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

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

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

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

… & 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

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

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

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.

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

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  

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

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

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)

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 (0.5-1.0 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

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