Aquifer Delineation and Suggestive Management ? A Case Study from North Twenty Four Parganas District, West Bengal

The Upper Nira River Basin (378.83 km2), in the Upland Deccan Traps is witnessing a transition from being a traditional rain fed, non-command entity to a predominantly surface irrigation command area. Understanding and accurately computing the change in groundwater storage is a vital component in groundwater estimation. The lava flows constitute 3 aquifers in the basin, UNR-1 , UNR-2 and UNR-3. The efficacy of the methodologies used for estimating the groundwater potential of the Upper Nira River Basin is evaluated. Groundwater assessment based on the GEC 2015 methodology has been undertaken to estimate a net available recharge of 4419 Ham in the aquifers and gross groundwater draft of 461.49 ham. The basin has been categorised as Safe due to low stage of exploitation (~11%). The people residing in the basin however face severe scarcity of groundwater during the summer season annually in spite of receiving copious rainfall (about 1500 mm) during the monsoon. The likely reasons for such a paradox are high surface runoff, low permeability, low storativity of aquifers, high base flow plus draft, etc. According to the new and simple aquifer-based methodology proposed in this paper the quantity of recharge (Q) for Aquifer UNR-1, Aquifer UNR-2 and Aquifer UNR-3 are 1146.70, 1691.02 and 16.97 km3 respectively. Thus, there is a difference in recharge to the tune of 1411 hams i.e. about 24% less recharge compared to the results obtained by the aquifer based methodology as per GEC (2015) guidelines. When the new recharge values are used in the GEC 2015 methodology a scenario close to reality emerges in the Nira River basin which proves the efficacy of the new methodology.

The high reliability of rural and urban settlements on groundwater in India and the individualistic nature of groundwater usage make groundwater management and governance extremely challenging. Groundwater resources development in India, even today, has progressively become synonymous with increasing the accessibility of the resource through more and more sources and meeting the growing demand through the infrastructure of distribution. Management of groundwater becomes selflimiting when the focus is on exploration for new sources, without understanding resource behaviour. On the other hand, experience has shown that bringing aquifers to the centre stage of groundwater management is important. The concept of aquifers changes the way in which communities begin to perceive groundwater and becomes the first step in developing socioecological resilience to groundwater-related vulnerability. Building resilience to groundwater-related vulnerability further includes developing a governance mechanism that strikes a balance between supply management and demand regulation through an understanding of the resource, i.e., the aquifer.Aquifer systems in India are highly diverse and complex because of the variation in their inherent properties such as storativity, transmissivity and groundwater quality. Aquifer vulnerability is a consequence of not only how the rampant exploitation and contamination of groundwater occur, but also how different aquifers react to these fluxes. Moreover, irrespective of the scales of groundwater accumulation and movement, micro-level analysis of aquifers becomes imperative because of the atomistic nature of groundwater access and use. A systematic hydrogeology-based approach that requires delineating aquifers, understanding the dynamics of groundwater and mapping the demand and dependence of community on the resource holds the key to decentralized groundwater governance in India. Such an approach can be undertaken through participatory monitoring, decision support and action.The inherently heterogeneous nature of aquifers and communities in western and central India demand a strategic application of mapping, characterizing and managing local aquifers through a participatory groundwater management protocol. This nuanced approach beginning with aquifers as both a resource and a system, ensures equitable, efficient and hence, the sustainable management and governance of aquifers in this region.

The Ground Water Resources play an important role in agro-economy of the Chhattisgarh State being heavily dependent on rain?fed agriculture. The Ground water resources are controlled by normal monsoon rainfall of 1201 mm with four aquifer systems, viz a) Sandstone aquifers, b) Limestone aquifers, c) Crystalline aquifers comprising granites, gneisses schists, ultrabasics and basalts of Archean, Proterozoic and Cenozoic age respectively forming discontinuous, unconfined and semi-confined aquifers, and d). Alluvial aquifers comprising alluvium, clays, silts, laterites etc. forming thin and extensive unconfined aquifers in several isolated patches and near major river courses. These are unconsolidated formations of Quaternary age. During pre-monsoon period in the 70% area of the state groundwater level remains under 5 to 10m, 21% under 10 ? 20 m and less than 1% under more than 20 mbgl. In the Post-monsoon period, 71% area shows the groundwater level in the range of 2 to 5 m, 24% area, 5 to 10m and 2% more than 10 m bgl. In general, 23% wells show rise in the range of 0-2m, 35 % 2-4 m and 42%, > 4 m in response to rainfall. Ground water quality is bicarbonate type and suitable for all purposes. Isolated patches of Arsenic, Sulphate, Fluoride and NO3 contamination have also been reported. Ground water meets 84.5 % and 14.5 % of total irrigation and drinking water requirements respectively. The annual ground water recharge has been estimated as 11,579 MCM. The existing ground water extraction for all uses is 4691MCM. Out of 146 blocks, 41 blocks have Stage of Ground Water Extraction < 30 %, 46 blocks, between 30 to 50%, 35 blocks within 50 and 70 % and 24 blocks have > 70%. The groundwater utilization over the years has increased drastically from 5.11 % in 1990 to 44.37% in the year 2017.The immediate attention is needed on (a) Creation of additional Irrigation potential, (b) Supply of contaminant free water through alternate source, (c) Promotion of rainwater harvesting and sartificial recharge with community participation,. (d) Regulation of overuse of ground water and (e) Sensitizing Farmers through incentivizing water efficient irrigation techniques.

Palghar, Thane, Raigad, Ratnagiri, Sindhudurg and Greater Mumbai districts of Maharashtra form the Konkan Coastal belt of Maharashtra. In the coastal areas the immediate effect of high groundwater development is often sea water intrusion. Although there were sporadic studies by earlier workers (Umrikar et al., 2007, Gupta et al. 2010) into some reported isolated cases of seawater intrusion in the coastal areas, this has been a maiden attempt to decipher the extent of seawater intrusion in the entire coastal tract of Maharashtra.The area is underlain by Dharwarian meta-sediments (Lower Precambrian age), Deccan Trap lava flows (Upper Cretaceous to Lower Eocene age), Laterites (Pleistocene age) and Coastal alluvial deposits (Recent to Sub-Recent age). Groundwater occurs under phreatic condition in the Coastal and riverine alluvium, laterites and weathered/fractured rocks. The area has been covered by systematic hydrogeological surveys, reappraisal Surveys and groundwater monitoring by CGWB. in these formations depth to water levels range from 0.6 m bgl to 8.07 m bgl. Groundwater is mildly alkaline with pH range of 6.9 to 9.0. Electrical conductivity ranges from 61 to 29370 ?S/cm at 25?C. Only two Samples from Dapoli in Raigad district show EC values higher than 3000 ?S/cm at 25?C. In general, water quality is good and suitable for domestic use and irrigation. In order to confirm the sea water intrusion, ionic ratios like Na:Cl, and Cl:CO3 + HCO3, were computed. From the analysis it is found that about 2 to 10 km wide coastal belt and the inland tidal backwaters are affected by salinity intrusion. It is revealed that about 55% of the analysed samples have indicated salinity ingress. The extent of sea water intrusion is more in the southern part progressively diminishing towards northern area. The maximum effect is observed in Sindhudurg district followed by Ratnagiri, Raigad, Palghar and Greater Mumbai.Over-exploitation of groundwater in pockets and diminishing seaward freshwater flow in the rivers are the major reasons for sea water ingression. Regulation of groundwater development in the coastal area and areas adjacent to estuaries, maintaining adequate stream flow, stopping of riverbed sand mining, construction of tidal regulators at suitable places and creation of fresh water barrier through rainwater harvesting and groundwater recharge are essential to control further sea water intrusion in the area.

Chemical quality of surface and groundwater of an area is influenced by the climate, hydrological conditions, soil characteristics and geological formation. Irrespective of their source, all natural waters contain some chemical constituents and their quality changes progressively as they traverse over the land surface or infiltrate downward due to various hydro-geochemical processes. Anthropogenic factors also contribute substantially towards quality change of both surface water and ground water. In the present study an attempt has been made to understand the aquifer vulnerability to pollution, at the regional scale (Goa State), which takes into account the intrinsic hydraulic and hydrogeological parameters and environmental impacts. It is noticed that a variety of activities, such as agricultural, industrial and urban land uses, are carried out in the area, thus exposing the aquifers to a wide range of contaminants. Groundwater quality data of Goa state for the pre-monsoon seasons of 2014 and 2018 were obtained from CGWB (Bengaluru) and analysed statistically. A regional scale approach was developed which is known as ABHESHT (Aquifer type, Boundary conditions, Hydraulic Head representing static water level, Environmental impact, Solute concentration, Head variation (Water Table Fluctuation) during pre-monsoon and post-monsoon seasons and Transmissivity). The method has been applied to Goa State, west coast of India and compared with the observed groundwater quality parameters. It is found that the model has successfully delineated the wells which are prone to pollution. Using GALDIT model, seawater intrusion impact was also assessed. The study revealed that the groundwater of Goa State did not show any significant pollution indicator, however, seasonal variations in water quality parameters were observed. It is also found that the North Goa coast as well as the other tourist spots spread over the entire state show signs of pollution at various locations (Anjuna. Baga, Mapusa. Concona etc). This calls for immediate attention from the concerned authorities.