Assessing the Sources and Transport of Fine Sediment in Response to Management
Practices in the Tahoe Basin using the WEPP Model
I. Project Team and Contact Information
Dr. Erin S. Brooks, Biological and Agricultural Engineering, University of Idaho, P.O. Box
442060, Moscow, ID 83844–2060; Phone: (208) 885–6562; fax: (208) 885–8923; email:
broo2789@uidaho.edu.
Dr. Jan Boll, Biological and Agricultural Engineering, University of Idaho, P.O. Box 442060,
Moscow, ID 83844–2060; Phone: (208) 885–7324; fax: (208) 885–8923; email:
jboll@uidaho.edu.
Dr. Joan Wu, Biological Systems Engineering, Washington State University, P.O. Box 646120,
Pullman, WA 99164–6120; Phone: (509) 335–5996; fax: (509) 335–2722; email: jwu@wsu.edu.
Collaborators: Dr. William Elliot (USDA–FS Rocky Mountain Research Station, Moscow, ID
83843), Dr. Pete Robichaud (USDA–FS Rocky Mountain Research Station, Moscow, ID 83843),
and Wes Chistensen (LTBMU, US Forest Service, Lake Tahoe, CA 96150).
Grants contact persons: University of Idaho: Leslie Thompson, phone: (208) 885–2145, fax
(208) 885–5752; email: lesliet@uidaho.edu; Washington State University: Dan Nordquist,
phone: (509) 335–7717, fax (509) 335-1676; email: nordquist@wsu.edu.
This proposal addresses Theme 2, Sub-theme A with overlap with Theme 3, Sub-theme A.
II. Justification Statement
Lake Tahoe is listed as impaired under Section 303(d) of the Clean Water Act for excessive
nutrient and sediment loading. The 1997 Lake Tahoe Presidential Forum initiated the
Environmental Improvement Program (EIP), to achieve environmental threshold values for water
quality and soil conservation following the 1979 Lake Tahoe Environmental Assessment report.
Since 1997, $1.1 billion has been invested by federal, state, and local government projects as
well as private contributions to implement and achieve EIP goals (TRPA, 2006). An impressive
$512 million has been spent directly on construction of watershed improvement projects. An
additional $500 million may be expended to complete projects currently in design. To capitalize
on the time and funds expended to achieve water quality thresholds in the Lake Tahoe basin,
future management of the basin requires physically-based modeling tools for evaluating the short
term and long term effects and risks of land use and climate change on lake water quality.
The success of the EIP relies heavily on the implementation of effective management practices to
minimize sediment and nutrient delivery to Lake Tahoe. Assessing the overall effectiveness of
these management practices on the hydrology and water quality (Theme 3) can become
quantitative and objective when modeling tools incorporate variability in climate, soils, geology,
topography, vegetation, and hydraulic structures. The Water Erosion Prediction Project (WEPP)
model is a process-based hydrology and erosion model that can be used at both small scales
(hillslopes, roads, small parcels, etc.) and large watershed scales to evaluate impacts of
management practices and climate change. WEPP provides a valuable tool for quantifying
sediment loading from small and large scale erosional ‘hot spots’ (Theme 2). One of the
advantages of the model is that when proper vegetative management files are created application
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of the model is relatively straight forward. The project team of five scientists has the knowledge
and experience in testing and developing these management scenarios. Therefore, they can
provide watershed managers with a powerful tool for assessing the effectiveness of alternative
management practices at various scales. To date, WEPP applications within the Tahoe Basin
have been at the project scale. We propose to expand those applications to the watershed scale.
Along with this, we will incorporate the newly developed watershed enhancements for predicting
onsite erosion and offsite sedimentation processes that have recently become a part of the WEPP
technology.
III. Background/Problem Statement
Since 1968, Lake Tahoe has experienced a decline in its water quality. Particularly, the overall
clarity of the lake, measured using a Secchi disk, has decreased from 31 m (102 ft) down to 22 m
(74 ft) in 2005. This decline has been attributed to excessive loading of nutrients and fine
sediment (< 20 microns). Murphy and Knopp (2000) describe the long history of cooperation
among federal, state, county, and local entities since 1968 to remediate this problem.
Tools currently being developed to evaluate the reduction in pollutant loading to Lake Tahoe as a
result of management practices are lumped hydrologic pollutant loading models. The US Army
Corps of Engineering (USACE, 2006) describe hydrologic and water quality assumptions and
limitations of these models. These limitations include: no hydraulic routing of runoff, constant
loss rates for BMPs, no specific hydraulic characteristics of diversion structures, total runoff
volume distributed among land uses based on imperviousness, specific source loading estimates
are not physically-based and have considerable uncertainty, user-defined delivery ratios
requiring subjective judgment, BMP effluent quality in storm water treatment is based on a
national database rather than a Tahoe-specific database. Although the report acknowledged that
more detailed, complex models may be able to better describe hydrologic and pollutant transport
mechanisms and overcome these limitations, process-based models were not selected in the
TMDL due to fear that “the level of complexity may conflict with the objective of making the
methodology practical for Lake Tahoe Basin implementers.” The report concluded that
refinements for estimating pollutant load reductions in BMPs should be considered. We propose
to provide this refinement in technology, coupled with a training program and one-on-one
coaching to show Lake Tahoe Basin implementers how to use these new tools.
– The Water Erosion Prediction Project (WEPP) Model
The WEPP model is a process-based model which simulates soil detachment, deposition,
transport and delivery through hillslope, channel, and structural impoundment units within a
watershed (Flanagan and Nearing, 1995). The model is based fundamentally on infiltration
theory, hydrology, soil physics, plant science, hydraulics, and erosion mechanics. Processes in
WEPP include rill and interrill erosion, sediment transport, and deposition, infiltration, soil
consolidation, residue and canopy effects on soil detachment and infiltration, surface sealing, rill
hydraulics, surface runoff, plant growth, residue decomposition, percolation, evaporation,
transpiration, snow melt, frozen soil effects on infiltration and erodibility, climate, and effect of
soil random roughness. Each hillslope can be divided into multiple overland flow elements to
simulate flow from one land type to another (e.g., drainage from a disturbed upland area through
a grass buffer).
Since its inception, the WEPP model was to become a wide-spread, physically-based
management tool for the evaluation of management techniques. Much time and money was
2
spent conducting experiments on a wide range of soil types across the country to develop
parameter sets for soil, residue, and vegetative properties. Management files describing key
temporal modifications to the plant, residue, and soil system (e.g., tillage, harvest, burning) were
developed for a wide variety of agriculturally- and forestry-based systems. Common structural
impoundments (e.g., sediment basins, culverts, filter fences, straw bales) are options in the
model. The model accepts long term daily climate data or single storm event data. An auxiliary
climate generator program, CLIGEN (Nicks and Lane, 1989), creates long term climate files if
meteorological data are not available.
Although the capability to apply the WEPP model to large watersheds has always been
theoretically feasible, applications were limited to small catchments until the release of
GeoWEPP (Renschler, 2003). GeoWEPP descritizes a watershed into hillslopes and channels
using a digital elevation model of the watershed. Soil survey and land use maps are used to
assign soil and vegetative management files to each hillslope. Using GeoWEPP, the model
recently has been applied to large watersheds where the hydro-dynamics within the stream
channel become important for simulating stream bank erosion. The stream channel component
of the model can be bypassed by feeding the runoff and subsurface lateral flow from hillslopes at
stream nodes to a fully hydro-dynamic model such as the CONCEPTS model (Langendoen,
2000; Conroy et al., 2006). Such integration is particularly useful in the Tahoe basin where the
CONCEPTS model has been tested and is currently being used as the stream channel erosion
model in higher order streams in the Tahoe Basin TMDL (Simon et al., 2003; 2006). In this
proposal, we will test and improve stream routing algorithms to improve model performance in
headwater streams and gullies.
Effectiveness of management designs can be evaluated with the WEPP model using either long
term, continuous daily climate data or using specific design storms. A particular advantage of
the model to the Tahoe Basin, which targets fine sediment (<20 microns), is its ability to predict
transport and delivery of specific size classes of sediment. Output from the model can be saved
at desired points within study watersheds (e.g., culverts, stream crossings) at various frequencies
(e.g., daily, monthly, yearly). Output of the model can be integrated with models currently being
implemented in the basin including the aforementioned full hydro-dynamic stream channel
model CONCEPTS and the Pollutant Load Reduction Estimator – Spreadsheet for Tahoe Storm
Water (PLRE–STS) (USACE, 2006). Collectively, these modeling tools will assist in the
development of the Lake Tahoe Total Maximum Daily Load (TMDL), and implementation of
future management plans.
The project team on this proposal has extensive experience, knowledge, and familiarity with
developing, modifying, and applying the WEPP model to forest, agricultural, and urban
watersheds, including BMP effectiveness evaluation. Over the last decade this team has made
significant improvements to the WEPP model and has developed interfaces for easier use of the
model. Among the improvements are the addition of Penman-Montieth evapotranspiration
algorithms (Wu et al., 2004a), subsurface converging lateral flow to represent variable source
area runoff (Wu et al., 2004b; Boll et al., 2006a; Crabtree et al., 2006), improving canopy
biomass routines for forested applications (Dun et al., 2006), and developing algorithms to
simulate the effect of structures and impoundments on runoff and sediment delivery (Wu and
Dun, 1998). The WEPP model now produces reliable, continuous simulations of streamflow and
sediment loading at the hillslope and watershed scales in mixed land use watersheds (Boll et al.,
2006a,b; Crabtree et al. 2006; see attached Figures 1 and 2). In Dr. Boll’s study funded by the
Conservation Effectiveness Assessment Program of the USDA-CSREES, WEPP and
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CONCEPTS models are used to evaluate the cumulative effects of erosion control management
practices in large watersheds. Dr. Elliot and Dr. Robichaud have over 20 years of experience
with WEPP at the USFS Rocky Mountain Research Station (USFS-RMRS) and have extensively
developed and validated the model for forested applications including sediment detachment and
delivery from forest roads, skid trails, and effects following fires (Ryan and Elliot, 2005; Elliot
and Wu, 2005; Robichaud, 2005; Robichaud et al., 2005; Covert et al., 2005). The USFS-RMRS
has developed user-friendly web interface tools to encourage increased use of the WEPP model
in forestry management applications (Elliot, 2004; see Figure 3). Dr. Elliot has hosted numerous
WEPP workshops to provide watershed managers with training on how to use the model.
Brooks et al. (2006) developed an approach for applying the model to large road networks. Wes
Christensen, a hydrologist with the US Forest Service working in the Lake Tahoe Basin
Management Unit (LTBMU) and a collaborator in this study (letter of collaboration attached) is
familiar with low-impact harvesting practices in the basin, has experience with the WEPP model,
and has been involved with projects throughout the basin where key hydraulic soil and vegetative
cover properties have been measured at various disturbed and undisturbed sites (Norman et al.
2006).
IV. Goals, Objective(s), and statement of hypotheses to be tested
The goal of this project is to develop a process-based tool that watershed managers in the Lake
Tahoe basin can use to objectively evaluate the impact of specific management practices on the
generation of fine (< 20 micron) sediment transport at the hillslope and watershed scales. This
tool will be complementary to existing hydrologic and pollutant loading approaches, and assist in
the design and evaluation process in hydrologically sensitive areas that will benefit from a sitespecific, physically-based modeling approach.
The primary objectives of the project are as follows:
1.) Simulate streamflow and sediment loading in large upland watersheds to the Tahoe basin
using the WEPP model. We will develop appropriate climate, soil and vegetative parameter files
for the Lake Tahoe region to greatly reduce the perceived complexity involved in the application
of WEPP to other regions in the basin. Hypotheses: the WEPP model will provide reliable
distributed and integrated predictions of fine sediment sources and transport in watersheds within
the Lake Tahoe basin; the model will indicate hydrologically sensitive areas or ‘hot spots’ in the
Lake Tahoe basin.
2.) Evaluate specific management practices relevant to the Lake Tahoe Basin using the WEPP
model. These practices may include management of vegetative surface cover and soil
compaction following fuel reduction by prescribed fires and/or mechanical thinning, stabilization
of road cut-slopes, locating and sizing of detention ponds, or re-vegetation of disturbed soils.
Hypothesis: the WEPP model can properly evaluate effectiveness of management practices
relevant in the Lake Tahoe Basin.
3.) Provide watershed managers with a protocol for assessing management practices with the
WEPP model. This protocol will be demonstrated at specific BMP sites within the basin.
Hypotheses: A finite number of soil and vegetation parameter sets exists for the Lake Tahoe
basin; with known soil and vegetation parameter sets, the WEPP model can be executed by
watershed managers in the basin facilitating more scientifically informed decision-making.
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V. Approach, Methodology, and Geographic Location of Research
The project will be carried out in three phases. Phase I will focus on application and assessment
of the model at the watershed scale. Phase II will focus on detailed application and development
of the model at specific ‘hot spots’ within the watershed. Phase III will include one-on-one
training to pass the technology on to watershed managers in the basin. “Watershed managers” in
this proposal are representatives working on assessment (e.g., TMDL development) and
implementation of local management practices (e.g., Lahontan Regional Water Quality Control
Board; Nevada Division of Environmental Protection; USFS-LTBMU; US Army Corps of
Engineers; USDA Natural Resource Conservation Service; Tahoe Regional Planning Agency;
University of California, Davis; county-level and private BMP contractors).
– Phase I (Yr. 1)
In the first month of the project, we will visit the Lake Tahoe Basin and meet with agency
personnel (USFS and others). The purpose of the first visit is to familiarize the team with all
watersheds for modeling, to learn about dominant processes and hydrologic controls on pollutant
transport, to visit field monitoring sites, and to become familiar with design elements of common
management practices applied in various catchments within the basin. In addition, the team will
gain further understanding of limitations of current qualitative modeling efforts and will find out
what type of modeling end product will be most useful to managers in the region.
We will develop the appropriate climate, soil and vegetation management, and topographic files
for undisturbed hillslopes and catchments in the basin. We will run the WEPP model to predict
streamflow and sediment loading in four upland watersheds in the basin: the headwaters of the
Upper Truckee River (14 mi2), Logan House Creek (2.1 mi2), General Creek (7.4 mi2), and the
Blackwood Creek (11 mi2). The Upper Truckee River watershed is known to contribute the
majority of the sediment to Lake Tahoe. General creek and Blackwood Creek watersheds will
provide a good comparison of the effects of disturbances. Both watersheds are located on the
west side of the basin. General creek watershed is relatively undisturbed compared to Blackwood
Creek watershed, which has been impacted by roads, grazing, gravel mining, anthropogenic
channel modifications, and logging. Since the eastern half of the basin receives less precipitation
than the western half of the basin, the Logan House Creek watershed represents small,
undisturbed watersheds with relatively low sediment loading. Each of these watersheds has
minimal residential or urban development. Hence, we can isolate upland responses from urban
responses. Long term (> 15 years) continuous daily streamflow and event-based sediment
concentration data are publicly available at the outlet of the watersheds through the US
Geological Survey. These data sets include measurements of the percent fine sediment (< 0.063
mm, silt and clay size) for water samples having high sediment concentrations. We will divide
the time series into periods for model calibration and model validation. Model accuracy will be
assessed using statistical methods (i.e., Nash-Sutcliffe, coefficient of determination and root
mean square error, see Brooks et al. (2007)) comparing predicted and observed daily streamflow
and both fine and total sediment loading. Drs. Brooks and Boll will develop, in collaboration
with Drs. Elliot and Robichaud, a basin-specific database for the WEPP technology. Dr. Wu and
a Graduate Research Associate will apply and, if necessary, improve the new stream channel
routing algorithms in WEPP. Our working relationship with Eddy Langendoen at the USDA
National Sedimentation Lab in Oxford Mississippi also allows us to transfer WEPP output to
CONCEPTS.
5
A second visit to the Lake Tahoe Basin will be scheduled six months into the project to present
progress on watershed applications to agency personnel and other scientists involved in
modeling. We will assess how well the model is able to identify potential ‘hot spots’ in the
watersheds relative to qualitative surveys and knowledge of local hydrologists. We will evaluate
the primary sources of uncertainty in model simulations and pursue sources of additional data to
reduce this uncertainty. A third visit during the first year of the study will be scheduled during
the major runoff season in the watershed to observe key hydrologic and erosion processes in the
basin.
– Phase II (end of Yr.1, and Yr.2)
In Phase II we will apply the model to small-scale management sites. This will include one or
two visits where Dr. Brooks and Dr. Boll will be working closely with Wes Christensen and
participating watershed managers to gather detailed information on the design, maintenance, and
history of each site as well as collect any critical soil and vegetative information to characterize
each site. We will seek out sites where BMP monitoring data are available. For example, the
USFS has been actively measuring runoff and sediment loading from disturbances associated
with the Heavenly Valley ski resort in the Heavenly Valley Creek watershed for over 10 years.
At several of these sites, we will apply the WEPP model using a series of hillslopes, channels,
and structural impoundments much like the large scale watershed applications to evaluate
human-induced disturbances, including roads. Background images of the catchment of choice
will be imported into the model to assist in developing the structure of the model (see Figures 4
and 5). This activity will extend previous efforts by USFS-LTBMU hydrologists who have
already used and have plans to use individual forest road and the hillslope components of the
model in projects like the Heavenly Valley ski resort site (USFS, 2005). We have permission to
use the Heavenly Valley data set in this project (Sue Norman, hydrologist with the USFSLTBMU, personal communication). Early response from managers in the region to the idea of
process-based modeling of both small and large scale management sites has been positive
(Catherine Schoen USFS-LTBMU Erosion Control Grant Manger, personal communication;
Dave Roberts, Project Lead, Lahontan Regional Water Quality Control Board). The number of
selected sites will depend upon the required detail and model complexity.
In collaboration with watershed managers we will develop a user-friendly protocol for applying
the model to unique sites around the basin. We will use a similar approach as in Elliot et al.
(1999), who developed a conceptual framework to represent the unique features of an unpaved
road (i.e., road surface, ruts, ditches, fill slope, and buffer) in a single WEPP hillslope
simulation. If necessary, cutslope erosion will be simulated using multiple hillslopes (Tysdal et
al., 1999). Management files have also been developed for typical forest thinning, prescribed
burn practices, and re-vegetation. Dr. Wu and a Graduate Research Associate, who have
experience refining and testing the hydraulic structures in the model, will investigate the
methodology and make improvements for unique management practices in the basin.
Assessment of the accuracy of the model will be made using adequate existing monitoring data
(e.g., flow and sediment loading data at the Heavenly Valley Ski resort) and by comparing
quantitative predictions with qualitative assessments of BMP effectiveness techniques currently
used in the basin.
– Phase III (end of Yr.2)
In Phase III of the project, we will present final results to watershed management teams, and
hold workshops for technology transfer. The strength of the WEPP model will be the large
database of soil and vegetation parameter sets. Many of these already have been tested and
6
validated, primarily by scientists on this proposal, over a wide range of applications similar to
those in the Tahoe Basin. With these parameter sets specific for Lake Tahoe Basin, application
of the model will be much simpler and straight forward than one would expect for a model that
includes so many physically-based processes, keeping calibration to a minimum. We will set up
GeoWEPP and WEPP Watershed models on a number of computers with appropriate climate
files and topography, soil and vegetation parameter sets developed in Phase I and II. All steps
involved in setting up hillslopes, channels, and impoundments as well as extracting information
from output files will be reviewed. Success of the technology transfer process will be monitored
by having workshop participants model a test catchment within the Lake Tahoe Basin.
7
References
Boll, J., E.S. Brooks, S. Dun, B. Crabtree, J. Wu, and W.J. Elliot. 2006a. Incorporation of
saturation excess processes into the Water Erosion Prediction Project (WEPP) model. Eos
Trans. AGU, 87(52), Fall Meet. Suppl., Abstr. H34C–04.
Boll, J., E.S. Brooks, B. Crabtree, N.S. Tosakana, J.D. Wulfhorst, L. Van Tassel, and R.L.
Mahler. 2006b. Evaluation of conservation practices at the watershed scale using
interdisciplinary analyses. Presented at the Managing Agricultural Landscapes Workshop,
Soil Water Conserv. Soc., Westin Crown Hotel, Kansas City, MO, October 11–13, 2006.
Brooks, E.S., J. Boll, W.J. Elliot, and T. Dechert. 2006. A GPS/GIS-based approach for sediment
detachment and delivery modeling on large road networks using WEPP. J. Hydrol. Eng. 11:
418–426.
Brooks, E.S., J. Boll, and P.A. McDaniel. 2007. Distributed and integrated response of a
Geographic Information System-based hydrologic model in the eastern Palouse region,
Idaho. Hydrol. Process. 21: 110–122.
Conroy, W.J., R.H. Hotchkiss, and W.J. Elliot. 2006. A coupled upland–erosion and instream
hydrodynamic sediment transport model for evaluating sediment transport in forested
watersheds. Trans. ASABE 49: 1713–1722.
Covert, S.A., P.R. Robichaud, W.J. Elliot, and T.E. Link. 2005. Evaluation of runoff prediction
from WEPP-based erosion models for harvested and burned forest watersheds. Trans.
ASABE 48: 1091–1100.
Crabtree, B., E.S. Brooks, K. Ostrowski, W.J. Elliot, and J. Boll. 2006. The Water Erosion
Prediction Project (WEPP) model for saturation excess conditions: application to an
agricultural and a forested watershed. Eos Trans. AGU, 87(52), Fall Meet. Suppl., Abstr.
H31C–1444.
Dun, S., J.Q. Wu, W.J. Elliot, P.R. Robichaud, and D.C. Flanagan. 2006. Adapting the Water
Erosion Prediction Project (WEPP) model to forest conditions. ASABE Annu. Int. Meet.
July 9–12, Portland, OR. ASABE Pap. No. 062150.
Elliot, W.J., C.H. Luce, and P.R. Robichaud. 1996. Predicting sedimentation from timber harvest
areas with the WEPP model. In Proc. 6th Fed. Interagency Sediment. Conf., p. 46–53.
Washington, DC.
Elliot, W.J., D.E. Hall, and D.L. Scheele. 1999. WEPP:Road (Draft 12/1999) WEPP interface for
predicting forest road runoff, erosion and sediment delivery. Tech. Doc. Online at
<http://forest.moscowfsl.wsu.edu/fswepp/docs/wepproaddoc.html>. Accessed January, 2007.
Elliot, W.J. 2004. WEPP Internet interfaces for forest erosion prediction. J. Am. Water Resour.
Assoc. 40: 299–309.
Elliot, W.J., and J.Q. Wu. 2005. Predicting cumulative watershed effects of fuel management
with improved WEPP technology. In Moglen, G.E. (ed.) Managing Watersheds for Human
and Natural Impacts: Engineering, Ecological, and Economic Challenges. Proc. 2005
Watershed Manage. Conf., July 19–22, Williamsburg, VA. 11 p.
Flanagan, D.C., and M.A. Nearing. 1995. USDA-Water Erosion Prediction Project: Hillslope
Profile and Watershed Model Documentation. NSERL Rep. 10. USDA-ARS Natl. Soil
Erosion Res. Lab., West Lafayette, IN.
Langendoen, E.J. 2000. CONCEPTS—Conservational channel evolution and pollutant transport
system: Stream corridor. ver. 1.0, Res. Rep. No. 16, USDA-ARS, Natl. Sediment. Lab.,
Oxford, MS.
Murphy, D.D., and C.M. Knopp. (eds.) 2000. Lake Tahoe Watershed Assessment. vol. 1. USDA
Forest Service, Pacific SW Res. Stn., Albany, CA. Gen. Tech. Rep. No. PSW–GTR–175.
736 p.
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Nicks, A.D., and L.J. Lane. 1989. Weather Generator. Chap. 2. In: L.J. Lane and M.A. Nearing
(eds.) USDA-Water Erosion Prediction Project. NSERL Rep. 2. USDA-ARS Natl. Soil
Erosion Res. Lab., Purdue University, West Lafayette, IN.
Norman, S., W. Christensen, J. O’Connell, and J. TenPas. 2006. Pre project fuels reduction
project soil quality monitoring report Crag units 3 and 4. USFS–LTBMU. Online at
<http://www.fs.fed.us/r5/ltbmu/documents/ecd/crag_soilmonitoring_finalreport_2005.pdf>.
Accessed January, 2007.
Renschler, C.S. 2003. Designing geo–spatial interfaces to scale process models: The GeoWEPP
approach. Hydrol. Process. 17: 1005–1017.
Robichaud, P.R. 2005. Measurement of post–fire hillslope erosion to evaluate and model
rehabilitation treatment effectiveness and recovery. Int. J. Wildland Fire 14: 475–485.
Robichaud, P., W. Elliot, F. Pierson, and P. Wohlgemuth. 2005. Modeling soil erosion and
mitigation after fires. Geophys. Res. Abstr., vol. 7, 00608.
Ryan, K., and Elliot, W.J. 2005. Fire effects and soil erosion models. Chap. 9. In: Neary, D.G.,
K.C. Ryan, and L.F. DeBano (eds.) Wildland fire in ecosystems: Effects of fire on soils and
water. Gen. Tech. Rep. RMRS–GTR–42, vol.4. Ogden, UT. p. 171–177.
Simon, A., E. Langendoen, R. Bingner, R. Wells, A. Heins, N. Jokay, and I. Jaramillo. 2003.
Lake Tahoe Basin Framework Implementation Study: Sediment Loadings and Channel
Erosion. National Sedimentation Laboratory Technical Report 39, USDA-ARS National
Sedimentation Laboratory, Oxford, Mississippi, 320 p.
Simon, A., Pollen, N.L., Langendoen, E.J. 2006. Influence of two woody riparian species on
critical conditions for streambank stability: Upper Truckee River, California. Journal of the
American Water Resources Association. 41: 99-113.
TRPA (Tahoe Regional Planning Agency). 2006. Online at <http://www.trpa.org/documents/
docdwnlds/EIP_FNL.pdf>. Accessed January, 2007.
Tysdal, L.M., W.J. Elliot, C.H. Luce, and T.A. Black. 1999. Modeling erosion from insloping
forest [low-volume] roads with WEPP watershed model. Presented at the 7th Int. Conf. LowVolume Roads, May 23–26, Baton Rouge, LA. Transportation Res. Record No. 1652, vol.
2, p. 250–256.
USACE, 2006, Final Rep. on the Pollutant Load Reduction Calculation Methodology
http://www.spk.usace.army.mil/projects/civil/tahoe/documents.html, p. 84–87
USFS (United States Forest Service). 2005. Heavenly Mountain resort environmental monitoring
program. Online at <http://www.trpa.org/documents/docdwnlds/Heavenly/HMPA_EIREIS_Volume_II/Appendix_3–1–D_RevisedEnvironMonitoringProgram.pdf>. Accessed
December, 2006.
Wu, J.Q., and S. Dun. 1998. Upgrading the WEPP Watershed Version for Forest Conditions.
Final Rep. submitted to USDA Forest Service, Rocky Mt. Res. Stn., Moscow, ID.
Wu, J.Q., S. Dun, W.J. Elliot, and D.C. Flanagan. 2004a. Modification and testing of the
evapotranspiration (ET) routines in the WEPP Model. Presented at the 2004 ASAE Annu.
Int. Meet., Ottawa, Can., Aug 1–4.
Wu, J.Q., S. Dun, W.J. Elliot, and D.C. Flanagan. 2004b. Subsurface water flow routines in the
WEPP model: Modification and validation. Presented at the 2004 ASAE Meeting, Ottawa,
Can., Aug 1–4.
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VI. Schedule of Events/Products & Deliverables
Proposed Project Timeline
Task
Year 1
Year 2
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
Field visits (3 per year)
Phase I –– Watershed scale modeling
Meet with local hydrologists, visit watersheds
Apply model to the four selected watersheds
Present progress on watershed modeling
Select specific management sites for Phase II
Phase II – Small scale modeling
Visit and collect site specific data and parameters
Apply model to small scale sites
Phase III – Technology transfer
Provide one-on-one training workshops
Reporting
The proposed project will produce a data base with parameter sets for climate, soil, vegetation,
and watershed delineations for application of the WEPP watershed tool the Tahoe basin. We
will provide analyses of water balance components, erosion sources, and transport pathways of
fine sediment from four watersheds. Interactions with implementers of management practices
will result in evaluation schemes for a suite of practices. We will recommend several monitoring
practices in conjunction with these interactive sessions. Data sets from the four watersheds in
the Lake Tahoe Basin will be analyzed and simulated with the WEPP model. We expect several
publications from this work. Finally, we will deliver group workshops and one-on-one coaching
on the applications of the new WEPP watershed technologies. Future funding may be requested
to incorporate results of the modeling work in the proposed project in a web-based system
similar to WEPP-FS interface tools (Elliot, 2004).
VII. Budget
The main contact for this project will be Dr. Erin Brooks at the University of Idaho. The total
funds requested for this project are $242,834. Funds are divided between the University of Idaho
($117,371), Washington State University ($85,463), and the Rocky Mountain Research Station
($40,000). Budgets and justifications for each institution are included on the following pages. If
cost share is required, we can provide details.
10
X. Figures
Figure 1. Observed and simulated streamflow in a 12.1 km2, snow dominated forested
watershed (Mica Creek Experimental Watershed, St. Joe National Forest, Idaho) using the
improved WEPP model.
Figure 2. Simulated and observed changes snow water equivalent depth using the improved
WEPP model (Mica Creek SNOTEL, Idaho).
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Figure 3. Screenshot of the USFS WEPP interfaces page with links to associated web-based
programs (http://forest.moscowfsl.wsu.edu/fswepp/).
Figure 4. Example of a WEPP watershed windows interface with delineated hillslopes and
channels over an aerial photo with elevation contours.
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Figure 5. Example of the WEPP hillslope windows interface with simulated erosion and
deposition on a hillslope with multiple land uses.
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