Total Nitrogen and Total Phosphorus Pollution Reshaped the Relationship Between Water Supply and Demand in the Huaihe River Watershed, China

As total nitrogen(TN)and total phosphorus(TP)pollution is the main source of water pollution in the Huaihe River watershed in China,it is important to understand how TN and TP pollution affect the relationship between water supply and demand.Quantifying their impacts and describing the spatiotemporal distribution of these relationships are necessary for furtherly deepening the theory of TN and TP pollution on water bodies,and this information is also particularly essential for managing water resources regionally.In this study,based on the potential water supply,the water demand and the Integrated Valuation of Ecosystem Services and Tradeoffs(InVEST)water purification models,we estimated the TN and TP pollution from agricultural fertilizer,livestock and poultry breeding,and rural residents in the Huaihe River watershed and simulated TN and TP impacts on the relationship between water supply and demand.We found that if the impact of TN and TP pollution on water supply was not taken into account,on average,there was excess water supply in 79.20%of the watershed and excess demand in 20.80%of the rest during 1980–2018.Under the TN concentration limit,Grade-Ⅱ(The water quality meets the secondary level of water body qualified in GB3838–2002,classified as Grade-II)water was the main watersupply type in 1980–2018,followed by Grade-Ⅰ and Grade-Ⅲ water.The total water shortage showed an inverted V-shaped trend:first increasing and then decreasing at the same period.The proportion of the water shortage of Grade-I water in the total water shortage was the largest,followed by Grade-Ⅱ and Grade-III water.Areas with excess demand were located on the north bank of Wang-Beng,Yishuhe,and Huxi regions,although the water in these sub-watersheds met the water quality standards of Grade-Ⅰ water.Under the TP concentration limit,Grade-Ⅱ and Grade-Ⅰ water were the main water-supply types.The overall water shortage trend first increased and then decreased,exhibiting an inverted V-shape from 1980 to 2018.The water shortages of Grade-Ⅰ and Grade-Ⅱ water showed similar inverted V-shape trend over time.Areas that met the water quality standard of Grade-Ⅰ included the north banks of Wang-Beng and Huxi regions,where there was a surplus of demand.This paper suggests a way to analyze the interaction between water pollutants and the water supply-demand ratio as the example of TN and TP pollution at a watershed scale,which can broaden water pollution theory for relative water resources departments when water supply and demand will be evaluated.

景观空间异质性对地表水质服务的影响研究——以河南省伊河流域为例

人类干扰使景观空间异质性发生了剧烈变化,进而对生态系统服务产生了严重影响。目前,针对景观空间异质性与生态系统服务的关联关系研究还较为薄弱。以河南省伊河流域为研究区域,以地表水质服务为研究对象,分析了地表水质服务的空间变化;通过以水质采样点为中心建立缓冲区,分析了不同尺度下的景观空间异质性特征,并与地表水质指标进行相关性研究,以探讨景观空间异质性与地表水质服务间的影响规律及响应机制。结果表明:(1)研究区地表水质状况整体上为西南、东北部较差,中部较好;(2)从景观组成来看,林地面积占比或斑块个数的增加有利于地表水质的提高;(3)类型水平上,林地的景观构型与化学需氧量的质量浓度在200 m半径缓冲区内显著相关(P<0.05),城镇用地的景观构型对地表水质的影响则在2000 m半径缓冲区内更为明显;(4)景观水平上,总磷的质量浓度受到景观构型变化的强烈影响(P<0.05),景观构型异质性越低,总磷的质量浓度就越高;(5)适当增加景观空间异质性可有效降低地表水质污染物的质量浓度,提高地表水质服务。研究结论可为伊河流域的空间开发及水环境保护政策的制定提供科学依据。