Research On Optimal Utilization Of Rainfall Flood Resources In Coastal Area

In view of the shortage and the low utilization rate of water resources in coastal area, and the phenomemon that a lot of water directly flows into the sea without be used, on the basis of soil and water conservation engineering, water resources management, limited water level dynamic control theory, by taking Rushan river basin in Shandong Province as the research object, this paper used methods and techniques such as the distributed hydrological model SWAT, SCS-CN model, VISUAL MODFLOW groundwater numerical simulation model, MAPGIS and ARCGIS to carry out the research on optimized utilization of the rain flood resources by using field investigation collection and experimental observation data. The thesis provides theoretical support and decision basis for both solving the contradictions of imbalanced between supply and demand of water resources and water resources optimal allocation. Research conclusions are as follows:(1) A distributed hydrological model SWAT of the study area was established to simulate the water flux to ocean, and water resources development and utilization potential was calculated. The results show that:1) the average water resources flux to ocean of the basin is196.95million m3, water into ocean of25%,50%and75%rain frequency throughout the year is261.15million m3,204.3million m3and126.76million m3respectively. An average water flux to ocean of flood season is150.64million m3, flux to ocean of flood season in25%,50%and75%rain frequency is212.38million m3,143.01million m3and88.73million m3respectively.2) an average of utilization rate of surface water resources is47.88million m3, usable surface water resource under25%,50%,75%rain frequency is60.96million m3,33.82million m3and24.11million m3respectively. An average of groundwater resources which could be mined is16.26million m3.3) In Rushan river basin surface water exploitation and utilization potential is116.39million m3, the exploitation and utilization of the groundwater potential is19.67million m3.(2) The surface water resources was calculated, and dispatching operation scheme of dragon horn mountain reservoir was made. Research shows that:1) in the low water year water resources was in shortage, in a typical year of75%frequency dragon horn mountain reservoir was short of agricultural irrigation water of2.92million m3; In a typical year of90%frequency it was short of24.16million m3, of which the agricultural irrigation water deficit is14.06million m3and production and living water deficit is10.10million m3;2)In a wet year (25%) and a normal flow year (50%), the dragon horn mountain reservoir remain29.62million m3,13.25million m3;3) multiple storage index method is used to calculate the Rushan rivers domain small reservoirs and shuitangba and shaft drawing groundwater supply amount:in25%,50%,75%and90%frequency level years, the total supply amount is41.59million m3,39.00million m3,35.86million m3and30.08million m3respectively, which could meet the irrigation area of232100mu,141500mu,104700mu and62100mu.(3) Method and way to optimize the utilization of surface water resources was proposed from the dynamic control of dragon horn mountain reservoir flood control level and space layout of rainwater collection measures. The results show that:1) an area of13.14km2is suitable for construction of water storage pits in the study area;49positions are suitable for the construction of a reservoir;31locations are Suitable for the construction of a dam;30locations are appropriate for building large open well; area of60.08km2is appropriate for courtyard catchment.2) the method of the homogenous frequency enlargement of different time intervals is used to convert the typical flood process line into the design flood process line. On this basis, criterion-peak and volume decision criterion was used to calculate and correct limited water level of each ten-day, it increases12.65million m3of the storage capacity in25%frequency level years.(4) underground reservoir numerical simulation model was established combined with VISUAL MODFLOW, and a single element method was used to calculate the water supply of underground reservoir under different frequencies. Research shows that:1) water resources is in shortage in low water years, the total water deficit is39.29million m3under the hydrologic frequency of90%, all of which is for agricultural irrigation water. In the hydrologic frequency of75%, there is lack of11.86million m3agricultural irrigation water.2) in median water year and wet year, it can meet the overall water;3) in different frequency of precipitation years (25%,50%,75%,90%) the underground reservoir storage index are0.68,0.92,1.22and1.61, the highest utilization rate appears in the dry year.(5) In the research area,"two low years and one normal years" and "four dry years and a wet years" of surface water and groundwater joint regulation mode were put forward. In the case of "two low years and one normal year", in dry year of90%frequency, water for life is more mined10.10million m3. In precipitation frequency of75%, agricultural production increases14.78million m3, groundwater injection volume is increased of17.79million m3in the flood season (June, July, August, September). In the flood season of the precipitation frequency of50%, groundwater injection volume increases5.03million m3. After that the underground water level restores. In the case of" four dry years and a wet years ", under precipitation frequency of75%, agricultural water supply increases14.78million m3, groundwater injection volume is increased of9.72million m3in the flood season. In the flood season of the precipitation frequency of25%, injection volume is increased4.87million m3. Then the underground water level restores.