Simulation Study On The Influence Of The 10 Meter Minimum Control Water Level Dispatching Plan Of Poyang Lake Proposed Water Conservancy Projecton Water Environment

To study the influence of the proposed Poyang Lake Water Conservancy Project on the water quality of Poyang Lake,based on the EFDC model,the two-dimensional hydrodynamic water quality model of Poyang Lake was constructed,and according to the planned Poyang Lake Water Control Project scheduling scheme,Choose three typical annual scenario simulations of Poyang Lake 2012(wet year),2008(flat water year),and 2007(dry year),combined with the scheduling plan of the water conservancy hub planning and the actual water level change,the research period is divided,from the perspective of time and space,the differences of TP and TN concentrations in typical years with/without hubs were analyzed,quantitative assessment of the impact of water conservancy project on the spatial and temporal distribution of water quality in Poyang Lake.The results show that:(1)In time,the whole year is divided into three time periods to study the changes of TP/TN concentration in hubs and hubless hubs.The two indicators have similar changes in the concentration of hubs and hubs at different time periods.From April to August,the flood gates were fully opened,and the concentration of TP/TN was not significantly different.The water level of the water conservancy project in SeptemberDecember and January-March was controlled above 10 m,and the capacity of the lake reservoir increased.The average concentration of /TN was lower than that of no hub.In wet year and flat water year,the entire lake area basically showed a TP/TN concentration range of 1-3 months greater than the September-December period.In the dry year,Poyang Lake entered the dry season in advance,and the whole lake area basically showed a decrease in TP/TN concentration from September to December,which was greater than the 1-3 month period.(2)The study area is divided into upstream(near Kangshan),middle reaches(near Duchang),and downstream(north of Songmenshan)to analyze the spatial distribution of the average concentration of TP in the presence/absence of hubs.The effect of regional TP concentration is different.In the wet year,the TP concentration in the hub project improved,and the improvement of TP concentration in the upstream and downstream of the lake area was greater than that in the middle reaches.However,the TP concentration in the middle reaches of the lake area during the water storage period was greater than that of the upstream and downstream reaches 18.33%;In flat water year,Project The improvement of TP concentration in the upper reaches of the lake area and downstream is large,especially the downstream decrease from the end of September to the end of December is more than 20%.The improvement of the TP concentration in the Poyang Lake hub of Pingshui is better than that of the wet year type,especially the Three Gorges water storage.During the period and dry season,the improvement rate is significant.The percentage of TP concentration reduction is less than 10% and more than 20%.In the dry year,the pivot project improves the upstream and middle reaches TP concentration better than the downstream in most periods,especially the Three Gorges water storage period and compensation.The adjustment period improved significantly,and the percentage of mid-course compensation adjustment period was even lower than that of the non-hub TP concentration,which even reached 31.89%.(3)There are also differences in the average concentration of TN in the upper,middle and lower reaches of the study area.The different ages and different scheduling periods of the Poyang Lake water conservancy project have different effects on the TN concentration in each area.In the wet year the TN concentration in the hub project decreased for most of the period,and the effect on the upstream concentration was the best.The second is the middle reaches.The hub water storage and the Three Gorges water storage period project have a higher TN concentration in the upper,middle and lower reaches of Poyang Lake.High trend.In flat water year,the hub project has better effect on the midstream and downstream concentration than the upstream.The average TN concentration in the upstream,midstream and downstream of the dry water storage period is smaller than that in the non-hub,and the TN concentration decreases gradually.More than 15%,the average value of downstream and midstream TN concentrations is close to 20%~30% compared with the non-hub reduction;In the dry year,the hub project has the best effect on the improvement of TN concentration in the upper and lower reaches of Poyang Lake,and compensates for the downstream of the regulation period.The concentration reduction is the largest,which is 5~10% higher than the upstream and midstream,reaching more than 30%,which may be closely related to the increase of the downstream flow rate of the floodgate.