Could the floods in Odisha that are still raging across the state been avoided? A team of journalists and social workers who toured around the Hirakud dam area argue that it certainly could have been. The floods in the region are being described as “man-made”. Far from controlling the floods, dams have only aggravated the situation. The dams were also allegedly allowed to be filled up to the brim in order to retain waters for a dry season so that they could supply power and water to resource-intensive industries in the state.
All eyes are now trained on the operation of the Hirakud reservoir with questions being raised about the dam operations, and fingers being pointed at, what is known, as the Rule Curve. The Odisha Water Forum and Baitarani Initiative tried to analyse the Rule Curve–based reservoir operation of Hirakud, to see whether the violations in rule curve prescriptions added to flood severity and woes, or the Rule Curve itself needs modification with changing circumstances and situations in the dam’s catchment and the reservoir capacity.
Based on an analysis of rainfall, runoff, siltation, reservoir level data over about 50 years (1957-2009) and this year’s floods along with post-Hirakud water-resources development trends in Chhatishgarh which contributes to 85 per cent of the dam’s catchment, the two organisations want the Rule Curve theory (developed in 1988) to be made more adaptive to changing climatic and development context and also the need of exploring a formal arrangement with Chhattisgarh over management of water and water information in the Mahanadi basin.
The Rule Curve was developed by a committee appointed by the Central Water Commission in 1988 for flood control during monsoons and maintenance of reservoir functions (irrigation and power production) post-monsoon. The Rule Curve prescribes reservoir levels in the dam to be between 590 feet and 595 feet between July 1 and August 1, which is close to the dead storage. This is to facilitate flood cushioning. In case there is a heavy inflow into the reservoir, water can be retained and discharged in a regulative manner. From August 1 the reservoir level is raise till October 1 when it is filled up to FRL (Full Reservoir Level).
This rule also says that if there are warnings from the Indian Meteorological Department (IMD), the reservoir should be emptied partially so as to accommodate floods and regulate the flow of the river. This, however, was not done since the rule is being followed blindly. According to Baitarani Initiative, the rule curve is premised on higher rainfall and inflow in July and August, and lesser rainfall in September. The committee had indicated that during the period of 30 years before rule curve (1957-88), there were only three instances of deviations of upper limit.
However, of late there seems to be more such deviations and more regular deviations. There is a clear shift towards more rainfall and runoff in the month of September. Probably the existing rule curve is unable to accommodate cushion to September inflows, the Baitarani study reasoned. Lack of appreciation of this shift and accommodation of this into the Rule Curve along with reduction in live storage capacity and unpredicted release from dams in Chhattisgarh, is decreasing the flood cushioning ability of the Hirakud dam. The old rule is simply not in keeping with fast-changing rainfall patterns and climate change.
There was also no coordination between the Odisha and Chhattisgarh governments, with the latter probably being more irresponsible. Over 90 per cent of Hirakud's catchment area lies in Chhattisgarh. The state has constructed five major and medium dams and about 150 small dams on the Mahanadi and its tributaries upstream of the Hirakud reservoir in the past 50 years. Though concerns have been shown regarding reduction in inflow (@ 5% per decade), the appreciation of the impact of changed inflow pattern due to the reservoir operation of these dams on the reservoir operation of Hirakud has not been very forthcoming. Through construction of dams and reservoirs in Chhattisgarh now there is interception of 24% (16,845 sq km catchment out of 83,400 sq km) of total catchment of Hirakud reservoir.
The reservoirs in Chhattisgarh were filled up to 90 per cent of their capacity on September 9. Sudden release of waters from these dams owing to heavy rainfall in the state led to peaking of the inflow into Hirakud. For example, the Bango Dam suddenly released 1.5 lakh cusecs in River Hasdeo on September 8 without allegedly informing Hirakud authorities.
One of the reasons why the dams in Odisha were allowed to be filled up to their brim, according to the team, was to retain dry for the dry months so that water and power can be channeled to industries, particularly mines, which require huge amounts of water.
The most alarming aspect of the floods has been the contaminated waters. Paddy is water resistant by nature and can survive several days being submerged in water. But it was found that in several regions, with just three days of waters, many fields have become totally rotten.
People have also been complaining about skin burns after coming into contact with the floodwaters. Preliminary medical studies indicate high levels of flouride content in the waters. Those to blame, according to the team, are mining companies which clear forests and dump their waste without following regulations. Moreover, they often release their waste into rivers.
