Transcript No Slide Title

A coupled hydrologic and crop dynamics model for studying climate change
impacts on agriculture and water resources
Kiran Chinnayakanahalli1, Jennifer Adam1, Claudio Stockle2, and Roger Nelson2
1Civil
and Environmental Engineering, Washington State University, PO Box 642910,Pullman, WA 99164-2910.
2Biological Systems Engineering, Washington State University, PO Box 646120, Pullman, WA 99164-6120.
*Email: [email protected]
1. Introduction
3. Crop distribution
 Agriculture is an important component of the Pacific Northwest (PNW ) economy. Agricultural commodities
produced in Washington alone have an annual value over $5 billion; nationally Washington State leads the
U.S. in production of apples, cherries, hops, and mint (Casola et al., 2005)
The hydrology of the Pacific Northwest (PNW) is expected to be significantly affected by climate change.
The climate change-induced stress on the availability of water resources during the growing season may
constrain irrigation and agricultural practices which will in turn affect crop production.
To assess climate change impacts on PNW agriculture, it is essential that we understand the relationships
between crop dynamics and the hydrological cycle. To accomplish this we have integrated a macro scale
hydrology model, the Variable Infiltration Capacity (VIC) model, with a cropping systems model (CropSyst).
Here we present details of the model integration framework that is being implemented
Objective
To develop a coupled hydrology and cropping systems model to project and compare
future water supply and irrigation water demand in Columbia River Basin for improved
water resources management.
LAND COVER
USA – USDA Cropland Data Layer (CDL)
Canada – derived from National
Ecological Framework for Canada
**Not all land cover types are shown in
the legend**
2. Model Integration
CropSyst
VIC
T
IP
T from 0, 1 & 2, IP
I
Q
W0
CropSyst is a multi-year multicrop daily time step simulation
model. The model simulates
transpiration, crop canopy and
root growth, dry matter
production, and yield (Stockle et
al., 2003).
W1
http://www.bsyse.wsu.edu/cropsyst
Variable Infiltration Capacity VIC invokes the crop model only when the land use type is a crop. The crop type is
(VIC) Model (Liang et al.,
determined by the crop distribution coverage (Section 3)
1994) is a spatially
When
the
land
cover
is
a
crop,
the
crop
model
is
informed
about
the
soil
characteristics
and
distributed, physically based
the
crop
type
at
the
beginning
of
the
time
step
model for simulating energy
Depending on the management options, VIC tells the crop model when the crop growth
and water balance
components.
should be started (sow date)
W2
Here, VIC is applied at
1/16th degree resolution
(Elsner et al. 2010)
A simplified version of the
CropSyst model is used for
integration with VIC
Redistribute W0
W1 and W2 to
CropSyst layers
ET0 , W0, W1, W2
Qb
VIC-Crop model Integration Variables:
T – Transpiration, IP – Interception capacity, I – Infiltration, Q – Runoff, Qb –
Baseflow, W0 W1 W2– Volumetric water content in layers 0, 1 and 2 respectively,
ET0 – Penman Monteith reference Pot. Evap.
Total yield,
Biomass
etc
At every time step, VIC passes on to the crop model the current soil water content, weather
condition, CO2 level, and reference potential evapotranspiration
The crop model then redistributes the soil water content from VIC soil layers to its soil layers,
simulates crop pheonology, and estimates crop growth, transpiration from VIC’s soil layers
and water requirements
VIC uses the returned transpiration to update its water contents (W0, W1 and W2)
VIC responds to the crop water requirements by applying the required quantity of water as
irrigation water. The application of irrigation water depends on the water availability and the
irrigation efficiency of the system
On reaching maturity, crop model harvests the crop and returns total crop yield and biomass.
The harvesting can also be controlled through management options; this feature is particularly
useful for perennial crops
4. Conclusions
Crop 1
Sow dateCrop type,
Start crop
Soil
growth
texture
At the beginning of each time step
To CropSyst
Soil water content
Weather condition
CO2 concentration
Reference Evapotranspiration
Land cover in
VIC grid cell
0
Time
Crop
harvest
 A spatially distributed hydrology-crop model is a useful tool for studying the impacts
of climate change on water resources, agriculture and the economy of the region
A coupled hydrology-crop model is developed that can simulate biomass growth,
crop yield, transpiration, and irrigation water demand
The results from this modeling approach are expected to help stakeholders and
water resource managers plan for a changing climate
5. References
Casola J. H, Kay J. E. et al. (2005) Climate Impacts on Washington's hydropower, water supply, forests, fish and
agriculture, Report from Climate Impact Group, University of Washington.
Elsner, M., L. Cuo, N. Voisin, J. Deems, A. Hamlet, J. Vano, K. Mickelson, S. Lee, and D. Lettenmaier (2010),
Implications of 21st century climate change for the hydrology of Washington State, Climatic Change, 225-260.
Liang, X., D. P. Lettenmaier, E. F. Wood, and S. J. Burges, (1994): A simple hydrologically based model of land
surface water and energy fluxes for general circulation models. J. Geophys. Res., 99 (D7), 14 415–14 428.
Stockle C. O, Donatelli M, Nelson R (2003) CropSyst, a cropping systems simulation model. Eur J Agron 18:289–307