Transcript Climate change impacts on Pacific Northwest Hydrology

Jennifer Adam and Josh Van Wie
Department of Civil and Environmental Engineering, Box 642910, Washington State University, Pullman, WA 99164
1. Introduction
3. Dryland Agriculture in the Palouse Basin
2. Methods and Tools
Four groups of socioeconomic scenarios allow a
range of future greenhouse
gas emissions.
OBJECTIVE: To investigate the potential for
conservation tillage (a.k.a. no-till) practices to
reduce the vulnerability of dryland (nonirrigated) Palouse Basin agriculture to
projected changes in climate.
5000
Observed and
DHSVM-simulated
hydrographs at the
outlet of the South
Fork of the Palouse
4000
Streamflow (cfs)
• The hydrological cycle of the western United States is expected to be significantly affected by climate change (IPCC-AR4 report). Rising
temperature and changes in the frequency and magnitude of precipitation events are anticipated to affect crop production, water availability and
quality, and flood risk in the PNW (Stockle et al 2009, Elsner et al 2009, Hamlet and Lettenmaier 2007).
• Agriculture is a vital part of the economy in the Pacific Northwest (PNW). In 2008, wheat production accounted for $1.7 billion, the third largest
value in the United States (NASS, 2009). The eastern side of the Cascade Mountains, which receives only 5-25” of rain annually, is particularly
vulnerable to drought. In the last decade, there have been 10-20% yield losses during severe drought years, with an average of $90 million/year
(NASS, 2009). This water-poor region is sensitive to potential changes in the regional hydrological cycle associated with global climate change.
•The challenge is to anticipate the probable effects of climate change on the hydrological cycle and make sound land use, water use, and
agricultural management decisions that will best serve the needs of agricultural production while protecting our freshwater resources.
• A system of models (see Box 2) are applied to assess the impacts of projected climate change on hydrology, water resources, and agricultural
productivity. Herein, we describe the application of this system of models to the Palouse Basin to evaluate the impacts of climate change on
dryland agriculture (see Box 3), and to the Columbia Basin to evaluate the impacts of climate change on irrigation water demand (see Box 4).
3000
Stream Network
Land Cover
Elevation
• We are applying the Distributed Hydrology Soil-Vegetation Model
(DHSVM) (Wigmosta et al. 1994).
• Tillage practices are represented by adjusting soil parameters
(such as porosity and hydraulic conductivity) and the partitioning
between infiltration, surface runoff, and evaporation over bare soil.
2000
Palouse River Basin
1000
Jan
Mar
May
Observed
Jul
Sep
Nov
Simulated
4. Irrigation Water Demand in the
Columbia Basin
Impact models and other tools are used
to explore the impacts of climate and
hydrologic change on agriculture and
water resources management.
The greenhouse gas
scenarios are used
to drive coupled
Atmosphere-Ocean
General Circulation
Models (AOGCMs)
to simulate future
climate. Output from
17 AOGCMs are
archived with the
IPCC.
The
downscaled
climate data are
used to drive
land surface
hydrology
models to
simulate the
hydrologic
cycle in an
altered climate.
OBJECTIVE: To project and compare future water
supply and irrigation water demand over the
Washington State portion of the Columbia River
Basin for improved water resources
management.
Columbia
River
Basin
• We are applying a system of linked models, including the
Variability Infiltration Capacity (VIC) hydrology model (Liang et al.
1994), a dynamic crop systems model (CropSyst: Stockle et al.
2003), a Columbia River Basin reservoir operations model (ColSim:
Hamlet et al. 1999), and an economic model.
• Funding for this project is being provided by the Washington
State Department of Ecology.
5. Conclusions
The future climate data from the AOGCMs
need to be bias-corrected and spatially and
temporally downscaled before they can be
applied to watersheds. One method is
called Bias Correction Statistical
Downscaling (BCSD; Wood et al. 2004).
• Application of down-scaled and bias-corrected AOGCM climate data to drive hydrologic models has the potential to improve our understanding
of the impacts of climate and hydrologic change on agriculture and water resources management. For example, this set of tools allows us to
investigate the potential for conservation tillage practices to reduce the vulnerability of dryland agriculture to potential growing season reductions in
precipitation. Over a much larger scale, we can apply this method to improve water resources management by projecting forward water supply and
irrigation water demand.
• The major challenge to both of these projects is the simplistic treatment of crops and agricultural practices in the hydrologic models. Therefore,
we are expanding the capabilities of the models by (1) including an algorithm for tillage practices in DHSVM, and (2) coupling VIC to a dynamic
crop growth model, CropSyst. The expanded capabilities of the models will enable further investigations into the linkages and feedbacks between
climate, hydrology, and agriculture.