Ecological Health & Function
CATEGORY: Flow Regime
Hydrograph Indicator
The hydrograph indicator considers the following components of the Yampa River’s flow regime:
Magnitude, timing, and duration of peak flows
Adequate peak flows are essential to river health and function. Snowmelt-driven peak flows during spring runoff are important for numerous watershed services, such as fishery support, riparian habitat quality, sediment flushing, water quality maintenance, recreation, aesthetics, and groundwater connection and recharge.
Magnitude, timing, and duration of base flows
Base flows are the low flows that occur after snowpack melt, during dry season, usually from late summer to early spring. They provide critical support of aquatic habitat and riparian connectivity when the stream needs it most after peak flows have receded. Sources of base flows are rainfall events and slowly percolating groundwater, and they can be augmented by reservoir releases and irrigation return flows in managed systems.
Total annual volume (the amount of water delivered to the riverscape from its contributing watershed) and hydrograph form (the shape of the hydrograph, including timing and duration of rising and falling limbs) are also important components of flow regime in the Yampa River Basin but are not included in the scoring for this indicator due to lack of available modeled data.
Hydrograph score by Section
Middle Yampa Segment
Steamboat
Segment
Upper Yampa Segment
Elk River
Segment
Lower Yampa
Segment
Score coming TBD
Dinosaur
Segment
Score coming 2027
Did You Know?
The flow data used for the Scorecard includes data modeled from streamflow gauges whose periods of record are approximately 40 to 60 years old. It also considers a streamflow trend analysis on the main stem of the Yampa River conducted by USGS over a 100-year time period.
Hydrograph examples are provided below. Example A shows the basic shape of a snowmelt-driven hydrograph, including seasonality of high and low flows. Example B shows the relationship between a typical hydrograph in a snowmelt-driven system and the snowpack itself.
Example A
Credit: CWCB (Colorado Water Plan 2015)
Example B
Credit: Doesken and Judson 1996
Did You Know?
Beaver activity helps mitigate the impacts of dams and reservoirs.
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While dams in the upper watershed block the passage of sediment, water, and wood through the system, the beaver activity that is present and active below Stillwater Reservoir and in the vicinity of Bear Lake and Yamcolo Reservoir mitigates some of these impairments to river health.
Beaver activity aids in slowing and spreading the water that flows through their complexes, often leading to the creation or expansion of wetlands. Beaver activity mobilizes wood into the system and stimulates riparian vegetation growth.
Without beaver dam complexes, snow and stormwater runs off the landscape at a faster rate, and causes stream channels to incise, eventually disconnecting them from their natural floodplain and degrading the riparian vegetation. Disconnected channels result in ecological degradation and make the landscape and ecosystem more vulnerable to disturbances from fire, erosion, and floods.
Beavers provide an important driver of long-term channel-floodplain connection, stability, and riparian corridor health. Historically, they were major drivers of the channel form, extent of wetlands, and biodiversity of the landscape.