随着人类活动强度的提高，很多地区的地下水呈现富营养趋势，地下径流（基流）已成为影响农业流域水系水质的重要途径；虽然地表和地下径流的非点源污染过程差异很大，控制策略也完全不同，但却还没有引起足够的重视。不能定量分析基流对非点源污染的贡献，就可能把过去遗留的地下水污染责任转嫁给现时的地表径流，误导减排分配，严重影响水质控制的预期效果。本项目将通过对典型农业流域不同自然条件与农作方式组合下的地下水水质变化的监测分析，研究地下水富营养趋势的预测模型；以此为基础，将在基流排放的非线性水库算法中引入浓度变量，并与溶质平衡连续方程相结合，构建直接分析基流营养物负荷量变化的数学模型。同时针对基流模拟验证难的技术瓶颈，利用多年的河流水文水质监测资料和研究积累，建立基流营养物负荷量计算的实测验证体系，实现定量分析河流中基流营养物负荷量的研究目标，推进我国的流域非点源污染分类溯源和定量控制理论与技术体系的发展。

With the continuously high application of chemical fertilizer in modern agriculture, nutrients are becoming the most common pollutant found in shallow aquifers worldwide. The contribution of nutrients derived from base flow might be growing up in many agricultural watersheds. However, due to the lack of quantitative approaches for determining base flow and its nutrient loading, we are still poorly understood in their impacts on river water quality, which may lead to shift groundwater contamination from historical responsibilities to the existing surface runoff, and seriously reduce the expected results of river water quality control. Based on groundwater quality monitoring with a series combinations of different natural conditions and agricultural practices in an agricultural watershed, this project try to build a model for predicting the variations of nutrient concentration in groundwater. On this basis, we try to introduce a nutrient concentration variable into a nonlinear reservoir algorithm, which used for characterizing the flow recession, and then combine it with the continuous solute balance equation to construct a mathematical model for directly calculating the base flow nutrient loads according to the variations of river flow. At the same time, this project will try to break the technical bottleneck of the simulation calibration and validation for base flow and its nutrient loads, supported by the advantage that we had accumulated the riverine hydrological and water quality data for more than 10 years. Through these researches for a 4 years period, we hope to achieve the goal for quantitative identification of nutrient load from base flow in rivers, to develop and improve quantitative control theory and technology system for non-point source pollution in watershed scale.