Remote Sensing Application Centre, IGSC- Planetarium, Patna – 800 001, India
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.
- Digital Basement Topographic Model ( DBTM )
To understand the unconfined aquifer geometry , hydro-geophysical parameters derived with the help VES data has been used as inputs to the Terrain Modeling Program and Digital Basement Terrain Model has been generated ( Fig. 1 ). In the present study, 200 ohm-m surface has been assumed as basement surface based on correlation with available drilling litho-log.
- Analysis of Hydro-geophysical Parameters at 11 m Depth
Depth of majority of dugwell are in between 9 – 11 m b.g.l. Keeping in view of local practices, variation of aquifer hydro-geophysical parameter at depth of 11m has been analyzed in sub-basin perspective. This has helped in categorizing the entire area into different groundwater development feasibility classes. It has given fairly accurate information for planning sustainable development of groundwater through dugwell.
- Estimation of Replenished Groundwater Reserves
In hard rock area, groundwater reserves are generally estimated on the basis of National Ground Water Estimate Committee norms ( Battacharya, 1990). Parameters selected for the calculation are as follows : Normal rainfall = 1200mm , Natural recharge = 10% of total precipitation ( Athawale et.al. ), Irrigation requirement = 0.40m (CGWB norms), Drinking water requirement = 40 liters per head ( PHED norms).
- Estimation of Aquifer Volume and Groundwater Reserves
In reality, aquifer material lying below the lower extreme of water table ( taken as 10 m b.g.l ) up to the basement surface is also storing utilisable groundwater. But it is rarely estimated. Due to uncertainty about the basement topography, realistic estimation are generally not being carried out. The utilisable groundwater reserves can be estimated if volume of aquifer material is known. In present study volume of aquifer has been calculated with the help of DBTM. Total volume of groundwater stored in aquifer material has been estimated by multiplying average aquifer porosity to the aquifer volume.
In study area, total average porosity of the aquifer has been assumed from the information available from other parts of the country under similar geological setting ( Karanth, 1994 ). The total volume of available groundwater within the aquifer has been further categorised on the basis of computation of effective porosity or specific yield. The retention porosity has been computed on the assumption that replenished groundwater is stored due to effective porosity of aquifer.
Outputs of the Project and its Application
Digital Basement Topographic Model ( DBTM )
At least 17 sub-surface basins ( Fig 1a-c )have been identified which show anomalous depth of basement. These sub-surface basins and overall regional basement topography has helped in understanding the Aquifer Storage and Recovery ( ASR )/ Artificial Recharge and Retrieval ( ARR ) area. DBTM is also useful in identifying recharge area and storage of recharge in sub-surface basins in much more convenient way. The approach/ methodology seems to be rapid and cost effective. The DBTM ( Fig 1 a-c ) has provided regional variation of aquifer which is essential for groundwater development and management in watershed perspective. DBTM and its correlation has shown that the approach/ methodology adopted in this project can optimised the process of groundwater exploration in hard rock area. The methodology/ approach has further improved the accuracy and authenticity of the groundwater exploration. The missing parameter’s of single planer feature i.e. remotely sensed lineament can be fulfilled through DBTM.
Sustainable Development of Groundwater
Based on water-table, depth of weathered material & its saturation, generalised yield prospects and analysis of hydro-geophysical parameters at depth of 11m helped in identifying the area most suitable ( 1346.00 ha. i.e. 6.36 per cent of sub-basin), suitable ( 4666.40 ha., 22.05 per cent ), marginally suitable ( 4298.20 ha., 20.30 per cent of the sub-basin ) and area not suitable( 9053.80 ha., 42.80 per cent ) for groundwater development through dugwell ( Fig. 2 & Table – 1 ) . Most suitable zone is a area where large scale dugwell development is possible without adversely affecting the regional groundwater resources. In the suitable area stress should be given on development surface water harvesting structures besides development of groundwater. Similarly in marginally suitable area more stress should be given on development & utilisation of surface water resource and groundwater development should be given lowest priority. Similarly in the area not suitable for groundwater development, stress should be given for 100 per cent utilisation of surface water. This zone can also act as recharge zone in regional perspective.
Table – 1: Feasibility for Dugwell Development
Category Lapasiya Watershed (ha.) Churchu Watershed (ha.) Alaunja Watershed (ha.) Total to sub-basin (ha.) Per cent Most Suitable zone 1203.70 0100.00 0042.20 1345.90 06.36 Suitable zone 1612.00 3000.00 0054.37 4666.40 22.05 Marginally suitable zone 0820.30 1582.00 1895.93 4298.20 20.31 Not suitable zone 3036.80 3000.00 3017.00 9053.80 42.80 Data gap 1791.52 – – 1791.52 08.46
Similarly area suitable for dugwell cum borewell has been identified which has been further cateogrised into different prospect zone ( Fig. 3 & Table – 2 ) i.e. most suitable ( 664.30 ha., 3.08 per cent ), suitable ( 5446.50 ha., 25.33 per cent ) and not suitable zone ( 13652.90 ha., 63.28 per cent ). The development as per feasibility map will reduce the chance of over exploitation of groundwater in area where aquifer is not suitable for dugwell cum borewell development.
Table – 2: Feasibility for Dugwell cum Borewell Deveopment
Category Lapasiya Watershed (ha.) Churchu Watershed (ha.) Alaunja Watershed (ha.) Total to sub-basin (ha.) Per cent Most Suitable zone 0510.50 0110.50 0043.30 00664.30 03.08 Suitable zone 3383.80 1251.70 0830.00 05465.50 25.33 Marginally suitable zone – – – – – Not suitable zone 2778.50 6247.40 4627.00 13652.90 63.28 Data gap 1791.52 01791.52 08.46
- Deep borewell
Based on DBTM and hydro-geophysical parameters, total 28 deep borewell sites have been identified which is supposed to provide sustainable yield without affecting the regional groundwater environment. Most of the sites are located in the broader fracture zones or in the sub-surface basins where high recharge to the aquifer is expected.
Groundwater Development and Management Possibility
In the entire Siwane sub-basin ( 19672 ha ), 2006 ha.m replenished utilisable groundwater reserves are available out of which a sum of 867 ha.m is already utilised for domestic need and providing irrigation to the rabi crops ( Table – 3 ) . The remaining groundwater reserve has potential to provide irrigation to 2278 ha ( 16 per cent ) area of sub-basin. Besides that huge amount ( 4061 ha. m ) of groundwater reserves lies below the existing dugwell depth ( i.e. 10 m b.g.l. ) and basement surface. This untapped groundwater reserve has potential to irrigated 10152 ha. ( 44 percent ) land of the sub-basin ( Table – 3 ). But this untapped groundwater reserves can only be utilised when suitable recharge mechanism will be developed for balancing the intake and outtake from the aquifer.
|Lapasiya watershed||Churchu watershed||Alaunja watershed|
|A||Area of watershed ( ha ), (under consideration)||6672||7500||5500|
|B||Aquifer effective porosity / specific yield (per cent)||2.50||2.86||3.00|
|C||Replenished groundwater reserve ( ha. m )||800||900||660|
|D||Utilisable groundwater reserves ( ha. m )||680||765||561|
|E||Drinking Water Requirement ( ha. m )||69||72||43|
|F||Existing utilisation of groundwater for irrigation purposes||252||274||158|
|G||Unutilised groundwater reserves||359||419||360|
|H||Irrigation potential of un-utilised groundwater reserves (ha)||718||838||720|
|H.1||Volume of aquifer material between two extreme of water table i.e. 5 – 10 m b.g.l. ( ha. m. )||37600||35269||25589|
|H.2||Volume of aquifer material below 10 m b.g.l up to basement surface ( ha. m )||88546||41362||22171|
|H.3||Utilisable groundwater reserve lying between 10 m b.g.l. up to basement surface ( ha. m )||2214||1182||665|
|H.4||Irrigation potential of available groundwater reserves below the 10 m b.g.l ( ha )||5535||2364||1330|
Prioritisation of Groundwater Developments and Management
It has been observed that all the three watershed under consideration have different groundwater development potential. The Lapasiya watershed located in the upper portion of the Siwane sub-basin, have greater potential for development and utilisation of groundwater in comparision to the other watershed. Lower reaches Alaunja watershed has lowest potential for groundwater development. Therefore highest priority for groundwater development and management should be given to Lapasiya watershed, and there after Churchu and Alaunja watershed. Groundwater development and utilisation in Churchu and Alaunja watershed should be carried out strictly according to the feasibility map prepared for large scale development of dugwell and dugwell cum borewell. Keeping in view of the expected over utilisation and its consequence on the groundwater environment, surface water harvesting structures sites have been planned in such a manner that it will also contribute to groundwater recharge.
Research Gaps and Future Line of Research
Present natural recharge estimation based on National Ground Water Estimate Committee of CGWB are not providing realistic picture.There is need for site specific natural recharge estimation. Representative sites may be located on the basis of remotely sensed data. Measurement in each hydro-geomorphic unit is required to get better results.
Geophysical electrical resistivity technique may further be refined for estimating the site specific aquifer porosity and yield estimation.
In present study groundwater reserve has been estimated on the basis of total average porosity. Estimation can further be improved if site specific porosity data will be incorporated in the calculation.
Groundwater losses due to seepage in unconfined aquifer system of hard rock needs attention.
There is need for field level experimentation for knowing the relation between artificial recharge process and sub-surface basins derived from DBTM.
There is need for developing dynamic groundwater model for predicting and forecasting the groundwater environment under changing intake and out take from the aquifer. For this purpose huge database on different parameters are required i.e. porosity, permeability, yield, rainfall, recharge, flow, seepage, withdrawal, aquifer geometry etc. DBTM may be used as one of important inputs to the Dynamic Groundwater Model.
- AIS & LUS ( 1988 ). Watershed Atlas of India, All India Soil and Land Use Survey, New Delhi.
- Athawale R. N. ( 1984 ). Nuclear tracer techniques for measurement of natural recharge in hard rock terrains. Proc. Int. Workshop on Rural Hydrogeology and Hydraulic in Fissured Basement Zones held at University of Roorkee, pp 71-80.
- Bhattacharya B. B. ( 1990 ). Hydrogeology and Groundwater Resources of Hazaribagh District, Bihar. Unpublished Report, CGWB, Eastern Region, Calcutta.
- Karnath K. R. ( 1994 ). Groundwater assessement, development and management, Tata McGraw Hill Publishing Company Limited, New Delhi.
- Kumar Ashok ( 1997 ). Natural Resource Management for Sustainable Utilisation and Management of Water Resources in Siwane sub-basin, Hazaribagh, Bihar, DST Project Report ( ES/011/212/95 ), BCST, Patna.
- Kumar Ashok, Sinha Ranjan and Prasad B. B. ( 1997 ). Digital Basement Terrain Modeling ( DBTM ) – A tool for sustainable utilisation and management of groundwater in hard rock area. National conference on emerging trends in development of sustainable groundwater sources held at Hyderabad from Aug. 17-28. JNTU.