Relationships between factors, such as lineament, slope, groundwater depth, precipitation/runoff, urban stormwater runoff, land use/land cover, structure soil and drainage density, were weighted based on their response to the presence of groundwater. High to low weight showed greater or lesser impact on groundwater potential, respectively. The integration of these factors with their potential weights was calculated through a weighted overlay analysis in a GIS environment to determine the potential groundwater zones. Surface runoff and infiltration rate are highly dependent on the slope or gradient which is also an important factor in the suitability of groundwater recharge, i.e. a steeper slope would produce greater runoff and less recharge. The slope in the study area ranged from 1 to 37%, according to IMSD guidelines (NRSA, 1995) classified into 5 classes, i.e. 0-1.00% (near level), 1.01-4.00 % (very gentle slope), 4.01-8.00% (slightly sloped), 8.01-16.00% (steep) and >16% (moderately steep). Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get Original Essay The class with slope having a higher value is assigned a lower rank due to the relatively high runoff while the class with a lower value is assigned a higher rank due to the flat surface ( Jhariya et al. 2016) . Another input to evaluate the recharge properties can be obtained through a detailed morphometric analysis of the drainage network. The density of the drainage network influences the recharge and movement of groundwater, as well as the presence of lineaments, faults, fractures, major or minor joints, it also provides pathways for the movement of groundwater and is very important hydraulically in as it is an important indicator of water level. percolation rate (Kumar et al. 2007) Edet et al. 1998; Shaban et al. 2006). The denser the drainage network, usually the lower the recharge rate. Drainage network extraction and analysis was prepared from topographic maps, field data and satellite images. Drainage densities were calculated in each of the grid squares following Murthy (Murthy 2000): Drainage density = LWS/AWS (3) Where LWS = total length of streams in the catchment and AWS = catchment area. Therefore, the obtained drainage density map reveals density values between 0 and 51.5 km/km2, reclassified into five categories, i.e. < 2.00 km/km2 as very low, 2.01-10.00 km/ km2 as low, 10.01-20.00 km/km2 as moderate. , 20.01-30.00 km/km2 as high and 30.01-51.5 km/km2 as very high drainage density. From a recharge perspective, greater weight was assigned to regions with very low drainage density, while low drainage densities indicate a high frequency of permeable surface flow compared to high drainage density, i.e. impervious surface of the terrain/rock formation. For groundwater, greater drainage density correlates with less water infiltration into the soil and produces greater runoff. The groundwater table was collected from Chittagong Water Supply and Sewerage Authority (CWASA), the static water level was obtained by subtracting the water depth elevation of different tube wells in 2016, and the water depth map was prepared groundwater. So the obtained depth of water level ranged between 18.28 m to 134.11 m and the study area was classified into 5 classes i.e. 18.28-28.34 m as groundwater table.
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