With water levels in dams "more critical than the 1987 and 1998 severe drought situations", the Electricity Generating Authority of Thailand (Egat) proposed yesterday that two major dams release less water to ensure stocks last for this month.
The Thai Meteorological Department said that downpours to alleviate the situation may not arrive till August.
The Royal Irrigation Department (RID), meanwhile, will send a team to look into the three-metre-deep collapse of a road in Saraburi's Nong Sua district by Klong Rapeepat.
During a meeting at the RID head office, agencies expressed concern over the effect of the drought on the Chao Phraya River Basin. Bhumibol Dam in Tak province, Sirikit Dam in Uttaradit, Khun Dan Prakan Chon Dam in Nakhon Nayok and Pa Sak Jolasid Dam in Lop Buri held water below the minimum reservoir level as of yesterday.
Another 14 dams contained only 30 per cent of capacity, the meeting was told.
The lack of dam-refilling rainfall at reservoirs - especially Bhumibol Dam and Sirikit Dam - in the first five days of July, prompted officials to claim the dams had 42 per cent less water than in 1987.
The RID plan to release eight million cubic metres of water from Bhumibol Dam and 17 million cubic metres per day from Sirikit Dam, must be cut to five million and 11 million respectively, an Egat official proposed. This was to ensure enough water to last the whole of July, or else it would affect the public's water usage, the official said.
RID deputy chief Suthep Noipairoj said a working team would investigate the real cause of the Nong Sua road collapse and check on roads at risk from subsidence. The team would study three possible causes: a drop in the underground water level after the RID failed to "send" water into irrigation areas; farmers' taking too much underground water; or natural conditions such as soil quality.
Council of Engineers deputy secretary-general Amorn Pimanmas said the road collapse might have been the result of a base failure, which could happen to a road running parallel to a canal. A "rapid draw down" phenomenon as water pressure within the soil built up, could lead to a base failure; soil underneath would slide towards the canal causing the road surface to collapse, he explained. But this base failure was more severe than usual, he said.
Amorn said other factors might be at play, such as how the road was built - if it soil was not compressed enough, water erosion, or the road having a heavy weight upon it.