The crest of the uncontrolled spillway is and is approximately long. When full, flood flows spill over the crest and down an long concrete chute. The water then returns to the river via an open rock cascade which gradually widens to at river level. Once Dartmouth Reservoir reaches 99% capacity, it is considered to be 'operationally full' and releases are then set to pass inflows downstream to prevent the level rising further. Releases are passed through the outlet works and power station whenever possible and water will only flow over the spillway if significant flood inflows enter from upstream when the storage is close to full. This approach reduces the chance of downstream flooding, maximises operating flexibility for hydro-power generation and protects the spillway.