Graduate student Chip Gianfagna, enrolled in ERE’s Engineering Hydrology and Hydraulics class, wants to see more white water for recreation and wildlife. His goal is shared by Meghan Hooker of American Whitewater, who reported on the societal and environmental benefits of restoring spring runoff flows to regulated rivers in the Nov./Dec. 2011 issue of the American Whitewater Journal.

White water can be found around the world, and in snow melt fed rivers it is often a spring / summer celebration.

The water resource engineering issues in this article are river and flow regulation and hydrograph augmentation by dynamic impoundments.  The article focuses on the difference in hydrographs between two similar rivers in California during the spring snowmelt period.  The rivers are the regulated North Fork of the Feather and the non-regulated North Fork of the American.  The regulated North Fork of the Feather has the recession limb after the peak quickly drop off to baseflow levels, diverting water to reservoir storage. The non-regulated North Fork of the American has a normal recession limb as shown in the figure below – which is much better for white water!

Example hydrograph with rising and falling limbs.

From a broader environmental perspective the article argues that flow manipulation in regulated rivers is bad for the natural ecology of river.  This includes very sudden increases and decreases in flow that negatively impact habitat, water quality, and flow patterns that many riverine species have evolved to depend on.  Examples include thermal and dissolved oxygen fluctuations, sediment releases, and scour associated with unnaturally high flows.  These claims are substantiated by Yarnell et al. who published a paper in 2010 entitled “Ecology and Management of the Spring Snowmelt Recession” in Bioscience.

This WRE issue also relates to the broader contexts of societal and economic issues.  Societal issues associated with manipulation of the spring runoff recession include recreational opportunities and our general view of ecosystem integrity.  Whitewater boating opportunities in the American West are largely considered to be at their peak during the spring and early summer snowmelt.  This results in swollen rivers with the flows necessary for kayaking and whitewater rafting.  In locations where the whitewater rafting industry is well established this can also represent a significant economic impact.

From a more holistic viewpoint the issue of unnatural spring runoff recession relates to our view of ecosystem integrity and what we as society value in the natural world.  This issue is best described by Aldo Leopold with his “wilderness for the sake of wilderness” argument.

In conclusion, the issue of manipulation of the spring runoff recession in regulated rivers in the West impacts both the ecology of the system, as well as the recreational and economic uses of the river.  The article suggests that natural spring runoff is desired from environmental, recreational, and preservation perspectives, and points out that in this case “what’s good for the river is good for recreation.