Groundwater Level Fluctuations and Associated Influencing Factors in Rangpur District, Bangladesh, Using Modified Mann-Kendall and GIS-Based AHP Technique

Abstract

Analysis of groundwater level fluctuations is critical to understanding groundwater system dynamics and the factors that cause groundwater level fluctuations. Although most of the earlier studies focused on time series trend analysis using typical non-parametric tests, groundwater level fluctuations in drought-prone areas of northern Bangladesh are still poorly understood. To this end, the present study aims to analyze groundwater level fluctuations from 1980 to 2019 and associated influencing factors on groundwater level oscillation using the modified Mann-Kendall test and Pearson’s correlation method. Using GIS-based analytical hierarchical process (AHP) techniques, this study also identifies potential groundwater zones in the designated area. The result showed that 42.5% of monitoring wells had groundwater levels from 4.5 to 5.5 m during the pre-monsoon, whereas 57.5% had groundwater levels from 2.5 to 3.5 m during the monsoon in recent years. Based on the annual average groundwater level, the result showed that 62.5% of monitored wells had a declining trend, and 37.5% had an increasing trend from 2000 to 2019. A negative correlation was observed between groundwater level and rainfall in all monitoring wells, as the area’s rainfall impacted the groundwater level fluctuations. There was also a substantial positive correlation between groundwater levels, extraction, and potential evapotranspiration. The groundwater potential zone mapping shows three primary groundwater prospect categories: poor (1.9%), moderate (34.16%), and excellent (63.94%). The findings will assist planners and policymakers in allocating groundwater resources in various sectors such as agriculture, drinking water, and industry.