A method for determining a contribution rate of pollution load in a water quality assessment section of an annular river network system based on water quantity constitute, comprising the following steps of:
- i) determining water quantity components in a research region, comprising a plurality of rainfall runoffs, wastewater discharge and water diversion;
- ii) constructing a river network water quantity constitute model, regarding the all water quantity components as conservative substances, and calculating water quantity ratios of the water quantity components in each water quality assessment section, wherein a construction method of the river network water quantity constitute model comprises:
- based on a water quality model, regarding the all water quantity components as the conservative substances, regardless of transformation and fate, and representing model results as volume ratios of all water quantity components, wherein n rivers are set, corresponding flow rates of rivers L1, L2, . . . , Ln-1 are q1, q2, . . . , qn-1 respectively, and the n−1 rivers all flow to the river Ln, which means that a water quantity of the river Ln is composed of water quantity of the rivers L1, L2, . . . , Ln-1, so that a flow rate of Ln is that q=q1+q2+, . . . , +qn-1, and ratios of the water quantity are L1:
- q1/q, L2:
- q2/q, . . . Ln-1:
- qn-1/q respectively;
- and assuming that concentrations of the conservative substances entering the river with the water flow are all 1.0, concentrations of the all conservative substances in the river Ln are L1:
- q1/q, L2:
- q2/q, . . . , Ln-1:
- qn-1/q respectively;
- and determining the water quantity ratios of the all water quantity components according to the concentrations of the conservative substances in the river;
- iii) collecting pollution loads and wastewater quantity of all wastewater discharges, and calculating a weighted average concentration of all wastewater discharge pollutants;
- using a hydrological model and a pollution load model to calculate a pollution load, a wastewater quantity and a water yield of land use types of all rainfall runoffs, and calculate a weighted average concentration of rainfall runoff pollutants;
- and acquiring a weighted average concentration of water diversion pollutants;
- iv) according to the water quantity ratios of the all water quantity components and the weighted average concentration of the pollutants, calculating contribution rates of the pollutants of the all water quantity components in the water quality assessment section in the research region;
- v) according to the calculation in step iv), obtaining a list of contribution rates of pollution loads of all water quantity components;
- and
- vi) according to the list of contribution rates of pollution loads obtained in step v), ranking the contribution rates of all water quantity components in the water quality assessment section, sequentially determining whether the weighted average concentrations of pollutants exceed a pollutant discharge standard, and if the weighted average concentrations exceed a standard threshold, then constructing sewage treatment devices to control pollution discharge concentrations of the water quantity components;
- and if the weighted average concentrations do not exceed the standard threshold, then controlling discharge amounts of the water quantity components.