Large irrigation dams fail to prevent floods and droughts and ensure water security for local farmers as impacts of climate change intensify, data analysis on the performance of irrigation projects in the northeastern region show.
Ban Kaeng Sila village in Khon Kaen's Ubon Ratana district is just one kilometre away from Ubolratana Dam, the largest irrigation dam in the Northeast with a storage capacity of 2.4 billion cubic metres of water, or nearly one million Olympic swimming pools.
But local farmers had to endure severe drought for three years between 2018 to 2020, as the dam's reservoir dried.
"We were suffering from a water shortage," said Suchit Phetdong, a farmer in Ban Kaeng Sila village.
"Not just lacking water for growing crops, but we also had insufficient water for our own consumption.
"We have Ubolratana Dam nearby, but the dam had no water.
"Our village relies on irrigated water from the dam for both consumption and farming because this area has no groundwater, so when the dam did not release water, we were in big trouble."
Mr Suchit said that due to the lack of irrigated water and severe drought during the past three years, many farmers had to stop growing rice for two years in a row, in 2019 and 2020, because there was no water for farming.
Most villagers, especially young people, left to find work in Bangkok to support their families.
"I think the dam can neither prevent flood nor drought," Mr Suchit said.
"We have to rely solely on rain to farm, even though we are close to the dam.
"The dam cannot protect us from floods either.
"When there is intensive rain, the low-lying land is inundated."
The difficulties of the people in Ban Kaeng Sila village struggling with a severe water shortage is just one example in the Northeast that indicates the inability of large-scale irrigation projects to prevent flood and drought.
Data shows severe water scarcity
According to data on the Ubolratana Dam provided by the Electricity Generating Authority of Thailand (Egat), the amount of available water in the dam's reservoir dropped below zero percent three times in the past 10 years during the dry seasons of 2016, 2019, and 2020.
The Royal Irrigation Department (RID) imposes water restrictions when the dam's water level falls below 30%. The dry period between April 2018 until October 2020 saw no water released for rice irrigation.
Looking at Khon Kaen's annual rainfall data, these periods of low storage water in Ubolratana Dam's reservoir are perfectly matched with the years of record drought in 2012-2015 and 2019, where the annual amount of rainfall in the province dropped more than 10% compared to 30-year average, according to the Meteorological Department.
Khon Kaen is a significant contributor to Thailand's rice crop. The one-two punch of Ubolratana Dam's water restriction measures and rainfall deficiency in 2019-2020 led to a sharp drop in dry season rice production.
The province saw its 87,442 tonne rice crop dropping to 13,687 tonnes in 2018 -- an 85% fall. Subsequent years saw a 90% reduction.
Dams are also vulnerable to intense rainfall. Tropical Storm Sonca in July 2017 quickly filled up the Huay Xai Kamin Dam in Sakon Nakhon and caused it to collapse, flooding farmland, homes, and businesses in Muang district.
Old dams fail to do the job
Asst Prof Sitang Pilailar, a leading water management expert at the Department of Water Resources Engineering, Kasetsart University, said large-scale irrigation dams often fail to mitigate flood and drought.
This was the result of weather anomalies in recent decades, which flowed in turn from climate change.
"As all of the irrigation dams are designed based on 30 years of water situation statistics at their location, the extreme precipitation pattern due to climate change is catching these dams off-guard, because they are unable to keep up with the rapid change in weather patterns," Asst Prof Sitang said.
State agencies have plans for over 48,000 new irrigation and water management projects nationwide with a budget of more than 353 billion baht, nearly twice the public health budget of 2021.
However, she said these projects are also designed based on historic water data and no estimated climate impacts have been taken into consideration.
According to the government budget plan for 2022, the RID will invest in 400 new water management projects with a budget of 27 billion baht in the Northeast in the next fiscal year.
Among them are two new irrigation dams, Lam Nam Chi Reservoir and Lam Saphung Reservoir in Chaiyaphum, and many detailed projects under the controversial 3.8-trillion baht Mekong-Loei-Chi-Mun River Management and Diversion megaproject.
Asst Prof Sitang warned that even though Thailand will have more projects which aim to improve water management and disaster prevention, they will face similar problems as the old ones and be unable to cope with gradually intensifying climate impacts.
"We need to focus more on investing in small-scale localised water management projects, such as digging ponds for each plot of farmland, which allow farmers to rely on their own water sources," she said.
"We also need to link up the irrigation projects that we have to create a cohesive water management system, which will allow us to better cope with weather extremes."
Large projects still needed
Nevertheless, Office of the National Water Resources (ONWR) secretary-general Somkiat Prajamwong insisted that large scale irrigation projects are still essential water management tools.
They are needed for expanding irrigated land and preventing flood and drought, especially for the northeastern region, where most agricultural lands are still outside irrigation system and more prone to water disasters than in other regions, he said.
"The authorities are well aware of the climate change impacts on the irrigation system and state agencies are working hard to improve water management in each local river basin to cope with the challenges," Mr Somkiat said.
"Despite some limitations to mitigate climate impacts, we still need more large-scale irrigation projects as tools for long-term water management."
This story is supported by the Mekong Data Journalism Fellowship jointly organised by Internews' Earth Journalism Network and the East West Center.