1. SNRI update on climate-change aspects of IRWM plan
Roger Bales, Mohammad Safeeq & collaborators
Topics in this talk
Sierra Nevada climate
Water balance
Climate impacts
Linking headwaters to groundwater
Photo: Margot Wholey
Dec 14, 2015

2. Extremes are part of California’s climate
Variability & drought
Extremes are part of California’s climate
Mar 27, 2010
Mar 29, 2015
Apr 3, 2017

3. Multi-year dry periods are part of our Mediterranean climate
1100 yr drought record
Reconstructed flows of San Joaquin R.
Color shading marks below-median periods 4+ yr long
1-6 per century
Multi-year dry periods are part of our Mediterranean climate
Meko et al DWR report

4. Snow-line changes reflect temperature increases in the Sierra Nevada
Rising snow line
Snow-line changes reflect temperature increases in the Sierra Nevada
Extremes in the past yr are not a sufficient guide to the future
Mar 31, 2011
Apr 3, 2017

5. Kings-Kaweah-Kern snowcover
Mar 31, 2011
Apr 1, 2017

6. Kings-Kaweah-Kern snowcover
Mar 31, 2011
Apr 1, 2017

7. Giant Sequoia & drought
Over 70 groves in southern Sierra Nevada
Survived the drought
Some quite vulnerable to a longer, hot drought
Su et al., 2017
G. Rom, Flickr

8. Topics in this talk
Sierra Nevada climate
Water balance
Climate impacts
Linking headwaters to groundwater

9. California water balance
Million AF
Precip: 200
Applied: 80
Water supplies
AF = 1233 Bm3
Agriculture: 80% (33 MAF)
Urban 20% (8 MAF)
Data from DWR, adapted from Nor. Cal. Water Assn.

10. Basic water balance
Precipitation = Evapotranspiration + Runoff + ΔStorage = +
snow & rain
Evapotranspiration refers to evaporation, sublimation plus water use by vegetation

11. We can measure & manage evapotranspiration on a basin-wide basis
Sierra Nevada
Precipitation =
Runoff +
Evapotranspiration
Map from CA Water Plan, 2013

12. Kings R. basin, annual water balance
1:1 line
Streamflow is linearly related to precipitation, as evapotranspiration changes little from year to year

13. Multi-year whole-basin water balance
Note that the 2016 value includes the effect of the 614 km2 Rough Fire.
P = ET + Q - ΔS
Bales et al., in review

14. Multi-year whole-basin water balance
Note differences in the (pre-drought) and drought).
P = ET + Q - ΔS
Bales et al., in review

15. Linking headwaters to groundwater
Topics in this talk
Sierra Nevada climate
Water balance
Climate impacts
Linking headwaters to groundwater
Lake Success
CADWR photo

16. Shifts in California’s temperatures & why it matters
Higher evapotranspiration
Higher environmental flow
Increase in the size of wildfires
More heat waves, a longer frost-free season & fewer cold snaps
A lack of snow accumulation during near-normal winter precipitation (a.k.a. warm snow drought)
A shift in precipitation phase

17. Warmer temperature = more evapotranspiration (ET)
Goulden & Bales, 2014

18. Kings R. average flow
Sorabi et al., in preparation

19. Topics in this talk
Sierra Nevada climate
Water balance
Climate impacts
Linking headwaters to groundwater

20. Reconnecting a fragmented system
Water in the balance – UC TV Sustainable California

21. Managing evapotranspiration
Even thin
Variable thin
1 km
Control
Managing evapotranspiration
Stanislaus-Tuolumne Experimental Forest
Basal-area decrease = 40-50%
Control
0.5
0.6
0.7
0.8
0.4
0.5
0.6
0.7
0.8
950
570
340
0.4
Even thin
Variable thin
NDVI
mm/yr
ET, mm yr-1
Control
Even thin
Variable thin
1985
1995
2005
2015
2.0
1.0
1000 mm
Mean WY precipitation
1985
1995
2005
2015
Year
J. Roche et al., submitted

22. 1-day peaks increased by more than 3 fold
Effect of temperature changes on groundwater-banking potential
90th percentile
Flood flows
Kocis and Dahlke, 2017
1-day peaks increased by more than 3 fold
Sorabi et al., in preparation

23. Whole-basin integration is key for Central Valley
Managed Recharge
Opportunistic Recharge
Reservoir reoperation
Groundwater is our dry-period reserve; & sustainable use requires both more recharge & less extraction

24. Climate-change & headwaters: climate-modeling projections
Historical variability in snowfall closely resembles the projected 2040-warming scenario (+1.8oC)
By 2080s (+3.0oC), mountain snowfall will be reduced to 17 MAF, 30% lower than the average snowfall in 10 warmest years
Snowpack storage in the Kings River Basin will decline by 50% under +4oC warming
Water yield in the Kings River Basin will increase under warmer climate
Flow will shift early in the year, i.e. more winter runoff

25. Management challenge
Water security is a major challenge facing California
Integrated water systems designed to manage green infrastructure & groundwater recharge is key to future water security

26. Comments? NSF Southern Sierra Critical Zone Observatory
Spread them out throughout the basin but can be constrained.
NSF Southern Sierra
Critical Zone Observatory