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Groundwater prospects analysis through hydrogeophysical parameters and hydrogeomorphic zonation - a case study in parts of Kewta Watershed, upper Barakar basin, Bihar
Relation between Hydrogeomorphic and Hydrogeophysical Properties
- Hydrogeomorphic and Depth of basement zones
Shallow buried pediments/ pediplain are supposed to have depth of basement/ cover material thickness less than 5 m. But depth of basement contours map shows that depth of basement is more than 5 m in some area (Table - 3) such type of variation is expected in hydrogeomorphic zonation. Out of total 1159.73 ha of deep buried pediplain (cover material thickness more than 15 m), 188.61 ha comes under the 5-10 m depth zone and 215.75 ha comes under the 10-15 m depth zone in basement contour map. Hydrogeomorphic zonation permits 1739.50 ha land whereas DBTM permits 1947.52 ha land suitable for dugwell development. The areal extent obtained through both the approaches has provided nearly similar results but class/ zone wise variation in areal extent exits in shallow buried pediment/ pediplain and deep buried pediplain. It has been observed that there is no distinct surface characteristic of sub-surface basins on the basement surface in remotely sensed data.
The moist river channels/ depressions identified in hydrogeomorphic map have relevance in groundwater development. These zones are getting enhanced recharge. Water table is shallow and seasonal fluctuation is less. Groundwater seepage also takes place in this zone. These zones have importance in shallow buried pediments / pediplain where groundwater prospects is poor. But these narrow and linear zones have not been resolved in DBTM due to lack of closely spaced field data set. In some parts of denudational hill, 5-10 m depth zone is passing. This is due to lack of sufficient ground control point taken into account in DBTM generation.
- Hydrogeomorphic zones and Hydrogeophysical parameters at depth of 11 m b.g.l.
The priority for groundwater development within the same hydrogeomorphic zone can be determined on the basis of variation of aquifer saturation at the depth of 11 m b.g.l. More than three priority classes exits within the individual hydrogeomorphic zone (Table - 3). In moderately buried pediment (midland) - 43.46 per cent, shallow buried pediplain - 97.53 per cent, shallow buried pediplain (midland) - 90.91 per cent, moderately buried pediplain - 47.09 per cent, moderately buried pediplain (upland) - 91.25 per cent, deep buried pediplain - 38.91 per cent of lands are not to be utilised for groundwater development. Lateral variation of aquifer saturation at 11 m depth does not permit entire land of same hydrogeomorphic zone suitable for sustainable utilisation of groundwater through dugwell. Based on integration of hydrogeomorphic and lateral aquifer saturation, 1879.59 ha land is not to be used for groundwater development. Hydrogeophysical parameter of deep buried pediplain indicates that top 10 m cover material consists of silt -clay and potential aquifer material (weathered) lies below this layer. Therefore effective utilisation of groundwater is possible only when depth of dugwell will go beyond the depth of silts-clay layer i.e. more than 10 m b.g.l.
Conclusion
It has been observed that hydrogeomorphic approach for groundwater prospects analysis is not a complete process. Hydrogeomorphic zonation coupled with DBTM and hydrogeophysical property of aquifer has helped in further delimiting the groundwater prospects zone. Similarly DBTM has not resolved narrow moist depression channel but it has been clearly mapped through remotely sensed data. The integrated outcome seems are more realistic as it has looked into the 3-D aspects of aquifer. Even the present study should not be treated as complete and it can be further improved if more and more well distributed field inputs i.e. porosity, yield, transmissivity etc. will be incorporated in analysis.
Acknowledgments
Authors are thankful to Prof. D. P. Singh, Project Director, Bihar Council on Science and Technology, Patna for giving constant encouragement for research work. Authors are thankful to Deptt of Science and Technology, Govt. of India for providing financial assistance to the project.
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