DOI: 10.5061/dryad.vx0k6dk2h
title: Baseflow adjusted snowmelt runoff and rainfall runoff from TerraClimate

description: We update the total runoff and runoff partitioned from snowmelt from
 TerraClimate using a modified water balance model that better accounts for
 baseflow lags in hydrology for use in basin level water supply
 availability at monthly time scales. These data complement existing
 TerraClimate 1-d water balance similations, but show much has improved
 montly correlative skill (median r=0.88) to observed streamflow across
 watersheds globally watersheds compared with the original method from
 TerraClimate (median r=0.75). These data can be used to quantify gaps in
 monthly water demand for downstream water uses including agriculture.
description: The original TerraClimate (Abatzoglou et al., 2018) runoff data
 (q) assumed that all water (rain plus snowmelt, P) in excess of the
 additional soil water holding capacity (maximum soil water storage minus
 soil moisture or SR) and monthly evapotranspiration (ET) – or water
 surplus – immediately runs off that month.  S = max(0,
 0.95*P - ET-SR) q = 0.05*P + S While
 this water balance approach may be valid at local scales, the approach
 does not account for a variety of factors including baseflow contributions
 or stream routing and transit time. Some studies show that the transit
 time for runoff to reach a basin terminus is up to a month (Allen et al.,
 2018). We updated the approach for simulating runoff to account for the
 contributions of baseflow and transit time following Wolock and McCabe
 (1999). Specifically, half of the surplus generated each month becomes
 runoff while the remaining half is carried over as surplus to the
 following month. 
 S<sub>update</sub>(month)=S<sub>update</sub>(month-1)+0.5*max(0, 0.95*P - ET-SR) q<sub>update</sub> = 0.05*P + 0.5*S(month) All forcing data come from TerraClimate but are run this this modification of the water balance model.
description: # Baseflow adjusted snowmelt runoff and rainfall runoff from TerraClimate
 [https://doi.org/10.5061/dryad.vx0k6dk2h](https://doi.org/10.5061/dryad.vx0k6dk2h) ## Description of the data and file structure Input forcing of temperature, snow water equivalent, soil moisture, and precipitation comes from [TerraClimate ](https://www.nature.com/articles/sdata2017191)at a 1/24th degree resolution globally. We use the runoff partitioning scheme from [Qin et al., (2020)](https://www.nature.com/articles/s41558-020-0746-8) to separate runoff from snowmelt from rainfall runoff. The original TerraClimate runoff data (q) assumed that all water (rain plus snowmelt, P) in excess of the additional soil water holding capacity (maximum soil water storage minus soil moisture or SR) and monthly evapotranspiration (ET) – or water surplus – immediately runs off that month.  TW =  S = max(0, 0.95*P - ET-SR) q = 0.05*P + S While this water balance approach may be valid at local scales, the approach does not account for a variety of factors including baseflow contributions or stream routing and transit time. Some studies show that the transit time for runoff to reach a basin terminus is up to a month (Allen et al., 2018). We updated the approach for simulating runoff to account for the contributions of baseflow and transit time following Wolock and McCabe (1999). Specifically, half of the surplus generated each month becomes runoff while the remaining half is carried over as surplus to the following month.  ## Context to reuse data The netCDF data provided here include data for total runoff (TerraClimate_runoffv2_YYYY.nc) and snowmelt runoff (TerraClimate_snowrunoffv2_YYYY.nc) where YYYY denotes the year. These data are monthly and gridded on a 1/24th degree grid following data inputs from the parent TerraClimate data. Total runoff combined rainfall and snowmelt runoff. The data yield monthly total runoff in units of mm. These data can be used in combination with the original climate and water balance data from TerraClimate available at the links below. ## Access information Other publicly accessible locations of the revised water balance data: * [https://climate.northwestknowledge.net/ACSL/YUE/WB/](https://climate.northwestknowledge.net/ACSL/YUE/WB/) TerraClimate data is available from the following sources: * TerraClimate, [https://www.climatologylab.org/terraclimate.html,](https://www.climatologylab.org/terraclimate.html) * Google Earth Engine: [https://developers.google.com/earth-engine/datasets/catalog/IDAHO_EPSCOR_TERRACLIMATE](https://developers.google.com/earth-engine/datasets/catalog/IDAHO_EPSCOR_TERRACLIMATE)