Here’s the release from the Bureau of Reclamation:
The Department of the Interior will conduct a spring disturbance flow release from Glen Canyon Dam, Arizona, beginning March 15 at 5 a.m. and ending March 26 at 8 a.m.
A spring disturbance flow is planned at Glen Canyon Dam from March 15 to March 26. It is expected to maximize ecosystem benefits to the Colorado River ecosystem through the Glen, Marble, and Grand canyons, while meeting water delivery requirements and minimizing negative impacts to hydropower production. The spring disturbance flow will not affect the monthly or annual release volumes from Lake Powell through Glen Canyon Dam.
The spring disturbance flow capitalizes on a unique low flow of 4,000 cubic feet per second for 5 days, which is needed to conduct maintenance on the apron of Glen Canyon Dam. This low flow will be followed by a gradual increase to higher releases that will culminate in a discharge of approximately 20,150 cubic feet per second for 82 hours. The peak release of the spring disturbance flow will stay within the maximum release levels allowed under normal operations.
This combination of low and high flows is expected to disturb river bottom habitats and may drive positive aquatic ecosystem responses like increased algae and insect production. This could increase aquatic insect prey available for endangered humpback chub, non-native rainbow trout, an important sportfish, as well as other wildlife. The spring disturbance flow may disadvantage brown trout in Glen Canyon by reducing survival of emerging fry. The spring disturbance flow may also provide new scientific information that can be used in future decision making.
Recreational users are reminded to exercise caution along the Colorado River through Glen and Grand Canyons during the entire spring disturbance flow period.