Geology Reference
In-Depth Information
The fitting criteria were based on:
probable orders of magnitude of the fitting parameters; and
the similarity between the hydraulic heads observed in the project wells
in the field and the simulated ones.
Groundwater Balance
In 2000, the balance (storage variation) is negative (Table 2). The withdrawals
are greater than the recharge and the storage decreases. The pumping wells
are in operation at 99.9% of normal capacity. The discharge from the
prescribed head-boundaries is 1.3% of the recharge, which is negligible. The
overflows are nil.
For 2001, the balance is positive. The recharge is greater than the
withdrawals and the stock increases. The pumping wells are in operation at
99.7%. The discharge from the prescribed heads is 1.8% of the recharge,
which again is negligible. The overflows are 0.2% of the recharge, which is
also negligible. The aquifer overflows are located near the draining meshes,
which seems logical.
In 2002, the balance is strongly negative. The recharge is weaker compared
to the other years and the withdrawals have increased. The pumping wells
are in operation at 97.6%. But the return flow is calculated on the basis of
the maximum demand and not on the basis of the actual withdrawals; in this
case, because the quantity of water that cannot be pumped is not negligible
compared to the demand for water, the prescribed return flow is slightly
over-estimated and the balance is optimistic. In fact, the return flows range
between 6,720,000 m 3 and 6,560,000 m 3 . The discharge from fixed heads is
3.1% of the recharge. The overflows are 0.2% of the recharge, which is
negligible and also located near the draining meshes.
Table 2. Annual water balance in Maheshwaram watershed
1/1/-31/12/2000
1/1/-31/12/2001
1/1/-31/12/2002
Recharge (m 3 .y -1 )
3,521,000
6,213,000
2,372,000
Return flow (m 3 .y -1 )
5,214,000
6,228,000
6,720,000
Outlet from fixed heads (m 3 .y -1 )
-46,000
-110,000
-74,000
Withdrawals (m 3 .y -1 )
-9,469,000
-11,293,000
-11,927,000
Groundwater overflows (m 3 .y -1 )
0
-13,000
-5,000
Storage variation (m 3 .y -1 )
-780,000
1,026,000
-2,912,000
Balance deviation (%)
-0.02
-0.02
0.42
Analyses of the Simulation/Calibration and Prediction
A comparison between the simulated heads and the measured ones for January
2001 under steady state conditions shows that most of the water levels are
well simulated and are falling on the 450 line. The comparison between the
 
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