Study On Water Environmental Capacity Of Liaohe River In Jilin Province

The water environmental capacity （WEC） is the ability for water toaccommodate the pollutants, which is the useful strategy to solve water pollutionproblems and achieve water quality optimization management. It is the important linkfor water resources protection and the sustainable development of society andeconomy. And it can provide the scientific proof to pollution gross control.In this work, we firstly summarize the domestic and foreign research progressand related theory of WEC. Then we choose the Liaohe River along Jilin province assubject investigated to analyze and research WEC. Liaohe River in Jilin proince is thesource region of Liaohe River, and the trans-boundary river of Jilin and Liaoningprovince. And moreover, it is the main headwater area as well as pollutant-holdingwater body of Siping and Liaoyuan municipality. Therefore, the research for WEC ofthis basin has the important practical significance.The paper investigates and analyzes pollution source of the basin, which has laiddown a firm foundation for the amount of pollutants reduction. The resultsdemonstrate as follows: during2006to2010, the wastewater discharge increasesgradually, the discharge of COD in point source displays downward trend, whileNH₃-N has a slight increase; of the total point source input to the watershed, thedischarge of COD in urban domestic wastewater accounts for81.1%and NH₃-N for91.5%; of the total pollution into the basin, the COD load to the valley amounts to74.6%from non-point source in2007～2010, and NH₃-N accounts for56.6%.In order to master the spatio-temporal patterns of water quality, we utilizes waterquality data of Liaohe River in Jilin province at12monitored sections monthlybetween2001and2010to assess water quality. The results show as follows: thesections of exceeding class V of surface-water standard in the drainage area accountsfor58.3%to66.7%of the total sections; river waters are primarily polluted by COD,BOD5and NH₃-N，and COD and NH₃-N are chosen as the indicators of WECcalculation. We calculate each mean period of COD and NH₃-N averaged over a4-year （2007～2010） used as corresponding period’s design concentration on ground that annual changes of ρ（COD） and ρ（NH₃-N） from2001～2010. And seasonalvariation regularity proofs further that the results of pollution source estimated isrationality, and it also indicates that it is necessary for the environmental capacity （EC）to calculate from different water period.On the basis of previous studies on integrated degradation coefficient （K） andanalysis of the characteristics of nature and society in the valley, we improvemethodology for K. According to each mean period of water quality averaged over a4-year （2007-2010）, pollution source during the same period and the average flowvelocity with the corresponding term for many years, we choose the two-point methodto compute K of the rainy, normal and dry season. The results show that KCODandKNH₃-Nvaries within0.01～0.709and0.005～0.59per day, respectively.According to the characteristics of water environment in this drainge basin,one-dimensional steady-state model is adopted to calculate the WEC. Firstly, wedivide the calculating unit and then, determine the designed condition andcorresponding model parameters. At last, we calculate separately the EC and reducedquantity （RQ） of pollutants for the rainy, normal and dry season. The results show: therelationship of the EC for COD and NH₃-N in different period is in the order ofhigh-water period> normal-water period> low-flow period; the EC for COD> that ofNH₃-N; the EC for COD and NH₃-N in three rivers is in the order of East LiaoheRiver> Zhaosutai River> Tiaozi River; in the present situation under the condition ofpollutants input to the basin, the ratio for reducing emissions of COD and NH₃-N indifferent period is in the order of low-flow period> high-water period> normal-waterperiod; the RQ of COD is higher than that of NH₃-N; the ratio for reducing emissionsfor COD and NH₃-N in three rivers is in the order of Tiaozi River> Zhaosutai River>East Liaohe River.Base on the above research, the paper puts forward some countermeasures andsuggestions to improve the water quality of Liaohe River in Jilin province whichinclude reconstructing and completing the urban drainage pipe system, adjusting theindustrial structure, strengthening the management of point source and non-pointsource, employing land treatment technology and technology of bank protection byaquatic vegetation，carrying out a plan for pollutant gross-control from each waterperiod, setting up transition zone, modulating industrial layout, perfecting nitrogenremoval of wastewater treatment plant and speeding up the diversion of water from the Songhua River to Liaohe River.