Toward a Greater Understanding of Snowmelt Hydrology in Utah

TitleToward a Greater Understanding of Snowmelt Hydrology in Utah
Publication TypeConference Proceedings
Year of Conference2017
AuthorsJulander, Randall P., and Clayton Jordan
Conference Name85th Annual Western Snow Conference
Date Published2017
Conference LocationBoise, Idaho

Visual inspection of annual hydrographs from most rivers in the western U.S. supports the notion that
snowmelt provides the majority of streamflow in these areas. In Utah, the snowmelt period of April-July provides
an average of 71% of annual streamflow with 29% coming in the remaining 8 months, begging the question: what
proportion of streamflow comes from snowmelt? Previous estimates have been rough and have ranged from 60% to
80% or so; uncertainty stems from complexities such as rain on snow events, the geographic and temporal
distribution of precipitation events, and the partitioning of rainfall/snowmelt into streamflow. However, the
quantification of streamflow derived from summer precipitation is fairly simple on streams that have no upstream
regulation. It can be reasonably assumed that any rise in flow with a corresponding storm event is due to
precipitation, and the event flow can be separated from the base flow component of the hydrograph. We find that the
contribution of summer-month precipitation to annual streamflow in Utah is extraordinarily low: typically 1% to
2%. Using soil moisture and well depth data we also demonstrate that vast areas of Utah watersheds are incapable of
producing event flow from summer precipitation due to consumptive losses from evapotranspiration and other
factors. We use these data to infer that 98% to 99% of streamflow in Utah watersheds originates from melting snow
and associated processes. This analysis is likely representative of areas within other western states that have cool
continental climates, abundant snowfall, long-duration snowpacks (meaning that substantial portions of the
snowpack do not typically melt during the winter), and sedimentary bedrock, such as eastern Nevada, western
Colorado, portions of Idaho and Montana, and elsewhere. (KEYWORDS: snowmelt, streamflow, Utah, soil
moisture, SNOTEL)