Study On The Roof Runoff Quality In Jinan Based On The Aquifer Recharge

The topography of Jinan is high in the south and low in the north,and the rainfallis abundant in flood season.So it is easy to flood in Jinan.The roof rain water is animportant part of city runoff.The control and utilization of city roof rainwater is anefficient method to relief city flood risk and increase the water supply.The over exploration of groundwater has caused a series of problems toenvironment with economic growth and the increase of population.Collecting the roofrain water and inject to the aquifer is an important measure to solve theseproblems.The quality of roof water should up to some standard before injected to theaquifer.The source of pollutants including:pollutants in natural rain water and rooffall.Most of the pollutants with high concentration come from roof fall.Theconcentration of the pollutants from the roof fall vary according to the build up andwash off rule.The initial split flow is an important roof water quality treatmentmeasure and most of pollutants can be removed from the roof water.The build up and wash off model was constructed on the base of build up andwash off rule.The concentration trend of the roof water pollutants can be modeled bythis model.The amount of initial split flow can be calculated with this model.TheSWMM model is also based on the build up and wash off rule.This model is moresuitable for the last roof water.The quantity of the initial split flow is decided by many factors and the amountof the collected roof water and the pollutants removal rate should be balanced first.The quantity of the initial split flow in Jinan should be6mm and the pollutantsremoval rate is60%.The specific research Content and results as follows:1.Sample the natural rain and roof water and then survey the concentration of thepollutants in these two types of water. The concentration change rule of the pollutantsin these two types of water can be found out by contrast.It can be found that thepollutants concentration of the natural rain water are low and stable however thepollutants concentration of the roofwater are higher and change with the precipitation process.The pollutants concentration change rule of the roofwater accord with buildup and wash off rule well.2.The build up rule of rooffall accord with the exponential growth rule.Theammount of rooffall is decided by the drought days and the accumulation ratedecrease with the time.The wash off rule of the rooffall coincides with exponentialrule too.The pollutants concentration of the initial roofwater is very high and thendecrease to stable state.3. The concentration change rule of the initial roofwater can be modeled by thebuild up and wash off model very well but the concentration of the terminal roofwateris failed to be modeled by this model for it ignores the pollutants of the natural rainwater.4.The removal rate of the pollutants can be caculated conveniently with the buildup and wash off model.And this model provide an convenient method to caculate theinitial split flow.