The Evaluation And Forecast Of The Gray Water Footprint In The Upstream Of Dahuofang Reservoir

As an important source of water supply in Liaoning Province,Dahuofang Reservoir is of crucial importance in the assessment and prediction of its upstream water quality.The traditional method of water quality evaluation mainly evaluates the pollution degree of water bodies without considering the mutual influence of water quality and water quantity.Gray water footprint theory provides a new idea for quantitative evaluation of the impact of water pollution on the quantity of water resources,and can reflect the impact of human activities on water quality more directly and directly.In this study,the gray water footprint theory was applied to calculate and evaluate the gray water footprint in the upper reaches of the Dahuofang Reservoir in different time dimensions,and the water pollution level was introduced to evaluate the water quality.The gray water footprint and the water pollution level in different time periods were simulated and predicted by using the optimized power exponent GM(1,1)power model,and verified the applicability of the GM(1,1)power model and predicted gray water footprint and water pollution levels from 2013 to 2014.Put forward prevention measures of total nitrogen which is the main pollutant upstream of Dahuofang Reservoir by analyzing the trend of water quality change.The main findings of this study are shown below:(1)The gray water footprint of the upper reaches of Dahuofang Reservoir reached a maximum in 2010 with gray water footprints in other years not much different,and water pollution level are less than 1 in inter-annual level;The water pollution level during the dry season from 2004 to 2012 is greater than 1,and the gray water footprint is not sustainable;In the wet season,water pollution level is less than 1,and the gray water footprint is sustainable;Water quality during the wet season has been better than the dry season,mainly due to a large amount of water during the wet season.(2)According to the research needs,choosing the right time dimension to calculate and evaluate the gray water footprint will result in more accurate and practical significance.(3)When modeling gray water footprint and water pollution level using GM(1,1)power model with optimized power exponent,the model accuracy meets the requirements and can be used for prediction.(4)The forecast results show that the gray water footprint in the next five years tends to increase,but water pollution level in the three periods of abundance,flattening and dryness decline,possibly due to the increase of water inflow.The water pollution level in the flood season and the peace period are all less than 1,so the gray water footprint is sustainable.Thewater pollution level in the dry season is still greater than 1,and the gray water footprint is not sustainable.The research shows that the gray water footprint is a new tool to evaluate water quality,which can quantify water pollution.The accuracy of water quality evaluation results is different under different time scales.The GM(1,1)power model is a model with high prediction accuracy and can be applied to the prediction of gray water footprint.The evaluation and prediction of gray water footprint can provide theoretical basis for anti-pollution and treatment and planning and management of water resources.