Long-Term (44 Years) Regional Groundwater Recharge Estimation for Agricultural Sustainability

The advancement of irrigated agriculture is indispensable to satisfy the growing food demands of the escalating worldwide population. It is also essential for accomplishing many of the UN's sustainable development goals (SDG) such as SDG1 (no poverty), SDG2 (zero hunger), SDG3 (good health and well-being), and SDG15 (life on land). However, without proper management, irrigation development can cause twin hydrological problems, i.e., rising groundwater level and salinization in irrigated regions. Long-term groundwater recharge estimation is essential for managing the above-mentioned problems of irrigated regions. This study formulated and employed a simple groundwater recharge model, which is a combination of the groundwater budget and seasonal groundwater level fluctuations. Estimated long-term (44 years, from 1976 to 2020) seasonal groundwater recharge was analyzed to appraise the twin hydrological problems of a study area in northwest India. The investigation is the first in the study region; it is simple to follow and it can be replicated in other regions of the world dealing with comparative issues. The analysis disclosed that the developed model performed very well in estimating groundwater recharge. This was verified statistically by high R-squared (0.987) and model efficiency (0.940) values and low mean error (0.011 m) and root-mean-square error (0.089 m) values. Analysis of various components of groundwater recharge revealed that more than 60% of the mean monsoonal recharge was provided by percolation alone due to the high paddy field portion. Higher average seasonal tubewell draft in the winter season always resulted in negative net recharge. However, yearly net recharge was consistently positive on account of higher monsoonal recharge. Consequently, the aquifer level rose at a mean rate of about 0.12 m annually throughout the study period. Because the groundwater level was already high, an additional rise would worsen the condition. Alternative management plans must be developed and realized for sustainable resource management in the region. As a follow-up action, three possible scenarios were investigated by using the model. The analysis of the scenarios disclosed that conjunctive water utilization needed to be increased for crop irrigation, which aids more groundwater withdrawal from the area. The other scenario suggested altered cropping with the reduced paddy cultivation because the paddy field contributed un-proportionately high recharge in the overall water balance of the region. The analysis suggested that implementing a combination of more than one change altogether would be more beneficial as compared to individual changes in baseline inputs. For example, altered cropping along with conjunctive water utilization would deliver more favorable results. The strategies described here are reliable in encouraging stakeholders/farmers to realize long-term sustainable goals.