Many reservoirs are about to be wiped out

Investigation by scientists at the Institute of Water Resources Research shows that many small and medium reservoirs in the northern provinces are about to end their life, the exploitation capacity has decreased by 50% .

Nearing the end of life

In the northern provinces, most small and medium reservoirs have been built and designed since the 1960s with an average life expectancy of 50 years, while most have been operating for over 40 years. Therefore, out of 185 reservoirs with a capacity of 1-10 million m3 in 18 northern provinces through surveys, many projects have been seriously degraded due to the rapid deposition rate.

West Lake - Hanoi (Photo: Flickr)

Mr. Quach Hoang Hai - Head of Geotechnics Department (Institute of Water Resources Research) said: "Currently only 60% of lakes reach 50-80% of the design capacity of rice irrigation, the remaining lakes due to insufficient water. had to switch to irrigate crops, some ponds designed to irrigate 200ha, now reduced to only 100 hectares ".

According to the initial assessment, in addition to causes due to climate, hydrological conditions, weather changes, vegetation changes, also due to human factors. That is, planning issues, many works are built in the same basin, so often overlapped, leading to a shortage of aquatic resources, many small dams designed not suitable for geological conditions. , hydrology, many works have not completed construction.

Mr. Hai judged that the above factors have led to the phenomenon of sedimentation in recent years taking place at a faster and faster speed and this is the direct cause of reducing the life of the lake. With the construction of the lakes mostly located in the valley, so when landslides occur, the amount of sand and soil has spilled into the reservoirs. But this amount of soil and rock does not penetrate into the belly of the lake or the dead volume, but deposited well into the useful capacity in the contours around the lake.

Because of this phenomenon, the amount of water in the lake is reduced and shorted quickly, leading to people having to use pumps to pump water up, so the amount of water in the lake cannot reach the designed capacity, Especially about the drought season.

In addition, many localities have developed fisheries and agricultural production next to reservoirs, due to the use of a large amount of water, so the water level in the lakes is increasingly depleted.

Must reinvest immediately

Among small and medium reservoirs, there are two types: State-invested and locally built. However, according to Mr. Hai, although the reservoirs still have to accumulate, water storage and irrigation capacity have decreased significantly, but very few have been reinvested. Yes, only the lakes are sometimes repaired by the State, and the local lakes have little investment.

Since many years, the area of ​​watershed forest has been reduced sharply (especially in Phu Tho area), so to overcome, in the short term, it is necessary to plant forests in areas where landslides often occur, soil erosion; At the same time, intercropping tree vegetation with thick roots to limit soil erosion; change the process of operation and opening and closing the lake water according to the construction design.

Mr. Hai also paid special attention to construction solutions such as creating terraced fields on steep terrain, digging small ponds and ditches on tributaries. For lakes located in low terrain, basin-shaped bellies need to be built with a roof and planted under a band to prevent erosion products from entering the lake.

But in order to implement the above solutions, Mr. Hai said that the Ministry of Agriculture and Rural Development needs to have synchronous investment measures for reservoirs, systems of canals, sluice gates, and reservoirs. In particular, small reservoirs built by localities are mainly based on experience, not according to a specific standard, so it is difficult to find technical design maps, so the localities They also need to be active in reinvesting and rebuilding the lake.