Mapping of heterogeneity on groundwater level and potential zones along expeditiously urbanizing tropical coastal regions

Abstract

The study of coastal groundwater potential is critical as freshwater availability is under tremendous stress due to increased coastal region development and noticeable monsoonal changing patterns over time. In addition to these factors, Odisha's coastal region has a larger drainage network in low-lying plains, which reduces freshwater recharge by increasing surface discharge. To sustain freshwater usage, the demarcation of the Groundwater potential zone (GWPZ) was done using Geographic Information System (GIS), Analytical Hierarchy Process (AHP), and Multi Influence Factor (MIF). Factors such as geomorphology, geology, land use/land cover, rainfall, lineament density, drainage density, elevation, slope, and soil were considered to accurately predict GWPZ. The AHP technique was used to construct a pairwise comparison matrix (PCM) and assign weights to each thematic layer, whereas the MIF method computes a recommended score for each layer based on the sum of the major and minor effect weights. The findings demonstrate that a significant portion of the study area falls into the "good" GWPZ (∼ 83% for both methods) category, indicating that the aquifer's storage is adequate. The output was validated by the Receiver operating curve (ROC) and groundwater prospects data. The ROC findings showed that the Area under curve (AUC) was 81% and 80.1% for AHP and MIF, respectively. This outcome signifies moderate to high precision indicating that the model could make accurate positive predictions. Analysis of pre-monsoon and post-monsoon water levels reveals spatial variations, with lower water levels indicating higher potential. Water levels in low-lying plains with high groundwater potential zones (GWPZ) are declining due to coastal erosion, sediment accumulation, limited infiltration, and increasing seawater intrusion. Continued groundwater abstraction may aggravate seawater intrusion despite favorable geological conditions. This study would be advantageous for coastal region decision-making involving water resource management and planning for sustainable development.