Groundwater Fluctuation in Response to Annual Rainfall in North-West Region of Bangladesh

Bangladesh is dependent upon groundwater to satisfy the enormous demand for domestic and agricultural water supplies. As reliable surface water resources have reduced significantly and the demand for water continues to rise there is an increase in groundwater reliance. In order to ensure future sustainability of groundwater supplies it is essential to make better utilization of such an important resource. A simplistic statistical approach (i.e., correlation) is done with the assumption that a strong relationship exists between these two variables particularly in case of a shallow unconfined aquifers. However, only 35% of the groundwater monitoring wells show high positive correlation with the corresponding rainfall observations. Poor statistics are found in cases where natural recharge condition might be absent due to the strong influence of irrigation withdrawal of GW or the closer proximity of the influent river(s) or the unfavorable impermeable topsoil condition. Some evidence shows that groundwater level is discharging to surface water level during the dry season while reversing behavior is observed during the wet season. Additionally, the study compares the GW level position during the dry (April–May) and wet (July–October) seasons for 1993–2017. Increasing dependency on groundwater over surface water shows a significant drop in groundwater position, especially during the dry season.