Interactions of Land Use and Global Environmental
Change on Watershed-scale Processes
Lars Pierce, Fred Watson, Melinda Mulitsch, Wendi Newman,
Adrian Rocha, Jodiah Nelson, Mark Fain, and others
Institute of Earth Systems Science & Policy
California State University, Monterey Bay
Seaside, California 93955
[email protected]
Water Resource Issues in the Salinas Valley:
How do LULC and global-scale environmental changes
(climate, CO2, etc.) influence water and carbon cycling?
How do the impacts of LULCC vs. GEC compare?
How effective are management policies designed to reduce
the impacts of land use change on water resources?
BGC Model
Integrated Water, C, N cycles
(Running et al. models)
CO2 P R
S A
PPT ET
Plant
Timestep: Daily
LAI
Leaf
Spatial Scale:
• Homogeneous plot (~30m)
• 1 vegetation, 1 soil layer
Driving Variables:
•Daily climate (T, ppt)
•Vegetation / Land Cover
•Leaf Area Index
•Soil text, depth, C, N
Key Processes:
Water: Rain/Snow, Interception,
Soil Moisture, ET, Runoff
Carbon: Photosynthesis,
Growth, Respiration, Turnover
Nitrogen: Uptake, Allocation,
Turnover, Loss
C
Leaf
N
Root
Tf
Root
CL
Soil
NL
Nup
H2O
C
N
RO
RH
Nloss Ndep
Material Flux
Constraint
Schematic flowchart of the BIOME-BGC Ecosystem Model.
Simulated Biomass (g m-2 yr-1)
1200
1000
800
600
400
200
0
0
200
400
600 800 1000 1200
Measured Biomass (g m-2 yr-1)
Figure 2. Measured above-ground biomass compared to the above-ground
biomass simulated using BIOME-BGC for the water x CO2 experiment in
the Jasper Ridge CO2 project (Field et al., 1997).
Photo courtesy of Fred Watson
Salinas Valley of the Future?
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•
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Atmospheric CO2: 700 ppmv
Temperature: +3.5 ± 2 oC
Precipitation: +25%, Seasonality?
Nitrogen Deposition
Land Use: Oak, Agriculture
•
•
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Separate vs. Combined Responses to Change
1994 - 96 Daily Climate for Salinas, California
Equilibrium Fluxes and Pools for NPP, Water Use
Agriculture: No N, Water Limitations; 3 crops/yr.
Lettuce Yield
growth
prep
growth
fallow
plant dry wt (g/m2)
600
1xCO2
2xCO2
1xCO2+T
2xCO2+T
500
400
300
200
100
0
60
90
120
150
180
210
240
270
300
330
day of the year
Not much effect on total yield; significant impact on timing of harvest
+2.5C (harvest 5 days earlier)
2xCO2 (harvest 10-15 days earlier)
Agriculture
Oak Woodland
Net Recharge (mm H2O/yr)
200
0
-200
-400
-600
-800
-1000
-1200
-1400
-1600
Ambient
T
T+CO2
T+CO2+PPT
T+CO2+PPT+N
-1800
LULC vs. Environmental Change
(Net Recharge = Runoff-Irrigation)
Plot-level Conclusions
• Oak Woodland
• Responsive to changes in CO2, T, PPT, N (10-30%)
• Large Interactions (5-15%)
• Agriculture
• Responsive to changes in CO2, T only (5-20%)
• Small Interactions (< 5%)
• Land Cover Change > Environmental Change
LULC vs. GEC at the watershed-scale
Photo courtesy of Fred Watson
Oak Woodland (26%)
Grassland (51%)
Chaparral (14%)
Crops (8%)
Urban (1%)
Land Use / Land Cover
Gabilan Ck Watershed (94 km2)
Derived from 1995 Landsat TM
Gabilan Ck Simulations
4 Simulations: LULC vs. Climate Change
• 1995 LULC (Present):
– Ambient & 2xCO2 Climate
• ~1800 LULC (Past, Ag/Urban -> Grassland):
– Ambient & 2xCO2 Climate
• Separate vs. Combined Responses to Change
• 1996 - 98 Daily Climate for Salinas, California
• Agriculture: No N, Water Limitations; 2-3 crops/yr.
Leaf Area Index vs. Satellite Reflectance
0.8
0.7
0.6
0.5
Landsat
0.4
TM
NDVI 0.3
0.2
0.1
0
-0.1
Natural sites (AccuPAR LAI)
Agricultural sites (Destructive LAI)
Fitted curve
0
2
4
6
8
10
Ground-measured LAI
12
Courtesy of Fred Watson, CSUMB
LULC vs. Climate Change @ Watershed-scale
Gabilan Ck Watershed
Net Recharge (mm/yr)
500
+41mm -44mm
400
300
Ambient
T+CO2
200
100
0
Present
Past
Land Use / Land Cover
(Net Recharge = Runoff-Irrigation)
Conclusions
• Plot scale
• LULC >> Temperature, CO2 Changes
• Watershed scale
• LULC ~ Temperature, CO2 changes
• 10% Ag/Urban Land Use
Simulated Effects
of ENSO on
Soil Moisture
and Evaporation,
1997 - 1998,
Chualar Creek
Oak Woodland
& Chaparral
Agriculture
Movie Link
Fred Watson’s Tarsier: http://science.csumb.edu/~tarsier/
MacaqueBGC
VSIM
Monterey County Land Use, 2000
Map created by Wendi Newman, CSUMB
Regional Hydro-Ecological Simulation System (RHESSys)
Parameter
Climate
Topography
Land Cover
Source
NWS
CIMIS
Derived Inputs
Temperature
Precipitation
Elevation
Slope, Aspect
USGS
TM
AVHRR
Vegetation
Type, Amount
Models
Outputs
MTCLIM
Microclimate
BGC
Runoff
Water Use
Water Stress
Macaque
Soils
NRCS
Soil Texture
Productivity
Land Use
AMBAG
Zoning
Density
Leaching
MTCLIM - climate interpolation model
BGC - ecosystem process model
NWS - National Weather Service
USGS - US Geological Survey
NRCS - USDA Natural Resources Conservation Service
AMBAG - Assoc. of Monterey Bay Area Govts.
TM - LANDSAT Thematic Mapper
AVHRR - NOAA Adv. Very High Resolution Radiometer
Irrigation Water Use
800
Irrigation (mm/yr)
700
600
500
400
300
200
100
0
1xCO2
2xCO2
1xCO2+T
2xCO2+T
+T - not much impact on irrigation water use (due to shorter crop rotation)
2xCO2 - 14% reduction in irrigation water use (1 less event)