Delineation of Phreatic Basaltic Aquifers in the Upper Nira River Basin, India and Evaluating the Efficacy of Methodologies Used for Estimating their Groundwater Potential ? A Case Study

The water sector in Maharashtra is facing critical challenges. First, uneven availability of water over space and time is the biggest challenge and secondly, dramatically increasing competing demands for water from different sectors are giving rise todisputes and conflicts. Of the total water used in the state, about 82% goes to irrigation, 12% for domestic water supplies, 4% forindustrial use, and the remaining for other uses such as livestock, hydro and thermal power generation. With the urban population of about 51 million (45%), and rapidly growing urban centres and industries, there is considerable gap in demand and supply of thestate's scarce water resources. This has posed serious challenges to water security. There can be only limited dependence upon the groundwater resources for the protective irrigation in the State as 85% area is Deccan basalt having limited ground water recharge potential. Also access to safe drinking and other domestics is a challenge in the rural areas of the State. Planning and Management of water resources in a coordinated and holistic manner is needed. Considering the scarcity of water in large part of Maharashtra and substantial utilisation by irrigation sector, there is a need to expedite measures for improving Water Use Efficiency (WUE) so that water saved in irrigation can be utilised for other non-irrigation purposes. The paper gives an overview of the water resources scenario in Maharashtra with reference to surface water and discusses various water management issues that need focused attention. The paper brings out the impact of decision of various water dispute tribunals on the water availability for the State and also the need for inter-basin and intra-basin water transfer. It emphasises the need for upscaling use of Micro Irrigation (MI), Pipe distribution system, large scale integrated MI systems throughout the State etc. for not only to save substantial amount of water but also to help in increase the productivity and quality of agriculture produce. The paper also touches upon the issues of water quality and flood management in the State.

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.

Surface water resources in Rajasthan are scarce and scanty owing to hot arid climatic conditions. Major parts of western Rajasthan are devoid of any major drainage system and are reeled under spells of chronic droughts. Average annual rainfall in the state is of the tune of 540mm, decreases westward and is even less than 150mm in the western most parts of Jaisalmer district. Annual Potential evapo-transpiration is also as high as 2060mm in parts of Jaisalmer district. There are 15 river basins in the state. There are also numerous natural as well as artificial freshwater lakes including Pushkar, Rajsamand, Nakki, Ana Sagar, Kayalana, Ramgarh, Foy Sagar etc. mainly in the southern and eastern parts of the state. Salt lakes include Sambhar, Kuchaman, Pachpadra, Didwana, Phalodi, Lunkaransar etc. Indira Gandhi Nahar (IGNP), Bhakara and Gang canals have been constructed to bring Himalayan water to the desert areas of western Rajasthan in addition to other major commands of Chambal, Mahi and Narmada canals etc. In Rajasthan, irrigation projects completed include 22 Major projects, 77 Medium projects, 660 Minor projects and 3139 Tanks have been transferred to Panchyat Raj Department. Usable water is of the magnitude of 16.05 BCM and the Gross Storage Capacity created is of the order of 14.547 BCM. The Live Storage Capacity created is about 11.99 BCM. Out of the total allocated share of 17.88 BCM under interstate water agreement, average annual water availability remains 12.66 BCM due to various climatic, political, institutional or hydrological reasons. In addition to various Central Government Schemes, Watershed schemes and Mukhyamantri Jal Swavlamban Abhiyan are also implemented in the state.

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.

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.

Air, Solar energy, Land, and Water are the four life support systems of which, only ?Water? is amenable for its development and management to meet human needs of water. Water Resource Development structures had to be compatible to the characteristics of ?Water Resource?. With the advancement of civilization, ingenuity of man prompted him to evolve different types and sizes of infrastructure to meet changing patterns and increasing magnitude of water demand. It also stressed the need to have an integrated approach in such development. Subsequently as a soft option, improvement in management of infrastructure was the next logical step. As the issue of complexities in the competing and conflicting demands on water surfaced prominently, need for taking a holistic approach towards them was thought of and there emerged the viable solution in the form of better governance of water resources. An attempt has been made here in below to present evolution of all these developments by citing a case study of Maharashtra State in the Peninsular India. It mentions at the end a ?Vision Statement? for the future development of the State in the water sector and an outline of future planning and policies which need to be adopted. In conclusion it states a framework of desirable actions to be taken in future, to transform the ?Vision? into a reality.