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Groundwater management and planning for siwane sub - basin in Hazaribagh district, Bihar
Ashok Kumar Remote Sensing Application Centre, IGSC- Planetarium, Patna - 800 001, India
Introduction
A project titled " Natural Resource Management for Sustainable Utilisation of Water Resources in Siwane Sub-basin, Hazaribagh under NRDMS scheme of Deptt of Science & Technology has been implemented by Bihar Council on Science & Technology, Patna with main objective to map / explore the various natural resources i.e. surface water, groundwater, land and soil. The thematic and spatial data has been analysed in the GRAM GIS environment for sustainable utlisation and management of groundwater. The study area is located in the upper reaches of Siwane sub-basin ( Latitude 240 0' - 240 10' and Longitude 850 15' - 850 30' ) . It falls on the Hazaribagh upper plateau and its northern & western limit are scarp zone of Hazaribagh upper and lower plateau. Topography is undulating in nature and geomorphologically it has been categorized as buried pediplain. Geologically area is part of Chotanagpur granite gneiss complex. The elevation varies from 540 - 620 m. Area receives 1000 - 1200 mm average rainfall. Its geographical area is 23000 hectares and administratively falls under the Katkamsandi, Hazaribagh, and Ichak blocks of the district. Entire study area has been divided into three watershed i.e. Lapasiya ( 8500 ha ), Churchu ( 8414 ha ) and Alaunja ( 6700) . Based on AIS&LUS watershed atlas. At present the area is mono-cropped ( aghani & kharif crops ) with limited rabi crops ( 7 per cent of the sub-basin ). Available rainfall is more that sufficient to sustain agriculture & household needs. But area still faces drought like condition even monsoon fails for a year. . Aquifer is unconfined to semi confined in nature and groundwater occurs under the water table condition. Aquifer is also not suitable to withhold sufficiently large percentage of rainfall as groundwater and only 5-10 per cent of total rainfall contributes to the groundwater. Due to unconfined aquifer system in the area further promotes time varying continuous decrease in water-table after the end of monsoon even there will not be any withdrawal from aquifer. To understand the groundwater storage and retrieval, aquifer geometry, porosity and permeability are the important parameters to be analyzed. In groundwater exploration besides routine geo-hydrological investigation, electrical resistivity ( VES ) exploration and remote sensing techniques are frequently used. The inputs generated from schematic survey through VES provides opportunity to analyse the 3-D aspects aquifer and broad fractures system. Need of the Project For optimal utilisation and management of the limited groundwater reserves, to meet increasing demand for supplementary irrigation & domestic need and also for accelerating the existing recharge phenomenon in the watershed, detailed information for basement topography, aquifer geometry and fracture systems are essential. The approach adopted for deriving above information, has been termed as " Digital Basement Topography modeling (DBTM). This has helped in understanding groundwater storage & retrieval system for sustainable utlisation of groundwater in close relation with surface water. The over all objective of the study was to provide scientific database for sustainable utilisation & development of groundwater and surface water. Estimation of groundwater reserve of entire aquifer system is essential for sustainable planning of utilisation and development of groundwater. Present planning process only looks into utilisation and development of replenished groundwater. Utilisation of groundwater, beyond the limit of replenishment, will create imbalance in intake and outtake to the aquifer and it will result into depletion of water table. The increased utilisation can be supplemented from utilisable groundwater available in aquifer between dugwell base and basement surface. For this, proper mechanism has to be developed to increase the recharge to the aquifer so that the balance between intake and outtake to the aquifer can be maintained. At present only 5-10% of annual rainfall is contributing to the groundwater through natural recharge process. Further, due to unconfined aquifer system, nearly 40-60 % of the total annual natural recharge gets lost through nala/ drainage channel. Therefore there is need to utilised the available reserves before it get lost as seepage or check the seepage loss through appropriate method. To meet the increased demand beyond the replenished limit, groundwater recharge is to be increased by accelerating the existing recharge process.
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