This is your official 2-week reminder for the Guardians of the Reservoir Challenge! Submissions are due on October 20th at 5 pm ET.
We have been receiving a few questions on the characteristics of reservoirs that your solution could work on. The Bureau of Reclamation and the U.S. Army Corps of Engineers (USACE) operates hundreds of reservoirs across the United States. While each reservoir is different, they typically share some common characteristics:
- Typical lengths range from 1 to 30 miles (2 to 50 km) upstream of the dam with sedimentation along the entire length.
- Annual reservoir sedimentation inflow rates typically range from tens of acre-feet per year to thousands of acre-feet per year. These sediment inflow rates are equivalent to tens of thousands of cubic yards per year to millions of cubic yards per year (tens of thousands of cubic meters per year to millions of cubic meters per year).
- Sedimentation includes the whole range of grain sizes, i.e. clay, silt, sand, gravel, cobble. Sand, gravel, and cobble tend to deposit as shallow deltas at the upstream ends of the reservoir. Clay and silt tend to deposit farther downstream along the reservoir bottom.
- Sedimentation typically includes submerged wood of various sizes (twigs to logs). However, woody debris is not a focus of this competition.
- Presently, nearly all inflowing sediments are trapped within water storage reservoirs and little, if any, sediments are released downstream. Existing dams were not designed to pass sediment downstream. Long-term sustainability of reservoir storage can only be achieved by transporting inflowing sediments downstream or removing sediments from the river system.
- With new capabilities, reservoir sediments possibly could be passed downstream from a dam, in various amounts, during all months of the year. Passing sediments downstream at concentrations that match the reservoir inflow would be desirable, but this is not a requirement of this competition.
- Limits on the downstream passage of reservoir sediment are not part of this competition. In practice, any such limits would be related to the capacity of the downstream river channel to transport sediment.
- Recovering past reservoir storage capacity loss would be great, but the sedimentation volume is typically too large to be economically feasible, would exceed the downstream sediment transport capacity, and is too large to be removed from the river system.
- Reservoir sedimentation is typically at water depths that range from 1 to 200 feet (0.3 to 60 m).
- Typical depths from the reservoir water surface to the lowest dam outlet are 30 to 150 feet (10 to 50 m), but these outlets were not designed to pass coarse sediment or wood.
- Reservoir water levels fluctuate both seasonally and year to year. Seasonal fluctuations may range from 2 to 20 feet (0.6 to 6 m). Year to year fluctuations can range from 5 to 50 feet (2 to 15 m).
- The height of the dam above the normal reservoir water level typically ranges from 20 to 100 feet (6 to 30 m). Spillways are typically 10 to 80 feet (3 to 25 m) above the reservoir water surface.
- The drop in elevation from the top of the dam down to the downstream river channel typically ranges from 50 to 300 feet (15 to 90 m).
- Reservoirs in northern USA latitudes typically have ice on the reservoir surface during winter while reservoirs in southern latitudes typically do not have ice. In cold regions, ice may be thicker than 1 foot (0.3 m).
- Certain life stages of fish and wildlife could require curtailment of sediment removal activities at specific locations within some reservoirs, but this is highly site-specific and not part of this competition. In general, solutions need to avoid widespread disruptions to fish, wildlife, and recreation throughout the reservoir.
- With low noise levels and unobtrusive lights, reservoir sediment removal activities could occur 24-hours per day, seven days per week.
We have presented four case studies of specific reservoirs to provide a more robust image of the diversity and variability of the reservoirs managed by BOR and USACE (view the case studies here). We encourage you not to get caught up in the details of these specific case studies. If you propose a solution that works for certain characteristics, we can likely find a reservoir with those characteristics where sediment removal solutions are needed.
We look forward to receiving your innovative ideas!