Kalabagh Dam: a macro look at some issues.
i) Water availability criteria for the western rivers: 80 per cent probability (8 out of 10 years) or average (5 out of 10 years).
ii) NWFP's diversions above rimstations: only ungaged civil canals or total including the existing weir controlled canals.
iii) Eastern rivers contribution: none at all or to include the component generated from their catchments draining into Pakistan.
iv) Future Indian uses on western rivers as permitted by 1960 Water Treaty: quantification.
This crucial national issue is very close to the heart of every Pakistani and particularly mine on account of extensive association of over 40 years with Indus Basin Irrigation System through: i) Officer on Special Duty, Water Development Organisation, Irrigation Department; ii) participation as Pakistan representative in tri-partite Water Treaty negotiations under the aegis of the World Bank; iii) involvement in finalisation of the Indus Basin Project (IBP) by Pakistan; iv) implementation of IBP and v) ad hoc distribution of Indus waters among the provinces in pre-Water Apportionment Accord (WAA) era. Therefore, I honestly feel that the basic controversy regarding water availability in the post-WAA scenario should be amicably resolved. Towards this, I venture to suggest a positive approach as outlined in the following. Before suggesting this approach, we should clarify some basic premises, assumptions, and norms universally followed for operation of very large integrated Irrigation system such as ours in the World. These are:
a) In no irrigation system, even regulated to the last drop is it possible to always provide a fixed level of uses or allocations. Such levels of allocations essentially set the targets to be achieved, or even exceeded, depending upon: river inflow conditions; availability of system withdrawal capability; storage (including their filling and drawdown criteria); and weather conditions.
b) It is fallacious assumption that under all inflow conditions a fixed level of uses (such as WAA Allocations) has to be met even at the cost of keeping the storages empty in Kharif. This is also evident from the fact that WAA has very clearly laid down the criteria for sharing of shortages under low river supplies.
c) For instance, since commissioning of Tarbela in 1976, the reservoir operation criteria have endeavoured a carry-over of between 0.5 to 1.0 MAF of storage for early Kharif, particularly for cotton sowing in Sindh. Over the years, due to sedimentation, physical capability for this carry-over has been somewhat diminishing. Notwithstanding this, even under low inflow conditions, such as early Kharif 1994, some water impounding has been resorted to to ensure reservoir filling before the end of Kharif. Incidentally, this also points to the early need of carry-over storages for meeting crucial early Kharif shortages in Sindh.
d) Water availability criterion for an extensive, integrated and reasonably regulated system, such as Indus, is the long-term average (5 out of 10 years flow) specially when storages are available. This issue was debated at length during Water Treaty negotiations under the aegis of the World Bank and finally the average concept adopted by the World Bank Water Apportionment Accord (1991) is also based on this concept.
e) For long-term water availability, very harsh criterion, for eight out of 10 years is rarely used even in a pure run-of-river system. In fact this criterion is only relevant when drinking water supply schemes are involved.
f) By adopting the eight out of 10 year criterion, very large water quantities are left out of planning. Besides, in years of below average flows the System has normally to contend with up to 80 per cent of the average withdrawals. Under those conditions, therefore, the System should not be tested for average withdrawals or System losses.
g) Though long-term (from 1922 onward) river inflow record is available, it will be preferable to use for this particular analysis the post-Tarbela (1976 onward) data. This will represent the recent factual position.
So far, determination of water availability is being attempted by starting with rim-station or "upstream end" of the System and then making adjustments for various related items. Whereas there is no disagreement on the items, there is wide divergence on determinations or assumptions to arrive at the final values. I find that one of the most controversial and significant items is the system losses. One way to approach it is by considering actual system behaviour, particularly after Tarbela. (This is a conservative approach because long-term system losses including pre-Tarbela period from 1960 onward would be lower).
In post-WAA scenario, the first charge on surplus supplies-after appropriate adjustments is to meet the additional allocations of about 12 MAF essentially in Kharif. The remaining surplus could then be available for further development of irrigation by provinces in accordance with their shares, as per Para 4 of WAA. Of course, reasonable need for escapages below Kotri to check Sea intrusion (Para 7 of WAA) would also have to be duly considered. To proceed with analysis under the suggested approach, the following steps are necessary:
i) Considering actual escapages below Kotri starting from full commissioning of Tarbela in 1976. As the present water availability is essentially limited to about 100 flood days, for this particular exercise, only Kharif season be analysed. During this 18-year period, escapages in Kharif varied between 9.4 to 75 MAF with an average of 35.2 MAF.
ii) Escapages below Kotri from 1976 to 1993 (preferably on 10-daily basis) be adjusted for: Eastern rivers actual contribution from Ravi and Sutlej. Indian uses on the western rivers as allowed under 1960 Water Treaty.
iii) Remaining surplus below Kotri, after adjustment for i) and ii) above, to be matched against additional WAA allocations to see whether these can be met, in part or full, under sequentially varying flow conditions.
iv) Any shortages in meeting WAA allocations, as per (iii) above, would establish the need and quantum of storage. It would also follow, automatically, that equivalent amount of water is available to fill a new storage as WAA pre-supposes that water for additional allocations is already available in the System though concentrated in the flood season.
v) In case it is, somehow, demonstrated that additional WAA allocations can be met without the need of any additional storage, the analysis can proceed further to determine remaining surplus water for sharing between the provinces including need for releases below Kotri.
Eastern Rivers' Contribution
I have taken note of divergent viewpoints from both sides. According to my judgement, an appropriate basis (though still conservative due to salvage of corresponding conveyance losses up to Kotri) seems to be an adjustment for actual 10-daily flows below Madhopur and Ferozepur. Fortunately, the data from 197693 is now available with Pakistan Commissioner for Indus Waters (PCIW) who periodically receives it from his Indian counterpart. By making this adjustment, after converting Kotri discharges to the common datum of rim-stations, the average Kharif escapages below Kotri come to 32.1 MAF (against present 35.2 MAF) with variation between 7.7 and 68.4 MAF.
Adjustment for Indian uses on Western Rivers: For this purpose, the basis of cropped area as adopted in Treaty seems realistic. According to available statistics, out of total permissible cropped area of 1.34 million acres on the western rivers so far India has developed 0.79 million acre. Whereas up to date Indian abstractions are automatically reflected in post-Tarbela river inflows, and consequent escapages below Kotri, the remaining cropped area of 0.55 million acres remains to be catered for.
Notwithstanding the above, it will be desirable to determine water requirements on a conservative basis. Chashma Right Bank Irrigation Project, now under implementation, is designed on the basis of scientific crop water requirements. For 60 per cent Kharif cropping intensity over a canal commanded area of 0.57 million acre the water requirement for remaining 0.55 million acre in India on the western rivers comes to a little over 2 MAF. Its abstraction by India can be assumed at the rate of 10,000 cusecs over 100 days flood flow period.
Meeting Additional Accord Allocations from Flow Surplus: After making the foregoing adjustments to post-Tarbela (1976-93) escapages below Kotri, remaining surplus has been computed which comes to an average of 30.2 MAF with variation between 7.2 and 66.4 MAF. Against this have been matched the additional allocations under WAA to see as to how much can be provided from flow supplies. Results of this study indicate that over the period 1976-93, the average Kharif shortage in meeting additional WAA allocations from flow surplus would be 3.3 MAF with a variation between 0 to 8.0 MAF. In eight below average years the shortage is between 3.7 to 8.0 MAF with a mean of 5.5 MAF. This clearly establishes the need for a sizeable storage if additional WAA allocations are to be met also in early and late Kharif particularly in below average years.
Water Availability for Filling Kalabagh Storage: It can be seen from the above study that in order to provide additional allocations during Kharif, an average storage capacity of 3.3 MAF would be needed water for which is available from the undisputed 12 MAF additional allocations provided in WAA. It is also a known fact that the on-line storages at Mangla, Tarbela and Chashma are depleting due to sedimentation. According to WAPDA studies, based on projection of update trends, the cumulative loss in live storage capacity of these reservoirs would be about 3 MAF by the year 2000. The reference year 2000 seems relevant because, even with most optimistic projections, the provincial irrigation schemes to utilize the additional WAA allocations would be hardly in place by this time.
i) Storage need to sustain Pre-WAA withdrawals (loss due to sedimentation of exosting reservoirs), 3.0 MAF.
ii) Average storage needed to provide additional WAA allocations during early and late Kharif season 3.3 MAF, total 6.3 MAF.
As against this, the live storage capacity of Kalabagh would be 6.1 MAF. So, in fact there might still be a nominal shortfall after full utilisation of new storage. Hence there will be need for undertaking the next storage (Bhasha) almost in continuation of Kalabagh to compensate for continuous loss of storage capacity in existing reservoirs and variability in surface flows. It is envisaged that uses of any new irrigation schemes to be developed from balance river supplies, could be met only after Basha. Hence it should, start immediately after commissioning of Kalabagh.
A concept is also often projected that Kalabagh envisages a storage of 6.1 MAF without canals and additional 12 MAF with canals. This needs examination. It should be clearly understood that a storage does not consume any water except insignificant evaporation-cum-seepage losses. Similarly, 6.1 MAF live storage capacity of Kalabagh will be needed to make up for the storage loss due to sedimentation and ensuring additional WAA allocations of existing irrigation system.
Regarding 12 MAF additional for canals, probably the reference is to the one-time proposed right and left bank canals from Kalabagh. These schemes were considered, though at a reconnaissance level, in pre-WAA era. In post-Accord scenario the allocations and shares from surplus water of all the provinces have been very clearly specified. It is, therefore, inconceivable that any one of the upper riparians (NWFP/Punjab) will be free to abstract water for any of their projects located anywhere. Furthermore, the proposals are hardly justifiable on economic grounds.
Under the WAA, the Indus River System Authority (IRSA) has since been established to distribute the allocated water amongst the provinces as well as clear all future water resource development projects. The IRSA is already effectively discharging its functions as demonstrated by fair distribution of extremely low supplies during late Rabi 1993-94 and early Kharif 1994. With passage of time-specially by the end of century when future irrigation development schemes including storages are expected to come on line-IRSA will be in a position to fully assert itself and thus create an atmosphere to trust and confidence between the provinces where no one would be permitted any unauthorized or unilateral use of water.
In conclusion, I will call on all patriotic elements to rise sense of Mr. Kazi for rising to the occasion by contributing positively to the national consensus-building efforts regarding Kalabagh Dam Project. A lot of time has already been lost in misdirected "technical foot-dragging" and the nation cannot afford to follow that course any longer. Failing this, the writing is very clear on the Wall: By turn of century the country would be facing perpetual food shedding in addition to the existing rather exacerbated, load-shedding and one shudders to think of the resultant disastrous consequences.
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|Author:||Hussain, Chaudhry Altaf|
|Date:||Jul 1, 1994|
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