Research On Water Quality Simulation And Water Environmental Capacity Based On WASP Model

South River plays a significant role in flood discharge and navigation in Yixing and Liyang,and the change of water quality will directly affect water quality of Dongjiu,Xijiu and even Taihu Lake.Recently,on the basis of the measures of pollution treatment taking by the local environmental protection department and town governments,water quality of the river has improved.Nevertheless,there are developed navigation in this area crisscrossed by waterways,which result in constraint factors of water quality reaching standard becoming complicated,and consequently water pollution is still prominent.Therefore,taking downstream of South River as the research object,combined with related hydrological conditions and water quality monitoring data from 2013 to 2015,the WASP(The Water Q uality Analysis Simulation Program)model was selected to simulate water quality and analyze sensitivity of the model parameters.Meanwhile,one-dimentional steady water quality model in the calculation methods of control section reaching standard was carried out on calculating water environmental capacity in different water periods of South River downstream.Finally,taking water environmental capacity of dry season as an example,respectively choosing population,GDP,and reciprocal value of discharging intensity to stand for social factors,economic factors and environmental factors,Gini coefficient was put forth on capacity assignment,and under the condition of pollution load,pollution reduction of each town was analyzed and discussed.The main results are summarized as follows.(1)Taking state-controlled section Xincunli as the section of calibration and verification for WASP model,the results found that determination coefficient R2 was above 0.80,and correlation coefficient r was above 0.90;the average relative error of ammonia nitrogen(NH3-N),chemical oxygen demand(COD),and total phosphorus(TP)were 21.2%,12.4% and 12.2%,which showed that the simulation values were consistent with practical monitoring data.Therefore,WASP model can be used as an effective tool to forecast and manage the water quality in this area.(2)In the process of model calibration and verification,sensitivity analysis for the model parameters suggested that dissolved organic phosphorus mineralization temperature coefficient(?83)was the most insensitive parameter for a mmonia nitrogen and chemical oxygen demand;dissolved organic nitrogen mineralization temperature coefficient(?71)was the most insensitive parameter for total phosphorus;phytoplankton maximum growth rate constant 20℃(GP 1)and global reaeration rate constant 20℃(K2)were sensitive parameters for ammonia nitrogen,chemical oxygen demand,and total phosphorus.(3)In 2015,the water environmental capacity of ammonia nitrogen was 131.03 t/a in dry season and 179.92 t/a in wet season,while that of COD and total phosphorus was 1370.07 t/a,60.05 t/a in dry season and 1541.18 t/a,50.47 t/a in wet season respectively.Meanwhile,the reduction rate of ammonia nitrogen and COD in dry and wet season were all above 50%,which suggested that the reduction task was arduous undoubtedly.(4)Taking the water environmental capacity in dry season as an example,capacity of ammonia nitrogen,COD and total phosphorus were 63.87 t/a,625.93 t/a and 28.63 t/a in Town Lichen,while that of ammonia nitrogen,COD and total phosphorus were 67.16 t/a,744.14 t/a and 31.42 t/a in Street K unlun.Compared with Town Lichen,water environmental capacity of Street Kunlun was larger,and its reduction rate was lower,which resulted from the difference in the construction of sewage networks.