Mountain snowcover interaction
with topography & vegetation
under a changing climate
DANNY MARKS
Northwest Watershed Research Center
USDA-Agricultural Research Service
Boise, Idaho
USA
RCEW (239 km2):
• 32 climate stations
• 36 precipitation stations
• 5 EC systems
• 14 weirs (nested)
• 6 soil microclimate stations
• 4 hill-slope hydrology sites
• 4 instrumented catchments
• 3 instrumented headwater
basins:
USC (0.25 km2, 186m relief)
ephemeral, groundwater dominated,
annual precipitation 300-500mm
RME (0.38 km2, 116m relief)
perennial, surface water dominated,
annual precipitation 750-1000mm
Johnston Draw (1.8 km2, 380m relief)
ephemeral, rain-snow boundary,
annual precipitation 500-600mm
45 - year (1960-2006) Climate Trends:
Annual precipitation & discharge are unchanged
– However, early spring flows are increased
– Summer flows are significantly reduced
•
Climate is warming
– All temperatures have increased
– Minimum temperatures increased the most
•
More precipitation falls as rain
– Smaller change at high elevation
– Large change at low elevation
•
Strong elevation effect
– Effects availability of water in summer
– More area at lower elevation
– Increase in winter ROS events
Reynolds Mountain East Study Catchment
(0.38 km2, 118 m relief)
Exposed Sites
Sheltered Sites
Four Snow Seasons Selected for Model Validation
1986, 1987, 1989 for SCA Data
1997 for ROS Event
I.
Verify Simulated Snow Distributions
* Time-series AP
II. Evaluate Terrain & Vegetation Shelter Effects on
* Simulated Snow Cover Energy Balance
* Snow Melt
* Runoff
Validation: Modeled and Observed SWE
(Point Comparison)
1986 Simulated Snow Distribution
Aerial
Photos
Modeled
SWE
1986 Simulated Snow Distribution
Aerial
Photos
Modeled SWE:
spatially constant
wind and
precipitation inputs
1986 Simulated Surface Water Inputs
Spatially Distributed Wind
and Precipitation Inputs
Spatially Constant Wind
and Precipitation Inputs
Four Snow Seasons Selected for Climate
Change Scenario Simulation
1984: cold & wet (1221mm Pcp, 826mm SWE)
1987: warm & dry (652mm Pcp, 263mm SWE)
2001: cool & dry (685mm Pcp, 362mm SWE)
2006: warm & wet (1148mm Pcp, 622mm SWE)
Validation: Modeled and Observed SWE (Point Comparison)
Simulated Snowcover Under
Climate Scenarios
I.
Temperature Was Adjusted
-2oC & +2oC
II.
Absolute Humidity & Thermal Radiation Adjusted
III. Albedo Adjusted
IV. Snow Distribution and Precipitation Adjusted for
phase change
Monthly SWE, Base & Scenarios (Basin Average)
Surface Water Input (SWI) Base & Scenarios (Basin Average)
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Simulated Daily SWE, 2006 Snow Season
94 mm
15%
417 mm
67%
178 mm
58%
10 mm
3%
286 mm
30%
731 mm
76%
525 mm
84%
583 mm
94%
285 mm
93%
836 mm
87%
306 mm
100%
895 mm
93%
606 mm
97%
408 mm
66%
236 mm
77%
961 mm
100%
81 mm
26%
869 mm
90%
69 mm
11%
131 mm
21%
18 mm
6%
550 mm
57%
No Snow
204 mm
21%