TITLE:
Use of SWAT to Model Impact of Climate Change on Sediment Yield and Agricultural Productivity in Western Oregon, USA
AUTHORS:
G. W. Mueller-Warrant, C. L. Phillips, K. M. Trippe
KEYWORDS:
Climate Change, Sediment Yield, Soil Water Assessment Tool, SWAT, Coupled Model Intercomparison Project 5, CIMP5, Nash-Sutcliffe Efficiency, NSE
JOURNAL NAME:
Open Journal of Modern Hydrology,
Vol.9 No.2,
April
28,
2019
ABSTRACT: Climate change predictions for the Pacific Northwest
region of the United States of America include increasing temperatures,
intensification of winter precipitation, and a shift from mixed snow/rain to
rain-dominant events, all of which may increase the risk of soil erosion and
threaten agricultural and ecological productivity. Here we used the
agricultural/environmental model SWAT with climate predictions from the Coupled
Model Intercomparison Project 5 (CMIP5) “high CO2 emissions”
scenario (RCP8.5) to study the impact of altered temperature and precipitation
patterns on soil erosion and crop productivity in the Willamette River Basin of
western Oregon. An ensemble of 10 climate models representing the full range in
temperature and precipitation predictions of CIMP5 produced substantial
increases in sediment yield, with differences between yearly averages for the
final (2090-2099) and first (2010-2019) decades ranging from 3.9 to 15.2 MT·ha-1 among models. Sediment yield in the
worst case model (CanESM2) corresponded to loss of 1.5 - 2.7 mm·soil·y-1, equivalent to potentially stripping productive topsoil
from the landscape in under two centuries. Most climate models predicted only
small increases in precipitation (an average of 5.8% by the end of the 21st
century) combined with large increases in temperature (an average of 0.05°C·y-1). We found a strong correlation
between predicted temperature increases and sediment yield, with a regression
model combining both temperature and precipitation effects describing 79% of
the total variation in annual sediment yield. A critical component of response
to increased temperature was reduced snowfall during high precipitation events
in the wintertime. SWAT characterized years with less than basin-wide averages
of 20 mm of precipitation falling as snow as likely to experience severe
sediment loss for multiple crops/land uses. Mid-elevation sub-basins that are
projected to shift from rain-snow transition to rain-dominant appear
particularly vulnerable to sediment loss. Analyses of predicted crop yields
indicated declining productivity for many commonly grown grass seed and cereal
crops, along with increasing productivity for certain other crops. Adaptation
by agriculture and forestry to warmer, more erosive conditions may include
changes in selection of crop kinds and in production management practices.