the evaluation of groundwater potential
The relationships among the factors, i. e. , lineament, slope, groundwater depth, rainfall/runoff, urban storm water logging, land use/land cover, soil texture and drainage density, were weighted according to their response for groundwater occurrence. High to low weight showed larger to smaller impact on groundwater potential respectively. Integration of these factors with their potential weights was computed through weighted overlay analysis in GIS environment to determine groundwater potential zones. Surface runoff and infiltration rate greatly depend on Slope or gradient which is also important factor of suitability of groundwater recharge i. e. higher slope would produce a higher runoff and less recharge. Slope in the study area ranged from 1 to 37%, as per IMSD Guidelines (NRSA, 1995) categorized into 5 classes i. e. 0-1. 00% (nearly level), 1. 01-4. 00% (very gently sloping), 4. 01-8. 00% (gently sloping), 8. 01-16. 00% (steep), and >16% (moderately steep)
Incline class having higher worth is designated lower rank due to fairly high runoff while the class having lower value is definitely assigned higher rank because of flat surface (Jhariya et ‘s. 2016). An additional input to evaluate the recharge property could be realized by detailed morphometric analysis in the drainage network. The density of the draining network impact on the groundwater recharge and movement as well as the occurrence of lineaments, problems, fractures, main or minor joints, and in addition provides route ways pertaining to groundwater activity and is hydraulically very important as it is an important indicator of normal water percolation price (Kumar et al. 2007)Edet et ing. 1998, Shaban et ‘s. 2006). Denser the draining network benefits usually the less charge rate. The extraction and analysis of the drainage network was well prepared from topographic maps, discipline data and satellite pictures. Drainage densities were determined in all the grid sq . following Murthy (Murthy 2000): Drainage density= LWS/AWS (3)Where, LWS sama dengan total period of streams in watershed and AWS = area of the watershed. Thus, the obtained drainage density map reveals thickness value starting from 0 to 51. five km/km2, reclassified into five categories my spouse and i. e.
From charge point of view, even more weightage was assigned to very low draining density regions, whereas, low drainage densities indicate large permeable surface stream consistency of the region compare to the high draining density i. e., impermeable ground surface/rock formation. With respect to the groundwater events, the higher drainage density relates to less infiltration of water to the earth and develop higher runoff. The ground water table was collected via Chittagong Hydrant and Sewerage Authority (CWASA), the static water level was obtained by subtracting the elevation of water interesting depth of different conduit well in 2016 and the groundwater depth map was well prepared. Then the attained depth of water level ranged between 18. 28m to 134. 11m and the study area have been categorized into 5 classes i. e. 18. 28-28. 34m since very shallow groundwater desk, 28. 35-45. 23m because shallow groundwater table, forty-five. 24 -64. 00m because moderate groundwater table, 64. 01-99. 09 m because deep groundwater table and >99. 10m as very deep groundwater table (Fig. 3 c). Wells with deeper drinking water levels during dry season indicates at considerable normal water extraction this really is a favorable internet site for boost. Thus, large score value was given intended for deeper water level (Duraiswami et al. 2009).
Lineaments influences the movement and storage of groundwater, to analyze the lineament with different spectral bands RS and GIS technique were applied. Lineament-length density is definitely obtained by the total period of all noted lineaments had been divided by the area under study pursuing Greenbaum (Greenbaum 1985). Lineament are extracted and then getting lineament denseness map simply by ArcGIS 10. 1 . Groundwater potential is definitely high around lineament area zones. The lineament denseness in the examine area as shown in Fig. 3 d is usually categorized in 5 classes i. at the. 1 . 91 kmkm2 while very high denseness. Runoff of the study place was predicted precipitation information for the Patenga stop using Hydrologic Engineering Center”Hydrologic Modeling System (HEC-HMS) v4. 0 model and the relevant input data for all 41 wards had been processed using Geospatial Hydrologic Modeling Extendable (HEC-GeoHMS) versus 5. 0. The details around the model installation can be found in Akter and Ahmed (Akter Ahmed 2015). The estimated space distribution of annual runoff ranging from several. 34-3. 49 m to get per year in the study area. The interesting depth is labeled into five classes we. e. three or more. 34-3. 38m, 3. 381-3. 43m, 3. 431-3. 51m, 3. 511-3. 55m and 3. 56-3. 58m
During rainy period, this kind of city experience urban thunderstorm water visiting as well as a few parts usually inundated due to tidal result. The details upon water logged locations plus the amounts were obtained from Akter et al. (2017) along with field data. For weighted common a minimum worth (0. 01m) was used available vulnerable areas. The water logging depth may differ between zero. 01 to 1. 828 m and the examine area is usually categorized in to five classes i. elizabeth. >0. 01m, zero. 011-0. 3088m, 0. 3089-0. 6096m, zero. 6097-1. 2192m and 1 . 2193-1. 828m. Land use/ land cover maps were prepared coming from RS data using closely watched classification in ERDAS IMAGINE software with field confirmation. The whole place were grouped into unwelcoming land, accumulation area, vegetation and normal water body (Fig. 3g). Drinking water bodies are continuous and excellent way to obtain recharge of groundwater. Consequently , water bodies were assigned highest weight for groundwater potential. The agricultural domains with enough vegetation cover promote the infiltration price and prevent surplus runoff and, therefore , will be assigned substantial rank intended for groundwater prospecting.
The rate of infiltration is straight proportional to the density of vegetation cover, i. electronic. if the surface area is have dense forest, the infiltration will be more and the runoff will probably be less. As a result barren gets are given medium weightage. Built-up area are given very low weightage as the infiltration price is very low. An average worth of 5 meter interesting depth soil texture was obtained from the numerous boreholes of the specific ward. The soil feel of research area shows ten dirt texture types, clayey soil is dominating most of the areas. Soil ranking was performed based on all their infiltration rate, i. at the., sandy soil with excessive infiltration price assigned bigger priority beat less priority for the clayey. The principal objective of any man-made recharge job is to harvesting as much runoff water since available. As a result, the higher the runoff drinking water, the greater this particular availability to get recharge. Appropriately, areas having higher surface area runoff receive higher scores.
