Stockholm Environment Institute Natural Heritage Institute CABY Watershed Modeling with WEAP CABY Planning Meeting May David Purkey and David Yates

Application of WEAP to the American River Basin

Catchment Delineation Based on six digit hydrologic units (HUC6). HUCs were subdivided if necessary to calculate inflows to key reservoirs. In addition to 56 catchments in the American River Basin, the Camp Creek and Sly Park Creek catchments were added to compute inflow to Jenkinson Lake.

American River Basin

Major Streams in Basin

Model Catchments

Catchment Characterization Land was categorized using the SSURGO soils and the CALVEG vegetation databases. –Soils were classified as shallow or deep. –Vegetation was classified as trees, shrubs, bare, urban, grassland, or wet. Resulting classifications were –Deep trees –Shallow trees –Deep shrubs –Etc.

Modeled Rivers

Modeled Reservoirs Aloha Hell Hole Loon Lake Echo French Meadows Caples & Silver Folsom Union Valley Ice House Sly Park Stumpy Mdw

Modeled Transfers

Climate Data DAYMET.org (Univ. Montana & NCAR) –Daily, 1-km gridded data were mapped o the centroids of each suib-catchment –Precipitation, temperature, humidity, and wind. Data were developed using observed climate data and terrain models.

Effect of Elevation on Temperature and Precipitation

System Operations

Middle Fork Project Operations Upper American River Project El Dorado Irrigation District

Middle Fork Project

Middle Fork Project Operations Logic Minimum flow requirements are based on Article 37 of the current FERC license. Reservoir minimum pool values are based on Article 36 of the current FERC license. Reservoir guide curves are average monthly storage values from –Min pool and min flows are a function of April 1 predicted WY Folsom inflow. –In effect June 1 – May 31.

Upper American River Project

Upper American Project

Upper American River Project Operations Logic Minimum flows are based on current FERC license. Reservoir critical and typical year rule curves were taken from Exhibit B of license application. –Both are a function of April 1 predicted WY Folsom inflow. –In effect April 1 – March 31.

EID Operations

El Dorado Irrigation District

EID Operations Logic Demands were taken from the Shared Vision Model. –Project 184 only demands. –Project 184 or Sly Park demands Served by Sly Park if storage is greater than 38,000 af –Sly Park only demands –Folsom or Sly Park demands Served by Sly Park if storage is greater than 38,000 af –Folsom only demand Model currently has Silver and Caples Lakes. Echo Lakes are represented by a inflow.

April 1 Predicted Water Year Inflows to Folsom Reservoir

Folsom Inflow Prediction Department of Water Resources has developed a regression equation: Inflow (TAF) = X X – 962 X = average observed rainfall (Oct – Mar) + average historical rainfall (Apr – Sep) (inches)

X – Avg. Observed Rainfall Average observed rainfall is calculated using observations from Blue Canyon, Pacific House, Foresthill Ranger Station, Georgetown, Colfax, and Placerville. In the model we use predicted rainfall from the corresponding catchments.

Modeled vs. DWR Water Year Folsom Inflows

Calibration Results

North Fork American at North Fork Dam

Upper Duncan

Caples Lake SWE

Upper Rubicon

Union Valley Natural Inflow

Soil Moisture at Blodgett F.R.S

Middle Fork American at Foresthill

South Fork American At Placerville

American River Inflows to Folsom

Climate Change (and other) Scenarios in WEAP

Wood, et al. 2002, ‘Long range experimental hydrologic forecasting for the eastern U.S.’, J. Geophys. Res. 107(D20). Jan, Feb.. Dec Bias Correction Obs 2 o GCM hist d p,t dp’=dp*d p dt’=dt+d t dp=p 2xCO2 /p Hist dt=t 2xCO2 -t Hist Climate Scenarios- Downscaling hist cc p,t t p cc =p hist *dp’ t cc =t hist +dt’ Spatial downscale Map back to obs

Probabilistic assessment of regional climate change A Bayesian approach that combines predictions from multiple AOGCM output (21 models) Probabilistic representation of temperature/precipitation change, at regional scales, incorporating natural variability Reconciles projections from different AOGCMs BIAS and CONVERGENCE criteria: Reward models that perform well in reproducing current climate/ discount models that show a large bias Reward models that form a consensus/downweight extreme Projections Avoids the Problems of being “Married” to individual GCM!!

Climate Scenarios- Probabilistic Projections A1B Seasonal Changes for Northern California from 21 AOGCMs Precipitation WinterSpringSummerFall Winter- equal likelihood of more or less precip.; no strong long term trend Spring, Summer Fall- more likelihood of less precip.

Climate Scenarios- Probabilistic Projections Temperature WinterSpringSummerFall A1B Seasonal Changes for Northern California from 21 AOGCMs Early 21 st Century warming of 0.8C Natural variability could mask early 21 st century anthropogenic warming.

Climate Scenarios - Probabilistic Projections These probabilistic projections are useful, for getting a “feel” for the climatic range suggested by AOGCM models. BUT.. How do we use this information given impact assessment needs? Impact assessment models need “REAL DATA”.. E.g. Climate time series, such as temperature, precipitation, wind, humidity, etc. This is the downscaling process…

Climate Scenarios - Probabilistic Projections K-Nearest Neighbor Downscaling Hist Avg PcpHist Avg. Tmp Yates et al. 2003, A K-nn algorithm for generating regional climate scenarios, WRR

Climate Scenarios- Probabilistic Projections WmDry 1 WmDry 5 WmWet 1 WmWet 5 historic Monthly Avg. Temperature for Alder Creek to 2030 C

Climate Scenarios- Probabilistic Projections WmDry 1 WmDry 5 WmWet 1 WmWet 5 historic Monthly Total Precipitation Data for Alder Creek – 2010 to 2030 mm

North and Middle Forks French Meadows Hell Hole

cms Runoff North Fork American historic

Climate Change and Hydropower for the main projects An ensemble of climate projections and their impacts on hydropower Gw-hrs Headline: Even Wet scenarios suggest a decline in production with given operating rules.

Project Storage

North Fork Water Temps- Unmanaged Watershed WARM Dry WARM Very Dry

Middle Fork Water Temps – Managed Watershed WARM Dry WARM Very Dry

Caples SWE

Upper Rubicon Streamflow

Loon Lake Storage