The cauvery conumdrum
The cauvery river is the lifeline of south karnataka and tamilnadu. The term “lifeline” gets abused but it does convey the right context for something like cauvery. Farmers in districts of mysore and mandya depend on it for irrigation for agriculture, cities like bengaluru and mysuru depend on it for drinking water, the entire agricultural community of delta districts of tamilnadu depends on it for agriculture, cities and towns in tamilnadu depend on it for drinking water. It has been the source of friction between the states of tamilnadu and karnataka with politicians and fringe groups using it for further their ambitions. Courts are involved and no one knows how to divvy up the water of the river between the two states.
All this leads to just “how much water is available in the cauvery basin”? What are the catchment areas of the river? What are the reservoirs along the course of the river?
Catchment Area
The primary catchment areas of river cauvery are the districts of kodagu in karnataka and wayanad in kerala. The primary season is the south west monsoon months of june-september. The rains in kodagu feed the cauvery river from its source somewhere near bhagamandala and the rains in wayanad feed the primary tributary of cauvery, the river kabini. Another tributary is the river hemavathi which is fed by catchments areas of hassan district in karnataka. The contribution of hemavathi is less compared to the other sources.
Reservoirs
There are a number of reservoirs in the cauvery basin. The primary ones are KRS (Krishna Raja Sagar) located in Mandya district in karnataka. It is capable of storing around 45 tmcft (Thousand million cubic feet) of water. The main reservoir across the river kabini is the kabini reservoir located in Mysuru district of karnataka. Kabini reservior has a capacity of about 15tmcft of water. The other smaller reservoir which feeds the cauvery river is the harangi reservoir located in kodagu district of karnataka. Harangi is much smaller and can store around 8 tmcft of water. Hemavathi reservoir located in hassan district can store around 35tmcft of water.
The Conundrum
So what is the “conumdrum”? The volume of water available in the cauvery basin is showing a steady decline over the years. A lot of it can be attributed to the marked reduction in rainfall in the catchments areas of the river (Kodagu and Wayanad). June and July are the primary months of rainfall and the last 2 years (2016,2017) paint a very bleak picture.
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Rainfall Data as of 30th June 2017 as compared to normal (Source: IMD)
Wayanad : -53%
Kodagu : -28%
This deficit directly reflects in the water levels of the reservoirs at the head of the river
Harangi : 30% full (2.44 tmcft available)
KRS: 7% full (3 tmcft available)
Kabini: 23% full (3.58 tmcft available)
Hemavathi: 10% full (3.49 tmcft available)
What is scary is that whether we are seeing a slow but permanent reduction rainfall in the cauvery catchment area. Below is the data at the end of June 2016. The geopolitical issue between the states of tamilnadu and karnataka is starting to rear its head again in 2017 with groups opposing the limited release of water from KRS and Kabini reservoirs to tamilnadu. This year is election year in karnataka which means the the karnataka state govt will take a hard stand towards release of water to tamilnadu citing insufficient rains and state of tamilnadu has a weak proxy government.
All in all, it is going to be very interesting. Expect to see road blockades between bengaluru-mysuru, between tamilnadu and karnataka soon. The start to the month of July has also been very poor on the rainfall front. Unless things change drastically in the next 2 week, we are looking at another drought in the cauvery basin and this one will be worse than the previous year.
