If you’re like me, when rafting you marvel at these amazing wild rivers and river canyons. Apparently, most wild rivers aren’t as wild as we might think.

According to a recent study by the US Geological Survey (USGS), people have negatively impacted the flow of most of the rivers across the United States. The study identified over 1,000 unimpaired streams to use as reference points to create stream flow models. The models were applied to estimate expected flows for 2,888 additional streams where the USGS had flow monitoring gages from 1980-2007. The estimated values for the 2,888 streams were compared to actual, measured flows to determine the degree to which streams have been altered. The study found that 86% of the streams had altered flows. That’s just about all of them.

River flows are altered by a variety of land and water management activities including reservoirs, diversions for agriculture and drinking water, groundwater withdrawals, wastewater inputs, and runoff from impervious surfaces like parking lots, sidewalks, and roads. Flow alterations are a primary contributor to degraded river ecosystems and loss of native species.

The study concludes, “A national priority of restoring natural streamflow magnitudes could be broadly implemented and would produce widespread and measurable ecological dividends.”

The study provides a lot of answers for when river users ask us river rangers why about invasive weeds, non-native fish, algae blooms, or other impacts they see in the river.

I first read about this study on American Rivers’ River Blog. If you’re interested, check out and support American Rivers work to protect and restore stream flows.