Nutrient pollution is a pervasive water quality problem. Stream restoration has been proposed as a novel approach to reduce loading and increase nutrient processing within streams. We summarize evidence from the literature on the efficacy of stream restoration for reducing nutrient loading and increasing nutrient removal in stream ecosystems. We also analyze published data on streambank phosphorus concentrations and riparian and stream denitrification rates to improve understanding of the potential benefits of stream restoration for phosphorus retention and nitrogen removal. Finally, we discuss the role of stream restoration in nutrient management and provide recommendations for practice and future research.
Nutrient pollution (i.e. nitrogen and phosphorus) is one of the leading causes of poor water quality in the U.S. and around the world. There are many sources of this pollution, including fertilizer runoff from farms and lawns, wastewater treatment plants, and pet waste. This pollution makes its way into our streams and rivers where it is transported down to lakes and the ocean — causing algal blooms and other problems. Streams have the ability to process and remove these nutrients, essentially cleaning the water as it heads downstreams. Unfortunately, we have damaged the ability of many streams to serve as these important filters — and in some cases have made them net sources of pollution.
Stream restoration attempts to undo some of this damage. While stream restoration is typically done to improve fish habitat or reduce erosion, it may have the potential to improve water quality as well. We reviewed a number of studies that examined how well restoration can both reduce pollution from streams (e.g. reduce erosion) and also improve the natural filtering capacity of these ecosystems. Results are mixed. In some cases, stream restoration does measurably improve water quality. Unfortunately, most projects are so small and isolated that they don’t have much of an impact. The pollution problems facing streams and other waterbodies are so severe that it is necessary to take a bigger approach. Looking at the entire watershed, identifying major sources of pollution, and targeting projects to address these will likely yield better results than the piecemeal restoration approach that is currently the norm. Still, if done right, stream restoration does have significant potential to improve water quality and we are hopeful that more holistic approaches to watershed management will become more common.