May 31 (UPI) -- New dams for hydroelectricity are altering Cambodia's Mekong River, and could threaten fish migration, livelihoods and regional food security -- and the predictable seasonal patterns that farmers and anglers depend on.
A new paper from the University of Illinois and Iowa State University, published this month in the Journal of Soil and Water Conservation, suggests officials partner with locals, who have a deep knowledge of the river, to address the problem. Their knowledge, along with technical and scientific findings, is important for developing effective strategies to adapt to the changing flows and uses of the river.
"Due to years of civil wars that destroyed infrastructure and hindered modernization, only a little more than half of the Cambodian population has access to electricity," Kenneth Olson, professor emeritus in the Department of natural Resources and Environmental Science at UI, said in a press release. "Hydropower is a critical building block for needed modernization. However, using the water resources for power presents difficult trade-offs for fishers and farmers."
The Mekong River and the Tonle Sap Lake and River area dominate the Cambodian landscape. The Tonle Sap River is a tributary of the Mekong River, which connects it with Tonle Sap Lake northwest of Phnom Penh, Cambodia's capital.
"This unique, complex hydrological system is strongly influenced by the Asian monsoon," Olson wrote. "During the monsoon season, the Tonle Sap Lake surface area enlarges to become four times greater than in the dry season and hold nine times more water by volume. The surface water level can change by more than 30 feet, so homes are either in floating villages or on stilts."
The phenomenon occurs because of the seasonal flooding that begins in May and June, which causes the Mekong River to back up into the Tonle Sap River and Lake. When the rain stops in November and water levels in the Mekong River begin to drop, flow in the Tonle Sap River reverses and becomes a tributary again. That means the smaller river flows northwest into the lake for six months out of the year, and reverses and flows into the Mekong River for the other six months.
The flooding brings needed sediments and nutrients for crops and fishing. But the sedimentation increase can also shut down dry-season navigation between the capital and regional centers because it makes the already-shallow lake even more shallow over time.
There are plans to build 11 more dams on the main stem of the lower Mekong River. River ecology scientists and environmentalists are concerned, however, about how the dams will affect the historically predictable downstream flows and seasonal flood patterns, which birds, fish and plant communities have adapted to over time.
Fish migration is the biggest concern, because of Cambodia's dependence on fish for high-quality protein and food security, and one of the dams under construction will block fish migration and could flood homes behind it.
"The tradeoffs among hydroelectricity production, food security, and fisheries' livelihoods are difficult and complex, and developing an integrated resource management plan is not an easy task," Olson said. "Broad participatory approaches that include local residents in the scientific and technical information exchanges can improve decision-making and better meet government, industry, and rural communities' goals."
Fishers and farmers can keep adapting if they're given opportunity, resources and tools, he said. The issues don't only affect Cambodia, though -- they impact the food security of urban people throughout Southeast Asia.