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Analysis of Changing Hydrologic Extremes using the VIC model
Daeryong Park and Momcilo Markus
Illinois State Water Survey
September 25 2012
Pecatonica River Watershed
� Area : 3,435 km2
� Location: Southern Wisconsin and Northern Illinois
� Outlet: Freeport, IL (USGS 056435500)
Study Goals
� To test the applicability of the Variable Infiltration Capacity model in a flood frequency study
� To provide an explanation for the decreasing trend in winter flood peaks at Freeport on the Pecatonica River.
Input Data (1/8° degree grid size-approximately 10x12 km)
� Vegetation Library File � From USGS Global Land Cover Characteristics Database (about 30
vegetation classes)
� Changes in surface roughness and leaf area index (LAI)
� Vegetation Parameter File � From North American Land Data Assimilation System
(NLDAS)
� Soil Parameter File � From NLDAS Parameters web site
� Extract soil characteristics from the Natural Resource Conservation Service’s State Soil Geographic Database (STATSGO)
� Climate Forcing File (1915~2009) � NCDC Daily Precipitation (mm)
� NCDC Daily Minimum and Maximum Temperature (°C)
� Daily Wind Speed (NCEP/NCAR)
Implementation Approaches
Classification Event Simulation Continuous Simulation
Period • Selected 10 major events,
one representing each decade
• Entire Period (1915-2009)
Focus • Streamflow in the outlet • Climate variables of five
stations
Adjusted variables for calibration
• Snow roughness by each event
• Soil parameters
• Snow roughness for every five years
• Other soil parameters are fixed.
Calibration Parameters of the VIC model
Soil Parameter Description Unit Range
Calibration objective
Bi Infiltration shape parameter None 0−0.4
Streamflow Calibration
Ds Fraction of Dsmax where nonlinear baseflow
begins None 0−1
Dsmax Maximum subsurface flow rate mm day-1 0−30
Ws Fraction of the maximum soil moisture where
nonlinear baseflow occurs; Ws > Ds None 0−1
D2 Depth of the second soil layer m 0.1−1.5
D3 Depth of the third soil layer m 0.1−1.5
Expt 1 Parameter describing the variation of Ksat
with soil moisture in the first layer None None
Expt 2 Parameter describing the variation of Ksat
with soil moisture in the second layer None None
Snow rough Snow roughness of snow pack m
0.0001-0.6
Snow Depth Calibration
Snow Calibration - Event Simulation -
(a) Dodgeville, WI; (b) Darlington, WI; (c) Martintown, WI; (d) Monroe, WI; (e) Freeport, IL
Snow Calibration - Continuous Simulation-
(a) Dodgeville, WI; (b) Darlington, WI; (c) Martintown, WI; (d) Monroe, WI; (e) Freeport, IL
Summary
� Snow fall, snow depth, snow melt and frost days show decreasing trend.
� Air temperature, bare soil temperature, precipitation, evaporation show increasing trend.
� Trends of these variables are consistent with increasing air temperature.
Conclusions
� VIC can simulate successfully snow accumulation and ablation process.
� VIC model can simulate peak event very accurately for event simulations.
� VIC provided a reasonable explanations for the decreasing winter flood peaks in the Pecatonica River