Relative impacts of climate change and land cover change on streamflow using SWAT in the Clackamas River Watershed, USA

Junjie Chen,Heejun Chang

doi:10.2166/wcc.2020.123

Abstract

Abstract To understand the spatial–temporal pattern of climate and land cover (CLC) change effects on hydrology, we used three land cover change (LCC) coupled scenarios to estimate the changes in streamflow metrics in the Clackamas River Watershed in Oregon for the 2050s (2040–2069) and the 2080s (2070–2099). Coupled scenarios, which were split into individual and combined simulations such as climate change (CC), LCC, CLC change, and daily streamflow were simulated in the Soil and Water Assessment Tool. The interannual variability of streamflow was higher in the lower urbanized area than the upper forested region. The watershed runoff was projected to be more sensitive to CC than LCC. Under the CLC scenario, the top 10% peak flow and the 7-day low flow are expected to increase (2–19%) and decrease (+9 to −20 cm s), respectively, in both future periods. The center timing of runoff in the year is projected to shift 2–3 weeks earlier in response to warming temperature and more winter precipitation falling as rain. High streamflow variability in our findings suggests that uncertainties can stem from both climate models and hydrologic model parameters, calling for more adaptive water resource management in the watershed.

Highlights

Global climate change (CC) and rapid urbanization are likely to have strong impacts on water resources around the world (IPCC )
This study aims to investigate the hydrologic response to CC and land cover change (LCC) of the Clackamas River Watershed (CRW) in the Willamette River Basin (WRB)
Our work aims to use these streamflow metrics as indicators of change and incorporate tightly coupled climate and land cover (CLC) change scenarios into our models to yield a reasonable range of impact scenarios between the lower and upper watershed in the near future (2050s) and the distant future (2080s)

Summary

Introduction

Global climate change (CC) and rapid urbanization are likely to have strong impacts on water resources around the world (IPCC ). Billions of people globally will not have sustainable access to clean drinking water due to the impacts of global warming (Mukheibir ; Schewe et al ). CC impacts the hydrologic cycles across multiple scales (Arnell & Gosling ; Hattermann et al ). Watershed scale hydrological predictions rely on the transfer of large-scale climate variables to more regional meteorological factors such as precipitation and temperature. The multi-ensemble means of different general circulation models (GCMs) have been popular among researchers for projecting future climate and impacts on streamflow. Using multiple GCMs as inputs may increase data and modeling uncertainties, as climate and water resource projections vary between each GCM (Guimberteau et al ; Thompson et al ; Shen et al )

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