two small units is 103.5 MW and for the large unit is 253.0 MW, for a total of 460 MW. If installed, Units 4, 5, and 6, each with a capacity of 220 MW, would bring the total generating capacity to 1,060 MW, making it one of the largest hydroelectric plants in Idaho. Operations The total usable storage capacity or active capacity of Dworshak Reservoir, including flood control, is . The inactive capacity (the portion of the reservoir's capacity below the power generating outlets and the lower river outlet works) is , and the dead pool (below the river outlet works) corresponds to a storage of . In addition, the reservoir has a surcharge capacity (above the spillway gates) of , bringing the maximum amount of water that can be retained behind the dam to . Most of the active capacity not used for flood control is used for power production. Because the Lenore dam on the Clearwater River was never built, Dworshak cannot be used as a peaking power facility. Thus, the power plant is operated as a base load plant, with a relatively constant release. Discharge rates from the dam only increase significantly during high water summers, when flooding requires the opening of the spillways. The power plant generates an average of 1.693 billion KWh each year. Water releases from Dworshak Dam are also controlled to optimize power generation at four downstream dams on the Snake River and four more on the Columbia River. Each winter, the level of Dworshak Reservoir is drawn down an average of to prepare for the North Fork's annual freshet, which once could reach more than after a heavy snowmelt. The reservoir is required to maintain a minimum of of winter flood-storage space, and dam releases are operated so that water levels reach a maximum of in July. However, annual flood control reservations vary with the amount of snowpack in the drainage basin above the dam. The annual flood-control drawdown generally begins in September and ends on April 1 of the following year; snowmelt floods are captured in the reservoir between April and July. Although the reservoir covers more than at full pool, the surface area decreases to at the lowest point of the drawdown. Flood storage space in Dworshak can be interchanged with other major dams in the Columbia River system, including large Columbia mainstem dams such as Grand Coulee, depending on