Geology Reference
In-Depth Information
area in case of percolation tanks with gross storage capacity varying from
71 to 220 thousand cubic metres (TCM) varied from 60 to 120 hectares (ha)
during 1997-98 and benefits extended up to 1.5 km down stream of percolation
tanks. In case of cement plugs with storage capacity varying from 2.10 TCM
to 7.42 TCM varied from 3 to 15 ha during 1997-98.
Alluvial Aquifers Bordering Mountain Front—Maharashtra
The prominent regional aquifer system for Tapi Alluvial basin paralleling
Saturn Mountain front is being extensively developed to meet the water
requirement of cash crops like banana and sugarcane. This has led to decline
of water levels by more than 8-10 metres during last 10-15 years. Large
number of wells have either gone dry or their yields have declined. The
Central Ground Water Board carried out artificial recharge studies in TE-17
watershed in Jalgaon district. The sub-surface storage potential of watershed
five metres below ground level was assessed as 85 million cubic metres
(MCM) compared to surplus monsoon runoff of 29.7 MCM. Artificial
recharge techniques like recharge through percolation tanks, recharge through
existing dug-wells, recharge shafts and through injection tubewells were
experimented. Percolation tanks in Bazada formation of Saturn foothills were
found to be highly efficient with efficiency as high as 97% and capacity
utilization going up to 400%. The zone of benefit extended to 5 km with
benefited area up to 400 ha.
Percolation Tanks in Hard Rocks in South India
Artificial recharge by percolation tanks is an ancient practice of water
conservation especially in the hard rock terrains of India. Hundreds of such
tanks are constructed every year in drought prone areas to augment
groundwater recharge from permeable river beds by constructing check dams/
dykes. Rate of infiltration from these tanks depend on local hydrogeological
conditions, topography and storage characteristics of the tank. Studies in
granites and basaltic terrains of South India indicate that the rate of recharge
from percolation tanks vary from 9 to 12 mm/day. The rate of infiltration
decreases with time due to silting. In ephemeral and seasonal streambeds,
recharge rates are comparatively high due to the reworking/removal of silt
during the dry period. Evaporation losses from the tanks are also high, being
about 4 to 6 mm/day (Muralidharan and Rangarajan, 2001).
Coastal Area—Saurashtra, Gujarat
After detailed hydrogeological surveys and groundwater draft estimation,
artificial recharge through pressure injection and surface spreading methods
was experimented in the alluvial area around Kamliwara in the Central
Mehsana. Source water for the test was drawn from the phreatic aquifer
