Geology Reference
In-Depth Information
19
Hydrogeology of Hard Rock
Aquifer in Kashmir Valley:
Complexities and Uncertainties
G. Jeelani
Department of Geology and Geophysics
University of Kashmir, Srinagar, India
INTRODUCTION
Groundwater occurs in varied geological formations. Its occurrence in
geological system is controlled mainly by the lithology (porosity and
permeability) and structure (fractures, faults, dykes). The unconsolidated
sediments referred to as continuous media, although vulnerable to
contamination under shallow conditions, always form important source of
water due to appreciable porosity and permeability. However, the water
supply from these aquifers is dwindling worldwide due to overexploitation,
global warming, easy exploitation, poor management etc. As the demand of
freshwater exceeds rapidly than its renewal, the groundwater levels have
gone down rendering a good number of wells dry. Hard rocks can also be
good aquifers only if the secondary porosity is developed in the form of
fractures or solution cavities and/or weathering. Fortunately all consolidated
subsurface rocks are fractured to some degree with a scale ranging from
microcracks to crustal rifts (Bonnet et al., 2001). The fractures generally
increase the hydraulic conductivity of the rocks if the discontinuities are
more permeable than the parent rock. Sometimes fractures may form barriers
to flow if the contained material is less permeable than the host rock.
Geological formations with fractures, solution cavities and large openings
are referred to as discontinuous media. The occurrence, exploration and
exploitation of groundwater in these media continue to intrigue and challenge
hydrogeologists (Narasimhan, 2005) due to very high heterogeneity and
anisotropy. Karst is commonly considered as the result of the solution process
of carbonate rocks, viz., limestone and dolomite (Bakalowicz, 2005).
Generally, fractured media do not constitute highly productive aquifers due
