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Water Erosion Research at Washington State University

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Water Erosion Research at Washington State University Joan Wu, Markus Flury, Shuhui Dun, Cory Greer, Prabhakar Singh Washington State University, Pullman, WA – PowerPoint PPT presentation

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Title: Water Erosion Research at Washington State University


1
Water Erosion Research at Washington State
University
  • Joan Wu, Markus Flury, Shuhui Dun, Cory Greer,
    Prabhakar Singh
  • Washington State University, Pullman, WA
  • Don McCool
  • USDA ARS PWA, Pullman, WA
  • Bill Elliot
  • USDA FS RMRS, Moscow, ID
  • Dennis Flanagan
  • USDA ARS NSERL, West Lafayette, IN

2
Major Funding Sources
  • In-house funding from various collaborating
    research institutes
  • US Forest Service Rocky Mountain Research Station
  • Inland Northwest Research Alliance
  • USDA National Research Initiatives Programs
  • US Geological Survey/State of Washington Water
    Research Center

3
The Needs
  • Protecting and improving water quality in
    agricultural watersheds are major goals of the
    USDA NWQ and NRI Programs
  • For many watersheds, sediment is the greatest
    pollutant
  • In watershed assessment, it is crucial to
    understand sedimentation processes and their
    impacts on water quality
  • To successfully implement erosion control
    practices, it is necessary to determine the
    spatio-temporal distribution of sediment sources
    and potential long-term effectiveness of sediment
    reduction by these practices

4
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  • Surface runoff and erosion from undisturbed
    forests are negligible
  • Stream formed due to subsurface flow has low
    sediment

7
  • Both surface runoff and erosion can increase
    dramatically due to disturbances
  • Models are needed as a tool for forest resource
    management

8
The WEPP Model
  • WEPP Water Erosion Prediction Project
  • a process-based erosion prediction model
    developed by the USDA ARS to replace the
    functional model USLE
  • built on fundamentals of hydrology, plant
    science, hydraulics, and erosion mechanics
  • WEPP uses observed or stochastically-generated
    climate inputs to predict spatial and temporal
    distributions of soil detachment and deposition
    on an event or continuous basis, along a
    hillslope or across a watershed
  • Equipped with a geospatial processing interface,
    WEPP is a promising tool in watershed assessment
    and management

9
The WEPP Model contd
  • WEPP Windows Interface
  • WEPP Internet Interface
  • GeoWEPP

10
Long-term Research Efforts
  • Goal
  • Continuously develop, refine and apply the WEPP
    model for watershed assessment and restoration
    under different land-use, climatic and hydrologic
    conditions
  • Objectives
  • Improve the subsurface hydrology routines so that
    WEPP can be used under both infiltration-excess
    and saturation-excess runoff conditions in crop-,
    range- and forestlands
  • Improve the winter hydrology and erosion routines
    through combined experimentation and modeling so
    that WEPP can be used for quantifying water
    erosion in the US PNW and other cold regions
    where winter hydrology is important
  • Continually test the suitability of WEPP using
    data available from different localities within
    and outside the US

11
Progresses Made
  • Numerous modifications to WEPP have been made to
  • Correct the hydraulic structure routines
  • Improve the water balance algorithms
  • Incorporate the Penman-Monteith ET method (UN FAO
    standard)
  • Improve the subsurface runoff routines
  • Expand and improve winter hydrology routines to
    better simulate
  • Freeze-thaw processes
  • Snow redistribution processes
  • WEPP new releases accessible at NSERLs website
    http//topsoil.nserl.purdue.edu/nserlweb/index.htm
    l

12
Ongoing Studies
13
Palouse Conservation Field Station (PCFS),
Pullman, WA
  • Laboratory and field experimentation on runoff
    and erosion as affected by freezing and thawing
    of soils

14
Tilting flume at PCFS
15
Experimental plots at PCFS
16
WEPP Applications at UB, Italy
  • Experimental Watershed, University of Bologna,
    Italy (Drs. Paola Rossi Pisa and Marco Bittelli)
  • Joint MS program providing source of students
  • State-of-the-science research facility

17
DEM Effects on WEPP Erosion Modeling
  • Paradise Creek Watershed, ID (Dr. Jane Zhang)

18
WEPP Applications for Watershed Erosion Modeling
  • Reeder Experimental Watershed at the USDA ARS
    CPCRC, Pendleton, OR (Dr. John Williams)
  • Paradise Creek Watershed, ID (Drs. Jan Boll and
    Erin Brooks)
  • Mica Creek Watershed, ID (Dr. Tim Link)

19
Long-term Research Efforts
  • Goal
  • Continuously develop, refine and apply the WEPP
    model for watershed assessment and restoration
    under different land-use, climatic and hydrologic
    conditions
  • Objectives
  • Improve the subsurface hydrology routines so that
    WEPP can be used under both infiltration-excess
    and saturation-excess runoff conditions in crop-,
    range- and forestlands
  • Improve the winter hydrology and erosion routines
    through combined experimentation and modeling so
    that WEPP can be used for quantifying water
    erosion in the US PNW and other cold regions
    where winter hydrology is important
  • Continually test the suitability of WEPP using
    data available from different localities within
    and outside the US

20
Comparison of Processes
Earlier versions of WEPP typically
overestimated Dp
21
Redistribution of Infiltration Water in WEPP
22
Code Modification
  • Provide options for different applications
  • a flag added to the soil input file
  • User-specified vertical hydraulic conductivity K
    for the added restrictive layer
  • e.g., 0.005 mm/hr
  • User-specified anisotropy ratio for soil
    saturated hydraulic conductivity
  • horizontal Kh ? vertical Kv, e.g., Kh/Kv 25

23
Code Modification contd
  • Subroutines modified to properly write the pass
    files
  • WEPPs approach to passing outputs
  • Subsurface flow not passed previously
  • Simplified hillslope-channel relation
  • All subsurface runoff from hillslopes assumed to
    enter the channel
  • Flow added and sediment neglected

24
A Case Application Modeling Forest Runoff and
Erosion
Dun, S., J.Q. Wu, W.J Elliot, P.R. Robichaud,
D.C. Flanagan, J.R. Frankenberger, R.E. Brown,
A.C. Xu, 2007. J. Hydrol (in review)
25
Study Site Hermada Watershed
26
Physical Setting
  • Located in the Boise National Forest, SE Lowman,
    ID
  • Instrumented during 1995-2000 to collect whether,
    runoff, and erosion data
  • 5-yr observed data showing an average annual
    precipitation of 954 mm, among which nearly 30
    was runoff

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28
Re-processed Precipitation
29
Watershed Discretization
30
Model Inputs
  • Topography
  • Derived from 30-m DEMs using GeoWEPP
  • 10-ha in area, 3 hillslopes and 1 channel
  • 40-60 slope
  • Soil
  • ? Typic Cryumbrept loamy sand 500 mm in depth
  • underlying weathered granite
  • Management
  • 1992 cable-yarding harvest
  • 1995 prescribed fire
  • West and North slopes with low-severity burn
  • South slope and channel unburned
  • Climate
  • 11/1995-09/2000 observed data

31
Results
32
Living Biomass and Ground Cover (WEPP v2004.7)
(a) and (b) unburned S slope (c) and (d)
burned W slope
33
Living Biomass and Ground Cover (WEPP v2006.5)
(a) and (b) unburned S slope (c) and (d)
burned W slope
34
Runoff and Erosion Obs. vs Pre. (WEPP v2004.7)
Observation Period 11/3/1995-9/30/2000
35
Runoff and Erosion Obs. vs Pre. (WEPP v2006.5)
Observation Period 11/3/1995-9/30/2000
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Summary
  • Numerous modifications have been incorporated
    into WEPP v2006.5
  • Specifically, changes were made in the approach
    to, and algorithms for modeling deep percolation
    of soil water and subsurface lateral flow
  • The refined model has the ability to more
    properly partition infiltration water between
    deep percolation and subsurface lateral flow
  • For the Hermada forest watershed
  • Vegetation growth and ground cover were described
    realistically
  • WEPP-simulated annual watershed discharge was
    compatible with field observation and predicted
    annual sediment yield was not significantly
    different from the observed
  • Nash-Sutcliffe model efficiency coefficient for
    daily runoff of -0.77 suggests further
    improvement on winter routines are needed

39
Thank You!
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