Why the Cauvery dispute needs science, trust and ecological renewal
The immediate crisis may be managed through compliance and dialogue, but lasting peace in the Cauvery basin will require far more than court orders. It demands transparent, science-based water management, real-time hydrological data, climate-responsive water allocation mechanisms, and, above all, the restoration of forests
‘The dispute between Karnataka and Tamil Nadu over the sharing of Cauvery water is a hundred years old. The Cauvery Water Management Authority (CWMA) ordered Karnataka on 28 July to release 3,500 cusecs of water every day for fifteen days. Biligundlu, a water-measuring station in Tamil Nadu, records the outflow from Karnataka. The CWMA was constituted by the Supreme Court in 2018 to oversee the implementation of the Cauvery Tribunal Award. The long-pending dispute was resolved by the Supreme Court in 2018, allocating 404.25 TMC to Tamil Nadu, 284.75 TMC to Karnataka, 30 TMC to Kerala and 7 TMC to Puducherry. In the same order, the Supreme Court also recognised 740 TMC per year as the drinking water requirement for Bengaluru.
Due to deficient rainfall during June and July this year, Karnataka’s reservoirs were 65.6% below the 30-year average level by the end of July. Karnataka moved the CWMA again, arguing that releasing water at this stage would jeopardise the water supply required for drinking purposes up to June 2027. The State argued that Tamil Nadu had already benefited from the earlier releases of water and would soon receive the North-East Monsoon. It further added that maintaining a flow of 3,500 cusecs would require a release of 7,000 cusecs from the upper reservoirs, considering the dry conditions of the riverbeds and transmission losses. Tamil Nadu opposed the move and charged Karnataka with not sharing the distress-sharing formula. The CWMA rejected Karnataka’s submission and directed it to continue releasing water according to the 28 July order. However, due to the sudden revival of the monsoon in early August, the four reservoirs, namely Krishna Raj Sagar, Hemavati, Kabini and Harangi, in the Cauvery basin are receiving an inflow of 81,000 cusecs of water a day. In view of this, the Karnataka Government conducted a meeting of representatives of all political parties and decided to comply with the direction of the CWMA. Despite this, Tamil Nadu is knocking on the doors of the Supreme Court.
The overall drought situation in Karnataka is quite severe. Mandya farmers are protesting over water for agricultural crops. Bengaluru is totally dependent on Cauvery water. Karnataka must present relevant data on the drought to the Central Government, concerned ministries and authorities. Furthermore, MPs from Karnataka should also raise the issue in Parliament. The Government should aggressively bring the data into the public domain and use back-channel communication to explain the prevailing hydrological conditions within the bureaucracy. A bilateral meeting between the Chief Ministers of the two states would be a welcome step, but it has been put off amid escalating tensions over the Cauvery water-sharing dispute. It is hoped that it materialises soon.
The crisis in Cauvery water sharing has been caused by a steep rainfall deficit in the catchment during the first two months of the south-west monsoon this year. The IMD and WMO have forecast a Super El Niño, which may impact the rainfall pattern from August/September onwards; however, the rainfall deficit during June and July is attributed to local weather conditions. The IMD’s forecast covered all regions of the country, but the Western Ghats region of peninsular India has registered a greater rainfall deficit compared with other parts of the country. However, the WMO’s latest update predicted the possibility of a positive Indian Ocean Dipole (IOD), which could offset the impact of El Niño.
El Niño is a climatic pattern involving the warming of surface waters in the central and eastern tropical Pacific and is linked with a weak monsoon and relatively harsher summers. The IOD is governed by the difference in sea surface temperature between the western and eastern tropical Indian Ocean. A positive IOD helps form stronger monsoon winds and can partly nullify the influence of El Niño.
The Cauvery water dispute between Tamil Nadu and Karnataka is a flashpoint in distress years, when reservoir levels are low and riverbeds are dry. In this opinion piece, let me bring out some short-term and some long-term solutions to deal with the issue.
Hydrologists are of the view that the principle behind sharing water in distress years is to distribute the shortfall proportionately between the states. In other words, the water received in the basin should be shared proportionately among all stakeholders. The principle is accepted by all, but the difficulty arises when stakeholders question the quantity of the rainfall deficit, reservoir storage, inflows, drinking water requirements, or any other data presented by the other side. A third-party assessment of the data may be acceptable to both sides.
Experts have flagged genuine issues and have called for updated studies on siltation in major reservoirs, accurate live storage of water, rainfall, and transparent real-time hydrological data. Any formula worked out on the basis of these data will inspire greater confidence among stakeholders and would be more acceptable. They also add that climate variability has made droughts more frequent. The allocations designed on a monthly schedule and based on a normal monsoon do not work in distress situations. The allocations must be made dynamic and should depend on science-based temporal and spatial data, certified by a third party.
Among the several reservoirs in the Cauvery basin, Krishna Raj Sagar, Harangi, Hemavati and Kabini are the main ones, where gates are opened to release water to Tamil Nadu. The catchments of these reservoirs were heavily forested, but, with the passage of time, anthropogenic pressures led to the degradation of forests in the catchments. As a result, large quantities of silt come down through streams and tributaries and get deposited in the reservoirs. The rate of siltation is directly proportional to the loss of tree cover in the catchments. Frequent desiltation of the reservoirs is not practical, as dewatering of reservoirs during the summer season is often avoided to save summer crops. A high proportion of the dead storage in the reservoirs contains silt. Continuous deforestation in the catchments will have to be prevented so that their water-holding capacity is not compromised.
The current tension between the two states can be resolved by exchanging authentic data, but the long-term solution can come only by preserving the landscape and avoiding changes in the land-use pattern of the catchments. The Cauvery catchments in Karnataka comprise good-quality forests as well as shola forests interspersed with grasslands. Apart from the legal and illegal cutting of trees to satisfy different interests, such as land grabbing and the felling of valuable trees, the grasslands are set on fire every year. Although the fire does not enter the sholas, it scorches all around their periphery. Every year, the sholas shrink, and so does their capacity to hold water.
The roots of trees in the sholas act like a sponge and store water during the rainy season. A stream originates from every patch of shola, carrying water downhill to join larger streams and tributaries before finally flowing into rivers. It is these rivers that feed water to the reservoirs. The flow of water in streams originating from the sholas continues even after the end of the rainy season, confirming that the water remains stored in the roots of the trees. As the sholas shrink, the summer flow in the streams depletes. A special drive must be undertaken to prevent fires and conserve the sholas, as well as all other forests in the river catchments.
This year’s drought has also triggered a war of words between the political parties of the two states. The Karnataka Government is set to revive its Mekedatu Project on the River Cauvery, planned to solve the drinking water problem of Bengaluru city. Tamil Nadu opposes the project, fearing that its share of Cauvery water would decline in future distress years. In my opinion, this project would be an environmental disaster, as 5,000 hectares of dry deciduous forests would have to be sacrificed. The loss of forests would make wildlife homeless and increase human-wildlife conflict. The population density of elephants in the area is quite high; elephants straying into villages would trample people and damage crops, creating an irreversible situation.
A stream originates from every patch of shola, carrying water downhill to join larger streams and tributaries before finally flowing into rivers. It is these rivers that feed water to the reservoirs. The flow of water in streams originating from the sholas continues even after the end of the rainy season, confirming that the water remains stored in the roots of the trees
The writer is the retired Head of the Forest Force, Karnataka; Views presented are personal.
