Artificial Recharge in India as an Effective insitu Water Security Intervention: Studies in Two Select River Basins

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.

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.

In western India, the states Goa, Gujarat, Maharashtra and Rajasthan having area of 0.11%, 5.97%, 9.36% and 10.41% of India respectively have 0.24%, 6.83%, 13.48% and 4.52% of the total population of the country. The area, except Goa which records high precipitation, receives moderate rainfall. Arid conditions prevail in north Gujarat and major part of Rajasthan. The utilization pattern of ground water is uneven across the region resulting in ground water stressed conditions and over exploitation in some parts, particularly the arid regions and sub-optimal ground water utilization in others. Water level varies widely being very shallow in the southern part and deep to alarmingly deep in the northern part, having deepest water level of the country in Bikaner district of Rajasthan. Water quality is of concern in the major parts. In considerable areas, some chemical constituents exceed the permissible limit for drinking water, and large patches with brackish to saline water are encountered in Rajasthan and Gujarat. Sporadic occurrences of Fluoride and Nitrate in ground water exceeding the permissible limit for drinking water are spread almost throughout the region which necessitates cautious use of ground water in these areas for drinking purposes. The stage of ground water development is 37%, 68% and 54% in Goa, Gujarat and Maharashtra respectively. In Rajasthan, the stage of ground water development is 140% and 164 out of 248 ground water assessment units are overexploited and 23 ground water assessment units in Gujarat are over exploited. This requires immediate judicious intervention without which some areas will not be able to meet even the drinking water needs. Groundwater withdrawal requires to be strictly regulated so that it does not exceed the annual recharge and also that it does not disturb the hydro-chemical balance. Alarming declines in groundwater levels warrant immediate attention for taking-up of recharge schemes to arrest further decline and augment the groundwater resources. In areas of scanty recharge, ground water should be allowed only for drinking water purposes. In other areas, along with water conservation and ground water augmentation measures, demand side management using micro irrigation techniques and change of cropping pattern etc should be religiously adopted.

Among the challenges faced by the world today in the area of health care, water is the greatest challenge, and this is particularly true for the developing countries. A large proportion of the world?s population relies on ground water as primary source for drinking and domestic use. In recent years, due to increase of population, urbanization, industrialization, use of chemical fertilizers, pesticide in agriculture, there is over increasing threat to surface and ground water quality. The indiscriminate use of ground water for irrigation and other purposes has resulted in sharp decline in ground water table and in changes in the natural geochemistry of ground water. In the largest areal state of the country i.e. Rajasthan higher concentration of all the three hydrochemical parameters viz. salinity, nitrate and fluoride in ground waters have adversely affected the lives of people in general and their socio-economic status in particular. Ground water of western, north-eastern parts of Rajasthan are facing problem of salinity, nitrate and fluoride, whereas central and southern parts are generally facing an acute problem of fluoride. Therefore, immediate action for mitigating the problems at government, semi-government or social levels are required for the welfare of countrymen.

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.