J.Q. Wu, S. Dun, W.J. Elliot, H. Rhee J.R. Frankenberger, D.C. Flanagan P.W. Conrad,

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22 Φεβ 2014 (πριν από 3 χρόνια και 8 μήνες)

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J.Q. Wu, S. Dun, W.J. Elliot, H. Rhee

J.R. Frankenberger, D.C. Flanagan

P.W. Conrad,
R.L. McNearny

Introduction


A crucial component of planning surface mining
operations as regulated by the National Pollutant
Discharge Elimination System (NPDES) is to
estimate potential environmental impacts during
and after mining operations


Reliable watershed hydrology and erosion
models are effective and efficient tools for
evaluating
postmining

site
-
specific sediment
control and reclamation plans for the NPDES

Objectives


The objectives of this workshop are


To introduce the newly developed WEPP
-
Mine, an online
GIS interface for the USDA’s WEPP model, as a
management tool for western alkaline surface mines


To apply WEPP
-
Mine, in a case application, to evaluate
pre
-

and
postmining

watershed hydrological and erosion
processes and impacts of BMPs at the Big Sky Mine,
eastern Montana, USA


To obtain feedback from and exchange with stakeholders
(state regulatory personnel, researchers, private
consultants) and other workshop attendees to further
refine WEPP
-
Mine

WEPP


WEPP (Water Erosion Prediction Project) was
initiated in 1985 as a new

generation water erosion
prediction technology for use by federal action
agencies involved in soil and water conservation
and environmental planning and assessment


WEPP was developed by the USDA

ARS with user
requirements collected from the Bureau of Land
Management (BLM), Forest Service (FS), and Soil
Conservation Service (SCS)


The WEPP model is a result of a large team efforts
involving many scientists and experts

WEPP
cont’d


WEPP was intended to replace empirically
-
based erosion prediction technologies (e.g.,
USLE) for assessing the soil erosion impact of
diverse land uses ranging from cotton fields to
mountain forests


It simulates many of the physical processes
important in water erosion, including infiltration,
runoff, ET, percolation, subsurface lateral flow,
raindrop and flow detachment, sediment
transport, deposition, plant growth, residue
decomposition, and changes in soil properties


WEPP
cont’d


The WEPP model can be used for common
hillslope

applications or on watersheds


In addition to WEPP core codes, the current
version includes a parameter database and various
interfaces, including a GIS and web

based
interfaces


WEPP technologies have been successfully used
in the evaluation of important natural resources
issues throughout the US and in many other
countries

WEPP Watershed


WEPP
discretizes

a
watershed into
hillslopes
, channel
segments, and
impoundments


An impoundment can
be on the channel
network or at the foot
of a
hillslope

WEPP Inputs


Climate


Observed daily values of precipitation (amount, duration,
relative time to peak, relative peak intensity),
temperatures (max, min), solar radiation, and wind
(direction, speed)


Generated with CLIGEN, an auxiliary stochastic climate
generator


Topography


Slope orientation, slope length, and slope steepness at
points along the slope profile

WEPP Inputs
cont’d


Soil


Surface soil hydraulic properties, erosion parameters, and
texture data for the soil profile


Soil properties of multiple layers to a maximum depth of
1.8 m can be input


Land management


Information and parameters for plant growth, tillage, plant
and residue management, initial conditions, contouring,
subsurface drainage, and crop rotation

WEPP Outputs


Event
-
by
-
event summary of runoff and soil erosion


Graphical output for soil detachment and
sedimentation along a slope profile


Daily water balance


Plant growth and residue decomposition


Snow accumulation and snowmelt and soil frost and
thaw


Dynamic change of soil properties


Sediment yield


Return
-
period analysis

WEPP Impoundments


WEPP simulates foothill small ponds behind


Filter fence


Straw bales


WEPP also simulates sediment ponds with
hydraulic structures


Drop spillway


Perforated riser


Culvert


Emergency spillway


Rock
-
fill check dam


Drop Spillway

Perforated

Riser

Culvert

Emergency Spillway

Rock
-
fill Check Dam

Filter Fence

WEPP Application to Mining
Areas


To simulate the effect of mining operations on soil
erosion and to evaluate sediment control BMPs,
typical WEPP applications to mining areas may
involve the assessment of


Premining

condition as a baseline against which other
scenarios can be compared


Postmining

with
revegetation


Postmining

with
revegetation

and a sediment pond


Postmining

with
revegetation

and a silt fence

WEPP
-
Mine


WEPP
-
Mine was developed based on the USDA’s
online GIS interface for the WEPP model


It provides functions specifically for applications to
mining areas


Using user
-
specified DEMs


Using reclamation maps


Simulating watershed
-
specific sediment ponds


It can be accessed using a web browser at
http://wepponlinegis.bsyse.wsu.edu/osm


WEPP
-
Mine Inputs


USGS 30
-
m DEM


USGS 2006 National Land Cover


NRCS SSURGO soil data


Spatial data automatically retrieved from the online
servers by default


Soil and
landuse

can also be customized within the
WEPP
-
Mine interface


Special permission is required for uploading user
-
specified DEMs and reclamation maps

WEPP
-
Mine Inputs
cont’d


CLIGEN
-
generated climate based on long
-
term
monthly statistics is currently used (the use of
observed climatic data will be implemented)


The CLIGEN database includes more than 2,600
weather stations across the US


Weather statistics of the station closest to the
watershed outlet is used by default


PRISM 800
-
m gridded monthly averages is applied to
the monthly statistics to account for location and
elevation differences from the CLIGEN station

WEPP
-
Mine Outputs


Channel network


Subcatchments


Watershed summary


Average annual values of the simulation results


Return
-
period and frequency analysis


Flowpath

soil loss map


Representative
hillslope

runoff map


Representative
hillslope

soil detachment map


Representative
hillslope

soil loss map

WEPP
-
Mine Output
cont’d


General Steps for WEPP
-
Mine
Applications


Select area of interest


Generate channel network


Select watershed outlet and
discretize

watershed
and
subwatersheds


View watershed summary


Customize watershed inputs


Run WEPP


Analyze WEPP simulation results

Computer Requirement


A computer connected to internet


A web browser


Following instructions on the web page (select and
click buttons)

Premining

Simulation


WEPP simulation for the
premining

conditions can
be accomplished by following the general steps for
WEPP
-
Mine application without customizing
watershed inputs

Premining

Simulation

cont’d

Postmining

Simulation


User
-
specified DEM is used for topographical inputs for
postmining

conditions


A reclamation map can be uploaded for
postmining

soils and land managements


Soils at the disturbed mining areas are composed of
mine spoils and a 0.6
-
m top soil layer if top soil is
applied during reclamation


Postmining

top soil is a mixture of the onsite soil
described in the SSURGO database


Surface soil hydraulic and erosion parameters were
adjusted according to reclamation stages

Postmining

Soil and
Landuse


Map unit

Description

Land
Managements

Surface
Soils

0

Undisturbed or
No Data

Shrub

SM Shrub

1

Disturbed

Facilities

Poor grass

Paved or Bare Rock

2

Not Reclaimed

Bare

Mine Spoil

3

Pre
-
Reclamation

Bare

Regraded

Mine Spoil

4

Natural
Revegetation

Poor grass

SM Top Soil

5

Seed Phase I

Good grass

SM Sod Grass

6

Seed Phase II

Good grass

SM Bunch Grass

7

Trail
-
complete

Low traffic road

SM Skid

User
-
Specified Maps


The required format includes


Raster map in ASCII


30
-
m resolution


UTM projection


0 for “no data”


The corresponding projection file for the map needs
to be loaded


The IP address of a user is verified for uploading
files to the WEPP
-
Mine server

User
-
Specified DEM

Reclamation Map

Sediment Pond


After a watershed is
discretized
, one can specify
sediment ponds


Impoundment inputs include dimensions of the pond
and related hydraulic structure parameters


Default pond dimensions (stage
-
area
-
length
relationship) are determined based on horizontal areas
encircled by two half ellipses separated by the widest
line of the area


Inputs for chosen hydraulic structures of a pond are
shown after clicking the “Set Structure Parameters”
button


User inputs override the default values

Sediment Pond
cont’d

Sediment Pond
cont’d

Case Application

Study Site


WEPP
-
Mine was
applied to Watershed III
in Area A, Big Sky
Mine, a major surface
coal mine in southeast
Montana

Big Sky Mine Area A


Mining completed in 1989


Major reclamation activities (
regrading
, topsoil
replacement, and
revegetation
) completed in 1992


Since 1984, many watersheds in the Big Sky Mine
have been monitored for channel flow and water
quality

Field Observations

WEPP Simulations


Four WEPP runs were made to examine model
performance in simulating the effect of three sediment
control BMPs


Premining

(natural) condition


Postmining

with
revegetation


Postmining

with
revegetation

and a sediment pond


Postmining

with
revegetation

and a silt fence

Inputs for
Premining


Oldest DEM available for the study area


NRCS SSURGO soil data


USGS National Land Cover dataset for
landuse

and
management


Soil and management data acquired using the online
WEPP GIS interface

Postmining

with
Revegetation


Topographic map taken from the “Big Sky Mine 2008
Annual Report”


Soil and management data for the disturbed areas
from the reclamation and bond status report


Soil and management data prepared based on field
observations

Watershed Delineation:
Premining

and
Postmining


Topographic, soil,
landuse
, and management
conditions vary from the mining to
postmining

period and differ from the natural,
premining

conditions

-5
0
5
10
15
20
25
0
20
40
60
80
100
120
140
Sediment Pond


A sediment pond set near the outlet of the watershed


Volume 60,000 m
3


One culvert 2.4 m above bottom


Culvert
i.d
. 18 cm

Silt Fence


A silt fence set on the toe of a
hillslope

near the
watershed outlet


Fence height 1m

Curtsey: USDA Forest Service

Rocky Mountain Research Station

Forestry Sciences Laboratory, Moscow, ID

Return
-
period Analysis


25
-
yr WEPP simulations were carried out using
observed precipitation and temperature for 1984

2009
from Colstrip climate station (5 mi northwest of the
site) and other required climate data generated using
CLIGEN


Return
-
period analyses were performed on field
observations and WEPP simulations


Runoff and sediment yields of WEPP
-
simulated events
with a return period of 2, 5, 10, or 20 yr were
compared with field observations

Return
-
period Analysis


Return periods were estimated using Chow’s
frequency factor method and
Gumbel’s

distribution
with an annual maxima series following
Patra

(2000)

)))
1
/(
ln(ln(
7797
.
0
45005
.
0
(







T
T
K
K
s
X
X
x
m
T
T
: the specified return period


X
T
: the estimated value for a return period
T

X
m

and
s
x
: the mean and standard deviation of the annual maxima of
the events

Results

Results

cont’d

Runoff, mm

Sediment

Yield, kg/ha

Return Period (yr)

2

5

10

20

2

5

10

20

Observed

0.7

2.3

3.3

4.3

0.8

2.0

2.7

3.5

Simulated

Premining

2.7

6.8

9.5

12.1

1200

3000

4100

5200

Postmining

&
Revegetation

6.8

15.9

21.9

27.7

7600

20300

28700

36700

Postmining

& Sediment pond

6.1

15.0

21.0

26.7

3300

10800

15700

20400

Postmining

& Silt fence

6.8

15.9

21.9

27.7

6700

17800

25200

32200

Results

cont’d


WEPP overestimated observed runoff and sediment
yield


However, WEPP simulation results showed the
effectiveness of the sediment control practices


A silt fence near the watershed outlet would help to
reduce sediment yield slightly from the
postmining

revegetation

condition


WEPP simulations indicated a sediment pond to be
more effective, with a reduction of sediment yield of
50%

Summary


WEPP
-
Mine was developed as a management tool for
evaluating potential environmental impacts during and
after mining operations


WEPP
-
Mine was applied to a watershed in Area A, Big
Sky Mine, southeastern Montana, to assess watershed
hydrology and erosion as impacted by surface coal
mining activities and
postmining

reclamation and
sediment control practices


Three commonly used BMPs:
revegetation
, sediment
basin, and silt fence were evaluated as
postmining

reclamation management plans


Additionally, a baseline scenario, the
premining

condition, was simulated

Summary
cont’d


The WEPP simulations demonstrated the effectiveness
of the sediment control practices


Future efforts are needed to


Further evaluate the WEPP
-
Mine performance through
systematic and statistical comparison of model results and
long
-
term field observations for different mines under different
geographic conditions in the western US


Continually refine and develop functions (filter fence, buffer
zone) specific for mining applications


Develop a comprehensive database of soil and management
for alkaline mines in the western US for using WEPP
-
Mine

Acknowledgment


Funding support from OSM; in
-
kind support from WSU, US
Forest Service, and USDA NSERL


Technical exchanges with and support from P. Clark and D.
Matt


Funding and technical support and data and information
from MT DEQ, T. Golnar, J. Calabrese, Dr. E.
Hinz
.


Funding and technical support and assistance in field work
from Rosebud Mine engineers and staff

Resources and References


http://www.ars.usda.gov/Research/docs.htm?docid=10621

(This USDA NSERL site
contains extensive documentation and references on the WEPP model, including the free
model downloads)


Key references on the overview of the WEPP model


Flanagan, D.C., Livingston, S.J. (Eds.), 1995. USDA
-
Water Erosion Prediction Project User Summary.
NSERL Rep. No. 11, Natl. Soil Erosion Res. Lab., USDA ARS, West Lafayette, IN, 139 pp.


Flanagan, D.C., Nearing, M.A. (Eds.), 1995. USDA
-
Water Erosion Prediction Project:
Hillslope

Profile and
Watershed Model Documentation. NSERL Rep. No. 10, Natl., oil Erosion Res. Lab., USDA ARS, West
Lafayette, IN, 298 pp.


Flanagan, D.C., Ascough II., J.C., Nicks, A.D., Nearing, M.A., Laflen, J.M., 1995. Overview of the WEPP
erosion prediction model. In: Flanagan, D.C., Nearing, M.A. (Eds.), USDA
-
Water Erosion Prediction
Project
Hillslope

Profile and Watershed Model Documentation. NSERL Rep. 10, Natl. Soil Erosion Res.
Lab., USDA ARS, West Lafayette, IN (Chapter1).


Laflen, J.M., Lane, L.J., Foster, G.R., 1991. WEPP

a next generation of erosion prediction technology. J.
Soil Water
Conserv
. 46, 34

38.


Laflen, J.M., Elliot, W.J., Flanagan, D.C., Mayer, C.R., Nearing, M.A., 1997. WEPP
-
predicting water
erosion using a process
-
based model. J. Soil Water
Conserv
. 52, 96

102.


Laflen, J.M., Flanagan, D.C., Engel, B.A., 2004. Soil erosion and sediment yield prediction accuracy using
WEPP. Am. Water Res. Assoc. 40, 289

297.


Selected papers on modifying and applying the WEPP model by Dr. J. Wu’s group


Pieri
, L., M. Bittelli, J.Q. Wu, S. Dun, D.C. Flanagan, P. Rossi Pisa, F. Ventura, and F.
Salvatorelli
, 2007.
Using the Water Erosion Prediction Project (WEPP) model to simulate field
-
observed runoff and erosion in
the Apennines Mountain Range, Italy, J.
Hydrol
. 336, 84

97.


Zhang, J.X., K
-
T Chang, and J.Q. Wu, 2008. Effects of DEM resolution and source on soil erosion
modelling
: a case study using the WEPP model, Int. J.
Geogr
. Info. Sci. 22, 925

942.


Dun, S., J.Q. Wu, W.J. Elliot, P.R. Robichaud, D.C. Flanagan, J.R. Frankenberger, R.E. Brown, and A.C.
Xu, 2009. Adapting the Water Erosion Prediction Project (WEPP) model for forest applications, J.
Hydrol
.
466, 46

54.


Dun, S., J.Q. Wu, D.K. McCool, J.R. Frankenberger, and D.C. Flanagan, 2010. Improving frost simulation
subroutines of the Water Erosion Prediction Project (WEPP) Model, Trans. ASABE. 53, 1399

1411.