| The plain river network region is developed place and has a large population. In river network, water system is very complex, and the water flow is intricate. The tidal river is transition section of river and ocean. In this section, water is not only influenced by upstream runoff, but also influenced by downstream estuary tide. The water regime is changeable, flow regime is unstable, and flow direction is changing at any time. Due to complexity of self-conditions, we could simulate water flow only using numerical method in most situations. The core problem is the establishment and solution of numeric model for river network. Meanwhile, establishing hydrodynamic model is the base of establishing other models.This paper is supported by National Science and Technology Major Project for Water Pollution Control and Treatment (NO. 2008ZX07208-009). On the basis of analyzing hydrodynamic conditions of Shuangtaizi Estuary, tidal river hydrodynamic and water quality model is established based on DHI Mike11 model system using collected river water regime, weather data and measured river salinity data. The river channel roughness n and longitudinal dispersion coefficient Ex are calibrated through measured water level and salinity data respectively. And then the rationality of model is validated. The major contents and research results are as follows:(1) The computation results show that the modeled level and measured level coincide well, the mean error is less than 15%. The local sensitivity analysis for channel roughness reveal that the water level of zhangmingjia monitoring station has the highest sensitivity while changing midstream channel roughness, downstream channel roughness takes the second place; the channel roughness of upstream has the lowest sensitivity. Downstream roughness of Raoyang River is larger than upstream. The upstream channel roughness sensitivity of Raoyang River could neglect compared with other reaches. Meanwhile, the roughness affects tidewater transmission period and tidal range. The volume of tidal prism of Raoyang River during three irrigation periods in wet year is respectively The proportion of upstream tidewater in the total demand water of reed field in three irrigation periods for wet year is respectively 1.09×10~7,1.17×10~7,1.61×10~7m~3. It's 1.35×10~7,1.3×10~7,2.54×10~7 m~3 for normal year;and 0.98×10~7,1.24×10~7,1.999×10~7m~3 for dry year.(2) Effects of rubber dam in the downstream of Shuangtaizi River on the tidal prism of Raoyang River were studied using the hydrodynamic and water quality model. The results show that the construction of rubber dam could increase the tidal prism significantly. Under the two hydrological scenarios, the tidal prisms of tributary increased by 18.3% and 16.9%, respectively. And the maximum tidal quantity in the Wanjintan gate increase by 32.7% and 31.2%, respectively. The construction of rubber dam has little effect on the salinity of tidal prism which is below the salinity limitation (<5‰) for irrigating. Therefore, water in Raoyang River can be used to irrigate reed field in summer.(3) The flood control level of Shuangtaizi River and its tributary-Raoyang River, are simulated under 5 disadvantageous combinations of upstream water level, downstream tide level and the regional drainage due to local heavy rainfall. Meanwhile, the flood control level for two sides of river reaches is simulated under the maximum flood level after constructing Panshan gate, the maximum measured tide level at estuary, and strong rainfall. But, the results of simulating reveal that flood control standard of Shuangtaizi and Raoyang River is generally low. The current situation of river levee can't resist high level flood. The computation results can provide scientific basis for river channel regulation and levee reinforcement of Shuangtaizi River and Raoyang River. |
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