Foreword

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.

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.

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.

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