Research On Dynamic Simulation Of Water Resources And Water Regulation Based On GIS In Plain River Network

For the developed water network in the plain river network region,the direction of river flow is uncertain,with a wide distribution range of the pollution discharge port,so the analysis of the water environment simulation is much more difficult.In order to have a good command of the current situation of hydrology and water quality,to achieve science and rationality of regional water resource dynamic simulation and water diversion regulation,this paper took the Xixi wetland located in plain river-net area as a case study,to tease and review the related concepts,theories,methods and researches in domestic and overseas of water resource dynamic simulation and optimal allocation.With the analysis of relationship between pollutant quantity inlets into river and water quality,precipitation and runoff and concentration,and so on.This paper combined the need of the development of social economy and water resource management in the plain river network region,and took the methods of multidisciplinary cross research.Under the condition of the water amount control,to analyze the water quality and quantity changes in wet,normal,dry season of typical years,to build up the models including rainfall flow and confluence model,non-point source pollution model,water quality model,water quantity model,dynamic pollutant-carrying capacity model,et al.And then proposed the suitable theoretical system and calculation pattern to proceed water function area dynamic management in the plain river network region.This paper predetermined water diversion and distribution process and improved the foreseeability of water regulation and allocation on the basis of simulation prediction for the future water quality in the study area.And then implemented simulation scheduling with integration of quantity and quality in the plain river network area by means of the integrated system which based on coupling of hydrology models and WebGIS.The research results provided important theoretical significances and practical application to water resource management in the plain river network region,and the main research work in this paper is as follows:(1)Comprehensive evaluation and analysis of water resources and water environment in the study areaAccording to water bodies' functional requirements in the study area,this paper adopted single-factor evaluation model to evaluate water quality based on the comprehensive consideration of water resources present situation and the main sources of pollutants.From the results of water quality assessment,the ratio of sections which satisfying the water quality standard for three years was about 15 percent before the Qian Tang water diversion project put into use,and it was over 50 percent after operation of the project,87%in wet season.That is to say,the Qian Tang water diversion project has a significant environment benefit,and the water quality improved obviously.But from the point of actual water quality monitoring data,the Qian Tang river water diversion project is still unable to make the regional water satisfying the water quality standard stablely,pollution caused by random discharge of life pollution and pollution carried by the water diversion is the reason of unsteadiness of water quality.The statistical results of total amount of pollutants discharged into the rivers showed that water diversion accounted for the largest proportion of COD,followd by the life pollution;domestic pollutant accounted for the largest proportion of ammonia nitrogen,followed by pollution carried by water diversion.Similarly,life pollution accounted for the largest proportion of total phosphorus,followed by pollution carried by water diversion.Thus,the main source of pollutants in the study area is pollution carried by water diversion and life pollution,and ammonia nitrogen accounts for a large proportion of non-point source pollution.Learning from pollutant composition analysis,the primary pollutant factor is ammonia nitrogen,followed by total phosphorus.From the analysis result of pollutants change process,we can summarize that the water quality of wet season of every section in the study area is better than in normal season.Moreover,from the view of the actual situation that water quality exceeded the standard generally caused by ammonia nitrogen with the flow of water,we can infer that the domestic pollution is the main source of pollution in the study area.(2)Research of coupled water quantity-and/quality models Research on water resources optimal allcation of watershed based on joint regulation of water quantity and water quality is the main direction of research field in water resources allocation at home and abroad.In this paper,data of rainfall,flow,water level and underlying surface were taken as the foundation,mathematical models was set up,including rainfall runoff model,confluence model,non-point source pollution model,water quality model,water quantity model,and dynamic pollutant-carrying capacity model etc,and the constructed models and parameters were adopted to simulate and validate the flow process and water level process and change process of main pollution factors concentration of the rivers in the study area.The results of model validation showed that water level process,flow process had a high accuracy of the model simulation.During the whole process of validation,the simulation and observation process of daily average flow were basically corresponding to the peak and valley,the correlation coefficient between the simulated and measured values was 0.82,the minimum value was 0.78.The results of the daily mean water level and the simulation results were basically coincident.The correlation coefficient between the simulated and measured values of the monitoring sections was 0.95,the minimum value was 0.94.Compared with the validation results of process of water level and flow,the validation error of the water quality process was slightly larger.This was mainly due to some monitoring sections location has the land use type for agricultural and rural residential,and a relatively dense population,such as:Lianhuagang and Fengjiiahe,the great randomness of domestic pollution emissions was the reason of the difficulty to carry water quality simulation.But we can infer that the water quality model could simulate the change process of the concentration of COD,ammonia nitrogen and total phosphorus in the study area well from the overall situation of the water quality process validation results.(3)Dynamic pollutant-carrying capacity,reduction of pollution load and prediction of water quality in typical yearsAccording to the results of rainfall frequency analysis of the study area,we determined the design typical year by combing with the typical rainfall years and the analysis results of tide level of Qian Tang River which is a self-flowing water source based on the condition of the lowest tide level in 2010.Then we used the rainfall runoff model in combination with the typical years of precipitation and evaporation data to calculate typical total annual runoff flow and pollutant quantity inlets into the rivers of XiXi Wetland.And the calculation results showed that there is little difference among the typical years at the aspect of total amount of regional water resources.Compared with the amout of non-point source pollution with the domestic pollution,the results showed that the main source of pollutants(COD,NH3-N,and TP)discharged into rivers in each tipical year was life pollution,and COD emissions in life pollution accounted for the highest proportion of total COD discharged into rivers,followed by TP and NH3-N.Under the condition of water diversion in present situation,we used the dynamic pollutant-carrying capacity model to calculate the pollutant-carrying capacity of the typical years,the result of the comparison of total amount of pollutants discharged into the rivers in the current year(2010)with the annual average pollution carring capacity of each typical year:the discharged quantity of ammonia nitrogen and COD were both more than the annual average pollution carring capacity of each typical year except for total phosphorus.Obviously,the water volume difference less than 10 million m3 has little influence on water quality of river network in the study area.Owing to non-point source pollution is not easy to be controlled,and domestic sewage is the main source of pollutants,so the life sewage should be controlled for pollutant reduction.In this paper,according to the calculations based on the dynamic pollutant-carrying model and total amount of pollutant discharged of typical years,the result shows that,the water quality could reached standard stably all year around if the life sewage was reduced to one third of discharge amount into the rivers or 10 percent of total production amount in current year.(4)Analysis of minimum amount of water diversion in typical years under the condition of water quality constraintsThrough the joint regulation of water diversion and monitoring of water quality to make reasonable regulating rules,the amount of water diversion adapted to pollutants discharge and reduction can be determined accurately in a whole year.In this paper,with the constraint of pollutant concentration of each section,based one tests and calculations,the minimum amount of water diversion for given water quality constraints in each typical year can be determined by a regulating scheme that the diversion should be given priority when concentration of contamination up to 90 percent of water quality standard limit,and otherwise setting the maximum flow of diversion to 10m3/s at ordinary times.The water regulating result for each typical year showed that the minimum amount of water diversion is much lower than the designed water diversion scale,further more,there is a great reduction of the minimum water demand between the minimum diversion amount and actual diversion amount of the current year.Even compared with the nomal year,there is big decrease in diversion.(5)Dynamic simulation and visual regulation of water resources based on GIS Through analyzing the advantages and disadvantages of various coupling mode of geographic information system and the hydrological environment models,and using the coupling method based on data exchange file,the water diversion project configuration management system was established.With the help of this system,the models datum could be extracted from database automatically by Model Builder modeling tool,with the aid of ArcGIS Schematics software,the logic relationship between river network nodes and channel center line was constructed,the river networks logic map was established,and the logical organization and management of hydrological models computational elements was implemented.By means of linear interpolation algorithm,the render effect of river pollutant concentration could be implemented to achieve the objective of static display and dynamic simulation for water quality and water quantity changes.The simulation calculation data could be obtained through data interaction between the diversion project configuration management system and the water environment mathematical models,as a result,the real time regulating and predictable scheduling of water diversion could be realized,which can provide technical support for optimization of water regulation scheme and water resources regulation decision.