Abstract
Many developing countries experience widespread groundwater declination. Sustainable management actions include generation of an accurate groundwater distribution based on an extensive groundwater monitoring network which is often cost prohibiting in the context of a developing country such as Bangladesh. Further, such knowledge is lacking for the Sylhet region where groundwater was documented to be under tremendous pressure. Specifically, the gap in the current literature exists regarding groundwater trends and its areal extent for this region. This paper bridges the gap in research by focusing on trends and spatial and temporal variation of groundwater level changes for this area. This study addresses this problem by creating groundwater level predictions at the ungauged areas using geostatistical methods applied to a detailed set of data. In this study, the spatial variability of annual-average depth to the water table at 46 observation wells in the Sylhet division in Bangladesh is analyzed for 2000, 2005, 2010, and 2015. The geostatistical analysis applies the ordinary kriging method with cross-validation to create the water table maps for the study area. The results indicate a substantial increase in groundwater depths during the studied period from 2000 to 2015 in some locations in the study area. Importantly, this work identifies the vulnerable zones in the area due to the groundwater lowering trend. The study adds to the groundwater management research in developing countries and focuses on the spatial and temporal groundwater variation. The findings from the modeling exercise contribute to identification of the vulnerable areas and therefore help policymakers in making informed decisions to manage groundwater resources in this sensitive region sustainably.
Highlights
The groundwater system, which is very dynamic by nature, constitutes about 98% percent of the Earth’s freshwater (Zaporozec 2004)
This study investigates the depth to the water table throughout the study area
The ordinary kriging (OK) is a standardized type of kriging and known as the best linear unbiased estimator (BLUE) (Cressie 2015). This method assumes that the data sets are stationary and exploits semivariogram, which approximates the values without bias and least variance, to determine the best fit for the spatial relationship model (Cressie 2015)
Summary
The groundwater system, which is very dynamic by nature, constitutes about 98% percent of the Earth’s freshwater (Zaporozec 2004). The increasing demand due to population growth and rapid industrialization has rendered it vulnerable which especially concerning in developing countries where resources for sustainable groundwater management are scarce. Over-abstraction, poor irrigation management, Groundwater declination is a common and widespread problem in developing countries; Bangladesh is no exception. Irrigation and household water supply in the country primarily depend on groundwater. It is declining at a rate of 0.1 to 0.5 cubic-meter per year (m3/yr) in the country (Dey et al 2017). The country’s groundwater resource needs proper management actions for sustainability
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