Climate Change Projections for USFS Lands
in Oregon and Washington

Project Overview

The purpose of this project is to use existing climate change datasets from the Climate Impacts Group (CIG) to summarize the the projected climate change impacts to United States Forest Service (USFS) lands in Oregon and Washington (Figure 1). Stakeholders in the Forest Service of this region were particularly interested in the variables that are likely to impact freshwater aquatic species, including projected changes in water availability, snowpack, and flood and low flow severities.

click image to enlarge

Pacific Rim Domain

Figure 1 Map of the study region showing boundaries for Bailey ecosections (left panel), Omernik level III ecoregions (middle panel), and HUC4 basins (right panel). Flow statistics are also summarized over the smaller HUC5 basins (not shown). The light green shading on each map indicates USFS lands.

Methods and Products

Our objective is to summarize climate and hydrologic projections for USFS lands in Oregon and Washington. Since individual national forests may contain numerous distinct ecological regimes and cross hydrologic boundaries, averaging over these has the potential to obscure important climatic changes and confound planning efforts. In order to avoid this pitfall, we chose to provide summaries that follow ecological and hydrologic boundaries, rather than administrative borders.

These summmaries are produced using results from the CIG Columbia Basin Climate Change Scenarios Project (CBCCSP, Hamlet et al., 2010). The CBCCSP dataset consists of an in-depth suite of high-resolution climate projections for the Columbia river basin and coastal drainages in Oregon and Washington. Specifically, the CBCCSP dataset includes a gridded 1/16th degree (~6 km) observationally-based historical (1915-2006) climate dataset (daily maximum temperature, minimum temperature, and precipitation). These are combined with climate projections using results from 10 Global Climate Model (GCM) simulations of 21st century climate (following the A1b and B1 scenarios), downscaled to 1/16th degree using the Composite Delta, Hybrid Delta, and Bias Correction and Statistical Downscaling (BCSD) methods of downscaling (Hamlet et al., 2010). These climate datasets are used to produce hydrologic products (e.g., runoff, evapotranspiration, soil moisture) for the historical and future climate projections using the Variable Infiltration Capacity (VIC, Liang et al., 1994) macroscale hydrologic model.

To produce the present dataset, the CBCCSP results were summarized at monthly time scales over both Bailey ecosections and Omernik level III ecoregions as well as the 8-digit and 10-digit Hydrologic Unit Code (HUC4/HUC5) basins (shown in Figure 1). The latter were used primarily to assess changes in runoff statistics and the snow season. Summaries are included for the variables listed in Table 1. Projected changes are summarized in tables, plots showing changes in the annual cycle, and maps showing the geographic pattern of changes. These results, as well as the methods used to produce the dataset, are all summarized in the project report.

Finally, we note another relevant CIG dataset (project website; Littell et al., 2010), which provides a simplified set of ecosystem-based summaries over a much wider domain. Covering nearly all of major basins in the Western U.S., this dataset is mentioned because it could be used to extend the present assessment to USFS lands in other regions.

Table 1 List of the variables summarized in this dataset
Variable Variable Name Units Monthly Aggregation Annual Cycle Table Annual Cycle Figure Map Summary Table Summary Plot
average daily temperature tavg °C average
maximum daily temperature tmax °C average
minimum daily temperature tmin °C average
precipitation precip mm total
runoff runoff mm total
baseflow baseflow mm total
combined flow (runoff + baseflow) combined flow mm total
flood statistics flood_gridcell_strflw_maxdaily cms n/a
low flow statistics lowflow_gridcell_strflw_7dyflow cms n/a
snow water equivalent (swe) swe mm 1st day
peak swe max_swe mm n/a
date peak swejd_max_swe days n/a
date 10% accum jd_10pc_accum daysn/a
date 90% accum jd_90pc_melt days n/a
length of snow season *numdays_10pcaccum_90pcmelt days n/a
relative humidity rh % average
vapor pressure deficit vpdPa average
actual evapotranspiration et mm total
potential evapotranspiration 1 **pet1 mm total
potential evapotranspiration 3 *** pet3mmtotal
soil moisture, layer 1 soilm1 mm 1st day
soil moisture, layer 2 soilm2 mm 1st day
soil moisture, layer 3 soilm3 mm 1st day
total column soil moisture soilmoistmm1st day

* the length of the snow season is defined here as the number of days between the date that 10% of the yearly maximum swe has accumulated and the date when 90% has melted.

**pet1 is calculated following the standard definition of potential evapotranspiration: natural vegetation (including stomatal and canopy resistance), and no water limit.

***pet3 is the same as pet1 except with vegetative resistance neglected: it includes only the effects of land surface characteristics and climate on evaporative demand.

Accessing the Data

Please use the contact information below to let us know how you plan to use the data -- we'd really like to know!


Funding for this project was provided by a grant from the USDA US Forest Service Region 6 Pacific Northwest Research Station.


Hamlet A.F. et al., 2010: Statistical downscaling techniques for global climate model simulations of temperature and precipitation with application to water resources planning studies. Chapter 4 in Final Project Report for the Columbia Basin Climate Change Scenarios Project.

Liang, X., D. P. Lettenmaier, E. F. Wood, and S. J. Burges, 1994: A Simple hydrologically Based Model of Land Surface Water and Energy Fluxes for GSMs, J. Geophys. Res., 99(D7), 14,415-14,428.

Littell, J.S., M.M. Elsner, G. Mauger, E. Lutz, A.F. Hamlet,, and E. Salathé. 2011. Regional Climate and Hydrologic Change in the Northern US Rockies and Pacific Northwest: Internally Consistent Projections of Future Climate for Resource Management. DRAFT report available online here.

Nakicenovic, N et al. (2000). Special Report on Emissions Scenarios: A Special Report of Working Group III of the Intergovernmental Panel on Climate Change.


Questions regarding this dataset can be directed to: