysed data in terms of water-year totals and for the four seasons. The commencement of the water year varies across the country – mainly from February–March in the south to September–October in the north. We summarized our findings for each of the 12 drainage divisions defined by Australian Hydrological Geospatial Fabric (Geofabric) and for continental Australia as a whole. We used statistical tests to detect and analyse linear and step changes in seasonal and annual streamflow. Monotonic trends were detected using modified Mann–Kendall (MK) tests, including a variance correction approach (MK3), a block bootstrap approach (MK3bs) and a long-term persistence approach (MK4). A nonparametric Pettitt test was used for step-change detection and identification. The regional significance of these changes at the drainage division scale was analysed and synthesized using a Walker test. The Murray–Darling Basin, home to Australia's largest river system, showed statistically significant decreasing trends for the region with respect to the annual total and all four seasons. Drainage divisions in New South Wales, Victoria and Tasmania showed significant annual and seasonal decreasing trends. Similar results were found in south-western Western Australia, South Australia and north-eastern Queensland. There was no significant spatial pattern observed in central nor mid-west Western Australia, with one possible explanation for this being the sparse density of streamflow stations and/or the length of the datasets available. Only the Tanami–Timor Sea Coast drainage division in northern Australia showed increasing trends and step changes in annual and seasonal streamflow that were regionally significant. Most of the step changes occurred during 1970–1999. In the south-eastern part of Australia, the majority of the step changes occurred in the 1990s, before the onset of the “Millennium Drought”. Long-term monotonic trends in observed streamflow and its regional significance are consistent with observed changes in climate experienced across Australia. The findings of this study will assist water managers with long-term infrastructure planning and management of water resources under climate variability and change across Australia.

Temporal and Spatial Distribution Characteristics of Flood Disasters with Different Intensities in Arid-Semiarid Region in Northern Xinjiang, China

Floods have devastating environmental and socioeconomic consequences. Flood disaster management is critical for the long-term management of water resources and agriculture in arid areas. Using the data on the number of deaths, destroyed homes, collapsed sheds, livestock deaths, and the crops affected area caused` by 1394 regional floods in Northern Xinjiang (As a typical arid-semiarid region of NorthWest China) from 1981 to 2019, the ratio-weight method and the dimensionless linear summation method was used to calculate the actual disaster damage exponent of flood disaster events. The damage exponent is further used to categorize the severity of disaster events into four grades: normal, moderate, severe, and extremely severe. The analysis results indicated that Bortala Mongolian Autonomous Prefecture experienced the highest frequency of catastrophic occurrences, while Ili River Valley experienced the highest intensity. The flood happened most often in Wenquan County. And Yining County suffered the worst calamity. The occurrence frequency and intensity of disasters from Grades 1 to 3 exhibited a unimodal distribution, with the majority and most vital occurrences in July, whereas the occurrence frequency and intensity of Grade 4 disasters followed a bimodal distribution, with the most occurrences in July and the strongest in April. The annual frequency of heavy rain and flood disasters in Northern Xinjiang increased by 7.7 times every 10 years, indicating a significant linear increase trend. The yearly occurrences of Grades 1 and 2 also increased linearly, by 5.2 and 2.0 times per decade, respectively. There was no linear tendency to increase or decrease flood disasters in Grades 3 and 4. The analysis and division of actual disaster damage are conducive to flood risk management, efficient prevention, and reducing disaster losses.

ОБҐРУНТУВАННЯ ГЕОБЕЗПЕЧНИХ ТА ГЕОМЕХАНІЧНИХ ПАРАМЕТРІВ РОБО-ТИ ГІДРОТЕХНІЧНИХ СПОРУД, РЕГУЛЮВАННЯ СТОКУ ТА УПРАВЛІННЯ ВО-ДНИМИ РЕСУРСАМИ ШЛЯХОМ ГІДРОГЕОЛОГІЧНОГО МОДЕЛЮВАННЯ

Purpose. The purpose of this work is the development and verification of the adequacy of the methodology for assessing the hydrodynamic and geomechanical impact of various drainage and hydrotechnical structures on the environment over time, based on hydrogeological modeling, which allows to substantiate the geosafe parameters of their long-term operation and management of water resources. Methods. The proposed comprehensive approach includes: collection and analysis of geological and hydrogeological data on the research area; numerical modeling of hydrodynamic processes; solving inverse problems; execution of predictive calculations regarding changes in the level of groundwater under the influence of drainage and hydrotechnical structures; analytical calculations of subsidence of the earth’s surface caused by this. Findings. According to the results of solving the inverse problems, it was proved that the deviation of the calculated marks of the groundwater levels on the model from the actually established ones does not exceed 0.3 m with a value of the water balance imbalance of 0.001%, which confirms the adequacy of the model and the correctness of the task of filtration characteristics, external and internal hydrodynamic boundaries . The solution of model forecasting problems made it possible to establish that the construction of two ponds with an absolute water mark of 54.0 m and a horizontal drainage 600 m long with a level mark of 56-57 m in the studied area leads to a decrease in groundwater and the elimination of areas under -fillings with a depth of less than one meter. It has been established that with the lowering of the groundwater level caused by the work of hydraulic and drainage structures, the maximum possible subsidence of the soil is 1.5 cm, which does not exceed the allowable subsidence for all types of buildings. Originality. The methodology for assessing the hydrodynamic and geomechanical impact of drainage and hydrotechnical structures on the environment has been substantiated and verified. The proposed method makes it possible to quantitatively assess the hydrodynamic regime and geomechanical state of rocks during long-term operation of these structures in areas with a complex geological structure under the significant influence of natural and man-made factors. Practical implication. The proposed method can be used in the design of new hydrotechnical and drainage structures, as well as the evaluation of parameters of their geo-safe operation, which ensure flow regulation and prevention of flooding of territories.

Protocol to Monitor Water Governance Based on Indicators for Rural Basins

The use of quality indicators guarantees the accurate monitoring of sustainability processes around the world. This work proposes a protocol to detail the indicators that make up the rural basin management index (GWI) in order to assess the degree of water management in a predominantly rural basin or region. The methodology contemplates the development of indicators to evaluate performance and its monitoring over time as the basis for planning. This research is based on the in situ evaluation of four municipalities within the department of Boyacá, Colombia, where there is a lack of a culture regarding the long-term planning and management of water and environmental resources. Water availability is the most sensitive factor in this context. This study raises the need for the use of monitoring systems in sustainability processes at the level of rural basins, as a result of the findings of four study cases, where processes with a low level of sustainability were evidenced.

The Role of Routine Programme for Monitoring and Evaluation on Sub-national Water Services in Kenya

Routine programme for monitoring and evaluation involves data gathering, analysis and reporting to ensure progress and ultimately achievement of project goals. This study determined the influence of routine programme for monitoring and evaluation on sub-national water services in Nyamira South Sub County, Kenya. A mixed method, cross-sectional and correlational design was used. Study findings were generated using quantitative interviews from a total of 480 household heads; and staff from the local water services company. Qualitative information was generated from discussions with 40 village elders. The study established that provision of water services in the study area was not sustainable, with only about 23 percent of households accessing water services. The study findings also revealed poor monitoring of the water services. However, the findings demonstrated a linear, positive, and significant association between routine programme for monitoring and evaluation and sustainability of water services. The Pearson correlation coefficient was 0.724 and p-values were 0.000 for both correlation and regression analyses. The findings support the strengthening of routine programme for monitoring and evaluation as a way of reinforcing the long-term management of water resources at sub-national level.

Responses of Soybean Water Supply and Requirement to Future Climate Conditions in Heilongjiang Province

Understanding future changes in water supply and requirement under climate change is of great significance for long-term water resource management and agricultural planning. In this study, daily minimum temperature (Tmin), maximum temperature (Tmax), solar radiation (Rad), and precipitation for 26 meteorological stations under RCP4.5 and RCP8.5 of MIRCO5 for the future period 2021–2080 were downscaled by the LARS-WG model, daily average relative humidity (RH) was estimated using the method recommended by FAO-56, and reference crop evapotranspiration (ET0), crop water requirement (ETc), irrigation water requirement (Ir), effective precipitation (Pe), and coupling degree of ETc and Pe (CD) for soybean during the growth period were calculated by the CROPWAT model in Heilongjiang Province, China. The spatial and temporal distribution of these variables and meteorological factors were analyzed, and the response of soybean water supply and requirement to climate change was explored. The result showed that the average Tmin, Tmax, and Rad under RCP4.5 and RCP8.5 increased by 0.2656 and 0.5368 °C, 0.3509 and 0.5897 °C, and 0.0830 and 0.0465 MJ/m², respectively, while the average RH decreased by 0.0920% and 0.0870% per decade from 2021 to 2080. The annual average ET0, ETc, Pe, and Ir under RCP4.5 for 2021–2080 were 542.89, 414.35, 354.10, and 102.44 mm, respectively, and they increased by 1.92%, 1.64%, 2.33%, and −2.12% under the RCP8.5, respectively. The ranges of CD under RCP4.5 and RCP8.5 were 0.66–0.95 and 0.66–0.96, respectively, with an average value of 0.84 for 2021–2080. Spatially, the CD showed a general trend of increasing first and then decreasing from west to east. In addition, ET0, ETc, and Pe increased by 9.55, 7.16, and 8.77 mm per decade, respectively, under RCP8.5, while Ir decreased by 0.65 mm per decade. Under RCP4.5 and RCP8.5, ETc, Pe, and Ir showed an overall increasing trend from 2021 to 2080. This study provides a basis for water resources management policy in Heilongjiang Province, China.

Hydrogeochemical and health risk assessment in and around a Ramsar-designated wetland, the Ganges River Basin, India: Implications for natural and human interactions.

Wetlands are the most productive and dynamic ecosystems, which have continuously been influenced by social and economic development. As a result, the pollution of wetland surface water and groundwater in adjacent regions has become an emerging global issue that requires constant monitoring and assessment. The current study investigates the natural and anthropogenic processes that influence surface and groundwater chemistry in and around Saman wetland (a Ramsar site) in the Ganges River Basin, India. Various physicochemical parameters are analyzed, and different hydrochemical indices are utilized to evaluate surface and groundwater quality for domestic and irrigation purposes. It is observed that the waters are alkaline in nature and dominated by moderately hard to hard types. An increase in the concentration of nitrate (NO3-) in Saman wetland water is noted, which is possibly due to the leaching of nitrogen ions primarily from fertilizers, pesticides, animal and human waste, and wastewater drained from brick and other factories. The elevated fluoride (F-) content in studied groundwater samples is mainly governed by geogenic processes. Furthermore, surface and groundwater chemistry are mainly controlled by weathering reaction (rock-water interaction), excluding a few wetland surface water samples that are placed outside the boomerang-shaped boundaries of Gibb's diagram, which suggests evaporated dominance. Water Quality Index (WQI) estimation suggests that around 57% of groundwater samples have poor groundwater quality for drinking purposes. Estimation of irrigation water quality indices suggests that surface water of Saman wetland is permissible for irrigation purposes; however, none of the samples have excellent and good class as per sodium (alkali) hazard. Furthermore, health risk assessment showed that NO3- and F- levels in the groundwater pose noncarcinogenic health effects, preferably to children, and thus is unfit for drinking purposes. For long-term water resource management and conservation of the Saman wetland, this study suggests proper awareness, appropriate remedial measures, and regular monitoring of the surface as well as groundwater quality monitoring in the study region.

Impact of climate change on future precipitation amounts, seasonal distribution, and streamflow in the Omo-Gibe basin, Ethiopia

This study projected the impact of climate change on the amount of precipitation, seasonal distribution, and streamflow of the Omo-gibe basin, Ethiopia. Projections of climate change using the results of high-resolution multimodal ensembles from fifteen regional climate models (RCMs) of the Coordinated Regional Climate Reduction Experiment (CORDEX)-Africa were statistically downscaled and bias-adjusted using a quantile mapping approach. Precipitation and temperature were projected under RCP 8.5 and RCP 4.5 emission scenarios. Climate and streamflow projections from a mean ensemble of RCMs in the near future (2025–2050), medium future (2051–2075), and far future (2076–2100) were compared to the reference (1989–2019). Mann-Kendall (MK) trend testing was used to determine if a change is statistically significant and to detect trends in temperature, precipitation, and streamflow. The Soil and Water Assessment Tool (SWAT) hydrological model was used to project the impact of climate change on the streamflow. According to RCP4.5 and RCP8.5, the emission scenarios predicted significant positive (rising) temperature, but significant negative (decreasing) precipitation and streamflow. The average temperature projected increases range from 2.40-3.34 °C under the RCP 4.5 emission scenarios and 2.6–4.54 °C under the RCP 8.5 emission scenarios. Annual average precipitation projected decreases range between 10.77-13.11% under the RCP 4.5 emission scenario, while the RCP 8.5 emission scenarios decrease range between 11.10-13.86% in the rainy summer season (June–August) and the irregular rain season (March–May). Projected annual average streamflow decrease range between 7.08-10.99% under the RCP 4.5 emission scenarios and 10.98–12.88% under the RCP 8.5 emission scenarios. Results on projected temperature increases and reductions in precipitation and streamflow will help to develop effective adaptation measures to reduce the ongoing impacts of climate change and draw up long-term water resource management plans in the river basin. Both the results and the multidisciplinary approach will be vital to irrigation and hydropower project planners.