The Rate of Decline and Trend Line Analysis of Groundwater underneath Dhaka and Gazipur City

Abstract

Groundwater is reported to account for 87% of all drinking water resources in Dhaka which has suffered a decline of up to 75 m in some specific location. Over-extraction of groundwater is an extensive social problem in Dhaka and Gazipur city which needs to be investigating thoroughly. This study presents the diagnosis of groundwater depletion pattern and the yearly rate of decline over the last three decades for Dhaka and Gazipur metropolitan area. Groundwater data were collected from the relevant institutions in order to analyse the trend line and the rate of decline of groundwater levels for more than 30 years period to understand the long-time variability. Ten individual stations datasets for GWL have been analyzed for Dhaka and Gazipur within a selected reference time period (1980-2012). The highest depleted GWL were found in the Mirpur station which is now 68 m below ground. To find out the time span when the depletion rate is highest, the rate of decline of all datasets has been computed which shows that 1998-2005 is the consecutive eight years time span with the fastest depletion rate. On the other hand, the annual trend-line analysis shows rapid depletion pattern after the year 2000.