Indravati-Kolab basins of Koraput as potential ground water reservoirs of the puranas in Orissa

Abstract

The Indravati-Kolab (Sabari) basins of Koraput district in Orissa (India) continue with the identical basins of the same name downgradient in Bastar district of the Chhattisgarh region of Madhya Pradesh. The sandstones, quartzites, and conglomerates of the Purana sequence are poor and problematic aquifers with occasional networks of four or more joints, including a master joint. Such networks of joints extend in depth to 30- 60 m. The Kanger calcic limestone is flaggy, but the Jagdalpur magnesian stromatolitic limestone is heterogeneous, resulting in classic development of karst in the Indravati-Kolab basins of Koraput district. With average rainfall in the range of 170-190 cm, wells in the micro- alluvial valleys and karst often are limited to 12 m in depth. Individual tubewells, 90 m deep, are capable of yielding 5-8 L/sec for a drawdown of 6 m, the piezometric zone being 4.5-15 m below ground level. The specific capacity ranges from 50 to 150 L/min/m of drawdown and yield potential is 150-300 cu m/day for a drawdown of 5-10 m, when developed under strict hydrogeologic control. The hydraulic conductivity ranges from 5-10 m/day and the specific yield is 3-8%, with a spacing pattern of 250 m. Laterites, although of limited extent, are of great significance from the point of view of the occurrence of seeps and springs in the highland areas and the richness of the groundwater potential. (See also W91-03311) (Rochester-PTT) .