Management of the Spring Snowmelt Recession in Regulated Systems

Sarah Yarnell, Gerhard Epke Amy Lind, Joshua Viers

Photo: R. Peek Spring Snowmelt Recession Ecology

• The one time annually where high resources are coupled with predictable flows • Results in high biodiversity (Gasith & Resh 1999)

Yarnell, S.M., J.H. Viers and J.F. Mount. 2010. BioScience 60:114-127. Regulated Flow Regimes

Yuba Rivers - WY 2011

NF Yuba MF Yuba SF Yuba 7000

6000

5000

4000

3000

2000

Discharge (cfs) Discharge 1000

0 1-Oct 31-Dec 1-Apr 1-Jul 30-Sep Quantifying the Flow Recession

Yarnell et al., 2010 Quantifying the Spring Recession Rate: Unregulated Basins in the Sierra Nevada

Indian Creek/Feather River

North Fork Yuba River North Fork American River Cosumnes River

Clavey River

Merced River

South Fork Daily recession rates are Kaweah River consistent across basins Kern River and elevations

N Epke, G. 2011 Daily Percent Change in Discharge

Daily recession rates: 1) decrease during the recession (on average from 8 to 4%), 2) are limited (typically < 20%) Calculating a Spring Recession Flow Regime

Yuba Rivers - WY 2011

NF Yuba MF Yuba SF Yuba 7000 Requires knowledge of: 6000 5000

4000 • hydrology of the regulated river 3000 2000

Discharge (cfs) Discharge 1000

0 • hydrology of an analogous 1-Oct 31-Dec 1-Apr 1-Jul 30-Sep unregulated river • limitations of the regulated system infrastructure • hydraulic-related thresholds for aquatic species of interest (e.g. maximum allowable ramping rates) • representative channel morphology of the regulated river

Rubicon River Example

• Regulated bypass reach below high-elevation reservoir • Regulated flows dominated by spring spills and baseflow • Unregulated NF American in same watershed

Use 2D hydrodynamic model to evaluate flow effects on native species Rubicon River Example

Rubicon River 800 calculated recession • Start the recession 600 proposed flows from spill at 700 cfs 400

when gain control of FlowCFS 200 0 the system 1-Jun 11-Jun 21-Jun 1-Jul Date • Decrease flows at rates Calculated Recession Flows Flow Schedule

similar to the natural Day Flow Step % change Flow Step % change rates (8-5%/day) 1 700 -- 700 -- 2 644 0.080 600 0.143

• Limit steps to 3 594 0.079 600 0.000 <20%/day 4 547 0.078 600 0.000 5 466 0.077 500 0.167 • Reach the minimum … … … … … instream flow within 42 40 0.052 40 0.000 43 38 0.051 35 0.125

45 days 44 36 0.051 35 0.000

45 35 0.050 35 0.000

Modeled Flow Recession Scenarios

Recession Ramp-down Scenarios Four Scenarios: 8% - 5% 9.5% 15% 30% Baseflow - 30 cfs Average Spring 800 Rate = 8%-4% 700 600 Constant Low = 500 9.5% 400 Flow (cfs) Constant 300 Medium = 15% 200 100 Maximum 0 Observed in 0 7 14 21 28 35 42 Day Nature = 30% Foothill Yellow-legged Frog Breeding Habitat

• Frogs lay egg masses in very low velocity locations at 20-40 cm depth • 3 weeks required for egg

masses to hatch and (Bondi C.B., S.M. Yarnell and A.J. Lind. 2013.) tadpoles to grow big enough to follow receding water’s edge

• → Flow recession of 10 cm per week will limit desiccation of eggs Spatial Niche Analysis

p y

2 Trout Fry Depth and velocity 1.8 Juv RBT Deep/Slow Deep/Medium Deep/Fast Adt RBT (Shallow guilds for aquatic 1.6 Water) Juv HH PM species of interest 1.4 Adt HH PM in the PCWA 1.2 Trout Spawning Medium/ Medium/Medium Medium/Fast Fast Middle Fork 1 Slow Adt S Sucker Juv S Sucker Project Depth(m) 0.8 FYLF Egg Mass 0.6 FYLF Tadpole Example: 0.4 Cal Roach Shallow/ Shallow/Medium Shallow/Fast Rainbow Trout Slow Sculpin / Spk Dace 0.2 Primary Niches Spawning 0 Shallow Juvenile Hardhead 0 0.2 0.4 0.6 0.8 1 Velocity (m/s)

Fry = Rainbow Trout, RBT = Rainbow Trout, HH = Hardhead, PM = Sacramento Pikeminnow , Spaw n = Trout Spaw ning, S = Sacramento, FYLF = Foothill Yellow -Legged Frog, Cal = California, Spk = Speckled, Juv = Juvenile, Adt = Adult Modeled Flow Recession Scenarios

Rate of Decreasing Stage (725 to 30 cfs) 45 40 35 30 25 20

cm / week 15 10 5 0 8-5% 9.5% 15% 30% Ramping Rate (% / day)

FYLF eggmasses – 30 cm average depth/3 weeks to hatch Modeled Flow Recession Scenarios

Duration of Recession

Native Species 725 cfs to 30 cfs 30% Emergence

15%

9.5%

Ramping Rate (%/day) Rate Ramping 8-5%

0 10 20 30 40 50 Days

FYLF – 3 weeks; Native spring spawning fish – 2-4 weeks Spatial Niche Analysis

Spatial Niche Distribution 60 725 425 220 77 32 Percent of modeled nodes 50 within each spatial niche at 40 each of five modeled 30 discharges (725 cfs – 32 cfs). Percent 20

10

0

Spatial Niche Diversity 7 6 5 Simpson’s Diversity Index 4 3 calculated from the distribution 2 of spatial niches at each of five Simpson's Diversity Index 1 0 725 425 220 77 32 modeled discharges Modeled Discharge (cfs) Implications for Regulated Systems

• Restoration of the spring recession achievable by modeling rates of change to increase hydraulic habitat diversity • Hydraulic diversity in both space and time is necessary to support the full complement of native aquatic species

• Key to diverse hydraulic habitat mosaic is to shift relatively slowly through time – allow for development of eggs and larvae within a spatial niche before the niche disappears

Application in Regulated Systems

Recession rates can be modeled as down-ramping rates from spill or an ecological flow pulse

Examples in California: USFS PM&E Spill Cessation Flow – South Fork Yuba River – South Fork San Joaquin River 300 250 – McCloud River 200 150

– North Fork Feather Cresta Reach Flow (CFS) 100 – Middle Fork American River 50 0 – Upper Yuba Rivers 1-Jun 6-Jun 11-Jun 16-Jun 21-Jun 26-Jun 1-Jul Acknowledgements

• Funding: California Energy Commission • Collaborators: US Forest Service, Placer County Water Agency, Ryan Peek, Craig Addley

Tuolumne River