79
Where,
S
GW
= Volume change in groundwater storage
W
p
= recharge from precipitation infiltration
W
r
= recharge from stream lakes and other natural water bodies
W
i
= recharge by canals, distributaries and other irrigation works
W
as
= recharge from surface water applied for irrigation
GW
i
= Groundwater inflow
GW
b
= Groundwater discharge to streams and springs
GW
e
= Evaporation loss of groundwater from capillary fringe
GW
et
= Evapotranspiration loss of groundwater from phrentophytic
Vegetation
GW
e
= Groundwater extraction by pumping and flowing wells
GW
o
= Groundwater outflow
GWn = Other items, if any
The equation is valid for a basin where it is possible to determine the
parameters.
Indian Seanario
Prior to 1970s, the subject of groundwater was sidelined. Geological Survey of
India and Exploratory Tubewell Organisations were the only two organizations
engaged in groundwater studies. The entry of World Bank for financing
agricultural projects saw a quantum jump of groundwater utilization for minor
irrigation. Heavy duty tubewells and shallow tubewells were sunk in large
numbers. The Government of India was, however, not ready with basin wise
ground water assessment. In the initial years, only empirical methods of rainfall
recharge was used. With a view to control and keep track of the rapid
development, Government of India at the advice of the World Bank, opened
State Groundwater Organisations in most of the states. Besides, guidelines
were framed to calculate groundwater recharge and groundwater draft. The
guidelines were framed by a Committee constituted by the Government of India
with representative from State Governments and National Bank for Agriculture
and Rural Development. These committees, known as Groundwater
