4　Model Validation and Application

Fig.4　Some Coupling Details at the Main Canal

4.1　Model validation

The model was validated by using the flood events with the number of 19990622,20030702,20040710.Due to the storage area and the spare storage area was not be used in the three flood,so only the water level at Nanyu station in south canal near No.5 intersection is taken as verification station.As can be seen from Table 1,the absolute error of the water level of the three typical floods are less than 0.2m.Figure 5 shows a comparison between the simulated and observed daily forebay water level of the 1st Hanchuan station and Fenshui pump station of 20030702 flood.A good agreement is achieved at the high water level stage.However,they are not consistent at the low water level stage.For the real operation rules of the first-level pump station is relatively free by hand,but the simulation operation rules is strictly carried out by computer.Such as the Fenshui pump station was stopped before the water level falling to 24.5m in the real,but in the model it will still run until the water level falling under 23.5m according to the scheduling rules.

Table 1　Model Performance during Three Flood Events in Diaocha Lake Area

4.2　Model application

Influenced by El Nino,In Meiyu rainy period of 2016 in Hubei Province,six rounds of heavy rainfall showed unprecedented extreme value.The five famous lake areas of the Plain lake area were all lost into emergency floods,the water level of the five famous lake either hit an all-time high or excessed the guarantee.The fourth round of heavy rainfall brought the study area to the highest water level of 26.87m on July 9th.And after that the rainfall intensity at the study area was not big,but the neighbouring Hanbei river basin was strongly influenced by the sixth round of heavy rainfall.Within 43 hours,the water level of downstream river at Minle sluice jumped more than 3m from 27.2m on July 18.On July 20,the government department concerned issued a series of flood diversion orders,including diverting flood into the Diaocha lake area by the Tianmen flood control sluice.In order to maximize flood diversion volume of the Hanbei River,and at the same time not obviously increase the waterlogging of the Diaocha lake area,the model was used to simulate the water level of drainage network after flood diversion under different discharge condition of the Tianmen flood control sluice.Figure 6 shows the water and rainfall condition during the Meiyu rainy period at main hydrological station and the comparison of simulated and observed hourly water level at Nanyu station under observed flood discharge of the Tianmen flood control sluice.The Tianmen flood control sluice opend at 6 o'clock on July 20 and closed at 15:30 on July 21,the total diverted flood was more than 1300 million m3,and at the same time the waterlogging in the Diaocha lake area was almost not increased.

Fig.5　Comparison of Simulated and Observed Daily Forebay Water Level of the 1st Hanchuan Station(left)and the Fenshui Pump Station(right)

Fig.6　Water and Rainfall Condition in 2016 Meiyu Rainy Period(left)and Simulation Results of Flood Diversion through Tianmen Flood Control Sluice(right)