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Parts of Tumkur District, Karnataka
Background Information
The average annual rainfall in the area is around 670-680 mm, with most of the rains occurring during monsoon.
The mean maximum temperature is around 30°C and the mean minimum temperature around 20°C. The annual potential evapotranspiration is over 1500mm with monthly rates of around 100 mm in November and over 160 mm in March.
The watershed has an undulating terrain forming gentle to moderate slope towards north:
The general ground elevation is around 850 m in the southern part of the watershed, with the highest elevation at 941 m.
The lowest elevation of 720 m is in the northern part of the watershed.
The southern boundary of the watershed forms the surface water divide between the Cauvery and Krishna basins.
The watershed is drained by 1st to 4th order streams. The drainage is dendritic with flow direction from south to north. It ultimately forms the Tore halla stream. The drainage is part of Vedavati sub-basin of Krishna basin. The area forms part of the watershed 4D3D8.
Figure 2.7: Drainage Map
Geomorphologically, the area is divided into two by a NW-SE oriented ridge formed by schist rock formation. On either side of the ridge, plain land is formed by the gneisses (see map below).
Figure 2.8: Land form map.
The study area is mainly covered with rock outcrops and fertile soil. The types of soils found in the area are Clayey, Clayey skeletal, Clayey mixed, Sandy clay, and Gravely clay (see soil map below).
The mixing of sand, clay and silt in different proportions influences the infiltration of water to the groundwater system.
Figure 2.9: Soil Map
Land Use
The land use and land cover map of the area indicates cultivated area as 52-63%, 4% is forest area and the rest is barren and/or used for human activities.
Agriculture is mostly represented by Kharif crop on the upland of the area and by plantations along the drainages, irrigated mainly by ground water.
Figure 2.10: Plantation along the stream / drainage courses.
Degraded forests occupy the southern parts of the study area and are formed on the schist rock formation. Surface water bodies correspond to the major drainages and show preferred orientation, indicating their structural controls.
Figure 2.11: Land use/ Land cover Map
Geologically, the area consists of rocks belonging to the Peninsular Gneissic Complex, schistose rocks of Sargur group, and Dharwar Super Group. The area is mainly occupied by migmatite granite gneisses, meta-basalts including ironstone and ultramafic complex rocks. It is criss-crossed by Younger intrusives (basic dykes). Small patches of Quaternary gravels are also observed.
The schistose rocks trend in NW to SE direction in the central portion of the area. Granites and granitic gneisses occupy the northern and southern part of the area.
Figure 2.12: Schistose rocks across the watershed exhibiting strike direction.
Figure 2.13: Stratigraphy of the area.
In the study area, four sets of lineaments have been identified, trending in NE-SW, NW-SE, N-S and E-W directions.
i. NE-SW oriented lineaments are mostly found in the western part of the area, generally in the hilly terrain formed by gneiss and schist.
ii. NW-SE oriented lineaments are abundant in eastern and southern parts of the area. These lineaments are generally traversing in gneisses.
iii. N-S and E-W oriented lineaments are very prominent in the central and western parts of the study area.
The lineaments which are confined to schist formations occurring in the eastern part of the area are attributed to good groundwater development potential.
Figure 2.14: Lineament map.