Analysis of hydrogeophysical properties of aquifer and reserve estimation for sustainable development of Groundwater in Kewta Watershed, Hazaribagh
Ashok Kumar, Savita Tomar, L. B. Prasad and B. B. Prasad
Remote Sensing Application Centre, IGSC-Planetarium, Patna-
800001, India
Abstract
In unconfined aquifer system of hard rock terrain ground
water occurrence mainly depends upon thickness of weathered material, its
physical and chemical composition and its saturation. Relative geomorphic
location of aquifer and basement topography also plays important role. Basement
topography helps in understanding the aquifer storage and retrieval system. Due
to unconfined nature of principal aquifer, seepage loss through channel also
needs attention. Precipitation and agro-climatic situation also governs the
aquifer system behavior. Therefore multi-layer information is required for
sustainable utilisation and development of groundwater.
In present study hydrogeophysical parameters generated from
vertical sounding, geohydrological, inferred fractures and geomorphic zones
derived from remotely sensed data has been analysed in Kewta watershed of upper
Barakar Basin, Hazaribagh. The study area is part of lower Hazaribagh plateau
and is part of pediplain developed over Chotanagpur granite gneiss and meta-
sedimentary. Study area falls between latitude 240 09' - 240 13' and longitude
850 20' - 850 28'. Topography varies from 600 - 450 m.s.l. In study area
electrical resistivity survey ( VES ), remote sensing and routine
geohydrological studies have been carried out. DBTM has also been prepared to
understand the aquifer storage and retrieval system. Attempt has been also made
to estimate the groundwater reserves of entire aquifer system Various spatial
and non-spatial data base related to groundwater has been analysed in GRAM++
window based Geographic Information System ( GIS ) for planning and management
of groundwater.
Result indicates that there are numerous sub-surface basins/
underground reservoirs, which can be used for groundwater storage and retrieval.
Reserve estimation indicates that entire aquifer has storage capacity to
irrigate 50 per cent geographical area of watershed. But present replenished
groundwater reserve has potential to irrigate only 30 per cent of the
geographical area of the study area and it has not been fully utilised. With the
help of DBTM, old river channel has been also traced out.
Introduction
In the study area, principal aquifer system is unconfined in
nature and groundwater occurs under the water table condition. The unconfined
aquifer system permits time varying continuous decrease in water table after the
end of monsoon even without withdrawal from the aquifer. For optimal development
and utilisation of the available groundwater reserves, detailed information for
basement topography, aquifer geometry and fracture systems are essential. These
parameters will help in understating groundwater storage & retrieval system.
Estimation of groundwater reserve of entire aquifer system is essential for
planning utilisation and development of groundwater. Existing conventional
planning process only looks into utilisation and development of replenished
groundwater and its utilisation beyond the limit will create imbalance in intake
and outtake to the aquifer. Utilisable groundwater reserve is also available in
addition to replenished reserve between dugwell base and basement surface. For
its utilisation, proper recharge mechanism has to be developed so that the
balance between intake and outtake to the aquifer can be maintained.
At present only 10-12 per cent of annual rainfall is
contributed to the groundwater through natural recharge process. But at the same
time nearly 40-60 per cent of the replenished reserves gets lost as seepage in
nala / drainage channel due to unconfined nature of aquifer. There is need to
utilised the yearly-replenished groundwater reserves before it get lost. In case
we exceed the replenished limit, then recharge to the aquifer is to be increased
to that limit. For this purpose suitable sub-surface basins/ fractures system
are to be located so that additional recharge other than natural recharge may be
stored and optimally utilised.
Study Area & Physiography
The study area is part of ‘Kewta watershed’ of Upper
Barakar basin of Chotanagpur plateau of Bihar and is administratively a part of
Hazaribagh district. Geomorphologically, it is a part of Koderma plateau (Lower
Hazaribagh) of Bihar. It is located in between the latitude 240 09' - 240 13'
and longitude 850 20' - 850 28'. The southern fringe of the watershed is a scarp
zone of upper and lower Hazaribagh plateau and is limited between topographic
contours of 600 - 450 meters m.s.l. Area other than scarp zone is typical
undulating pediplain developed over granite gneiss. The regional slope of
pediplain is towards west with maximum height 450 meters in east and minimum 430
meters in the west. In the present study only pediplain area of Kewta watershed
has been taken into consideration and its areal extent is 2961 hectares.
Geohydrology
Weathered granite gneiss serves as principal aquifer in the
study area. Groundwater occurs under water table condition and aquifer is
un-confined / semi confined in nature. The geohydrological condition
predominantly permits utilisation of groundwater through dugwell. Dug-cum-borewell
and deep borewell is possible in limited area having thick weathered horizon or
fractured basement. Water table varies between 4 - 11 m b.g.l. The yield of
dugwell depends on the thickness of weathered and fractured horizon and nature
of aquifer material. In study area, dugwell depth normally does not go beyond 11
m b.g.l.. It has been observed that variation of water table in deeply weathered
zone is between 7 to 10 m. Seasonal fluctuation in water table is about 1 m. In
moderately weathered zone, water table varies between 4.5 - 7.5 m on uplands. In
this zone, there is less seasonal fluctuation in water table. In shallow
weathered zone, water table in the month of January is below 6.5 m on uplands
and less regional variation. But seasonal variation is between 3 - 4 m.