Scorching summer heat to evaporate up to 7 tmcft water across lakes,dams in Karnataka

High temperatures and evaporation rates strain reservoirs; farmers likely to rely more on borewells as surface water levels dip across regions

Some districts, especially in North Karnataka, are experiencing temperatures of around 40 degrees Celsius, which will only go up in the coming days. 

BENGALURU: With scorching heat, Karnataka is expected to lose up to 7 tmcft of water from all the reservoirs, tanks, rivers and other surface water resources this summer, forcing farmers and others to depend on ground water for drinking and agricultural purposes.

Some districts, especially in North Karnataka, are experiencing temperatures of around 40 degrees Celsius, which will only go up in the coming days. GS Srinivas Reddy, former director, Karnataka State Natural Disaster Monitoring Centre (KSNDMC), said the evaporation is around 6 mm per day during April and May and it will go up to 150 mm. This roughly translates to 0.3 metre, or 1 foot, for two months. “Be it a tank, river or reservoir, water during summer gets evaporated by 1 foot,” he said.

Reddy said that at many places, farmers use flood irrigation to water their crops, where evaporation is high. This causes more water loss, though awareness has been created on using sprinklers or drip-irrigation systems. “Water is also lost due to transpiration, where plants and vegetation let out more water and demand more frequent watering,” he explained.

Under such situations, it is common to depend on groundwater, which dries up borewells. “When water from surface sources evaporates, people look for ground water which is a common source of water for drinking,’’ he said. Last year, evaporation was slightly lesser at 6 mm per day.

That was because of good pre-monsoon rain during April-end and May that had filled up dams and water bodies and turned soil moist, lessening evaporation.

A senior official from the Agriculture Department said farmers, especially from south-interior and northern parts of the state, look for summer crops. “If the crop is good, water evaporation/ transpiration is also high and vice versa. Though the state government stresses drinking water as a priority, farmers use water from canals and other sources to get better crops,’’ the official said.

As per KSNDMC data, many major dams have less water compared to last year, which is partly because of evaporation.