Study Of Water Quantity And Sluice Regulation In The Bird Habitat Optimization Project Area Of Chongming Dongtan

Regulation and management of water resources in coastal wetland ecological protection areas are very important.Water level and salinity are important contents of regulation,affecting the growth of birds and tidal flat plants.Sluice siltation is also a non-negligible problem during water regulation.After the project of ecological control of Spartina alterniflora and improvement of birds'habitats in Shanghai Chongming Dongtan wetland,the water depth and salinity must be maintained in appropriate ranges to meet the needs of birds foraging,rest and plant water requirements in the habitat area.It is necessary to grasp monthly water demand based on the water balance formula and the amount of water missing is taken from Suitang River.Suitang River will also draw water through the sluice gate from outer Chongming Dongtan when its water level is lower than demand.It is also necessary to know the transport process of salinity and sediment in Suitang River.The water intake channel outside the sluice is easy to be flattened,and it is necessary to know the silted time when sluice closed and the scouring effect.It has great value in scientific research and project application to carry out research on the above problems in the management of protected areas.Study on water level and water depth change and water transfer plan in the habitat area.The water loss,such as evaporation,plant evapotranspiration and soil infiltration,and precipitation process are considered.The different types of wetland area are counted.Based on the principle of water balance,the spatial and temporal changes of the water level and water depth of the C area and the Suitang river in each habitat area are obtained;the time and magnitude of draining and drawing water in the C area habitat and the Suitang river are given out,which provides a basis for optimizing the engineering area to formulate scientific water and drainage schemes.The results show that for the habitat areas C1N,C1S,C2E,C2W and C4 the annual loss of water are 82,450,213,696,36,240,39,286 and 163,922 m~3 respectively;the displacement to the Suitang river is 43,254,71,751,16,336,12,732 and 11,070 m~3respectively;and the magnitude of draining water from Suitang river are 22,768,110,328,11,137,3,052 and 80,520 m~3,respectively.The Suitang river's annual water loss is 343,177 m~3,and total water intake needed from the outer sluice is 309,439 m~3.Simulation of water intake and material transport process in Suitang River.Based on the ECOM-si model,the three-dimension numerical model of hydrology,salinity and sediment for the Suitang river was established to demonstrate whether the water intake conditions exist in the habitat area.The open boundary conditions at the sluice are specified by the water level,salinity and suspended sediment concentration(SSC)which are calculated by the large regional model of the Yangtze River Estuary.Using the measured water level,current speed and direction,salinity and SSC in the habitat area in July 2018,the model was validated and the calculated results are in good agreement with the measured data.The wind-driven current,variation of water level,salinity and SSC in the Suitang river and the amount of water intake during sluice open for two days in January and July were simulated and analyzed.In July,the total amount of water intake from the outer sluice is 795,064 and 807,736 m~3 when the outer salinity is higher and lower,respectively.In January,the total amount of water intake is 873,102 m~3 during sluice opening for two days.Total amount of water intake from Suitang River meets the needs of the internal habitat area.Under the influence of wind stress,the north wind causes the salinity to transport to the north more,and the south wind promotes the salinity to transport to the south more because there exists compensation current at bottom layer which has the same direction as the wind direction and the salinity is higher than that at surface layer.Most of the sediment transported through the open sluice deposits near the sluice in the Suitang river.Simulation of siltation degree and scouring effect in water intake channel outside the sluice of the project area.The three-dimension hydrological and sediment numerical model of the water intake channel was established.Based on the weir flow module and the three-dimension numerical model of hydrology,salinity and sediment for Suitang river,the gate hydraulics formula was used to calculate the water flux through the sluice.Using to the elevation observation data of the longitudinal section along the water intake channel before and after the opening of the sluice in July 2018,the critical movement stress of the bed sediment was calibrated.The calculated erosion and siltation is in good agreement with the measured data.The calculation results of siltation and deposition show that the water intake channel downstream the sluice is approximately fill and level up due to sediment deposition after the sluice is closed for three months,and the siltation degree is the highest near the sluice.After two months of natural siltation and in the case that the Suitang river has been retained water to 3.0 m and the sluice is open during higher tidal level,the average amount of erosion in the water intake channel reaches 625 mm after one day of open sluice.The erosion by tidal current and open sluice is the most effective way for desilting the water intake channel.