Evaluation of spatio-temporal dynamics of water table in NW Bangladesh: an integrated approach of GIS and Statistics

Abstract

The aims of this study are to determine and evaluate the spatial and temporal changes in the groundwater table for the period of 1991–2009 and probable causes of changes of water table depth in northwest (NW) Bangladesh. Trends analyses have been done by linear regression, Mann–Kendall Trend Test and Sen’s slope estimator; and spatial analysis by Geographical Information Systems (GIS). The results show decreasing trends in dry and monsoon seasons and annual average groundwater level except a few discrepancies in NW Bangladesh, though the magnitudes of changes very spatially and methodically. Very strong declining trends with high magnitude of changes in all three series that are significant at 99 % confidence level found in the central part of the area where the rate of changes vary from 0.82 to 0.2 m/year in dry season, from 0.67 to 0.2 m/year during monsoon season and 0.6 to 0.1 m/year in annual average time series. Declining trends with low rate of changes are found in the rest of the areas except some pocket areas. The drop of groundwater level is also very high in the central part. Falling trends and drop of groundwater level indicate unsustainable withdrawal of groundwater over the study area. Findings of study indicate rigorous abstraction of groundwater for irrigation, decreasing trend in rainfall and surface geology of the area are attributed to rapid declining trend in groundwater level. Situations will be irreversible if necessary steps are not taken beforehand.