Climate Adaptation In Vennar Sub Basin in Cauvery Delta Project (CAVSCDP) (Assisted by Asian Development Bank)
- TamilNadu is one of the most water-stressed states in India.
The mean annual rainfall is 912mm of which 48% comes from the erratic North-East monsoon (October-December) and 32% from the South West Monsoon (June-September). Of the 17 major river basins in TamilNadu,
the Cauvery Basin is the largest. The Cauvery river flows through the states of Karnataka, Kerala, TamilNadu
and the Karaikkal enclave of the Puduchery Union Territory.
Around 54% of its cards ment area lies within TamilNadu.
- The availability of water resources in the delta is unreliable and flooding is common especially in the tail end reaches during the North-East monsoon.
Meanwhile, climate change projections indicate an intensification of floods due to heavy rainfall and sea level rise. Storm rainfall is predicted to increase by 19%.
In coastal areas, flooding will increase because sea-levels are projected to rise from 0.29m to 0.87m by 2100. Also,
the maximum temperature will rise by 1.00c – 1.50c accordingly to climate projections, and minimum temperatures will increase by a larger 20c-30c.
The rising temperature are to increase the crop water requirements and increase the evaporation losses.
- Despite high level of water stress due to sharing of Cauvery water among the states,
recurring flooding, increasing risk of climate change and the longstanding dispute prevented investment towards improving the irrigation
and drainage systems in the delta beyond essential maintenance and undertaking only emergent repairs.
These result that the very old irrigation and drainage systems are dilapidated and unable to effectively convey irrigation
and flood waters which lead to inequitable distribution of irrigation water, increased flooding due to overtopping or breaching of embankments.
Further the tail end regulators are not functioning properly which lead to seawater ingress along the channels.
- Moreover, the availability of quality ground water in the lower reaches of the delta is limited as a result of variable recharge and saline aquifers.
The communities along the lower costal reaches of the delta are particularly disadvantaged since they have access to neither fresh groundwater nor fresh surface water which negatively affects the agriculture production in these areas.
The climate change is expected to exacerbate such vulnerabilities, so as to upgrade the infrastructures urgently to have better water management to meet the present and future needs
- At the field level, water use is generally inefficient because of high distribution field losses,
low priority given to water conservation and high water consumptive crops.
Rising temperatures and uncertainties in respect of future rainfall, floods demonstrate the necessity of stronger water management.
- Following the 2013 Supreme Court decision, the Water Resources Department within the Public Works Department prepared the Cauvery Modernization proposal,
which includes the rehabilitation of most of the flood control and irrigation infrastructures and improvements to on-form irrigation systems in the Cauvery delta.
The four main irrigation systems in the delta are Lower Coleroon Anicut, Cauvery, Vennar and Grand Anicut. Of the four,
the Vennar system is considered to be the most critical in terms of vulnerability to flooding and in need of improvements.
- With the above background, the Government of Tamilnadu requested Asian Development Bank (ADB) financing to upgrade the Vennar system.
This project is consistent with ADB’s country partnership strategy, 2013-2017 for India which seeks to overcome water insecurity and help communities adapt to climate change and to promote efficient
and sustainable water management in agriculture.
This project is also aligned with the aim of the Government of India’s National Water Policy, 12th Five year plan, National water mission and with the state Government’s Twelfth five year plan-(2012-2017).