Inefficient dam operation threaten India-Bangla Rivers

Inefficient dam operations threaten India-Bangla Rivers


Sandrp – the South Asia Network on Dams Rivers and People – in its latest bulletin published on Saturday 9 June has questioned the huge live storage of 27659 MCM (million cubic meters) water in 91 reservoirs in India on May 31 last only about a week before the onset of the southwest monsoon.
Sandrp has asked, “Why so much water in these dams close to the onset of the monsoon? For example, as India awaits the onset of monsoon from early June, a scrutiny of the CWC’s RSB dated May 31, 2018 should not be looked at just from the point of water scarcity in the reservoirs by comparing with the storages in same week in previous year or average of last 10 years as most media has done. The scrutiny at this stage (as also earlier stages) should also look at how much water is there in various reservoirs as the monsoon inflows would start into these reservoirs within weeks.”

Map Showing the location of Bansagar Dam, Sone River, Ganga River and Patna via SANDRP

Map Showing the location of Bansagar Dam, Sone River, Ganga River and Patna via SANDRP

Why is this important? It may be recalled as to what is the basic logic of creating reservoirs. The basic logic is that while most of the rain, the primary source of our water, is available in 3-4 monsoon months (June-Sept), but we need to store that water to make it available for the rest of the 8-9 non-monsoon months. The reservoirs are created at huge social, economic and environmental costs for this basic purpose. So the optimum use of the reservoir would be when we have been able to use up most of the water stored in these reservoirs in 2017 monsoon, before the onset of 2018 monsoon.”
“Reservoir managers and government officials, however, have to be also prepared for the contingency of rainfall deficit in early monsoon, so that the water stored in reservoirs can be used during such a contingency. However, for this purpose, not more than 5-10% of live storage capacity is required. Particularly when almost none of India’s reservoirs are designed to carry over water beyond next monsoon.
“What this means that is that if any dam has water storage of more than 5-10% of its live storage capacity, than, we are not using the reservoir optimally. If the water was supposed to be used before the next monsoon, why was it not used? This signifies the first level of sub-optimal use of the reservoir.
“When we check CWC’s weekly RSB of May 31, 2018, we find that there are at least seven reservoirs that have over 1000 Million Cubic Meters (MCM) of water in live storage and there are eleven more reservoirs that had between 500-1000 Million Cubic Meters (MCM) of water in live storage. The total water stored in the live storage of the 91 reservoirs on May 31, 2018, was 27659 MCM.”
“Is there any justification for such high storage in the reservoirs just before monsoon? Let us look at some of these reservoirs and their river basin situation.
“Bansagar: This reservoir on Sone River (Ganga Basin) in Madhya Pradesh is an interstate project between Uttar Pradesh, Madhya Pradesh, and Bihar. In Aug 2016, when monsoon was less than halfway through, massive water releases from this dam contributed hugely in creating unprecedented flood disaster in Ganga basin in Bihar. The Bansagar reservoir on the morning of Aug 19, 2016, started releasing close to 16000 cumecs (cubic meters per second) water, which led to the floods in Ganga two days later. On June 25, 2016, when Bansagar Reservoir filling started, the reservoir already had about 1809 MCM water. This year, with even higher storage, Bansagar could again create another massive flood in the downstream areas including in Bihar.
“Gandhisagar: This massive reservoir on Chambal River is also in Ganga Basin and there is Chambal Ghadiyal Sanctuary downstream from this dam. The government keeps saying it has no water for the Sanctuary, but as we see, the reservoir had 1154 MCM water in live storage, which could have been used for a number of purposes including for sustaining the Chambal River through the Ghadiyal Sanctuary.
“Ganga Basin: There are at least three dams in the table above (Bansagar, Gandhi Sagar, and Rihand) that are in Ganga Basin. Even though the Prime Minister has pledged to rejuvenate Ganga, the government has been unable to allocate any water for rejuvenation of Ganga. The situation of Ganga this summer of 2018 is so precarious that at many locations people are crossing the river by walking across. Now we have these three Ganga Basin reservoirs with over 4000 MCM water, but that water won’t be used for Ganga?”
“Clearly, so much water in live storage in all these dams just days before the monsoon raises serious questions.
“Further sub-optimality and risk of a flood disaster. It should be noted here that water already stored in the live storage in these dams means that this space will not be available for storage of monsoon inflow during monsoon 2018. This signifies further suboptimality in use of these reservoirs. Moreover, as we saw in case of Bansagar Dam creating flood disaster in Bihar in Aug 2016, all these reservoirs could also be the source of additional flood disasters during 2018 monsoon, thus creating additional risk.
To illustrate, Tenughat Dam in Jharkhand over Damodar River, in fact, took advance action by releasing excess water on June 4, 2018, before the onset of monsoon after informing the downstream state. The reservoir had 318 MCM water in live storage on May 31, 2018, equal to 39% of live storage capacity. The live storage was reduced to 303 MCM on June 6, 2018. It may have been useful if the reservoir had taken more advance action and put the water to more optimum useful purpose.”
The sub-optimal operation of the dam reservoirs in India has serious implications for the rivers at downstream which could have been sustained by avoiding unnecessary storage of excess water during the dry season. The excess water stored has not only drastically reduced the downstream river flows below their levels of sustainability, as ‘at many locations (of the Ganga in India) people are crossing the river by walking across,’ but also created the risk of compulsion to release excess water when refilling of rainwater will start this season, and cause flooding.
After the onset of the monsoon soon, the situation runs the risk of turning disastrous in the form of massive floods. Sandrp coordinator Himanshu Thakkar has warned devastating floods like those of 2016 in Bihar and by extension in West Bengal and Bangladesh. He has pointed out that before the Bansagar Reservoir filling started in 2016, the reservoir already had about 1809 MCM water. This year the storage of water in this reservoir located between Uttar Pradesh, Madhya Pradesh, and Bihar is even higher than that of 2016. – GreenWatch Dhaka News Desk


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