2.1.2.3 Retention projects

•Dongpinghu Lake

Dongpinghu Reservoir is an important diversion works on the lower reach of the Yellow River. It is located within Shandong province with the total area of 627 km², the current total operation capacity for flood control is 3.05 billion m³, out of which, new lake covers 2.16 billion m³, and old lake covers 890 million m³. The main function of Dongpinghu is to solve issue of flood control on the narrow section below Aishan, and control release discharge not greater than 10,000 m³/s below Aishan station, to guarantee the safety of Jinan city, railway between Tianjin and Shanghai, as well as large area along both banks below Aishan. Meanwhile, it has the function to regulate and store flood occurring on the Wenhe River. There are five intake gates such as Shiwa, Linxin, Shilibao, Xuzhuang, Gengshankou in Dongpinghu Lake with diversion capacity 8,500 m³/s, and there are three outlet gates such as Sigai, Chenshankou and Qinghemen with total outlet capacity 3,500 m³/s.

•Beijindi Retention area

Beijindi retention area is located on the left bank, 190km far away below Huayuankou, Zhengzhou city, where is near area between main dykes of the Yellow River and Beijindi. And it was approved to be constructed in 1951 by State Council, and it is one of important structure measures to defense flood beyond standard on the lower reach of the Yellow River. The effective diversion of water in Retention area is 2 billion m³, the total retention area is 2,316 km² which involves in 2,166 natural villages, 67 townships, 7 counties and Henan, and Shandong provinces, with population of 1.5723 million. The operation principle of Beijindi Retention area is as follows: if the flood at Huayuankou station occurred above 22,000 m³/s, and if the flood could not retained by Sanmenxia, Guxian and Luhun reservoirs combining with partially operation of Dongpinghu, it should be submitted to the State Council for approval of operation of Beijindi Retention area to divert water. Qucun diversion gate, Zhangzhuang outlet gate and pre-left outlet on the dyke below outlet gate have been used for releasing water back to the Yellow River.

•Qihe River Widened works

Qihe River Widening Area is mainly to solve the issue of ice-run flood on the narrow section of Jinan, when the special flood occurs on the Yellow River, it can be used to retent part of flood. The total area of it is about 106 km² with effective retention capacity 390 million m³. And Doufuwo diversion gate has been constructed near the main dyke and Dawu outlet gate has been constructed on the lower part of extension area to the Tuhaihe River.

•Kenli Widened Area

The Kenli Widened area locates in Kenli county, Shandong province, with main purpose of ice-run control, next to flood-control, sediment warping and irrigation in ensuring the safety of the inhabitants along the both banks and the development of the oil field production and agriculture. There are two inlets structures built in the main dyke at Mawan and Caodian and one outlet built on the lower part of the widened area at Zhangqiuwuzi. The widened works has an area of 123.33 km², with retention storage 327 million m³.

• Dagong flood detention area

In 1956, the Dagong flood detention area was built up in order to fight against the extraordinary flood. The area locates in between the main dyke on the northern bank of the Yellow River south-east in Xinxiang city and the Beijindi Dyke with flood dentention area 2,040 km² covering areas of Fengqiu, Changyuan, Yanjin and Huaxian counties, Henan province. As operation, the floodwater will mostly flow through the Taihang canal into the Beijindi detention area and regress to the Yellow River through the outlet at Zhangzhuang, meanwhile, partial floodwater will regress to the Yellow River through the Taihang dyke and downward to Dacheji, Changyuan county. The Dagong detention area dose not equip with flood detention inlet structure, but with simple spillways cofferdam on the floodplain, one hundred meter away from and before the main dyke of the Yellow River at Dagong village, Fengqiu county, by bricking of galvanized wire rock cages and, one cut-off wall 1.5 m deep and 1.0 m wide made of galvanized wire rock cage was set up upstream and downstream and both tips were protected.

2.1.3 Non-engineering measures for flood control

The main non-engineering measures for flood control are flood control organization system, flood control communication system, hydrological observation and forecasting system, decision-making support system, regulation and commanding system, and, flood detention and retention basin management etc.

Flood control organization system: Under the leadership of the State General Headquarters for Flood Control, all the provinces along the Yellow River have established flood control headquarters and its administrative offices. The administrative chiefs of each level, governments should be the commmander who will be responsible for all affairs of flood control. The administrative offices for the Yellow River flood control are located in the Yellow River management units, responsible for the daily works of flood control.

The emergency squads for flood fighting are composed of the Yellow River specials team, mass team, the Liberation Army, and, the armed policemen.

Communication system for flood Control: The Yellow River special communication network is composed of advanced communication means like microwave, "a point to multi-sites" microwave, wireless system, satellite, mobile communication, short wave, ultra short wave and PADX. Each means of communication is complemented and perfected each other. The all above means of communication have provided a reliable communication means for Flood Control. And also Warning Information Feedback System has been installed in the floodplain and retention area to guarantee the masses safely remove from there when the extraordinary flood occurs.

Hydrological forecasting system: There are 458 hydrometric stations, 58 water level stations, 2,376 rainfall stations all together in the Yellow River basin. At present, the way of observation is still done by hand. And, some self-recorder instrument have been only installed in a very few rainfall stations. The basic facilities of hydrometric stations are relatively completed. The method used for flood forecasting is still conventional way. The forecasting methods adopted in the Yellow River usually are decided through many years tests of flood forecasting and repeatedly revising based on practicality, physical cause of formation and a vast amount of observed data. Those methods are flexible to operate and easy to calculate which has formed a set of relatively completed and applied forecasting method for storm flood and ice run flood of the Yellow River Basin. And the methods basically have met the requirements of flood control combining with the main stream and its tributaries.

The decision¨Cmaking support system: The system was established based on the hydrological observation and forecasting data, rich historical data and the principle of regulation of flood control. And, the pre-scheme of flood regulation can be to quickly work out by using modern computer technology. And the data will be continuously revised in real time and will be provide reliable support for decision-making of flood control.

Management of retention basins: The task of detention basin administration is to well manage the retarding works, work out a plan for remove and relocation, conduct basic technical work of detention operation, and, protect retarding facilities.

Relying on engineering and non-engineering flood control measures mentioned above, and 12 times floods with the discharge above 1000m³/s (including 1958 flood with discharge 223000m³/s) have been conquered to bring about a radical change in the history.

2.1.4 Examples of River flood

2.1.4.1 1958 flood

On July 17, 1958, a peak discharge of 22,300 m³/s happened at Huayuankou Station where the maximum flood has been observed. The flood arrived at Lijin Station on 25^th with peak discharge of 10,400 m³/s. This flood was formed mainly because of heavy rainfall happened in the trunk and tributaries area below Sanmenxia. The peak discharge has the characteristics of high water level, great volume, sharp coming, low sediment concentration and long duration. The discharge greater than 10,000 m³/s at Huayuankou Station had maintained for 81 hours and the total volume of flood in 7 days was 6.1 billion m³. The water level along 400km long narrow section, where is mostly located in Shandong Province, had exceeded the guaranteed water level, in which, the water level at Luokou Station had exceeded 1.09m. The time of exceeding guaranteed water level of each place was between 35~80 hours respectively. After natural retarding in Dongping Lake, the water level at some sections in the lake was 0.1m higher than that of the crest of lake dykes, and making the situation very dangerous. Through about million of people and the army men day and night hard working, more than 600km long secondary dykes had been rush repaired and disasters of dyke breaching had been prevented. According to statistics that there were more than 1,290 various danger situations occurring in Shandong section where flood situation was grimmer. But they were out of danger one by one after rush repair. This was a successful case of flood control by relying on dykes because there was no reservoir on the Yellow River at that time.

2.1.4.2 1982 flood

On August 2, 1982, a peak discharge of 15,300 m³/s occurred at Huayuankou Station located on the lower Yellow River, which was the second major flood comparing with 1958 flood since the Yellow River came back to its original course. This flood was also formed by rainstorms happened in the reach from Sanmenxia to Huayuankou. The flood volume of Huayuankou Station in 7 days was 5.002 billion m³. The floods with discharge greater than 10,000 m³/s lasted 52 hours and the average sediment concentration was 32.1 kg/m³. The section from Huayuankou to Sunkou had been silted. Comparing with 1958 flood of 22,300 m³/s occurred at Huayuankou Station, even discharge along the channel was 6,000~7,000 m³/s less, but the flood level was about 1m higher at the section from Huayuankou to Sunkou, and, 2.09m higher at Liuyuankou because of aggradation of the channel. In this flood, dykes and vulnerable spots of the 887km long Yellow River by the flood were in danger for about 1,079 times. 310,000 army soldiers and people took part in rush repair through emergency mobilization and retarded floods to Dongping Lake. Finally the flood flowed into the sea safely.    

2.1.5 Flood Control Benefit on the Lower reach

The economic benefit of flood-control on the Lower reach is calculated upon the overall benefit through operation of the flood-control works on the lower Yellow River, the Sanmenxia Reservoir, and the flood-control works on the Yi, Luo and Qin Rivers as well as the non-engineering flood-control works. For 38 years from 1951-1987, the accumulated static investment has been about 3.987 billion RMB (price in those years) in flood-control. Among which, infrastructure 2.366 billion RMB, institution fee 860 million RMB, operating fee 638 million RMB, and resettlement fee 123 million RMB. The labor input converted is equivalent to 760 million RMB. The flood-control economic benefit amounted to 50.492 billion RMB (those years price), prevented 927,000 hm² of cropland from being flood, and, created negative benefit 695 million RMB. The net flood-control benefit will be 45.05 billion RMB if deducting the total investment and negative benefit as well as the labor input converted. The flood-control benefit will be 61.788 billion RMB if calculation upon the unchangeable price in 1980.  Up to now, the central government has already invested 7 billion RMB in flood-control, the total benefit of flood-control and hazard reduction may reach to 400 billion RMB if adding the indirect economic benefits.