1. Science issues Water balance/cycling in snowmelt dominated catchments
remote sensing: SCA mapping
ground based: SWE network design
Implications for understanding & modeling:
Hydrology: partitioning of snowmelt
water resources: tools to estimate amount & timing of snowmelt
nutrient & energy cycling, aquatic system response

2. Emerald lake, 1985-98 (Sierra Nevada)
Outflow N greater when snowmelt occurred later in the year
DIN retention less in years with deep, late snowpacks
Sickman et al., 2001

3. Modeling N cycle at Emerald lake
plant uptake
leached
g m-2 a-1
denitrification
Note mineralization changes in wet vs dry years – made up by denitrification & plant uptake respond, as does leaching/export
net mineralization
discharge
Meixner & Bales, 2002

4. Emerald lake: discharge ANC
1950
1960
1970
1980
1990
Multi-decadal simulations of basin hydrochemistry using 47-year reconstructed streamflow record & snowpack depletion curves
Multi-year wet periods lead to lower stream ANC
Meixner et al., 2004

5. … & lower soil pH
Climate variability (5-10 fold changes in snowpack) much more important than doubling of acids in precipitation (10 vs 1 µeq L-1)
Meixner et al., 2004

6. Research needs & advances
Continuous (hourly or so) measurements as a diagnostic tool
flowpaths & water balance
biogeochemical processes
Integrated studies of water, C/N & energy cycles – as climate changes
disciplinary integration
integration across landscape
modeling as well as measurements

7. Instrumentation: water, energy & carbon cycling in SW subalpine forests
Canopy
Mt Bigelow 30 m tower
Eddy correlation system

8. Research infrastructure: hydrologic observatories (HO’s)
Address science questions at larger scales than current research catchments (nested scales)
Coordinated physical, chemical & biological measurements over the long term
Consortium of Universities for the Advancement of Hydrologic Science, Inc. (CUAHSI)
Another FAQ.

9. Concept for a Sierra Nevada HO
HO made of 3-5 clusters of instrumented (sub)catchments along latitudinal transect
Will also include elevational transects along one or more of the locations
Include stand-alone intensive research sites in between
Focus mainly above the reservoirs
Need to also consider gradients other than climatic

10. Scope of HO science
stimulate study where hydrologic & biogeochemical understanding of the water cycle is currently most limited
facilitate this research by:
measuring hydrologic phenomena over representative spatial scales & long time periods
creating a legacy of well-designed & documented long-term observations & experiments
providing baseline data & short-term process studies for conducting major synthesis & theoretical efforts
fostering emergent collaborations among scientists & decision makers
providing information for the identification, assessment & solution of societal problems

11. Broad science driver for HO
What: hydrologic systems are subject to multiple perturbations (jolts) that result in responses that we are currently poorly equipped to predict (examples …)
how pulses & changes propagate through the system
time lags & delays of stresses in comparative systems are compelling issues
Why: multiple factors are increasing the stresses on these systems, e.g. climate variability & change, land use change, water demand patterns …
How: HO science addresses this deficiency by providing a platform for research into the controlling processes & for testing predictive tools

12. Some specific science drivers that will influence design of a Sierra Nevada HO
Climate warming perturbations on a climate system that is already highly variable:
patterns of precipitation & snowmelt
patterns of vegetative water use
Habitat restoration efforts – aquatic & riparian – in a variable climate
coupled groundwater & stream response to changes
patterns of nutrient spiraling in streams
The potential for long-term droughts
patterns of rain/snowmelt partitioning, soil moisture, ET …
patterns of groundwater recharge, stream baseflow ..
Increasing potential for damage from floods
elevational patterns of changes in hydrometeorology
patterns of sediment generation & transport

13. Measurement priorities
Continuous
Ground-based hydrometeorology instrument clusters
Extended snow & soil moisture instrument cluster
Flux towers along gradients
Electrical conductivity, nitrate, silica in selected streams
Stream stage & groundwater levels
Periodic
Snowcover, snowpack, soil moisture
Stream, snow, rain, dry deposition, spring, groundwater chemistry
Something related to sediment
Characterization
Topography, soils, forest canopy, landcover, geology
LIDAR (vegetation properties)

14. Thoughts on HO management
Lead PI (1-2 mo) – position could rotate, like LTER PI
Institutional Co-PI’s – makes decisions (may need subset as excom) – institutional contribution to leveraging, responsibility for some aspect ( mo)
Affiliated investigators (any institution or agency) – must agree to data sharing policy (TBD)
Advisory committee (2-4 persons)
Ad hoc committees for distribution of special funds
Project manager (Ph.D. level scientist) – full time
Admin assistant – full time
Business manager – full time

15. Thoughts on HO budget Personnel $1.2 M Equipment & supplies $1.0 M
Laboratory analyses $0.8 M
TOTAL $3.0 M