The Royal Irrigation Department has unveiled a two-pronged plan to divert runoff from the Kaeng Krachan dam into an irrigation system on both sides of the Phetchaburi river and into a drainage klong before reaching the Phetchaburi dam.
The contingency plan is designed in anticipation that more water, up to 230-250 cubic metres/second, will pour into the Phetchaburi river on August 12. The first prong entails the diversion of 55 cubic metres/second of water into irrigation system on both sides of the river and another 35 cubic metres/second of water into D9 drainage klong.
RID said that this measure would cut down the volume of runoff by up to 90 cubic metre/second before it reaches the Phetchaburi dam and, hence, reduces the volume of water flowing downstream into Phetchaburi river and mitigates the impacts on five downstream districts namely Kaeng Krachan, Tha Yang, Ban Lat, Muang and Ban Laem.
The second prong entails drainage of between 140-150 cubic metres/second of water through the Phetchaburi dam into the Phetchaburi river after water has been drained out of the river into the sea and the strengthening of embankments on both sides of the river.
The RID has predicted that up to 100 cubic metres/second of water or 8.64 million cubic metres of water will spill over the spillway of Kaeng Krachan dam on August 10. In the meantime, 210 cubic metres/second of water will be drained downstream from the dam into Phetchaburi river and the drainage volume will be increased to 230-250 cubic metres/second if there are more rains in the Phetchaburi river basin.
Deputy Prime Minister Chatchai Sarikalya on Monday met with representatives of relevant agencies to discuss water situation in Kaeng Krachan dam. He later flew in a helicopter to survey the dam and Phetchaburi river.
The second announcement issued by the ad hoc crisis centre at noon on Monday said that runoff from Kaeng Krachan’s spillway will affect low-lying areas on both sides of the Phetchaburi river in Kaeng Krachan, Tha Yang, Ban Lat, Muang and Ban Laem districts.
The runoff was anticipated to reach Phetchaburi dam at midnight tonight and eventually to Muang and Ban Laem districts at about midnight Tuesday night and will swamp low-lying areas up to 50 cm deep.
Regarding the current condition in the Phetchaburi river, volume of water accounts for 30-40 percent of the river space, hence, making the river capable of absorbing more water to be drained from Kaeng Krachan dam.