Kaveri 101

1. See the map to Identify the 4 major reservoirs in Karnataka : Hemavathy, Harangi, KRS and Kabini. Inflows and Outflows to all 4 reservoirs are monitored and known and this forms the basis of all calculations
2. The river flows into TN and at Biligundlu there is a measuring station that tells you how much water flows into TN from Karnataka
3. The water that flows into the river downstream of KRS and Kabini is measured at Biligundlu , is expected to flow in from about 22,000sqm and in an average year can contribute about 80TMC.
4. About 740TMC is the total water that is expected to flow into the river (from all states)
5. Of this the following allocations have been made (the states are entitled to the following volumes of water
   1. Kerala: 30TMC
   2. Karnataka: 270TMC
   3. TN : 419TMC
6. The total inflows into the river from Karnataka is 462TMC. Of the 462 TMC, Karnataka can keep 270TMC for itself and has to give TN 192 TMC (this is measured at Biligundlu). For the purpose of this post, we assume that the basis of this split is agreed upon (270 keep, 192 give)
7. So if you see the only real numbers that matter are, irrespective of rainfall across the catchment, based on the total inflows in Karnataka,
   What Karnataka keeps                                           270
   -----------------------------                          =              ------
   What Karnataka gives TN                                      192

Hence if the total inflows in Karnataka was 100TMC, Karnataka can keep 58.44 TMC and send to TN 41.56TMC. Hence one would not need to base it on the % rainfall deficit/surplus – but on actual inflows. The inflows can be measured on a daily basis, the corresponding keep and give numbers calculated and released at some predetermined/useful frequency. It seems fair ? And simple ?

Now the inflows to/from all reservoirs are known , the additional inflow from 22,000sqm at Biligundlu is also known. This should make the actual sharing numbers even in a deficit year – a reasonable and clear calculation

Thanks to zenrainman's FB post on the same topic for a slightly more elaborate description,

And whats TMC ? That for another post :)