The Research On Operation Characteristics Of Water Environment System Of The Small Basin

This paper embarks from the water environmental pollution control of the basin level, according to the basic theory of the water environment system, research the operation characteristics of the water environment system by selecting the stream segment Quxian small river basin. This paper on the basic information of the general situation of natural environment investigation of water environment of small basin, water space structure based on, the river basin water environment system was generalized, the analysis of the system structure of the small basin water environmental system, and to determine the water quality response area of 270km2, the length of the river is 49.5km.Based on the basic profiles of a small river basin in Quxian segment, according to Qu county years hydrological data and stream river basin water system spatial structure, the area is divided into 13 sections, selected rainfall period (P=5, P=2) and non rainfall period as a typical case study, the hydrodynamic operating characteristics. By calculating the parameter matrix analysis shows that:p=5, the channel is the final output flow 585.42m3/s s, p=2, the channel is the final output flow 321.84m3/s, and the two conditions of all sections in a uniform flow state of change, rendering gradually increasing trend; no rainfall instream flow substantially unchanged.During the period of rainfall, the flow rate is larger than that of the non rainfall period, but the flow rate of the rainfall period and the period of the non rainfall period shows the trend of decreasing first and then decreasing gradually, and the trend of the change is consistent with the change trend of the slope.Based on the current situation of pollution sources and hydrodynamic characteristics, the degradation process and the characteristics of oxygen transport of water environment are studied. The establishment of reasonable water quality response prediction model, and based on the optimization analysis, the calculating value of the three hydraulic conditions of each section of the water quality parameters, P=5, K1 value range:0.16～0.33/d; KN values range: 0.12～0.30/d;K2 value range:0.24～0.39/d.P=2,K1 value range:0.13～0.29/d; KN value range: 0.09～0.25/d; K2 value range:0.22～0.36/d. Non rainfall period, K1 value range is: 0.09～0.27/d; KN value range is:0.07～0.23/d; K2 value range is:0.19～0.32/d. Overall trends from 3 data point of view, K1 p=5＞K1 P=2＞K1, P=0; KN,P=5＞KN,p=2＞KN,P=0, K2.p=5＞K2,p=2＞K2, p=0. Combined with changes in water quality parameters calculation results and analysis of water environment quality in the study area, through the analysis:rainfall period than in the non rainfall period River self purification ability strong, comprehensive attenuation coefficient, river reaeration ability; dissolved oxygen concentration in each section can meet the river fish survival minimum oxygen requirements. In the case of pollutants into the river conditions during P=5 working conditions, river water quality does not meet the section 5 after river fish survive lowest oxygen demand (5mg/L) requirements, the output section of the final dissolved oxygen concentration was 2.74 mg/L; p=2conditions during the dissolved oxygen content of the river after section 4 has fallen below 5mg/L, dissolved oxygen concentration in the river after the steep drop section 10, section 12 to a dissolved oxygen content close to 0; non-rain period, the dissolved oxygen content of section 2 after the river has fallen below 5mg/L, the dissolved oxygen content to section 11 gradually approaching to zero, because the description of rainfall runoff into rivers, river flow increases, resulting in river trail pollution ratio increases, which facilitates mixing dilution of pollutants, purification level relatively quickly, but the combination of no pollutants into the river under the circumstances known distribution of dissolved oxygen content in the contamination of pollutants into the river when the intensity of rainfall is small, rivers dilution and self-purification capacity is not enough to degrade pollutants into the river. In addition, non-small rainfall of river flow, flow rate is small, a serious shortage of river self-purification capacity, long distance appear black smelly river. According to the conclusion of water quality operation under 3 working conditions, the pollution control measures such as pollution control, artificial rehabilitation and water conservation forests were proposed.