Water security is a top concern for social well-being, and dramatic changes in the availability of freshwater have occurred as a result of human uses and landscape management. Elevated nutrient loading and perturbations to major ion composition have resulted from human activities and have degraded freshwater resources. This study addresses the emerging nature of streamwater quality in the 21st century through analysis of concentrations and trends in a wide variety of constituents in streams and rivers of the U.S. Concentrations of 15 water quality constituents including nutrients, major ions, sediment, and specific conductance were analyzed over the period 1982–2012 and a targeted trend analysis was performed from 1992 to 2012. Although environmental policy is geared toward addressing the long-standing problem of nutrient overenrichment, these efforts have had uneven success, with decreasing nutrient concentrations at urbanized sites and little to no change at agricultural sites. Additionally, freshwaters are being salinized rapidly in all human-dominated land use types. While efforts to control nutrients are ongoing, rapid salinity increases are ushering in a new set of poorly defined issues. Increasing salinity negatively affects biodiversity, mobilizes sediment-bound contaminants, and increases lead contamination of drinking water, but its effects are not well integrated into current paradigms of water management.

中文翻译：

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美国河流水质动态变化的景观驱动因素。

水的安全是社会福祉的头等大事，由于人类的使用和景观管理，淡水的供应量发生了巨大变化。人类活动导致养分负荷增加和对主要离子组成的干扰增加，并使淡水资源退化。这项研究通过分析美国河流和河流中各种成分的浓度和趋势来分析21世纪河流水质的新兴性质。15种水质成分的浓度包括营养素，主要离子，沉积物和比电导。在1982年至2012年期间进行了分析，并在1992年至2012年进行了有针对性的趋势分析。尽管环境政策旨在解决长期存在的营养过富问题，这些努力取得了不均衡的成功，城市化地区的养分含量不断下降，而农业地区的养分含量几乎没有变化。此外，在所有人类主导的土地利用类型中，淡水都被迅速盐化。在控制营养的努力不断进行的同时，盐度的快速增加也带来了一系列新的，定义不清的问题。盐分的增加对生物多样性产生不利影响，动员了沉积物结合的污染物，并增加了饮用水中铅的污染，但其影响并未很好地纳入当前的水管理范式。在控制营养的努力不断进行的同时，盐度的快速增加也带来了一系列新的，定义不清的问题。盐分的增加对生物多样性产生不利影响，动员了沉积物结合的污染物，并增加了饮用水中铅的污染，但其影响并未很好地纳入当前的水管理范式。在控制营养的努力不断进行的同时，盐度的快速增加也带来了一系列新的，定义不清的问题。盐度的增加对生物多样性产生不利影响，动员了与沉积物有关的污染物，并增加了饮用水中铅的污染，但其影响并未很好地纳入当前的水管理范式。