The tollgate weir tells the story of the water in the west –its lean years, its banner years, its flood year, and rain on snow years. Tollgate weir spans a wide range of streamflow over its 50 plus years and integrates the water from the upper portion of the catchment. Studies over the years have shown that 85% of water that comes through this weir comes from only 15% of the watershed, the snow dominated headwater areas. Suspended sediment has also been documented at this and 9 other weirs. Above this weir, relatively little water is diverted to irrigation or other management. The weir was replaced in 1965 following the 1964 flood event.