GIS-based assessment of non-equilibrium pattern between groundwater recharge and irrigation draft in a semi-arid region of Rajasthan, India

摘要

Over-exploitation of groundwater for irrigation can result in drastic reduction in groundwater level in Jodhpur district of western Rajasthan, India. In this study, we used the long-term trend analysis of seasonal groundwater level data to predict the future groundwater scenario in 33 villages of Jodhpur district, assessed the impact of water harvesting structures on groundwater recharge and explored the non-equilibrium between groundwater recharge and irrigation draft in the study area. Analysis of groundwater level data from 26 observation wells in 33 villages in the pre-monsoon period showed that groundwater level decreased continuously at the rate of 2.07 m/a. With this declining rate, most of the tube wells(including the well with the maximum depth of 193 m) are predicted to become completely dry by 2050. Behavior of temporal groundwater level data in the study period(from 2004 to 2012) can be explained by different geospatial maps, prepared using Arc GIS software. Statistical analysis of the interpolated maps showed that the area with the maximum positive groundwater recharge occupied 63.14% of the total area during 2010–2011 and the area with the maximum irrigation draft accounted for 56.21% of the total area during 2011–2012. Higher groundwater recharge is attributed to the increase in rainfall and the better aquifer condition. Spatial distribution for the changes of average groundwater recharge and draft(2008–2009 and 2011–2012) showed that 68.50% recharge area was in positive change and 45.75% draft area was in negative change. It was observed that the area of the irrigation draft exceeded that of the groundwater recharge in most of the years. In spite of the construction of several shallow water harvesting structures in 2009–2010, sandstone aquifer zones showed meager impact on groundwater recharge. The best-fit line for the deviation between average groundwater fluctuation due to recharge and irrigation draft with time can be represented by the polynomial curve. Thus, over-exploitation of groundwater for agricultural crops has result in non-equilibrium between groundwater recharge and irrigation draft.