Water Environment Carrying Capacity And Regulation Strategiesof Typical Small Watershed

With the rapid development of economics, the traditional treatments of small watershed can not meet the requirements of new management. At the beginning of this century, the Beijing government put forward the conception and thinking of construction of clean and ecological small watershed, therefore, carrying out the study of water environment carrying capacity and regulation strategies of typical small watershed can provide the provide technical support and services for management and protection of mountain watershed of Beijing.This study focused on the water environment carrying capacity, together with the requirement of the ecological development of Yanqi demonstration area, taking the Yanqi River as the study case, and constructed a "simulation-control" system of water environment carrying capacity based on previous studies.The main results are as followings:(1) Identifying the factors that restrict the water environmental carrying capacity of the Yanqi RiverWith the comprehensive conditions of nature, society, economics and environment of Yanqi watershed, water resources shortage, bad water quality, simple economic structure, and natural disaster are the four factors that restrict the development of the Yanqi wastershed.(2) Developing the methodologies for modeling water environmental carrying capacity of the Yanqi RiverAccording to the characteristics of water environment and the condition of basic data, we constructed the model which can simulate precipitation and runoff in mountain watershed, and can simulate sewage pollutant diffusion characteristics in the Yanqi River. Through data exchange in each model, it can reflect the characteristics of rainfall, surface runoff, river flow and pollutant diffusion. The results can provide technical support for water environmental carrying capacity of small watershed.(3) Constructing of the method to compute the pollution into the river and its effects on the water qualityThrough field monitoring, field observation, numerical simulation, we construct the relationship between the pollution emissions and its loading into rivers. Meanwhile, we determined the main pollution sources and pollutants into the river, proposed the contribution rate of the main pollution source. The results can provide some important data for computation of water environment carrying capacity of Yanqi River Basin.(4) Studying of water environmental carrying capacity of Yanqi watershed based on different scenariosWith the developed model and the data from the field measurements, the TP and TN daily loadings of Yanqi River were 2.00kg/d and 12.42kg/d, and year loading were 730.54kg/a and 4533.96kg/a under the water quality standards. Under the pollutant from the residents in the watershed and no fish farm, the TP and TN daily loadings of Yanqi River were 1.49kg/d and 7.54kg/d, and year loading were 544.89kg/a and 2751.85 kg/a。Based on the results of the main pollutant sources contribution, fish farm emissions is the primary constraint. The contributions of foreign tourist were 0.082kg/thousands person/time,0.423 thousands person/time, respectively. Without considering the basin occupied by fish farms sewage water environmental capacity of the premise, the daily maximum reception Yanqi Basin scale should be appropriate to 17,400 people.in full consideration of the comprehensive management of potential pollution conditions, Yanqi Basin daily maximum foreign tourist population size can carry about 17,600 passengers/ day.(5) Proposing the measurements to improve carrying capacity of Yanqi watershedImproving the unit length of the river water body purification capacity, reducing the occupation of river water, and improving the river hydrodynamic conditions, can effectively improve the assimilative capacity of water bodies watershed, improve water environment carrying foreign tourist population size. Meanwhile, strengthening the various types of pollution by sewage management and pollution control, particularly in raising the level and improve enterprise management level commercial fish in fish farms, fish farms to improve the drainage of wetlands end of the treatment process, to minimize crowding sewage basin water environmental capacity is limited, can provide as much space as foreign tourist population bearing basins, increase the carrying capacity of the water environment.