Excessive Water Withdrawals Research Articles

Anthropogenic vs. climatic drivers: Dissecting Lake desiccation on the Iranian plateau

Lakes are indispensable to ecological balance, supporting biodiversity and human welfare. Despite their importance, lakes around the globe are diminishing at an alarming rate, presenting substantial environmental challenges exacerbated by climate variability and human-induced pressures, such as unsustainable land management and excessive water withdrawals. This study offers an extensive analysis of the desiccation phenomena affecting major lakes on the Iranian plateau, dissecting the complex interplay of contributing factors. We examine meteorological, hydrological, and agricultural drought conditions using indices like SPI, SDI, and SPEI to gain nuanced insights into drought dynamics. This study sheds light on the factors that contribute to the drying up of lakes and quantifies the impact of anthropogenic and climatic drivers on this phenomenon. The findings indicate that the area of all lakes has declined dramatically after the change point, ranging from 51% in the Urmia Lake to an impressive rate (i.e. 100%) in Southern Hamun. Despite the stable rate of meteorological droughts (increasing in temperature by about 1 °C since the 90s and stable precipitation patterns across most basins), the research highlights the ongoing struggle against severe hydrological and agricultural drought conditions. The study delineates the predominant role of anthropogenic activities in the diminishing lake inflows and the consequential drying of the lake, accounting for approximately 100 % in five of the seven lakes.

Bioassessment of multiple stressors in Afrotropical rivers: Evaluating the performance of a macroinvertebrate-based index of biotic integrity, diversity, and regional biotic indices

Many streams and rivers outside conservation areas across the Afrotropics face multiple stressors from land use change, urbanization, and excessive water withdrawals. Thus, there is a need to develop cost-effective tools for assessing and monitoring ecological changes to inform management decisions. Studies utilizing macroinvertebrate communities as indicators of the ecological condition of streams and rivers in the Afrotropics use diverse methods, including diversity, richness, biotic and multimetric indices. However, some of these indices are region- or country-specific, which limits their general use across multiple regions or countries. In this study, we address this challenge by testing and comparing the performance of diversity and richness indices (e.g., Shannon-Wiener and Simpson), regional biotic indices (the African Scoring System Version 5 [SASS5], Tanzanian River Scoring System [TARISS] and a biotic index developed for the Ethiopian highlands [ETHbios]), and a macroinvertebrate-based index of biotic integrity (M-IBI) in assessing the ecological condition of Afrotropical rivers with the transboundary Mara River, Kenya and Tanzania, as a case study. In this study, we analyzed water and habitat quality degradation caused by multiple stressors such as land use change, organic pollution and flow alteration and the corresponding responses in macroinvertebrate communities. We utilized macroinvertebrates data collected from 143 sites covering the entire gradient of the river and its major tributaries in Kenya and Tanzania. To develop the M-IBI, we used 12 metrics that describe macroinvertebrate community richness, composition, tolerance to disturbances (indicator taxa), and the composition of functional feeding groups. Although all the biotic indices were sensitive to poor water quality and human disturbance of the river, the M-IBI performed better than biotic indices (SASS5, Tanzanian River Scoring System, and Ethiopian highlands), diversity and richness indices by having a higher discriminatory ability of site categories according to different levels and types of disturbance. Diversity and richness indices performed poorly and failed to discriminate between stressor gradients in the river. This study demonstrates a need for testing and evaluating indices or protocols before adoption and use in biomonitoring streams and rivers in other countries and regions. There is an even greater need to assess the tolerance of macroinvertebrate taxa before inclusion in biotic indices for improved performance as discriminators of multiple stressors.

High-Resolution Deformation Monitoring from DInSAR: Implications for Geohazards and Ground Stability in the Metropolitan Area of Santiago, Chile

Large urban areas are vulnerable to various geological hazards and anthropogenic activities that affect ground stability—a key factor in structural performance, such as buildings and infrastructure, in an inherently expanding context. Time series data from synthetic aperture radar (SAR) satellites make it possible to identify small rates of motion over large areas of the Earth’s surface with high spatial resolution, which is key to detecting high-deformation areas. Santiago de Chile’s metropolitan region comprises a large Andean foothills basin in one of the most seismically active subduction zones worldwide. The Santiago basin and its surroundings are prone to megathrust and shallow crustal earthquakes, landslides, and constant anthropogenic effects, such as the overexploitation of groundwater and land use modification, all of which constantly affect the ground stability. Here, we recorded ground deformations in the Santiago basin using a multi-temporal differential interferometric synthetic aperture radar (DInSAR) from Sentinel 1, obtaining high-resolution ground motion rates between 2018 and 2021. GNSS stations show a constant regional uplift in the metropolitan area (~10 mm/year); meanwhile, DInSAR allows for the identification of areas with anomalous local subsistence (rates < −15 mm/year) and mountain sectors with landslides with unprecedented detail. Ground deformation patterns vary depending on factors such as soil type, basin geometry, and soil/soil heterogeneities. Thus, the areas with high subsidence rates are concentrated in sectors with fine sedimentary cover and a depressing shallow water table as well as in cropping areas with excess water withdrawal. There is no evidence of detectable movement on the San Ramon Fault (the major quaternary fault in the metropolitan area) over the observational period. Our results highlight the mechanical control of the sediment characteristics of the basin and the impact of anthropogenic processes on ground stability. These results are essential to assess the stability of the Santiago basin and contribute to future infrastructure development and hazard management in highly populated areas.

WATER QUALITY INDEX AS A TOOL TO ASSESS WATER QUALITY OF SASTHAMKOTTA FRESHWATER WETLAND, A RAMSAR SITE IN INDIA

Lakes are versatile ecosystems thatperform valuable functions such as recycling nutrients,attenuating floods, recharging groundwater and also serve the water needs of the human populace.Nowadaysthe quality of surface water is getting deteriorating at a rapid pace due to excess waterwithdrawal and various anthropogenic activities. In this study, the water quality status ofSasthamkotta lake, a fresh water wetland in the south western part of India which is also a Ramsarsite is determined in terms of Central Pollution Control Board National Sanitation FoundationWater Quality Index. The study was carried out from the month of October 2018 to the month ofSeptember 2019 and parameters namely dissolved oxygen, faecal coliform, pH and biochemicaloxygen demand were analysed to determine the water quality status of the lake and the same wasmapped using Geographical Information System. It was found that major part of the lake comesunder the category good (Central Pollution Control Board National Sanitation Foundation WaterQuality index [CPCB-NSFWQI] ranging from 78 to 80). Localised moderately good water quality(CPCB-NSFWQI ranging from 76 to 78) was observed at sampling stations namely Bharanikkavuand Anjalimooduand very good water quality(CPCB-NSFWQI ranging from 80 to 82) was foundat the sampling stationnamely Kerala Water Authority main pumping station during the postmonsoonand the pre-monsoon season respectively. It was also found that the major portion of thenorth eastern part of lake comes under moderately good water quality during the monsoon season.Densely populated catchment area of the lake, physical setting of the lake characterised by steepslopes on three sides and excess runoff during rainfall could be attributed to the moderately goodwater quality of the lake. Water quality parameters namely faecal coliform exceeded thepermissible limits as per the Bureau of Indian Standards for drinking purpose at all the samplingstations throughout the study period. The designated best use of Sathamkotta lake belongs to thecategory ClassA (non-polluted source) (as per the various classes given by the Central PollutionControl Board based on the CPCB-NSFWQI values obtained during the study period.

Flow alterations in rivers due to unconventional oil and gas development in the Ohio River basin

Unconventional oil and gas (UOG) exploration and development in the Ohio River basin has been a controversial issue for the past decade. The process of extracting gas and oil from shale formations utilizes significant amounts of water with little to no recycling in the region. The environmental risks to date have largely focused on air and water quality, with some attention paid to noise pollution. This study examines the risk for excessive water withdrawals and potential for negative impacts of low streamflow, which have largely not been addressed, as basin-wide studies have indicated that UOG will not significantly alter flow at large scales. The smallest watersheds, however, are often not monitored and therefore no historical record of flow is present. Using modelled estimates of historic flow, the impacts of UOG-related water withdrawals in HUC12 watersheds (approximately 1st to 3rd order streams) across the eastern Ohio River basin were estimated. Modelling of the effect of well operations showed that >10 % and >20 % reductions in streamflow occurred at least episodically in 53 % and 42 % of the HUC12 watersheds analyzed, respectively, amounting to 8.8 % and 2.4 % of active days. Although such severe reductions were usually infrequent in a particular stream, they could have lasting negative impacts on the stream biota. These flow reductions have the potential to affect downstream users, including regionally-endangered species. The legal framework surrounding water withdrawal permitting should have a substantial impact on flow reduction, but a lack of sufficient monitoring and clear reporting of water withdrawal sources hinders effective monitoring and protection of stream and riparian habitats.

Dietary changes could compensate for potential yield reductions upon global river flow protection

Non-technical summaryGlobally, freshwater systems are degrading due to excessive water withdrawals. We estimate that if rivers’ environmental flow requirements were protected, the associated decrease in irrigation water availability would reduce global yields by ~5%. As one option to increase food supply within limited water resources, we show that dietary changes toward less livestock products could compensate for this effect. If all currently grown edible feed was directly consumed by humans, we estimate that global food supply would even increase by 19%. We thus provide evidence that dietary changes are an important strategy to harmonize river flow protection with sustained food supply.Technical summaryTo protect global freshwater ecosystems and restore their integrity, freshwater withdrawals could be restricted to maintain rivers' environmental flow requirements (EFRs). However, without further measures, reduced irrigation water availability would decrease crop yields and put additional pressure on global food provision. By comparing the quantitative effects of both global EFR protection and dietary changes on regional and global food supply in a spatially explicit modeling framework, we show that dietary changes toward less livestock products could effectively contribute to solving this trade-off. Results indicate that protection of EFRs would almost halve current global irrigation water withdrawals and reduce global crop yields by 5%. Limiting animal protein share to 25, 12.5 and 0% of total protein supply and shifting released crop feed to direct human consumption could however increase global food supply by 4, 11 and 19%, respectively. The effects are geographically decoupled: water-scarce regions such as the Middle East, or South and Central Asia would be most affected by EFR protection, whereas dietary changes are most effective in North America and Europe. This underpins the disproportionally high responsibilities of countries with resource-intensive diets and the need for regionally adapted and diverse strategies to transform the global food system toward sustainability.Social media summaryCombining dietary changes and global river flow protection could contribute to a more sustainable food system.

Potential effects of excessive water withdrawal from boreholes drilled in the Antalya (Turkey) travertine plateau and well interactions

Potential effects of excessive water withdrawal from boreholes drilled in the Antalya (Turkey) travertine plateau and well interactions

Groundwater Extraction Reduction within an Irrigation District by Enhancing the Surface Water Distribution

Today, in developing countries, the low surface water distribution efficiency and the lack of supplying water needs of farmers by surface water resources are compensated by excessive aquifer water withdrawal. This mismanagement has caused a sharp drop in the groundwater level in many countries. On the other hand, climate change and drought have intensified the pressure on water resources. This study aims to evaluate novel strategies for developing surface water distribution systems for stress reduction of the Najafabad aquifer in Isfahan, central plateau of Iran. The performance of several strategies for agricultural water distribution and delivery, such as hydro-mechanical operating system, manual-based operating system, and centralized automatic operating system, was evaluated in this study. In the first step, two indices, i.e., water distribution adequacy and dependability, were obtained using a flow hydraulic simulation model. Then, the water distribution adequacy map and amount of reduction in the water withdrawal of existing wells were determined for each strategy. Finally, using the MODFLOW groundwater simulation model, the changes in groundwater levels due to the normal and drought scenarios (15 and 30%) were extracted during five years for each strategy. The findings for the normal scenario showed that the centralized automatic operating system strategy had the most significant impact on agricultural water management in the surface water distribution system with a 30% increase in agricultural water distribution adequacy index compared to the current situation. This strategy increased the groundwater level by 11.6 m and closed 35% of the groundwater wells. In this scenario, the hydro-mechanical operating system strategy had the weakest performance by increasing the aquifer level by only 1.31 m. In the 15% and 30% drought scenarios, the centralized automatic operating system strategy exerted the best performance among other strategies by increasing the aquifer water level by 10.18 and 9.4 m, respectively, compared to the current situation. Finally, the results showed that the spatial segmentation of the aquifer exerted better efficiency and better monitoring in the more susceptible regions.

AGRICULTURAL IRRIGATION AND THE IMPACT OF IRRIGATION ON WATER RESOURCES IN THE EUROPEAN UNION AND TURKEY / Avrupa Birliği’nde Ve Türkiye’de Tarımsal Sulama Ve Sulamanın Su Kaynakları Üzerindeki Etkisi

Agricultural production and water resources are among the most important issues from the past to the present. The interdependence of these two concepts is quite high. As the world population increases, the needs will undoubtedly increase. Accordingly, while the demand for agricultural production increases, resources remain limited. Water is important for all sectors in the economy. Since it is the main input of agricultural production, it is of vital importance for increasing agricultural production. Excessive water withdrawal for agricultural irrigation, especially in developing countries, has a negative impact on resources. Sustainable use of water resources is getting worse with the addition of pollution problem to excessive water withdrawal. In this study, by being dealt with the impact on the water resources of irrigation in the European Union and Turkey and it will be examined whether it is sustainable or not.

Development of water reuse: a global review with the focus on India.

The availability of freshwater is evolving as a serious threat to the living community throughout the world due to rapid industrialization, urbanization, and rising population. The depletion of groundwater due to excessive water withdrawal and reduced recharge and pollution of the water sources also contributes to this water crisis. The rising pressure on water supplies encourages the use of treated wastewater as an alternative resource. In this study, a global outlook of the developments in water reuse is presented with a focus on the Indian scenario. It can be observed that though there is a scope for water reuse in India owing to the generation of a high volume of wastewater, it is often squandered due to limited research and guidance, and unreliable institutional framework. It is suggested that the reuse of wastewater requires the development of an integrated approach considering all the factors related to technical feasibility, financial viability, and social acceptance together with a guiding management structure that may augment the existing water supplies.

Assessing subsidence of Mexico City from InSAR and LandSat ETM+ with CGPS and SVM

This study presents an enhanced analysis of the subsidence rates and their effects on Mexico City. As a result of excess water withdrawal, Mexico City is experiencing subsidence. We integrated and analyzed Interferometric Synthetic Aperture Radar (InSAR), Continuous Global Positioning Systems (CGPS), and optical remote sensing data to analyze Mexico City’s subsidence. This study utilized 52 ENVISAT-ASAR, nine GPS stations, and one Landsat ETM+ image from the Mexico City area to understand better the subsidence rates and their effects on Mexico City’s community. The finding of this study reveals a high amount of correlation (up to 0.98) between two independent geodetic methods. We also implemented the Support Vector Machine (SVM) analysis method based on Landsat ETM+ image to classify Mexico City’s population density. We used SVM to compare Persistent Scatterer Interferometry (PSI) subsidence rates with the buildings’ distribution densities. This integrated study shows that the fastest subsidence zone (i.e., areas greater than 100 mm/yr), which falls into the above-mentioned temporal baseline, occurs in high and moderate building distribution density areas.

Global water scarcity including surface water quality and expansions of clean water technologies

Water scarcity threatens people in various regions, and has predominantly been studied from a water quantity perspective only. Here we show that global water scarcity is driven by both water quantity and water quality issues, and quantify expansions in clean water technologies (i.e. desalination and treated wastewater reuse) to ‘reduce the number of people suffering from water scarcity’ as urgently required by UN’s Sustainable Development Goal 6. Including water quality (i.e. water temperature, salinity, organic pollution and nutrients) contributes to an increase in percentage of world’s population currently suffering from severe water scarcity from an annual average of 30% (22%–35% monthly range; water quantity only) to 40% (31%–46%; both water quantity and quality). Water quality impacts are in particular high in severe water scarcity regions, such as in eastern China and India. In these regions, excessive sectoral water withdrawals do not only contribute to water scarcity from a water quantity perspective, but polluted return flows degrade water quality, exacerbating water scarcity. We show that expanding desalination (from 2.9 to 13.6 billion m3 month−1) and treated wastewater uses (from 1.6 to 4.0 billion m3 month−1) can strongly reduce water scarcity levels and the number of people affected, especially in Asia, although the side effects (e.g. brine, energy demand, economic costs) must be considered. The presented results have potential for follow-up integrated analyses accounting for technical and economic constraints of expanding desalination and treated wastewater reuse across the world.

Where is the Planetary Boundary for freshwater being exceeded because of livestock farming?

Livestock production has significant impacts on the environment, including due to the use of water. In this study, we provide a spatially explicit estimation of livestock blue water use, by analyzing feed crop water use and livestock drinking water. For the past four decades, livestock water use has increased from 145 km3/year in 1971 to 270 km3/year in 2012 with an increasing trend of 1.36%/year. The proportion of livestock drinking water use has remained relatively stable at around 10% of total water use attributable to livestock production. Several hotspots of water use, including eastern China, northern India, US high plains, are identified in terms of the long-term averages, while South America and Central Africa show the most rapidly increasing trends. In USA, climate change is found to contribute most to the changes in water use attributable to livestock, while feed cropping intensity and land use change are the dominant driver in China and India, respectively. Though, in total, livestock water use makes a relatively modest contribution to the Planetary Boundary (PB) that has been proposed for anthropogenic water use (4000 km3/year), we argue that this aggregate number is not particularly meaningful, so we identify places where livestock is a major contributor to the unsustainable use of water, in northern India, part of the Middle East, Northern China and Central US. 7% of rivers where excessive water withdrawals mean that there is insufficient residual flow to sustain the aquatic environment (which we take to be the local manifestation of a PB) have been tipped over that boundary because of livestock farming, whilst in a further 34% of rivers, livestock farming on its own exceeds the water PB. Our results provide new and more geographically specific evidence about the impact that the meat industry makes on the PB for water.

Exploring consumption-based planetary boundary indicators: An absolute water footprinting assessment of Chinese provinces and cities

The water planetary boundary (PB) has attracted wide academic attention, but empirical water footprint research that accommodates local biophysical boundaries remains scarce. Here we develop two novel quantitative footprint indicators, the water exceedance footprint and the surplus water footprint. The first measures the amount of excessive water withdrawal (exceeded amount of water withdrawn against local water PBs) and the latter evaluates the potential of surplus water that can be sustainably utilised (amount of surplus water available within local water PBs). We quantify the extent to which demand for goods and services in Chinese provinces and cities are driving excessive withdrawal of local and global water resources. We investigate both territorial and consumption-based water withdrawal deficit and surplus against local water withdrawal PBs. We also trace how PB-exceeded water and surplus water are appropriated for producing certain commodities. In 2015, China’s domestic water exceedance reaches 101 km3 while the total water exceedance footprint is 92 km3. We find that 47% of domestic excessive water withdrawal is associated with interprovincial trade. Exceeded water transfers were dominated by agricultural trade from the drier North to the wetter South. A revised virtual water trade network informed by exceedance and surplus water footprint metrics could help address sustainability concerns that arise from the trade of water-intensive commodities. Our findings highlight that policy targets need to accommodate PB exceedance of both direct and virtual water use.

The key role of water resources management in the Middle East dust events

Dust events in the Middle East have resulted in serious environmental problems in many countries in the area. The dust activities in the Middle East were intensified in recent years due to many factors including climate change, drought, and poor water management strategies. This paper investigates the dust activity during 1980–2010 in the Lower Mesopotamia and southwestern Iran and demonstrates that the dust activity in the study area has increased after 1999. This study investigates the role of surface temperature, precipitation, water resources, vegetation, and surface wind velocity on the development of dust events during the study period. This investigation is performed using the correlation analysis of the normalized value of the 5 and 10 year moving average of the mentioned parameters to evaluate the role of each parameter on the increase of dust activity in the last decade of the study period. The correlation analysis demonstrates that the dust activity has the highest correlation and relationship to the water resources of the Tigris and Euphrates rivers and indicates the key role of water resources management on the dust activity in the study area. It is shown, The large scarcity of the Tigris and Euphrates rivers water resources has occurred when there was not a sharp reduction in the average precipitation in the study area. Hence, the excessive water withdrawal through the dam construction projects could be considered as the main reason of large reduction of the Tigris and Euphrates rivers water resources and high dust activity in the Middle East during the last decades.

The effect of dewatering on freshwater mussel (Unionidae) community structure and the implications for conservation and water policy: A case study from a spring-fed stream in the southwestern United States

The availability of freshwater to meet human and natural ecosystem needs remains the ultimate challenge of ecologically sustainable water management. This issue is particularly true in the southwestern United States, such as Texas, where water resources are already over allocated. The San Saba River, located in central Texas, exemplifies this issue as excessive water withdrawal has resulted in intermittency for as much as two-thirds of its length. The effect of this dewatering on aquatic species such as mussels is not well known, which is problematic because five species of high conservation concern occur in this river. The goal of this study was to examine how dewatering may have affected the distribution of these species and to identify options for mitigating this threat. Comparing species-per-unit-effort (SPUE) and catch-per-unit-effort (CPUE) between these reaches, we found SPUE and CPUE were 3.7 and 7.9 times lower, respectively, in intermittent reaches than in perennial reaches. Using fuzzy ordination, we found that mussel assemblage structure differed between intermittent and perennial reaches despite both historically sharing similar fauna. Evaluating habitat, we found differences in mussel-mesohabitat associations between perennial and intermittent reaches. Current water policy and regulatory tools to mitigate this issue are insufficient, which raises serious questions about how states like Texas, located in arid and semi-arid regions, will be able to protect aquatic ecosystems under the specter of ever increasing population growth and climate change.

Hydroclimatic drivers of the growth of riparian cottonwoods at the prairie margin: River flows, river regulation and the Pacific Decadal Oscillation

Cottonwoods, riparian poplars, are facultative phreatophytes and can obtain water from shallow soil moisture originating from rainfall, or from the deeper capillary fringe above the alluvial water table that is recharged by river water infiltration. The correspondence between cottonwood growth and river flows should reveal the dependency upon alluvial groundwater and subsequently, the vulnerability to reduced river flows. To explore this association, we analyzed historic growth patterns of plains cottonwoods (Populus deltoides) along the Red Deer River (RDR), which is at the northwestern limit of the North American Great Plains. We developed chronologies of yearly radial increments (RI) and basal area increments (BAI) and explored correspondences with the environmental records from the past century. In this semi-arid region, the RI or BAI were not correlated with local precipitation while negative correlation with growth season temperature (T) (r = −0.37, p < 0.01) could reflect reduced growth with hot summers. There was correlation between growth and annual river discharge (Q, and particularly log Q that approximates river stage) and this increased with two year averaging (r = 0.51, p < 0.01), reflecting carry-over in the watershed hydrology and in the ecophysiological response. There was correspondence with the Pacific Decadal Oscillation index (PDO, r = −0.45, p < 0.01), which provides multi-decade transitions that influence Rocky Mountain headwater precipitation and other weather characteristics, and river flows. The combination of Q, PDO and T provided the strongest multiple regression model, accounting for 44% of the historic growth variation (52% correspondence for 1953–2013). The RDR was dammed in 1983, enabling winter flow augmentation, but summer flows were sustained and cottonwood growth and the streamflow correspondence persisted. This indicates that it is the pattern of dam operation and not damming per se that determines the fate of established riparian cottonwoods downstream. This study revealed that these cottonwoods are phreatophytic and dependent upon alluvial groundwater that is recharged from the river. This provides a research strategy to determine whether riparian woodlands along other regulated rivers are similarly groundwater-dependent and could be vulnerable to river flow reductions from excessive water withdrawal for irrigation or other uses, or with climate change.

Spatial assessment of the potential of groundwater quality using fuzzy AHP in GIS

In this study, fuzzy AHP method is used for extracting the water quality indicators based on the Schuler standard and World Health Organization (WHO) guidelines during a 20-year period. For this purpose, the best fit of the zoning model was performed. Furthermore, by comparing the standard errors, the continuous Raster layer was extracted from the important parameters used in generating the qualitative potential assessment index. The classified layer was generated by integrating continuous layers in the GIS environment and with the use of Python programming. The similarity of the outputs of both methods indicates the presence of large sections of aquifers in the middle and southwestern regions of Iran in the “temporarily drinkable” and “bad” classes. The calculations showed that the majority of aquifers that were located in the “inappropriate” class during the first 10 years fell to less valuable class types. Based on the results of the model, there is a direct correlation between the drop in water resources and the decline in the quality indices. In addition, in the Urmia and Bushehr coastal aquifers, due to excessive water withdrawal and salty water penetration, the quality of the table water is in critical condition. Based on the results of the research, the aquifers in the range of Zagros and Alborz mountains show the least change in water quality. The reason for this is the depth of the aquifer and the ability to recharge it.

Mapping of Salinity Ingress Using Galdit Model for Sirkali Coastal Region: A Case Study

A model is traced to evaluate and enumerate the significance of vulnerability to seawater intrusion due to excessive ground water withdrawals and some anthropogenic activities at coastal aquifers. So taking these issues into account few thematic maps which were influencing the saline water intrusion were prepared and overlaid using Geographical Information Systems (GIS). Based on GALDIT method, the groundwater vulnerability cartography has been assessed. To reckon the GALDIT index it requires six parameters like aquifer type, aquifer hydraulic conductivity, depth to groundwater level (AMSL), distance from the shore, impact of existing status of seawater intrusion and thickness of the aquifer. This GALDIT is the indicator scores and summing them and dividing by the total weight for determining the relative role of each one. Apart from this an identification of saltwater intruded area is done by using indicators of saltwater intrusion like Cl/(HCO3 + CO3) ratio and Na/Cl ratio. The vulnerability areas are classified as moderate with an area of 147.31 sq. km and low covering an area of 168.72 sq. km respectively based on the thematic maps. The final thematic map can be used for management of the coastal ground water resources.

Study on Scope of Roof Top Water Harvesting for Recharging Ground Water for Combating Excess Ground Water Withdrawal for Rice Cultivation in the District of Nadia in West Bengal

Investigation was conducted for all the blocks in the district of Nadia, West Bengal to estimate the over exploitation of ground water and to examine the possibility of mitigation of it through artificial ground water recharge. There were approximately 1.16 x 109 m3 irrigation water requirement except monsoon month (June to September) for rice cultivation. The estimated ground water recharge was found approximately 0.82 * 109m3. Thus, approximately 0.34 * 109 m3 of ground water was found over exploited every year if irrigation demands entirely satisfied through ground water. This 0.34 x 109 m3 of overexploitation could be mitigated if approximately 3.88 x 108m2roof top water harvesting structure along with the recharge facilities were created. The estimated cost for this purpose was approximately ` 666.488 billion. The creation of this facility may also contribute to large extent in domestic water supply along with the improvement of arsenic contaminated ground water of this district.