Assessment of groundwater level trends and drought in coastal purba Medinipur, West Bengal using groundwater level index
摘要
The annual groundwater accessible for extraction in India is reported to be 398.08 billion cubic meters (bcm), while the actual extraction stands at 239.16 bcm, indicating a groundwater drought across the country. This scenario is largely attributed to meteorological conditions and the rising population. Focusing on the coastal region of Purba Medinipur, the area is facing a significant lack of pure fresh groundwater due to overconsumption and the intrusion of brackish water into the aquifer. Despite receiving heavy annual rainfall ranging from 1550 to 1950 mm, 70.87% of this precipitation falls during the monsoon season, leaving only 29.13% for non-monsoon months. This seasonal distribution has contributed to the groundwater drought observed in Purba Medinipur. The region has exceeded its safe yield of groundwater during the pre-monsoon period, with a decrease in aquifer recharge attributed to urban development (1.71% annual increase in built-up area) and an increase in barren land (13.97% per year). While the area has seen a 7.69% per annum increase in water bodies, these are primarily used for saline fish farming, further complicating water availability. Data collected from 213 tubewells between 2010 and 2023 revealed a declining groundwater level. The Mann-Kendall test and Sen’s slope estimator methods were applied to analyze the trend. The dominant sandy soil in the area, combined with its elevation relative to the Bay of Bengal, has led to an encroachment of seawater from various directions. From 2010 to 2014, groundwater levels remained stable, but subsequent years saw a decline due to changes in land use and unchecked water extraction, culminating in a serious groundwater crisis. To address this issue, solutions such as rainwater harvesting, the installation of injection wells, and the construction of hydraulic barriers to separate brackish from fresh groundwater are recommended.