This report is intended to summarize major findings that emerged between 1992 and 1995 from the water-quality assessment of the South Platte River Basin Study Unit and to relate these findings to water-quality issues of regional and national concern. The information is primarily intended for those who are involved in water-resource management.

A nontechnical publication that describe the major findings of the NAWQA (National Water-Quality Assessment) Program on water-quality issues of regional and national concern. The first 2 sections provide a general overview of findings on nutrients and pesticides and their implications for water-resource management and protection. More detailed discussions of the sources, distributions, and potential effects of these chemicals are provided in subsequent sections. Numerous color illustrations.

In Wide Rivers Crossed, Ellen Wohl tells the stories of two rivers—the South Platte on the western plains and the Illinois on the eastern—to represent the environmental history and historical transformation of major rivers across the American prairie. Wohl begins with the rivers’ natural histories, including their geologic history, physical characteristics, ecological communities, and earliest human impacts, and follows a downstream and historical progression from the use of the rivers’ resources by European immigrants through increasing population density of the twentieth century to the present day. During the past two centuries, these rivers changed dramatically, mostly due to human interaction. Crops replaced native vegetation; excess snowmelt and rainfall carried fertilizers and pesticides into streams; and levees, dams, and drainage altered distribution. These changes cascaded through networks, starting in small headwater tributaries, and reduced the ability of rivers to supply the clean water, fertile soil, and natural habitats they had provided for centuries. Understanding how these rivers, and rivers in general, function and how these functions have been altered over time will allow us to find innovative approaches to restoring river ecosystems. The environmental changes in the South Platte and the Illinois reflect the relentless efforts by humans to control the distribution of water: to enhance surface water in the arid western prairie and to limit the spread of floods and drain the wetlands along the rivers in the water-abundant east. Wide Rivers Crossed looks at these historical changes and discusses opportunities for much-needed protection and restoration for the future.

Nutrients in water are necessary for productive aquatic ecosystems, but in high concentrations, nutrients such as nitrates, ammonia, and phosphates can adversely affect aquatic life and human health.