The hydraulic downpull forces that will be caused by 2-minute closures of the 16.5- by 21.0 foot Glendo Dam outlet works fixed-wheel gate were computed. Previous model studies (Hydraulics Laboratory Report No. Hyd-421, February 8, 1957) evaluated the hydraulic downpull for a stable condition of flow with the gate stationary at various openings. The present computation showed the added downpull caused by water trapped in the shaft above the gate during rapid closures to be about 4,500 pounds for gate openings larger than 3 feet. No additional downpull occurred at openings smaller than 3 feet. The maximum downpull of 40,000 pounds that occurs at 0.25 foot gate opening remains the maximum and unchanged. (Author).