Exploring driving forces of large-scale unsustainable groundwater development for irrigation in lower Ganga River basin in India

Abstract

Groundwater is the replenishable and dynamic resources on the earth. Understanding the sustainability of water management is, therefore, the crucial factor in faring about agriculture, economy and environmental conditions. This study investigated the sustainability of large-scale groundwater-based irrigation by identifying the trend in groundwater depth (GWD) and explored the driving factors to characterize the identified trends in the lower Ganga River basin (LGRB) in India with an area of 195,601 km2. Trends were identified in the in situ observation groundwater data (total wells = 527) by applying innovative trend analysis (ITA), Mann–Kendall (MK) test or modified MK (mMK) and Sen’s slope estimator. The obtained results of all the methods confirmed that GWD in most of the studied wells had an increasing tendency in LGRB during 1996–2017. ITA showed that almost 85.39%, 62.23%, 85.39% and 57.12% wells for pre-monsoon, monsoon, post-monsoon and winter seasons, respectively, showed increasing trends. The rapidly increasing trend (slope: 5.22–136.33 cm/year) in monsoon season indicates shallow groundwater resource depletion, and groundwater abstraction exceeds the groundwater recharge. Findings also revealed that shallow pumps would not be functioning in the future for large-scale irrigation since shallow water is becoming scarce due to increasing water depth. In spite of irrigated areas continued almost the same (1997–2014), decreasing rainfall along with unplanned development of water resources is primarily identified as the main driving force for groundwater depletion at a large scale. Planned water management is urgent for ensuring sustainable irrigation water management.