Aquatic Ecoregion And Control-Unit-Based Management Technology Of Water Quality Target In Dongliao River Watershed

Dongliao River watershed, as the headwater region of Liao River, the situation of water environment is imminent. Water scarcity and degraded water quality have posed great threat to the industrial and agricultural production, resident life and ecological environment in Dongliao River watershed. In addition, it is lack of analysis on the water Environment Characteristics and water quality target management technology in Dongliao River watershed. Total quantity control system of pollution source-pollution discharge-water quality is also not established. So it can not implement effective supervision and management of pollutants, causing the water quality control and improvement of Dongliao River in extremely difficulty.The study is based on the actual demand of water pollution control in main typical river and the great demand of national pollution control. Under guidance of "regionalization, classification, grading, staging" water environment management theory, taking Dongliao River as study area, the regional characteristics and health status of aquatic ecosystem were studied, and spatial heterogeneity and drive mechanism of regional environmental factors were identified. The method and technology of aquatic ecoregion and control unit devision were established. The pollution loads in control unit were modeling and calculated. Based on WASP model, the input-response relation between pollution loads and water quality was established. The technology and methods of control-unit-based water environment capacity calculation and pollution loads reduction were studied and control-unit-based management technology of water quality target in Dongliao River watershed was established. The results provide technology support for the security and health of aquatic ecosystem and general scheme establishment of water pollution control in Dongliao River. The main contents include:1. Investigation and characteristic analysis of aquatic ecosystem in Dongliao River watershed(1) The investigation and analysis of aquatic ecosystemAccording to the characteristics of the natural conditions in Dongliao River, the investigation and analysis of physical, chemistry and hydrology characteristic of Dongliao River water body was carried out in July and October2010, April2011. In September2010, water quality, riparian zone vegetation and soil, sediment, the species, quantity and distribution of aquatic organisms were investigated and analyzed. The results showed that the concentration of TN went beyond the standard greatly, then were ammonia nitrogen, TP, CODMn·The water quality was mainly Class V, and monitoring reaches could not come up to the water quality target in functional area.(2) Assessment of aquatic eco-health in the watershedBased on investigation of hydrology, water quality, aquatic organisms and habitat condition, the analytical hierarchy process and fuzzy synthetic evaluation method were used to set up assessment index system of aquatic eco-health and evaluate the aquatic ecos-health grade in Dongliao River watershed. The results showed that among18samplings, there are two health, one sub-health, five threshold, ten morbidity, which illustrate that the aquatic eco-health condition of Dongliao River is not optimistic.2. Aquatic ecoregion and control unit devisionBased on the field investigation results and the related data of Dongliao river (spatial information data, hydrology and water quality, meteorological data, geology geomorphology, vegetation, water source distribution and socioeconomic status), the main control factors that influencing the aquatic ecosystem pattern in Dongliao River watershed were identified and the division method and index system of first, second and third level aquatic ecoregion were also established. Dongliao River watershed can be divided into2Grade I aquatic eco-regions,4Grade II aquatic eco-regions,13Grade III aquatic eco-regions. Considering the Grade III aquatic eco-regions, pollution influence area, integrity of hydrological unit and administration cell, operability of pollution control, Dongliao River watershed can be divided into14control units based on GIS technology.3. Estimation of pollution loads in control unitAccording to the spatial and attribute database of Dongliao River watershed, SWAT model was applied to establish non-point source pollution model. First, the whole watershed was divided into35sub-basins and357HRU. Then the observed monthly streamflow data from2005to2009were used to calibrate and validate the model. Finally, the model was used to simulate the non-point source pollutant loads (nitrogen, COD) in2009, analyze the temporal and spatial distribution characteristics of non-point source pollution.(2) Estimate the point source pollution loadAccording the statistical data and pollution source census data, pollution discharging coefficient method was used to estimate the discharge amount of point source pollutants.(3) Pollutant source solution analysisThrough the analysis of pollution loads accounting results, the ammonia nitrogen load in upstream mainly came from livestock and poultry raising, and the ammonia nitrogen load in downstream mainly came from agricultural non-point source pollution. The COD load mainly came from livestock and poultry raising, agricultural non-point source pollution and domestic discharge. In general, the ammonia nitrogen and COD loads were mainly from livestock and poultry raising, agricultural non-point source pollution. The contribution rates of agricultural non-point source pollution to ammonia nitrogen and COD loads were22.5%,50%, respectively, and that of livestock and poultry raising were71.8%,34.6%, respectively.4. Establishment of input-response relationship between pollutant and water qualityApplied WASP7software, the water quality of control unit in Dongliao River is modeled, which explains the temporal and spatial distribution characteristics of ammonia nitrogen and COD. Then the response relationship of water quality with pollution load was set up. The results showed that the concentration of ammonia nitrogen and COD were highest in segment8and10, which was located in the Liaoyuan city, and the concentration of ammonia nitrogen in this segment was highest in dry period, while the concentration of COD in this segment was highest in normal water flow period. The concentration of pollutants in other segments changed little in temporal and spatial distribution.5. Calculation of water environment capacity in control unitAccording to the water quality target and design hydrological conditions, the input-response relationship of pollutant and water quality was applied to calculate the water environment capacity of control unit using the trial-and-error method. The AHP (the analytic hierarchy process) was used to calculate the weighted ratio of the water environment capacity in each control unit to the water environment capacity of the study area, and the water environment capacity was allocated in each control unit. The results showed that the NH3-N environmental capacities in25%,50%,75%assurance rate and30Q10design flow in Dongliao River was1754.75t/a,720.33t/a,155.69t/a,56.18t/a, respectively. The COD environmental capacities in25%,50%,75%assurance rate and30Q10design flow in Dongliao River was158055.23t/a,67651.49t/a,13977.00t/a,1104.31t/a.6. Control-unit-based management technology of water quality target in Dongliao River watershedBased on the TMDL in total load control technology of pollutants in watershed, the ration apportionment method was used to allocate permitting pollution load to point source and non-point source and the margin of safety was also considered. Then the reduction load of pollution was calculated according to different flow pattern. Finally the control-unit-based water-quality target management technology scheme for Dongliao River was proposed.