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This study examines land use transformations and their impact on groundwater quality fluctuations in Chengalpattu district, Tamil Nadu. Chengalpattu is a rapidly urbanizing coastal region in South India. Landsat 5 and 9 satellite imagery were utilized to create land use land cover (LULC) maps for 2011 and 2021, with overall accuracies of 82.20% and 85.71%, respectively. The analysis showed significant growth in built-up and fallow lands due to urbanization, which has altered LULC. Groundwater Quality Index (GQI) was generated using seven groundwater quality parameters, adhering to World Health Organization (WHO) standards. The mean GQI showed slight fluctuations during pre- and post-monsoon periods, with a declining trend in pre-monsoon seasons. The study area predominantly experiences moderate groundwater quality, with fewer areas of low and high quality. The findings indicate that land use transformation significantly impacts groundwater quality, emphasizing the need for sustainable urban planning and water resource management in the region.

The overexploitation of coastal aquifers is one of the important reasons for the salinity of groundwater due to seawater intrusion (SWI). This study assesses the hydrochemical changes of the Ghaemshahr-Juybar (GH.-J.) plain. For this purpose, specific statistical methods, modified Piper diagram groundwater quality indicators ( GQI Piper mix and GQI Piper dom ), groundwater quality index specific to seawater intrusion ( GQI SWI ), and hydrochemical facies evolution diagram (HFE-D) along with GIS (Geographic Information System) techniques were applied to identify the spatiotemporal changes of salinity in coastal multilayer alluvial aquifer. The results show that the chemical composition in the GH.-J. aquifer is basically controlled by three main factors: (1) Caspian SWI and fossil saltwater penetration from an underlying layer, (2) reverse cation exchange process, and (3) feeding by domestic sewage, agricultural activities, and use of nitrate chemical fertilizers. The investigation of the hydrogeochemical facies evolution process shows that due to the reduction of extraction from wells, saltwater infiltration has significantly decreased. Therefore, according to the geological and lithological conditions of the aquifer and exposure to seawater, it is possible to prevent the entry of saltwater from the confined aquifer into the unconfined aquifer and the saltwater intrusion by developing well optimal operation policies in order to control withdrawal from semi-deep wells and the elimination of deep wells. This practical approach to managing the salinity of coastal aquifers is suitable for the allocating groundwater resources and for use in the development of aquifer simulation models. [ABSTRACT FROM AUTHOR]

Introduction Groundwater is the sole source of water for drinking, irrigation, and industrial uses in many arid and semi-arid regions of the world. Groundwater can be contaminated by natural as well as anthropogenic influences. Residential, municipal, commercial, industrial, and agricultural activities can all affect groundwater quality. Groundwater contamination results in poor drinking water quality, loss of water supply, high cleanup costs, high costs for alternative water supplies, and/or potential health problems. In Iran, dependence on groundwater has increased tremendously in recent years. Groundwaters can be contaminated by natural as well as human influences. Land use changes, residential and agricultural activities can affect the quality of groundwater. Groundwater contamination can lead to poor drinking water quality, loss of water resources, high cleanup costs, high costs for alternative water sources, and problems for watershed health. In Iran, dependence on underground water in most watersheds has increased greatly in recent years. Therefore, the evaluation, protection and proper management of underground water resources is very necessary for optimal and sustainable use of water resources. Water quality assessment includes the assessment of the physical, chemical and biological nature of water in relation to its natural quality, human effects and intended uses, especially uses that may affect human health and the health of the water system itself. The use of geographic information system technology has greatly simplified the assessment of natural resources and environmental concerns, including groundwater. In groundwater studies, GIS is commonly used to analyze site suitability, manage watershed assessment data, estimate groundwater vulnerability to contamination, model groundwater flow, model solute transport and leaching, and integrate groundwater quality assessment models with spatial data to create Spatial decision support systems are used. This study attempts to assess the influence of changing land-use patterns on the groundwater quality in the Dehram, Fars province. The study area is an agricultural developing region with land development progressing at a fast pace. The objective of this article is to demonstrate the influence of land-use transformations, land-use transition, on the quality of groundwater using geographical information systems. The study also aims at evaluating the significance and applicability of a groundwater quality index (GQI) generated using geographical information system (GIS) approach for the assessment of groundwater quality in a medium sized catchment. Moreover, a simple methodology for the preparation of a groundwater quality sustainability map, for use in planning and management decisions by local government authorities, is developed in this work. Materials and Methods The water samples were collected from 6 wells in the study area in 2021, which are added to the urban water system for drinking purposes. For 2014, the available data were used to observe the general changes in the quality of underground water during this period. Sampling in the summer season, due to the lack of water in this season, by taking water from wells in the area and injecting it into the drinking water system, in three repetitions for the year 1400 according to the standard method of the American Public Health Association (APHA) with field sampling and the available data of year 2013 were used to show seasonal changes in different water quality parameters during both years. Therefore, samples were taken from each well of the available data three times in 2013 and three times in summer (July to August) 1400. The geographic coordinates of the sampling wells were recorded manually using a Garmin e-Trex GPS receiver. The hydrochemical data obtained from the laboratory analysis of the water samples were linked to the spatial database of the sampling points. Spatial data shapefiles were prepared in vector format showing the locations of sample wells along with associated hydrochemical data. To evaluate the location of the sampling wells according to the potential sources of groundwater pollution, these shapefiles were placed on the land use map. Then, point shape files were used to prepare variable concentration maps by applying Kriging interpolation method. The GQI proposed was used for quality assessment. To generate the index, seven parameters listed in World Health Organization guidelines for drinking water quality were selected from the main dataset. Six parameters (Cl-, Na+, Ca+2, Mg+2, SO4-2, and TDS) can be categorized as chemically derived contaminants that could alter the water taste, odor, or appearance and affect its ‘‘acceptability’’ by consumers. NO-3 was categorized under chemicals that might inflict ‘‘potential health risk’’ and a guideline value of 50 mg/l was assigned. The GQI integrates the different water quality parameters to give a quantitative index value that can be used for spatio-temporal provides in groundwater quality. In the present study, the land use/cover map for two different periods (2013 and 2014) was prepared to evaluate land use and land cover transition patterns using Landsat satellite images from ETM+ sensors (2013) and OLI (2014). Results and Discussion The land-use pattern has changed drastically with the increased agricultural and built-up area at the expense of other land uses. The analysis reveals a rapid deterioration of groundwater quality related mainly to the increase in built-up land, drought and land-use change in agricultural lands and uncontrolled withdrawal of water by farmers from wells in the region. Mean GQI decreased from 86.42 to 57.36 over a period of 7 years from 2014 to 2021, which indicates a decrease in water quality. The quality of groundwater in the region in 2014 has a desirable quality and is in a very suitable range. But in 2021 the water quality changed from very good and good to poor and bad. Conclusion GQI and land use were integrated into GIS to yield groundwater quality, in terms of water quality. Zones of sustainable and unsustainable groundwater use were demarcated for better decision making related to land use allotment in this rapidly changing region. The GQI index provides the possibility of mapping the spatial changes of groundwater quality in the study area, which shows that the water quality of the area is generally good, but the deterioration has started with the onset of urbanization. The main sources of pollution identified in this study are agricultural and residential activities. Although agricultural activities and the application of fertilizers related to it have been the main factor in reducing the quality of groundwater, in addition, this study showed that the increase in urbanization has a dominant contribution to pollution in the region. Agricultural activities must comply with methods that ensure minimal impact on groundwater. This study also shows the effectiveness of GIS in groundwater quality assessment. Similarly, GIS-based assessment techniques can be used to characterize groundwater contamination preferably in large watersheds. Of course, the selection of parameters and weights may be different in each location depending on the prevailing land use conditions.

Introduction Groundwater is the sole source of water for drinking, irrigation, and industrial uses in many arid and semi-arid regions of the world. Groundwater can be contaminated by natural as well as anthropogenic influences. Residential, municipal, commercial, industrial, and agricultural activities can all affect groundwater quality. Groundwater contamination results in poor drinking water quality, loss of water supply, high cleanup costs, high costs for alternative water supplies, and/or potential health problems. In Iran, dependence on groundwater has increased tremendously in recent years. Groundwaters can be contaminated by natural as well as human influences. Land use changes, residential and agricultural activities can affect the quality of groundwater. Groundwater contamination can lead to poor drinking water quality, loss of water resources, high cleanup costs, high costs for alternative water sources, and problems for watershed health. In Iran, dependence on underground water in most watersheds has increased greatly in recent years. Therefore, the evaluation, protection and proper management of underground water resources is very necessary for optimal and sustainable use of water resources. Water quality assessment includes the assessment of the physical, chemical and biological nature of water in relation to its natural quality, human effects and intended uses, especially uses that may affect human health and the health of the water system itself. The use of geographic information system technology has greatly simplified the assessment of natural resources and environmental concerns, including groundwater. In groundwater studies, GIS is commonly used to analyze site suitability, manage watershed assessment data, estimate groundwater vulnerability to contamination, model groundwater flow, model solute transport and leaching, and integrate groundwater quality assessment models with spatial data to create Spatial decision support systems are used. This study attempts to assess the influence of changing land-use patterns on the groundwater quality in the Dehram, Fars province. The study area is an agricultural developing region with land development progressing at a fast pace. The objective of this article is to demonstrate the influence of land-use transformations, land-use transition, on the quality of groundwater using geographical information systems. The study also aims at evaluating the significance and applicability of a groundwater quality index (GQI) generated using geographical information system (GIS) approach for the assessment of groundwater quality in a medium sized catchment. Moreover, a simple methodology for the preparation of a groundwater quality sustainability map, for use in planning and management decisions by local government authorities, is developed in this work. Materials and Methods The water samples were collected from 6 wells in the study area in 2021, which are added to the urban water system for drinking purposes. For 2014, the available data were used to observe the general changes in the quality of underground water during this period. Sampling in the summer season, due to the lack of water in this season, by taking water from wells in the area and injecting it into the drinking water system, in three repetitions for the year 1400 according to the standard method of the American Public Health Association (APHA) with field sampling and the available data of year 2013 were used to show seasonal changes in different water quality parameters during both years. Therefore, samples were taken from each well of the available data three times in 2013 and three times in summer (July to August) 1400. The geographic coordinates of the sampling wells were recorded manually using a Garmin e-Trex GPS receiver. The hydrochemical data obtained from the laboratory analysis of the water samples were linked to the spatial database of the sampling points. Spatial data shapefiles were prepared in vector format showing the locations of sample wells along with associated hydrochemical data. To evaluate the location of the sampling wells according to the potential sources of groundwater pollution, these shapefiles were placed on the land use map. Then, point shape files were used to prepare variable concentration maps by applying Kriging interpolation method. The GQI proposed was used for quality assessment. To generate the index, seven parameters listed in World Health Organization guidelines for drinking water quality were selected from the main dataset. Six parameters (Cl-, Na+, Ca+2, Mg+2, SO4-2, and TDS) can be categorized as chemically derived contaminants that could alter the water taste, odor, or appearance and affect its ‘‘acceptability’’ by consumers. NO-3 was categorized under chemicals that might inflict ‘‘potential health risk’’ and a guideline value of 50 mg/l was assigned. The GQI integrates the different water quality parameters to give a quantitative index value that can be used for spatio-temporal provides in groundwater quality. In the present study, the land use/cover map for two different periods (2013 and 2014) was prepared to evaluate land use and land cover transition patterns using Landsat satellite images from ETM+ sensors (2013) and OLI (2014). Results and Discussion The land-use pattern has changed drastically with the increased agricultural and built-up area at the expense of other land uses. The analysis reveals a rapid deterioration of groundwater quality related mainly to the increase in built-up land, drought and land-use change in agricultural lands and uncontrolled withdrawal of water by farmers from wells in the region. Mean GQI decreased from 86.42 to 57.36 over a period of 7 years from 2014 to 2021, which indicates a decrease in water quality. The quality of groundwater in the region in 2014 has a desirable quality and is in a very suitable range. But in 2021 the water quality changed from very good and good to poor and bad. Conclusion GQI and land use were integrated into GIS to yield groundwater quality, in terms of water quality. Zones of sustainable and unsustainable groundwater use were demarcated for better decision making related to land use allotment in this rapidly changing region. The GQI index provides the possibility of mapping the spatial changes of groundwater quality in the study area, which shows that the water quality of the area is generally good, but the deterioration has started with the onset of urbanization. The main sources of pollution identified in this study are agricultural and residential activities. Although agricultural activities and the application of fertilizers related to it have been the main factor in reducing the quality of groundwater, in addition, this study showed that the increase in urbanization has a dominant contribution to pollution in the region. Agricultural activities must comply with methods that ensure minimal impact on groundwater. This study also shows the effectiveness of GIS in groundwater quality assessment. Similarly, GIS-based assessment techniques can be used to characterize groundwater contamination preferably in large watersheds. Of course, the selection of parameters and weights may be different in each location depending on the prevailing land use conditions. [ABSTRACT FROM AUTHOR]

Surface and groundwater resources are two important sources in meeting agricultural, urban, and industrial needs. Random supply of surface water resources has prevented these resources from being a reliable source of water supply at all times. Therefore, groundwater acts as insurance in case of water shortage, and maintaining the quality of these resources is very important. On the other hand, studying vulnerability and identifying areas prone to aquifer pollution seems necessary for the development and optimal management of these valuable resources. Identifying the vulnerabilities of the aquifer areas to pollution will lead to a greater focus on preserving those areas. Therefore, groundwater quality assessment was performed in this study using the groundwater quality index (GQI), and groundwater vulnerability to pollution was assessed using the DRASTIC index. GQI is developed based on the values of six quality parameters (Na+, Mg2+, Ca2+, SO4 2-, Cl-, and TDS). The DRASTIC index is developed based on the values of seven parameters (depth to the water table, net recharge, aquifer media, soil media, topography, impact of vadose zone, hydraulic conductivity). The zoning of both indexes has been done using geographic information system (GIS) software. The results show that the GQI of the region was about 93, and its DRASTIC index was about 86. Therefore, the quality of aquifer groundwater is excellent, and its vulnerability to pollution is low. [ABSTRACT FROM AUTHOR]

Ulaanbaatar City, Mongolia is rapidly becoming urbanized and attracts great attention because of environmental issues. This study was performed to assess the status of groundwater quality in Ulaanbaatar at an early but growing stage of urbanization, focusing on nitrate contamination in relation to land use. Along with high total dissolved solids and NO 3 − concentrations, significant contamination of groundwater is indicated by positive loadings of NO 3 −, Cl− and δ15N-NO 3 − along the first principal component of the principal component analysis (PCA). Based on the concentrations and δ15N values of nitrate, groundwater is classified into two groups: Group I (baseline quality) and II (contaminated). Nitrate in Group II water in urbanized (esp. peri-urban) areas is higher in concentration (> 10 mg/l NO 3 −) and N-isotopic values (> 10‰ δ15N-NO 3 −), while pristine hydrochemistry is observed restrictedly in grassland and forest areas. Other ions (e.g., Cl− and SO 4 2−) are also higher in Group II water. The δ15N-NO 3 − values in Group II water in combination with the spatial distribution on the land use map indicate that nitrate originates from untreated sewage effluents including pit-latrine leakage in peri-urban areas, while nitrate in Group I water originates from soil organic matter. The relationship between nitrate concentrations and δ2H (and δ18O) values of water suggests that nitrate enrichment is also influenced by evaporation during groundwater recharge. With the help of PCA for compositional data, we suggest a hydrochemical index for groundwater contamination assessment; i.e., the Groundwater Quality Index (GQI) that consists of three variables (concentrations of dissolved silica, nitrate and chloride) and can be used to delineate zones vulnerable to nitrate contamination as a crucial step for the efficient monitoring and management of groundwater quality. The study results suggest an urgent need for the management of unsealed pit latrines that are common in peri-urban areas with high population density. Unlabelled Image • Degradation of urban groundwater quality in Ulaanbaatar, Mongolia is significant. • Nitrate contamination is land-use dependent and originates from sewage effluents. • Hydrochemical and isotopic data are evaluated using a PCA bi-plot. • Subcomposition of NO 3 −, Cl−, and SiO 2 represents major hydrochemical processes. • Groundwater quality index (GQI) is proposed to evaluate groundwater quality status. [ABSTRACT FROM AUTHOR]