The two reservoirs are located in a picturesque hilly wet zone rainforest just off Colombo.
The Hungarian Exim bank will give a loan of 22.3 million dollars to expand the treatment plant at Labugama and a 23.7 million dollar loan to boost the plant at Kalatuwawa under a tied aid programme.
The capacity of the Labugama treatment plant will be increased to 60,000 cubic metres per day from 40,000.
Kalatuwawa plant's capacity will be upgraded to 90,000 cubic metres from 71,000.
A treatment plant at Ambatale, which draws water off the Kelani River also supplies around 150,000 cubic metres per day to supplement the demand in the city.
Sri Lanka's western province, which has the capital city and has 1.5 million (7.5 percent) of the total 20 million population and consumes over 795,000 cubic metr