Evaluating net effects of wet meadow restoration on water and streamflow Paul Noël Gordon Grant Caroline Nash, Sarah Lewis John Selker Daugherty Global Institute PNW Research Station College of Earth, Ocean & Atmospheric Sciences Biological and Ecological Engineering University of Nebraska USDA Forest Service Oregon State University Oregon State University
Familiar landscape in the West
Illustrations by Restoration Design Group for American Rivers Restoration Channel re-alignment Plug-and-pond Beaver analogs/reintroduction Photo: USDA Forest Service Region 5 Photo: Oregon Watershed Enhancement Board Photo: NOAA NW Fisheries Science Center
Post-restoration landscape demonstrates “greening” of valley bottom (example from SilviesValley Ranch) Sagebrush Riparian Camp Creek Silvies River Basin, OR 4.5 years after restoration 4 years prior to restoration
? Discharge Time Incised Restored Increased streamflow How do we evaluate the effects of wet meadow restoration on water and streamflow?
A water budget identifies relevant fluxes P P Restored Q in Q in Incised ET ET S S Q out Q out ∆ Q = Q in + ∆ Storage + ∆ Evapotranspiration
T otal drainable storage = water that can flow out of floodplains by force of gravity Incised (3 meters) Maximum water table elevation Less storage Restored (0.33 meter) More storage
Laterally drainable storage = quantity of water that can flow laterally into channel Incised (3 meters) Maximum water table elevation More storage Restored (0.33 meter) Less storage More incision = taller drainage face = larger wedge of laterally drainable water
Loheide and Gorelick, 2007 Hammersmark et al., 2008 Restored Incised ET peaks are later and higher in restored meadows Restored meadows use Mesic plants use more water than xeric plants more water for ET
P P Restored Q in Q in Incised ET ET S S Q out Q out ∆𝑅 𝑝𝑣𝑢 = less drainable storage + more evapotranspiration Both changes suggest restoration decreases late summer streamflow
Incised & restored meadow scenarios - Discharge Deeply Incised (3 meters) All scenarios produce very small volumes of water in Log Q Discharge (m 3 /s) late summer 0.1 m 3 /day = 0.000001 cms = 0.00004 cfs Moderately Incised (1m) Restored (0.3m) Range in start times September 1 ( June 1-15) Time (day of year)
Incised & restored meadow scenarios - Evapotranspiration Volume of ET is larger in restored meadows Volume (m 3 ) Time (day of year)
For all scenarios, ET is much greater than discharge Volume of Water (m3) ET Q Time (day of year)
Wet meadow restoration is not likely to increase late- summer streamflow • Although restoration increases total storage in the floodplain, the amount of water available for streamflow actually decreases . • Floodplains are not the major source of water - volumes of water available for drainage are very small in ALL scenarios. • Restoration does make more water available for plants , who happily use it. • Clear benefits to riparian vegetation and habitat from more plant available water.
Thinking about restoration as a learning environment • There are many things we don’t yet understand about how wet meadow restoration affects watersheds • Downstream effects (both quality and quantity) • Effects on fire (introducing fire breaks into landscape) • Effects on plant, animal, and aquatic communities Restorations are full scale experiments…how best to capitalize on them?
Thank you to our funding sources, collaborators, and field assistants For more information contact: Gordon Grant, Gordon.grant@oregonstate.edu USDA PNW Research Station USDA PNW Climate Change HUB USDA Northwest Climate Science Center
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