Predicting future US water yield and ecosystem productivity by linking an ecohydrological model to WRF dynamically downscaled climate projections
Quantifying the potential impacts of climate change on water yield and ecosystem productivityÂ (i.e., carbon balances) is essential to developing sound watershed restorationÂ plans, and climate change adaptation and mitigation strategies. This study links anÂ ecohydrological model (Water Supply and Stress Index, WaSSI) with WRF (WeatherÂ Research and Forecasting Model) dynamically downscaled climate projections of theÂ HadCM3 model under the IPCC SRES A2 emission scenario. We evaluated the futureÂ (2031â€“2060) changes in evapotranspiration (ET), water yield (Q) and gross primaryÂ productivity (GPP) from the baseline period of 1979â€“2007 across the 82 773 waterÂ sheds (12 digit Hydrologic Unit Code level) in the conterminous US (CONUS), andÂ evaluated the future annual and monthly changes of hydrology and ecosystem productivityÂ for the 18 Water Resource Regions (WRRs) or 2-digit HUCs. Across the CONUS,Â the future multi-year means show increases in annual precipitation (P ) of 45 mmyr-1Â (6 %), 1.8 C increase in temperature (T ), 37mmyr-1Â (7 %) increase in ET, 9 mm yr -1Â (3%) increase in Q, and 106 gCmô€€€2 yrô€€€-1 (9%) increase in GPP. Response to climateÂ change was highly variable across the 82, 773 watersheds, but in general, the majorityÂ would see consistent increases in all variables evaluated. Over half of the 82 773 watersheds,Â mostly found in the northeast and the southern part of the southwest wouldÂ have an increase in annual Q (>100mmyr-1 or 20 %). This study provides an inte20Â grated method and example for comprehensive assessment of the potential impacts ofÂ climate change on watershed water balances and ecosystem productivity at high spatialÂ and temporal resolutions. Results will be useful for policy-makers and land managersÂ in formulating appropriate watershed-specific strategies for sustaining water andÂ carbon sources in the face of climate change.