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Native and desired nonnative fish downstream of Glen Canyon Dam are food limited—meaning that if more or larger invertebrate food items were available, there would be more and larger fish. Aquatic insects have complex life cycles that include egg, larvae, and pupal stages that are aquatic while adults have wings and are typically terrestrial. Aquatic insects are a fundamental component of river food webs and the primary prey for fish and many species of birds, lizards, fish, and even other invertebrates. Identifying the factors that limit production and diversity of the insect prey base is important when making management decisions, especially when those decision affect endangered species, like humpback chub (Gila cypha).
SBSC scientists participate in outreach, such as be interviewed for podcasts. Listen to this episode of Making Waves about how SBSC scientists engage with citizen scientists on the Colorado River.
Bug Flows have recieved a lot of media attention. Below are links to selected news stories from various outlets.
In rivers, many aquatic insects lay their eggs right at the water line. In pre-dam era, water levels did not vary much on hourly or daily time scales, so this strategy ensured that eggs would stay submerged long enough to hatch. However, because of hydropower production at Glen Canyon Dam, the river now experiences a daily “tide” as more water is released during daylight hours to meet higher demand for electricity during the day. Then at night, when energy demand is lower, less water is released from the dam resulting in a drop in water levels. The magnitude of this tide during summer months is around 2-3 feet, depending on location. For insect eggs laid at the high-water mark, when river flows drop these eggs become desiccated and die, typically within a few hours. USGS research has shown that these daily high and low tides created by hydropower operations are an important factor that contributes to the low abundance and diversity of aquatic insects in Grand Canyon.
Bug flows are experimental releases from Glen Canyon Dam that were designed to increase the abundance (number of individuals) and the diversity (number of types) of insects in Grand Canyon by improving egg laying conditions for insects. The Bug Flow experiment was tested at Glen Canyon Dam on weekends from May through August of 2018-2020. During the experiment, hydropower operations continued as normal during weekdays, resulting in daily tides. On weekends, however, a steady low-flow was released from the dam (see figure of hydrograph) to try to improve egg laying conditions for aquatic insects. Because demand for electricity is typically low during weekends, the design of the Bug Flow experiment improves egg laying conditions for insects while minimizing negative impacts to hydropower production. The goal of the Bug Flow experiment is to support healthier wildlife populations through increases in the production and diversity of the aquatic insect prey base.
Outreach and Science Communication related to Bug Flows
Southwest Biological Science Center scientist studying the aquatic food base in the Colorado River participate in outreach activities within and outside of the USGS.
Outreach produced outside of USGS: (note links are to organizations outside of the USGS)
Below are other science projects associated with this project.
Below are publications associated with this project.
Below are partners associated with this project.