Long-term variation of hydro-meteorological parameters and their impact on groundwater of unconfined aquifer

Hydro-meteorological parameters significantly influence groundwater storage in unconfined aquifers. Although the unconfined aquifer is closer to the surface, the dry conditions have an impact on the water level. The relationship between the hydro-meteorological parameters and the unconfined groundwater level (GWL) has not received much attention or study. Hence, the impact of hydro-meteorological parameters (e.g. rainfall (RF), air temperature (T), and potential evapotranspiration (PEV)) on the GWL is studied over West Bengal, India. The region is categorized into four zones (zone-1, zone-2, zone-3, and zone-4), considering the geo-hydrological scenario. GWL raised by ≈ 1.63 m, 3.51 m, 3 m, and 2.24 m owing to the RF of ≈ 880 mm, 953 mm, 1083 mm, and 1593 mm during monsoon in zone-1, zone-2, zone-3, and zone-4, respectively. The groundwater table is 6.9 m, 95.2 m, 22.3 m, and 80.2 m in the respective zones during winter. The groundwater flows seasonally from zone-2 to zone-1 and zone-3 and, similarly, from zone-4 to zone-3 and zone-1. In zone-1, as RF increased in monsoon, the shallow GWL occurred, and PEV caused water loss. PEV and T have a dependency on deeper GWL in other seasons. PEV and T are critical factors in zone-2’s GWL depletion in all seasons. Winter, pre-monsoon, and post-monsoon showed a correlation between the deeper GWL and PEV and T in zone-3 and zone-4. When sufficient RF occurred, the deeper GWL enhanced to a shallower GWL. In monsoon, recharge of the unconfined aquifer occurred owing to RF. The deeper GWL developed in post-monsoon because of lower RF and increased PEV and T.