Our reporter Wang Tianqi
Yesterday, Guanting Reservoir, the first large reservoir built after the founding of New China, celebrated its 70th birthday.
In May 1954, Guanting Reservoir was completed. This is the largest controlled water conservancy project on Yongding River, and it is an important barrier to stop the flood of Yongding River from threatening the downstream.
During the 70 years of wind and rain, Guanting Reservoir has played a great role in flood control, water supply and irrigation. From the cradle of water conservancy in new China to the vivid practice of ecological civilization construction in the new era, Guanting Reservoir keeps pace with the times and walks calmly.
It is estimated that by 2035, Guanting Reservoir will restore the function of drinking water source in Beijing. By then, Guanting Reservoir will glow with new brilliance.
The Cradle of Water Conservancy in New China
Guanting Reservoir is located in the upper reaches of Yongding River, at the junction of Beijing and Hebei in the northwest of Beijing. The Yongding River was flooded in history. After the founding of New China in 1949, the CPC Central Committee decided to build Guanting Reservoir to eradicate the flood and make good use of Yongding River resources. Guanting Reservoir is named because the dam is located in Guanting Town, Huailai County, Hebei Province.
Guanting Reservoir started construction in October 1951 and was completed in May 1954. It is the first large reservoir built after the founding of New China. Over the past 70 years, Guanting Reservoir has supplied 42.9 billion cubic meters of water and generated 8.7 billion kWh of electricity for the downstream areas of Beijing, Hebei and Tianjin. Since 1953, Guanting Reservoir has held more than 1000 cubic meters/second of floods for 8 times, basically eliminating the flood disaster in the lower reaches of Yongding River. In last year’s "23.7" catastrophic flood in Haihe River basin, Guanting Reservoir closed its floodgates and held 79 million cubic meters of flood, with a flood retention rate of 100% and a peak clipping rate of 100%, which greatly relieved the flood discharge pressure of the downstream river.
Guanting Reservoir is also the cradle of water conservancy in New China. In the process of building the reservoir, under extremely difficult conditions, the older generation of water conservancy experts carried out a lot of experiments and technological innovations, and invented advanced technologies, processes and equipment such as Guanting wave formula, Guanting evaporation conversion coefficient, and China’s first water level telemeter, which have been used for reference in the construction and management of other reservoirs. Water conservancy experts who have participated in the construction of Guanting Reservoir have successively invested in the construction of many reservoirs in Beijing, such as Miyun Reservoir and Ming Tombs Reservoir. Mr. Zhang Guangdou, a well-known expert in water conservancy and hydropower engineering in China, once participated in the construction of Guanting Reservoir, and later presided over the construction of Miyun Reservoir as the chief design planner, creating a miracle of "retaining flood in one year and completing it in two years".
Purification of incoming water quality by three constructed wetlands
In late spring and early summer, the No.8 Bridge wetland located at the entrance of Yongding River in the upper reaches of Guanting Reservoir is lush, with streams, small lakes and islands interwoven, which looks like a beautiful ecological picture.
The construction of this wetland is not to enjoy the beautiful scenery, but to purify the water in the reservoir. "No.8 Bridge Wetland has built various forms of wetlands such as forest wetlands, stream wetlands, lake wetlands, island wetlands and terraced wetlands, and planted 11 kinds of aquatic plants such as reeds, calamus and lotus flowers, which can purify water." Fu Xinlei, director of Yongding River Bank Management Office of Guanting Reservoir Management Office, said that the water coming from the upstream from west to east enters the No.8 Bridge Wetland after being adjusted by the gates of three water retaining weirs on the main river, and can stay in the wetland for 72 hours before entering the reservoir. It was found that the water quality of the upstream influent was obviously improved after the wetland purification treatment, and the removal rates of ammonia nitrogen, total phosphorus and total nitrogen in the water ranged from 26% to 88%.
It turned out that the water quality of Guanting Reservoir was good for more than 10 years after its completion, but since the 1970s, the water quality of Guanting Reservoir has gradually deteriorated due to industrial development, direct sewage discharge, non-point source pollution of agricultural planting around the reservoir area, and sharp drop of upstream water. Although it has been treated several times, the results are not significant. The water quality of Guanting Reservoir once reached or even worse than V in the dry season. In 1997, Guanting Reservoir was forced to withdraw from the drinking water source system of the capital, and it was only used for industrial water and environmental water of urban rivers and lakes.
It is urgent to pay off the water quality. In the 21st century, Guanting Reservoir has implemented a number of measures, such as dredging emergency water supply, constructing artificial wetlands, proliferation and discharge, and preventing water bloom. Ecological protection zones and sewage treatment plants have also been established in the upstream and downstream basins of the reservoir to remove pollution and improve water quality.
In 2003, the Heituwa constructed wetland located at the entrance of Yongding River upstream of Guanting Reservoir was opened and put into use the following year. The upstream water is purified by aquatic plants in the wetland, most of which are intercepted by suspended substances such as algae, and nitrogen, phosphorus and other substances are also effectively absorbed, and the water quality in the reservoir is obviously improved. In 2007, Guanting Reservoir resumed the function of Beijing standby drinking water source.
Adhere to ecological management. In 2019 and 2021, No.8 Bridge Wetland, which is about 10 kilometers away from Heituwa Wetland, and Guishuihe Wetland, which is located in the northeast of the reservoir area, were built and put into use. The three wetlands form a water purification system with high integration of water purification, water ecology and water landscape, and jointly protect Guanting Reservoir.
Li Xiaohong, director of Beijing Guanting Reservoir Management Office, said that at present, the constructed wetland of Heituwa, the water purification wetland of No.8 Bridge and the water purification wetland of Guishui River have formed a total wetland area of 330 hectares, with an annual treatment capacity of 153 million cubic meters. Since the operation of the three wetlands, about 1.2 billion cubic meters of upstream water has been treated. After the water flows through the wetlands, the purification effect is remarkable, and the removal rate of total nitrogen and ammonia nitrogen is the most obvious, which can reach more than 50%. "At present, the water quality of the reservoir can be kept stable at the third-class standard of surface water (except fluoride index)." Li Xiaohong said.
Dredging helps restore the function of drinking water source
In recent years, Guanting Reservoir has returned to public view because of its important position.
From 2001, the water storage capacity was less than 100 million cubic meters, to 2003, when Cetian Reservoir concentrated water delivery to Guanting Reservoir, and then to 2019, when the Yellow River water was transferred across the basin for the first time, the water storage capacity of Guanting Reservoir gradually increased. By April 13, 2022, the total storage capacity of Guanting Reservoir reached 692 million cubic meters, setting a new high in 26 years. Since Beijing began to try the ecological water supply of Yongding River in 2017, Guanting Reservoir has accumulated nearly 2 billion cubic meters of water supply to the downstream ecology, helping the Yongding River to pass through the whole line.
According to the Beijing Urban Master Plan (2016 -2035), Guanting Reservoir will resume its drinking water source function in 2035. For this goal, Guanting Reservoir is still making unremitting efforts.
This year, Guanting Reservoir carried out a pilot project of dredging, which has been put into construction.
Lai Yuan, chief designer of Guanting Reservoir Dredging Pilot Project, introduced that the pilot project plans to dredge about 11.54 million cubic meters, mainly to clean up underwater silt, and at the same time take into account the siltation area on the water beach. "The dredging scale of more than 11 million cubic meters this time is calculated according to the underwater topographic parameters of the reservoir and the designed dredging surface." Laiyuan said that on the one hand, dredging can increase the strategic water resources reserve of Guanting Reservoir, clear the area where the sediment pollution of Guanting Reservoir is relatively concentrated at present, help to further pay off the water quality, and also increase some flood control storage capacity, which provides a strong guarantee for restoring the function of drinking water source of Guanting Reservoir.
Laiyuan told reporters that the sediment removed through the dredging pilot project will also be recycled and consumed, and will be filled into the current gaps, ditches and pits in Huailai County around the reservoir to help the local economic construction; Part of the silt will also be made into bricks and green soil for the construction of the reservoir waterfront.
The dredging pilot project is planned to be completed in about two years. After the completion of the project, a professional evaluation will be conducted to determine whether the expected effect has been achieved. "This pilot dredging project is an exemplary guiding project. If the effect meets expectations, it will continue in the future." Laiyuan said that according to the calculation, in order to achieve the goal of restoring the function of drinking water source in Guanting Reservoir in 2035, Guanting Reservoir needs a total of 210 million cubic meters of dredging.
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