Impact of Hydro-meteorological parameters on Ground water resource and potential source identification at Port Blair city, Andaman and Nicobar

Abstract Understanding hydro-meteorological drivers and spatial flow dynamics is critical for sustainable urban groundwater management in fragile island ecosystems. This study presents a comprehensive assessment of climate variability, groundwater recharge dynamics, and potential source distribution across Port Blair City, Andaman and Nicobar Islands, spanning 2000 to 2023. Long-term meteorological analysis reveals that warm ENSO (El Niño) events significantly suppress rainfall frequency and volume across the region. Although the annual wet days remain steady at 135 ± 11 days, pre-monsoon precipitation exhibits a declining trend (-17mm/year), coupled with increasing pre-monsoon evapotranspiration (+ 6.13 mm/year). Primary groundwater recharge occurs between April and December, where total precipitation (~ 2627mm) exceeds evapotranspiration losses (~ 363 mm). Shallow unconfined aquifers display rapid seasonal response, peaking at depths of ~ 0.4m below ground level (BGL) following the September rainfall peak. However, long-term trends show a post-monsoon water level decline of 0.038m/year, driven by urban expansion, abstraction, and rapid marine discharge. Time-series forecasting using an Exponential Triple Smoothing (ETS AAA) model projects this downward trajectory to continue through 2030 without intervention. Hydrogeological mapping indicates that shallow groundwater (0–2\(\:\text{m}\) BGL) dominates the urban landscape. Formations within the Mithakhari Melange yield the highest groundwater potential (> 1-3L/s to >3L/s). Water table contours reveal prominent radial flow divergence and key recharge/discharge zones in the southeastern, northwestern, northeastern, north-central, and southern sectors. To mitigate localized depletion and capture excessive monsoonal runoff, targeted artificial recharge structures and large-diameter dug wells are recommended within these identified high-potential discharge zones.