Geology Reference
In-Depth Information
10
Groundwater Balance at the
Watershed Scale in a Hard
Rock Aquifer Using GIS
J.C. Maréchal, L. Galeazzi and B. Dewandel
Water Department, Unit “Water Resources, Discontinuous Media”
BRGM, Montpellier, France
INTRODUCTION
The high stress on ground water due to abstraction of large quantities of
water through pumping for irrigation threatens the sustainability of agricultural
development. This is mainly the case in hot and dry areas such as Hyderabad
where the aquifers are located in hard rocks.
Therefore, it is necessary to adapt the exploitation of ground water to its
availability. For that purpose, it is indispensable to have suitable tools able
to assess either the water balance of the aquifer or its renewable reserve.
In this paper, a methodology for water balance evaluation using
Geographical Information System is presented and applied to a study case.
The different flows from or to the aquifer are listed and analysed in order
to present a final spatial groundwater balance. The study area is a watershed
centred on the village of Maheshwaram in Ranga Reddy district, Andhra
Pradesh, India. The piezometric map of the aquifer indicates water level
depletion in areas with high concentration of pumping wells (Fig. 1).
COMPONENTS OF THE GROUNDWATER BALANCE
Flows are divided in two categories: in- and out-flows (Fig. 2). First ones
are flows coming in the watershed. They are positive and contribute to the
recharge of the aquifer. The second ones correspond to water leaving the
aquifer and contribute to the discharge of the aquifer.
Percolation flow (
INF
) from the ground to the aquifer through the soils
and rocks can be diffused (through the whole surface area), or can take place
at various specific places through preferential flows in cracks or fracture
zones and from specific structures such as water tanks, trenches, old brick
