Runoff (mm)
4 layers: Runoff (mm), Runoff (mm) GCM Ensemble 2010-2040, Runoff (mm) GCM Ensemble 2040-2070, Runoff (mm) GCM Ensemble 2070-2100
Layers
| Layer | Period | Units | Earth Engine | Download | Catalog |
|---|---|---|---|---|---|
| Runoff (mm) | released 2026-11-02 | mm/year | Runoff_mm | 363.6 MB | item |
| Runoff (mm) GCM Ensemble 2010-2040 | 2010 to 2039 | mm/year | Climate_Ensemble_2010-2040_Runoff_mm | 367.2 MB | item |
| Runoff (mm) GCM Ensemble 2040-2070 | 2040 to 2069 | mm/year | Climate_Ensemble_2040-2070_Runoff_mm | 374.1 MB | item |
| Runoff (mm) GCM Ensemble 2070-2100 | 2070 to 2099 | mm/year | Climate_Ensemble_2070-2100_Runoff_mm | 383.5 MB | item |
Description
Runoff (mm)
Mean annual runoff for the 1981–2020 historical period. Continuous hydrologic simulation was driven by the University of Washington Climate Impacts Group (CIG) gridded, bias-corrected WRF-NARR historical precipitation (Mauger and Won 2024); see the Precipitation (mm) layer for details on the forcing data. Potential evapotranspiration (PET) inputs are gridded monthly mean values from TerraClimate (Abatzoglou et al. 2018).
Runoff (mm) GCM Ensemble 2010-2040
Mean annual runoff for the 2010–2040 climate normal period. The period includes 2010 and runs through 2039; the end year is exclusive. Continuous hydrologic simulation was driven by each of the 11 University of Washington Climate Impacts Group (CIG) bias-corrected GCM precipitation projections (Mauger and Won 2024); see the Precipitation (mm) GCM Ensemble 2010–2040 layer for details on the forcing data. Total annual runoff was calculated for each GCM and year, averaged across the 11 GCMs for each year (the ensemble mean), and the yearly ensemble means were averaged over the period. Land cover, soils, slope, and the monthly potential evapotranspiration (PET) inputs from TerraClimate (Abatzoglou et al. 2018) are the same as for the historical runoff layer, so differences from that layer reflect the change in precipitation alone. The projections do not account for future changes in evapotranspiration.
Runoff (mm) GCM Ensemble 2040-2070
Mean annual runoff for the 2040–2070 climate normal period. The period includes 2040 and runs through 2069; the end year is exclusive. Continuous hydrologic simulation was driven by each of the 11 University of Washington Climate Impacts Group (CIG) bias-corrected GCM precipitation projections (Mauger and Won 2024); see the Precipitation (mm) GCM Ensemble 2040–2070 layer for details on the forcing data. Total annual runoff was calculated for each GCM and year, averaged across the 11 GCMs for each year (the ensemble mean), and the yearly ensemble means were averaged over the period. Land cover, soils, slope, and the monthly potential evapotranspiration (PET) inputs from TerraClimate (Abatzoglou et al. 2018) are the same as for the historical runoff layer, so differences from that layer reflect the change in precipitation alone. The projections do not account for future changes in evapotranspiration.
Runoff (mm) GCM Ensemble 2070-2100
Mean annual runoff for the 2070–2100 climate normal period. The period includes 2070 and runs through 2099; the end year is exclusive. Continuous hydrologic simulation was driven by each of the 11 University of Washington Climate Impacts Group (CIG) bias-corrected GCM precipitation projections (Mauger and Won 2024); see the Precipitation (mm) GCM Ensemble 2070–2100 layer for details on the forcing data. Total annual runoff was calculated for each GCM and year, averaged across the 11 GCMs for each year (the ensemble mean), and the yearly ensemble means were averaged over the period. Land cover, soils, slope, and the monthly potential evapotranspiration (PET) inputs from TerraClimate (Abatzoglou et al. 2018) are the same as for the historical runoff layer, so differences from that layer reflect the change in precipitation alone. The projections do not account for future changes in evapotranspiration.
How runoff was simulated
All four runoff layers above come from the same continuous simulation setup; only the precipitation input changes.
Continuous hydrology simulation was performed using regional pre-calibrated parameters. Batched simulations were run for combinations of land cover, soils, and slopes across the Puget Sound domain.
To allow for parallel computations, HSP2 (Hydrologic Simulation Program–Python), an open-source Python implementation of HSPF developed by RESPEC (RESPEC 2026), was used to model rainfall-runoff responses. Regional calibration factors for the Puget Lowlands Ecoregion were used as developed by Dinicola (1990) and updated by Clear Creek Solutions for the Western Washington Hydrology Model (Department of Ecology 2024).
HSPF calculates discharge for three flow-paths: surface flow,
interflow, and groundwater flow, referred to as SURO, IFWO, and
AGWO respectively. We report only SURO and IFWO, consistent with
Ecology guidance.
Areas classified as water are not modeled, and their runoff is set to zero.
More information, including verification of results can be found in the technical reference.
Layer Access in Earth Engine
The JavaScript below loads this layer in the Earth Engine Code Editor. An Earth Engine account is required. The "open" links above show each asset's details in the Code Editor.
This page covers 4 layers: "Runoff (mm)", "Runoff (mm) GCM Ensemble 2010-2040", "Runoff (mm) GCM Ensemble 2040-2070", "Runoff (mm) GCM Ensemble 2070-2100".
// Import the layer data dictionary
var data = require('users/stormwaterheatmap/apps:data/public')
// To view data dictionary, print to the console:
print('Data:', data)
// Get this layer from the layer data dictionary:
var layer_name = data.rasters["Runoff (mm)"]
// Add the styled layer to the map:
Map.addLayer(layer_name.layer)
// Raw image for analysis:
var raw_image = layer_name.layer.eeObject
Map.addLayer(raw_image, {}, 'Runoff (mm)')
Visualization
Colormap ice_r, from 25 to 1016 mm/year.