The government is facing a challenge of adding more water in 38 major dams across the country during the one-and-half month golden period of rainfall after realising that less water has flowed into the dams than expected.
State agencies, including the military, are looking into the cause of "missing" water.
Somkiat Prajamwong, secretary-general of the Office of the National Water Resources, said the cabinet is concerned about the water situation because many dams nationwide share the same problem of less water inflow and this may lead to a critical drought problem next year.
"We want to know whether less rainfall is truly the cause of the problem or whether water has been kept by certain groups. We want to know where it [the water] went missing. Our challenge is how to keep every drop of water in the dams," he said, adding that state agencies, including the military, had discussed a solution that will be sent to cabinet shortly.
No more details were available on what is likely to be proposed.
He also quoted concerns raised by Deputy Prime Minister Prawit Wongsuwon, saying that if water can't be stored in the dams, there is no use to build more.
He said it was important to make sure all dams in the eastern region are full of water to support activities related to the Eastern Economic Corridor. Currently, there is 33.8 billion cubic metres of water nationwide or 41% of the total carrying capacity of dams.
However, only 10.01 billion cubic metres or 17% is usable.
Reservoirs in the North, Central and the Western regions have had more outflow than inflow between May 1 to July 28 or 2.04 billion cubic metres of outflow compared with 957 million cubic metres inflow in the North, 55 million cubic metres compared with 37 million cubic metres in the Central region, and 2.5 billion cubic metres compared with 671 million cubic metres in the West.
Meanwhile, in the Chao Phraya River basin, only 685 million cubic metres of water is left for use, which is less than the Royal Irrigation Department (RID)'s water distribution plan for this year requiring 930 million cubic metres of discharged water from now until the end of October.
He said fixing the problem requires pumping water from the tail end of the dam to allow it to be stored inside and clearing obstacles which prevent water flow into the dams due to human activity or structures in the water.
Other long-term measure regarding water diversion to dams include the Yuam River diversion project to Bhumibol dam in Tak province, which is now before an expert committee from the Office of Natural Resources and Environmental Policy and Planning (ONEP).
The project will add more water to dams by expanding the full storage capacity of 10 billion cubic metres.
However, the dam can only hold four billion cubic metres of water on average during the rainy season, which means there will still be room to store water, he added.
Meanwhile, Taweesak Thanadechophol, RID deputy director-general, said people should think about water conservation as increased inflow alone may not solve the problem.
More rainfall is picked for next month, lasting until October, making it the best time to preserve water in dams. He also suggested farmers postpone any plantation plans until there is more frequent rainfall.