An insect spends most of its life beneath the surface of the water before ever taking flight. It has become the focus of a rather unusual river-management project involving the Colorado River.
On September 16, 2025, the Bureau of Reclamation temporarily lowered flow releases from Davis Dam as part of an experimental study.
The goal of this action is to aid local efforts to reduce caddisfly populations in communities immediately downriver from the dam. This operation will not utilize pesticides or any other means to directly control caddisfly populations.
For a few hours, the river will expose a life stage usually hidden beneath the water’s surface for most of the year.
Lower water levels leave caddisflies exposed
Flow releases from Davis Dam will be approximately 2,300 CFS from 5 AM MST through 2 PM MST. This low-water level will expose areas of the riverbank that would normally be underwater.
Reclamation stated that caddisfly pupae and larvae are vulnerable once they are left exposed when water is pulled away from the banks. Once exposed, caddisflies will be susceptible to drying out as well as increased predation by wildlife.
Instead of implementing a new method to control caddisflies, this operation utilizes existing natural processes within the river corridor.
Wildlife, including birds and bats, are expected to prey on the exposed insects.
Large swarms create problems beyond the river
Caddisflies play a normal role in the health of aquatic systems. During their initial developmental stages, the insects live under the surface of the water.
Their larvae construct protective casings from sand, sticks, and other debris found in rivers and streams.
Adult caddisflies appear similar to small moths and serve as indicators of water quality.
However, problems arise when large quantities of adults emerge in localized areas. Swarms congregate around sources of light, boats, buildings, and other structures located near rivers.
Residents and businesses have identified caddisflies as a persistent annoyance, primarily where tourism and recreation generate income.
The Bureau of Reclamation said the insects are considered a nuisance by local residents and businesses, particularly those serving visitors.
In response to concerns expressed by Bullhead City and Laughlin, that operation took place at their request. The effort is part of an ongoing caddisfly abatement research study focused on evaluating potential management strategies.
A dramatic drop in water supply for just 9 hours
More than just the caddisflies will experience changed river conditions during the temporary flow reduction. Reclamation has cautioned all river users to increase safety precautions during these 9 hours of reduced flow releases.
Boating activities may encounter additional hazards while water levels are lower.
While flows are lower, sand bars may form in areas previously covered by flowing water.
As river levels fluctuate, riverbanks may become unstable. Floating debris and submerged objects can also relocate or come into view while the river adjusts to lowered flows.
River users may encounter conditions that differ from those usually found below Davis Dam.
After the special operation ends, regular release schedules will resume.
Flow reductions could become another tool
Scientists, federal reservoir operators, and representatives from local communities provided input on the research plan. The operation supports Colorado River communities according to Reclamation.
Officials must continue to consider water delivery requirements, power generation at dams, and recreational usage of the Colorado River.
Additionally, officials have indicated that planned operations may change if environmental or operational conditions require adjustments.
The 2025 test helped evaluate whether temporary flow reductions can assist local caddisfly management efforts.
Any future use of this approach would still need to balance water delivery needs, power generation, and recreational usage. Community concerns along the Colorado River would also remain part of the equation.
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