upalco unit replacement project project area project summary project features crystal ranch reservoir big sand wash reservoir runoff vs. demand

runoff vs. demand Flows from the Yellowstone and Lake Fork drainages peak in May and June when snow melt in the higher reaches of the drainages is occurring. The irrigation season in the Upalco Unit runs from April to October. River flows are normally sufficient to meet irrigation demands only during the peak runoff (graphic). Storage facilities on the Yellowstone and increased storage on the Lake Fork River would allow the capture of peak flows in excess of irrigation demand, as well as some of the flows that pass through the Upalco Unit during the non-irrigation season. Releases from storage would increase the irrigation season. Diurnal fluctuations (graphic) during the peak flow period can vary drastically. Storage on the Yellowstone River would level out these day to night fluctuations, making it easier to keep diversions constant.