1. Hydrological and meteorological conditions
The basin has a warm temperate monsoon continental climate, with oceanic climate characteristics such as moist air, warm winters and cool summers, and a mild climate. The multi-year average temperature is 11.8℃, the average temperature in the coldest month is -2.9℃, the average temperature in the hottest month is 25℃, the extreme maximum temperature is 39.6℃, and the extreme minimum temperature is -19.6℃. The multi-year average frost-free period is 200 days, and the maximum frozen soil depth over the years is 0.5m. Due to the influence of atmospheric replenishment conditions, geographical location, topography and other conditions, precipitation within the territory has the characteristics of uneven spatial and temporal distribution, and alternating abundance and dryness. The multi-year average precipitation is 686.7mm, the minimum annual precipitation is 388.5mm (1986), the maximum is 1185.3.0mm (1964), and the wet-to-dry ratio is 3.5. The period of continuous occurrence of good and bad times is generally 2 to 3 years. The four months of the flood season from June to September contain more than 70% of the annual precipitation.
2. Runoff
According to the restored natural runoff data of the Neijiahe Menlou Reservoir Hydrological Station from 1952 to 2001, the average natural runoff of the Menlou Reservoir for many years is 207 million m3, of which the flood season is 6 to In September, it was 159 million m3, accounting for 76.8% of the annual water supply. There are great inter-annual changes. The maximum annual runoff occurred in 1964 at 552.42 million m3, and the minimum annual runoff occurred in 1999 at 8.78 million m3. The ratio of abundance to dryness was 63.
According to the restored natural runoff data of the Waijiahe Fushan Hydrological Station from 1956 to 2004, the multi-year average natural runoff at the Waijiahe Fushan Station is 202 million m3, of which the flood season from June to September is 169 million m3. Accounting for 83.6% of the annual water supply. The inter-annual variation is also great. The maximum annual runoff occurred in 1964, which was 564.96 million m3, and the minimum annual runoff occurred in 1999 and 2000, which were both 00,000 m3.
3. Flood
In the "Flood Control Plan for the Lower Section of the Waijia River in Yantai City, Shandong Province" compiled by the Yantai Water Conservancy Construction Survey and Design Institute in November 2009, the flow rate was adopted respectively. The design flood was calculated using two methods: data and heavy rainfall data. After comparative analysis, it was finally determined to use the design flood deduced from the flow data as the design flood calculation result of Dagu Jiahe River.
To deduce the design flood of the Jiahe River in Dagu from the flow data, firstly calculate the frequency based on the maximum peak flow in the 57 years measured at Fushan Station in the Waijiahe River from 1952 to 2008, and obtain the design frequency peak flow of Fushan Station, and then The design frequency peak flow of the Waijia River interval is deduced through the hydrological analogy method (the flood in the Waijia River interval is the flood generated within the Waijia River basin area of ??1072km2 and the basin area below the Neijiahe Menlou Reservoir of 145km2, totaling 1217km2); the inflow flood of the Menlou Reservoir and The spillway discharge flow adopts the calculation results in the "Preliminary Design Hydrological Analysis and Calculation Report of the Menlou Reservoir Danger Relief and Reinforcement Project in Yantai City, Shandong Province" compiled by the Hebei Water Conservancy and Hydropower Survey and Design Institute in 2008; the floods in the Waijiahe interval and the Menlou Reservoir are combined. The superposition of flood discharges at different frequencies and at staggered periods is the design flood of the Dagu Jiahe River. After calculation, the design flood peak flows of Dagu Jiahe River once in 50 years and once in 100 years are 5567.7m3/s and 6774.8m3/s respectively; the design flood peak flows in 50 years and once in 100 years at the confluence of the Inner and Outer Jiahe River are respectively are 5407.5m3/s and 6542.6m3/s.
4. Tide level
There is no tidal data at the mouth of Jiahe River. This calculation borrowed the measured tidal data from Yantai Port 8km away. The tide here is mainly controlled by the tidal waves of the Yellow Sea. It is a regular semidiurnal tide. The seasonal changes of the tide are also very obvious. Its annual change curve is a peak and a valley type. The trough is in the winter half of the year, with the lowest from January to February, and the peak is in the second half of the year. It is highest in August, with annual variation ranging from 45 to 49 cm. Since floods mostly occur during the flood season, the calculation uses the highest tide level data measured in Yantai Port during the flood season, and Gumbel's Type I limit distribution law is used for calculations. The theoretical frequency curve and the empirical frequency curve of the high tide level are drawn. The two curves match well.
Finally, it was found from the theoretical curve:
The average high tide level for many years: 1.78m;
The high tide level when P=1%: 2.39m;
P=2 High water level at %: 2.28m;
High water level at P=5%: 2.15m;
High water level at P=10%: 2.04m;
High tide level at P=20%: 1.91m.