| Semi-humid region pollution is serious, and the aquatic ecological environment is worsen, which affect seriously national economy sustainable development and people's living standard further to increase, we enhance the water pollution control, in order to restoration aquatic ecosystem. This research, regards Dawen river in semi-humid region as example, has put forward water pollution control projects and aquatic ecological environment restoration measurements. Main research contents as follow:(1) Investigation and assessment of pollution sources. By analyzing assessment, water quality of Dawen river basin above 89% length is V or super V grade in Dawen river basin. Main pollutants are BOD5, SS, COD, and petroleum etc.(2) Water environmental quality assessment. The paper has assessment water environmental quality by choosing five river cross sections and large-medium size reservoirs in Dawen river basin. Assessment indexes were selected as follow 8 items: pH, DO, CODcr, total hardness, NH3-N, NO2-N, As, and phenol. The assessment result expresses that water environmental quality of five reservoirs is good. Course of river cross sections, except the upper stream Shapo, are V or super V grade, express that Dawen river basin main channel and main subsidiary one have been suffered serious pollution.(3) Water quality simulation. Water quality model of Dawen river basin has been established. According to the water quality data, we predict and monitor water quality. Water quality simulation result of present level year reflects basic actual condition. Water quality predict results of planning level year state clearly, BOD5 has up-trend, DO has descend trend, further makes known that water quality of Dawen river has much more worsen trend.(4) Analysis of water environmental capacity and calculation of pollutant cut down amount. According to water quality target of planning level year each river, water environmental capacity has been calculated, and pollutant cut down amount in each river. CODcr reduction rate of control cross sections is between 60%-90%. It has provided the basis of optimum planning of water pollution control in whole river basin.(5) Aquatic ecological restoration targets are established in semi-humid region, when establishing aquatic ecological restoration targets, first, the paper has designed index system that reflects aquatic ecological condition, then, considered economic & society development target and water resources condition in river basin. It has selected restoration base year that is 60's beginning and 70's end of 20th centuries.(6) Analysis of Ecological environment water demand in semi-humid region.Ecological environment water demand of Dawen river as follow: the minimum environment water use of channel, city river lake water use, groundwater instauration water use, wetly environment water use, soil and water conservation ecological water use, and channel water use of water quality request.(7) Allocation of aquatic ecological environment water use in semi-humid region. Water resources allocation in 2005 level year as follow: ecological water use amount is 690.3 million m3, shortage of ecological water use is 100 million m3, so we adjust the increases rate of industry production value. Water resources allocation in 2010 and 2020 level year as follow: ecological water use amount is 917.8 million m3, shortage of ecological water use is 200 million m3. We adjust increases rate of industry production value, it can increase ecological water use . All kind of ecological water demand is basic satisfied.(8) Planning scheme of water pollution control based on requires of aquatic ecological environment restoration target in semi-humid region. Considering water quality treatment cost function, the paper has put forward optimum planning of sewage outlet, obtained the whole river basin optimum planning scheme, and got the best position, capacity and efficiency. Water pollution control measures are pollution sources control, engineering te...
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