With the continuous increase in water use/ commitments since
independence, particularly after signing of Indus Water Treaty, 1960,
and construction of dams, barrages and link canals, one would have
expected that the net water availability scenario would have been
continuously assessed and updated. The criteria for water availability
computation should also have been clearly spelled out right from the
start. However, no such exercise was carried out till 1987, when for
the first time, water availability computations were made by
WAPDA
for the Committee on Water Resources and Management of the
National Commission on Agriculture. This exercise depicted two
scenarios, one based on average water availability for a period of 64
years (1922-1986) on pre Water Accord conditions and the other based
on 4 out of 5 years flows i.e. 80% probability. The criteria of water
availability indicated by WAPDA in their report for the Committee were
as under:
``In considering the potentially available surface supply, it has to be kept in view that the flows are quite variable from year to year and until there is storage capacity large enough to absorb the above average flows for carry over into subsequent years, the development would have to be based on the levels of flows which can be relied upon at least 4 years out of 5. This would apply not only to the direct use of the flows but also to the creation of additional surface storages.''
The same criterion of 4 out of 5 years water availability was re-confirmed in the document ``Integrated Valley Development Programme'' prepared by President of Pakistan, Farooq Ahmed Khan Leghari, when he was Minister for Water and Power in the year 1990.
After signing of the Water Accord, WAPDA calculated post Water Accord availability in the year 1992. Subsequently, in December, 1994, WAPDA carried out another exercise for water availability on the post Accord conditions. However both these post Accord computations were made only for mean year basis and no exercise was made for 4 out of 5 year basis.
The computations made by WAPDA for water availability in 1987 (Pre Accord) and in 1992 and 1994 (Post Accord) are reproduced in Table 1.
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| 1 | Western River Rim Station Inflows | 137.27 | 123.59 | 137.91 | 143.1 |
| 2 | Eastern River Contribution | 2.00 | 1.50 | 1.30 | 4.0 |
| 3 | Uses above Rim Station | 5.50 | 5.50 | 5.70 | 5.3 |
| 4 | Losses and Gains (Inclusive of flows ) below Rim Station | 10.00 | 8.00 | 10.00 | 10.0 |
| 5 | Outflow to sea | 5.00 | 3.00 | 10.00 | 5.8 |
| 6 | Net Available for utilization (1+2+3-4-5) | 129.77 | 119.59 | 124.91 | 136.1 |
| 7 | Canal Withdrawals/ Accord Allocations | 106.79 | 103.44 | 117.35 | 117.4 |
| 8 | Balance Available(6-7) | 21.98 | 16.15 | 7.56 | 18.7 |
| 9 | Authorized uses by India out of Western Rivers | 2.00 | 2.00 | 2.00 | 2.0 |
| 19.98 | 14.15 | 5.56 | 16.7 | ||
Table 1: WAPDA's Calculations Of Water Availability From Western Rivers
On Pre-Accord And Post-Accord Conditions (figures in MAF)