Computing System Construction of Water Environment Carrying Capacity in Huaihe River Basin
淮河流域水环境承载能力计算系统的构建

In this paper, the overall designs and mathematical model of water environment carrying capacity, as well as the system structure and application of water environment carrying capacity computing system in Huaihe River Basin are presented. The carrying capacity of water environment in river basin is reached by calculating the upper limit of the socio-economic scale that watershed can carry under the "good status of water environment". The system is based on an integrated "socio-economic-water resource-water environment" model which is coupled with the socio-economic system model, the water resource transformation relation model and the simulation model of water environment system. The population size is a key indicator to reflect the water environment carrying capacity of the basin, and iterative algorithm is used to get the maximum population size of different water environment carrying capacities. This system also contains a subroutine for ecological water requirement model. The mean value of the results from the Tennant method, base flow method and the 7Q10 method is considered as the ecological water requirement for each calculation unit. To calculate the water environment carrying capacity, the constraints of the water quantity, water quality, the total amount of pollutants into the river, ecological water requirement, per capita GDP and the per capita grain possession should be taken into consideration. The boundary conditions, control conditions, variable parameters and the result analysis of the measurement model for water environment carrying capacity are integrated in the visualized interface with the databases, geographic information systems and visual programming technology. By classify the indicators of water environment carrying capacity, the calculation units of Huaihe River Basin are divided into five categories of water environment carrying capacity, including complete bearing, bearing, mild overload, moderate overload and severe overload. This system can be effective in understanding the present situation of basin water environment carrying capacity and analyzing the scenario in future years or in different frequency inflow conditions. Either in different years or in different water quantity and quality control conditions, the calculation units should also be in different categories. The development of this system can be a beneficial exploration for digitalized management of watershed environment. It can also be an effective evidence to support the decision-making in the management of water environmental carrying capacity in the basin.