Transcript Climate Change, Biofuels, and Land Use Legacy

Climate Change, Biofuels, and
Land Use Legacy:
Trusting Computer Models to Guide Water Resources
Management Trajectories
Anthony Kendall
Geological Sciences, Michigan State University
Collaborators: David Hyndman (MSU), Bryan Pijanowski
(Purdue), Deepak Ray (Purdue)
Central question
How will Great Lakes water resources change
during this century?
Summer 2100 (A1B)
• In response to:
– Climate change
– Land use change
– Land use
intensification
– Agricultural demand
shifts (e.g. biofuels)
Miscanthus
Source:
at Great
Pijanowski
Lakes
Bioenergy
Research
Center
Sources:
USCB
and USDA
Source: IPCC AR4
We need models to answer this question
• Temperature and precipitation changes:
– Regional and global climate models
• Soil moisture, streamflow, lake level
changes:
– Hydrologic and crop models
• Land use changes:
– Land transformation and economic models
Major changes are likely in store, but what
can we expect?
Answer depends on what scenarios we assume
Consider widest range of feasible scenarios.
Great Lakes Region 2005 - 2095
Source: Multi-model ensemble, Annual average of monthly data, CMIP-3 database
Which model do we choose?
One solution: multi-model ensemble averages
Great Lakes Region 2005 - 2095
Source: Multi-model ensemble average and standard deviation, annual average
of monthly data, A1B scenario, CMIP-3 database
Annual temperatures forecast to rise
significantly
Source: Multi-model ensemble, Monthly data, A1B scenario, CMIP-3 database
Precipitation forecast to increase
Source: Multi-model ensemble, Monthly data, A1B scenario, CMIP-3 database
No significant changes forecast for summer
rainfall
Source: Multi-model ensemble, Monthly data, A1B scenario, CMIP-3 database
How will these changes impact regional
water resources?
• Hydrologic models must be robust to changes in
both climate and land use
– Many statistical models cannot be applied confidently
• New class of hydrologic models has emerged
that directly simulate physical processes of both
surface- and ground-water
– Integrated Landscape Hydrology Model (ILHM) is one
such tool (Hyndman and Kendall, 2007; Kendall and
Hyndman, in Review)
Integrated Landscape Hydrology Model
(ILHM)
• Simulates nearly complete terrestrial water cycle
• Hourly water fluxes calculated within each model
cell
Select ILHM fluxes
Climate and land use forecasts
• For Muskegon
River Watershed
(MRW) in central
lower Michigan
• Average of 24
GCM outputs
• Three emissions
scenarios (A1B
shown)
Land use change scenarios (MRW)
• Forecast land use using the Land Tranformation
Model (Pijanowski)
• Three change scenarios for 2050 (above) and 2095
Average Recharge Anomaly (cm)
Monthly groundwater recharge anomalies
• More frequent snowmelt: More late fall and winter recharge,
less spring recharge
• Longer growing season: Drier summer soils, less late summer
and early fall recharge
Implications of simulated groundwater
recharge changes
• More winter recharge
– Higher early spring water table
– Higher peak flows during spring
• Less spring recharge
– Earlier decline of water table
– Lower baseflow levels, longer low-flow period in
streams
• Overall increased groundwater resource
– Altered seasonal availability
• Agree with regional summaries
– i.e. IPCC AR4, USGCRP National Assessment
Important water quality impacts
• Increased sediment transport
– Higher peak and mean flows
• Increased threat of sewer overflows
– Extreme precipitation event increases
• Warmer water temperatures
– Warmer air temperatures
– Lower summer baseflows
– Mitigated by groundwater response?
• Changes to groundwater transport of nutrients
and contaminants
Pathways of water from precipitation to
streams
RUNOFF – FAST - DAYS
GROUNDWATER
DISCHARGE – SLOW - DECADES
Groundwater is a major provider of annual
streamflows
Sources: USGS OFR 03-263
Travel times of water in groundwater
aquifers can be very long
• Full impacts of
land use change
on stream water
quality can take
decades to even
centuries
• Predominantly in
areas with thick
saturated aquifers
and deep water
tables
Surface Watershed
Travel Times (years)
0 - 10
11 - 15
16 - 25
26 - 50
51 - 100
101 - 200
201 - 500
0 12.5 25
±
50 Kilometers
Source: Pijanowski et al. (2007, E&S)
To what land use is current water quality
responding?
• How different is this from today’s land
use?
– Land Use Legacy
• Land use legacy maps combine
groundwater travel times with historical
land use change information
– In practice: need models for both
Groundwater travel time model
• Can be
simulated with
a variety of
existing
models
Surface Watershed
Travel Times (years)
0 - 10
11 - 15
16 - 25
26 - 50
51 - 100
101 - 200
201 - 500
0 12.5 25
±
50 Kilometers
Source: Pijanowski et al. (2007, E&S)
Backcast land use change model
Source: Ray and Pijanowski (2009)
Comparison of legacy and current maps (MRW)
20%
10%
75%
Source: Ray and Pijanowski (2009)
Land use legacy maps have varying utility
Source: Ray and Pijanowski (2009)
Multi-decadal forces and system responses
• Climate change: Changes occurring over many
decades that may inexorably alter water quantity
and quality
• Land use change: Shifts in population, global
economic demand, and agricultural production
will place new stresses on water resources
• Land use legacy: Water quality may still be
responding to land uses from decades prior
– Similarly, management actions taken today may take
decades to be fully realized
Bringing long-term modeling into the
management loop
• Managers have long relied on steady-state or
short term system models
• Long-term drivers, and long-term responses,
require new and different approaches
– Uncertainties expand and multiply, and must be
explicitly addressed
– Multi-model ensembles, multiple scenarios can help
to identify range of model predictions
• Promote cooperation between universities and
water managers
Thank you!
• Please submit questions to the hosts
• Feel free to contact me:
– kendal30 at msu.edu
• Funding Acknowledgements: