Table 1 Landsat 8 band information used for the NDVI analysis. with groundwater (Table 2). All the thematic layers are inte- grated into the GIS domain, and assigned weight values are collectively summed for each class in the attribute table (Table 4). The groundwater zones are delineated into five dif- ferent classes according to the highest value gained as excellent groundwater potential zone and lowest gained value as nil or poor groundwater potential zone (Table 4). Table 2. Groundwater and infiltration weightage assigned to the individual class for a thematic layer (Manap et al., 2013). area in the watershed are particularly suited for rainfed crops like short-staple cotton, groundnut, jowar, and tur dhal. Soils in the region are found to contain a high concentration of sol- uble salts which are either critical for growth or critical for ger- mination. Clay, sandy clay, and silt clay are dominant soils and food crops are the major agricultural practice. Soil map can be prepared using the high resolution satellite images and along with extensive field data (Ismail and Yacoub, 2012). Available secondary maps from the National Bureau of Soil Survey and Land Use Planning (NBSS and LUP) Ban- galore and satellite images are used to map the soil types of the area (Fig. 3). Clay, sandy loam and sandy clay loam together covers 70% of the total land area. The soil depth varies from 25cm to 100 cm (Fig. 4). The gravelly sand soils possess more open spaces to fill the water than the compact clay or silt soils. The dry clay soil exhibits multiple cracks in the top layer that enhance rapid infiltration. However, the wet clay soil has more water holding capacity than the infiltration rate. The weight is assigned based on the texture and depth of the soil (Table 2). Figure 2. LULC classification map of Doddahalla watershed. Figure 3. Soil textures classification map of Doddahalla watershed. Table 3. Rate of soil infiltration in the different soil texture (Ibrahim-bathis and Ahmed, 2016). 3.6. Drainage density Table 4 Area statistics, weightage values and their corre- sponding rankings for Groundwater potential zone in Dodda- halla watershed. Figure 4 Soil depth map of Doddahalla watershed. Figure 5 Soil infiltration pattern map of Doddahalla watershed. Figure 6 Annual rainfall map of Doddahalla watershed. Figure 8 Drainage density map of Doddahalla watershed. Figure 7 Slope map of Doddahalla watershed. Figure 9 Lineament density map of Doddahalla watershed. For mapping groundwater prospect zones individual thematic maps are prepared from the satellite data, toposheet, field sur- vey and available secondary data. A thematic map classified into different subclasses, and each is assigned a weight value according to the interrelationships between the occurrences Groundwater potential zone map is essential for the agricul- tural watershed like the Doddahalla watershed. Rainfall is irregular, and the area is not well irrigated from canals or channel irrigation. There is no perennial water reservoir or tanks to supply water for agriculture throughout the year. Hence, the farmer is forced to drill wells for the crop irrigation and domestic water purpose. Mapping groundwater prospect zones is a systematic effort and prepared by considering signif- icant governing factors, which influence soil infiltration and enhances groundwater. The present groundwater prospect map satisfies and exposes the meaningful information and best site for the groundwater exploration (Fig. 11). Thick vegeta- tion, tree plantation, and agricultural field are given high weight in the land use theme. Water penetrates to the ground through the roots of trees and plants. Weathered pediplain and Figure 10 Geomorphology map of Doddahalla watershed. Figure 11. Groundwater potential zone map of Doddahalla watershed.
