They are doing maintenance on the dam and I think they might not have enough water in the pool.
https://www.usbr.gov/pn/grandcoulee/lakelevel/index.htmlLake Roosevelt Water Level
PROVISIONAL DATA - Subject to change
The elevation of Lake Roosevelt was 1222.2 feet above sea level at 3 p.m. on May 1, 2018. The level of the lake is expected to remain in the 1221.5 – 1222.5 range through May 4. Refill of the lake is predicted to begin on May 5.
At this time, Lake Roosevelt is below the minimum 1232 feet elevation needed to operate the Gifford-Inchelium Ferry. The lake is predicted to reach 1232 in the May 10 – 12 timeframe.
Grand Coulee is operating to meet the flood control elevation of 1222.7.
Flood control is the MAXIMUM allowable level of the lake in order to be able to accommodate the spring runoff. Elevations may be lower than the flood control elevation due to power operations, river operations, drum gate maintenance, emergency situations or other unforeseen circumstances.
The lake level target provided in this report is only a prediction and subject to change without notice due to power operations, river operations, emergency situations, changes in weather or other unforeseen circumstances. Lake level forecasts are updated by 3 p.m. each day. Please call 1-800-824-4916 for the updated 24-hour forecast.