Due to regular inflow of water, the spillways of Rawal Dam were opened three times in May. The last time the dam’s spillways were opened in May was back in 1992. Active rainfall in Murree also led to regular inflows in Simly Lake and its spillways were opened five times in this month. — File photo
Due to regular inflow of water, the spillways of Rawal Dam were opened three times in May. The last time the dam’s spillways were opened in May was back in 1992. Active rainfall in Murree also led to regular inflows in Simly Lake and its spillways were opened five times in this month. — File photo

ISLAMABAD: The authorities have issued internal alerts for Simly Lake and Rawal Lake, both of which have reached their peak capacity because of rainfall in Murree this month.

The main catchment areas of both lakes are in the Murree hills, which receive some of the highest levels of rainfall in the country. Although the average monthly rainfall for May is 83.4 millimetres, Murree has received 168.4mm of rain in May this year.

“The rainfall was 85mm more than normal in Murree, because of which the ground was wet and all the areas that recharge water flow were active, leading to regular flow from various streams into the Korang and Soan rivers,” an official from the Punjab Irrigation Department said.

The constant inflow from small streams caused the water level in Rawal Lake to cross its highest level, because of which the dam’s spillways were opened for around six hours on Friday.

Both lakes are at peak capacity because of above average rainfall in Murree area and need constant monitoring

The official said that since the constant inflow helped the water level reach almost 1,752 feet - the lake’s maximum capacity - the water in the reservoir was reduced by two feet.

Rawal Lake supplied around 100 acre feet of water to Rawalpindi every day. Currently, even without any rainfall the inflow is almost equal to the outflow, and any light precipitation in the region including in and around parts of Islamabad, could fill the lake to capacity.

A similar situation has been reported in Simly Lake, which was built over Soan River and is one of the capital’s main water sources.

With the current water level slightly over its maximum capacity of 2,315ft, the inflow into the lake was approximately 24.3 million gallons daily (MGD) and outflow was 30.2 MGD.

“Since the conditions were at the best level, even the slight 0.3mm rainfall Friday nighthelped the water level rise because there was a constant flow from the small streams coming from the hills,” an official from the Metropolitan Corporation Islamabad posted at Simly Dam said.

“The Murree area has a different geographical setting as the winds from the north or the moist winds of southeast either precipitate or bring droplets there, that is why the whole area has heavy vegetation,” the official said, adding: “This also helps maintain a continuous supply of streams from the area.”

There is no rain forecast in the immediate future, but all the relevant authorities have placed their staff on alert during the Eid holidays as the water level is already too high and constant monitoring is required.

With pre-monsoon rains expected from June 15, there is a chance that the spillways of both dams will be opened in the last week of May to accommodate gradual inflows in coming weeks.

At this time later year, Rawal Lake was at 1,750ft, which is around 1.5ft below the highest level, and the water in Simly Lake was at 2,290ft, which is 25ft below peak level.

Published in Dawn, May 24th, 2020