A modelling approach in evaluating the effect of climate and LULC on groundwater level of Cochin, Kerala, India

This study assessed the impact of land use and land cover (LULC) dynamics on groundwater changes in the Greater Cochin region of Kerala, India, over the last three decades. Future groundwater resource scenarios under changing climate and LULC were calculated quantitatively using a hydrological model and a groundwater flow model. For this purpose, remote sensing data, in-situ field observations, RCM data, computational hydrological, and groundwater flow models were used. A series of LANDSAT satellite data sets were used to analyse the historical LULC dynamics of Cochin from 1994 to 2020. The analysis indicated that the LULC changes affect groundwater recharge and historical analysis showed a decline in the recharge process. Hence the impact of LULC changes on groundwater is quantifiable. Therefore, in the next part of the study, an evaluation of the effect of LULC changes forecasted for the future was carried out using modelling. The SWAT model was used for this purpose. The projected estimate of groundwater recharge rate for projected LULC shows a decline in recharge rate of 20% in the near future, 27 % in the middle future and 30% in the far future.  The long-term effect of LULC dynamics and climate change on the groundwater table was modelled using B-GIS. The primary input for the BGIS model was the groundwater recharge distribution map, the output from the SWAT model. A drastic decline in groundwater recharge is projected for the near future compared to the middle and far future. Among various scenarios analysed, a decline of approximately one to three meters in the average groundwater level is observed for the future worst-case scenario. In a nutshell, the study indicates that the groundwater resources in the study area are at risk due to climate and LULC changes.