Research On Water Quality And Algae Monitoring And Forced Water Circulation Technology In Cascade Reservoirs

With the speeding up of urbanization in our country,urban water pollution isbecoming more and more serious.Investigation of Shenzhen cascade reservoirs,thewater quality situation and the growth of algae are monitored and analysised.Toimprove water quality and inhibit the growth of algae, the forced water circulatindevice was designed.The monitoring sampling and laboratory analysis are used toresearch the water quality and algae interannual variation law of time and space.Xili Reservoir is light eutrophic,Tiegang Reservoir and Shiyan Reservoir aremoderate eutrophic.Effectively identified the water quality sensitive areas of XiliReservoir are Dongjiang water inlet and Baimang river,the water from Dongjiang ishigh quantity、high flow-rates and high sediment content,so that the TN and TPcontent are higher,baimang river is in moderate eutrophication condition. The waterquality sensitive areas of Tiegang Reservoir are Jiuwei and Liaokeng. The waterquality sensitive areas of Shiyan Reservoir is Water intake,witch is in heavy eutrophicstate,mainly affected by the external pollution.Effectively identified the dominant groups of algae in three reservoirs are groupP(Aulacoseira granulata)、B(Cyclotella,d＜15mm)、C(Cyclotella,d≥15mm) and groupD(Synedra Ehrenberg), belonging to diatom.Its characteristic is living in the volatileand nutritional water,reflecting strong water mixing and thermalinstability.Filamentous cyanobacteria,represented by S1and SNgroups,were dominantin the wet season at high temperature in Tiegang Reservoir and Shiyan Reservoir.The high risk period of algae outbreak for the three reservoirs is April toSeptember.The high risk areas of algae outbreak are similar to water sensitive areas.The optimum operation condition for pilot test of the forced water circulation is3.5kW for power and250mm for impeller size,under this condition,the influencerange is at least80m.The water mixing effect is perfect after continuous operation.The relative oxygen enrichment rate is as high as70.3%,the relative change rate ofalgae is60.1%of the underlying water.Pilot test has no obvious influence on waternutrient level.