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CREP Wetland Final Report August 31, 2009
1
Identification of Suitable Sites for
Constructed Wetlands to Remove Nitrate
Final Project Report to the Indiana State Department of Agriculture
Dr. Jane Frankenberger, Agricultural and Biological Engineering, Purdue University
Dr. Indrajeet Chaubey, Agricultural and Biological Engineering, Purdue University
Dr. Eileen Kladivko, Agronomy, Purdue University
Margaret McCahon, Graduate Research Assistant, Purdue University
CREP Wetland Final Report August 31, 2009
2
Contents Introduction .................................................................................................................................................. 3
Criteria Used for Wetland Siting and Design ........................................................................................ 5
Data Layers .................................................................................................................................................... 6
Locating Suitable Sites .................................................................................................................................. 8
1. Sufficient Watershed Area from Tile-drained Land ....................................................................... 8
2. Wetland may be Located at the Interface between Closed and Open Drains ............................ 10
3. Wetland is on Cropland ............................................................................................................... 10
4. Topography Lends itself to Wetland Placement ......................................................................... 11
Wetland Design ........................................................................................................................................... 13
5. Desired Wetland Size is 0.5-2% of its Watershed Area ............................................................... 13
6. No More than 25% of the Wetland is Greater than Three Feet Deep ......................................... 14
7. The Surrounding Buffer Must Extend Four Feet above Wetland Surface, and Should Not Exceed
Four Times the Size of the Wetland .................................................................................................... 14
An Example Wetland Design (Site 8) ................................................................................................... 14
Applying Wetland Design Criteria to Wetland Designs ...................................................................... 15
Nitrate Removal Estimation ........................................................................................................................ 17
Conclusions ................................................................................................................................................. 21
References .................................................................................................................................................. 22
Appendix ..................................................................................................................................................... 23
I. Locations where Suitable Wetlands are Designed ...................................................................... 23
II. Wetland Design Characteristics and Nitrate Removal Efficiencies ............................................. 24
III. Wetland Designs at Each Site ...................................................................................................... 25
CREP Wetland Final Report
Intensification of agricultural practices in the Midwest has led
runoff and subsurface drainage, potentially impacting the water quality downstream and hypoxia in the
Gulf of Mexico. In heavily tile drained land,
losses in the form of nitrate. The 200
thirty percent of its five-year running average by 2015
reduction will require significant nutrient load reduct
Midwest.
Constructed wetlands have been shown to be an effective practice to reduce nitrate load
Midwestern crop land. Strategically targeting sites that intercept high nitrate loads and sizing th
wetlands according to the characteristics of their watersheds can maximize wetland efficiency while
minimizing costs and maintaining productive agriculture (Crumpton, 2001).
Determining suitable wetland sites for effective nitrate removal begins as a cla
combining various GIS layers to determine potentially suitable sites. An innovative aspect of this GIS
analysis is calculating the watershed area
which ensures that these wetlands intercept large flows and maximize nitrate r
landscape. This is the concept that forms the basis for Iowa’s CREP program (USDA, 2001; Tomer et al.,
2003).
Figure 1: Wetlands funded by Iowa’s CREP program treat drainage water from
nitrate removal, (Photo from http://www.fsa.usda.gov/Internet/FSA_File/crepphotogallery.ppt
August 31, 2009
3
Introduction
Intensification of agricultural practices in the Midwest has led to increased nutrient losses in surface
runoff and subsurface drainage, potentially impacting the water quality downstream and hypoxia in the
Gulf of Mexico. In heavily tile drained land, characteristic of parts of Indiana, there are great nitrogen
s in the form of nitrate. The 2008 EPA action plan calls for a reduction of the hypoxic zone to
year running average by 2015 (Gulf Hypoxia Action Plan, 2008)
reduction will require significant nutrient load reductions from large contributing areas throughout the
Constructed wetlands have been shown to be an effective practice to reduce nitrate load
Midwestern crop land. Strategically targeting sites that intercept high nitrate loads and sizing th
wetlands according to the characteristics of their watersheds can maximize wetland efficiency while
minimizing costs and maintaining productive agriculture (Crumpton, 2001).
Determining suitable wetland sites for effective nitrate removal begins as a classic GIS problem,
combining various GIS layers to determine potentially suitable sites. An innovative aspect of this GIS
analysis is calculating the watershed area (also called the contributing area) draining to each location,
lands intercept large flows and maximize nitrate reduction
This is the concept that forms the basis for Iowa’s CREP program (USDA, 2001; Tomer et al.,
Figure 1: Wetlands funded by Iowa’s CREP program treat drainage water from at least 500 acres, to maximize
http://www.fsa.usda.gov/Internet/FSA_File/crepphotogallery.ppt)
August 31, 2009
to increased nutrient losses in surface
runoff and subsurface drainage, potentially impacting the water quality downstream and hypoxia in the
there are great nitrogen
EPA action plan calls for a reduction of the hypoxic zone to about
(Gulf Hypoxia Action Plan, 2008). Such a
ions from large contributing areas throughout the
Constructed wetlands have been shown to be an effective practice to reduce nitrate loads leaving
Midwestern crop land. Strategically targeting sites that intercept high nitrate loads and sizing the
wetlands according to the characteristics of their watersheds can maximize wetland efficiency while
ssic GIS problem,
combining various GIS layers to determine potentially suitable sites. An innovative aspect of this GIS
to each location,
eduction in the
This is the concept that forms the basis for Iowa’s CREP program (USDA, 2001; Tomer et al.,
at least 500 acres, to maximize
)
CREP Wetland Final Report August 31, 2009
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The watershed used for this analysis was the Middle Wabash-Little Vermillion 8-digit HUC, limiting
suitable sites to within Indiana (see Figure 2). The goals of this work were to (1) complete a GIS analysis
to target suitable locations for constructed wetlands, (2) perform a site-specific analysis to create
preliminary designs at each suitable site and estimate the nitrate removal achieved for each design, and
(3) document the methodology clearly and completely so that it may be applied in other watersheds.
Figure 2: Middle Wabash – Little Vermillion Watershed (HUC 05120100) used for the GIS analysis.
CREP Wetland Final Report August 31, 2009
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Criteria Used for Wetland Siting and Design
We used a number of criteria in the siting and placement of wetlands (see box). We developed these
criteria based upon the Iowa CREP criteria, knowledge of Indiana agricultural practices, and discussions
with the following people:
� Staff of the Indiana State Department of Agriculture, Division of Soil Conservation, at a meeting
in Indianapolis on March 9, 2009
� Several people involved in wetland siting for the Iowa CREP program from Iowa State University
and the Iowa Department of Agriculture and Land Stewardship
� The State CREP Steering Committee and Technical Committees, at a meeting in Indianapolis on
June 1, 2009
Wetland Siting Criteria
1. Wetland has sufficient watershed area from tile-drained land (500-2000 acres of tile-
drained land, exclude streams to reduce permitting needed)
2. Wetland may be located at the interface between closed and open drains
3. Wetland is on cropland
4. Topography lends itself to wetland placement
Wetland Design Criteria
5. Desired wetland size is 0.5-2% of its watershed area
6. No more than 25% of the wetland is more than 3 feet deep (“deep wetland”)
7. The surrounding buffer must extend four feet above wetland surface, and should not
exceed 4 times the size of the wetland
CREP Wetland Final Report August 31, 2009
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Data Layers
Publicly available data layers were used in this analysis, so that the procedure could be continued on all
other Indiana watersheds. These datasets are described in Table 1 and shown for the 8-digit watershed
in Figure 3. An ArcInfo license of ArcGIS (ESRI, 1999-2006) and Arc Hydro tools (ESRI, 2007) were used
for the GIS analysis.
Table 1: Datasets used in the analysis
Data layer Source dataset How the layer was used in the analysis
Streams National Hydrography Dataset
(NHD), high resolution streams,
downloaded June 2009
Used to eliminate streams as suitable locations for
placing wetlands, and to approximate the location
where closed drains empty into open drains
Elevation National Elevation Dataset (NED),
with one-third arc second
resolution
Used to find watersheds, describe how water
flows through the landscape, and create contours
for wetland design
Roads TIGER 2008 Census data, “edges” Used to break up separate crop fields and also for
locating different wetland sites
Cropland National Land Cover Dataset
(NLCD), selecting the field
“cultivated crops”
Used for locating suitable sites for wetland
placement and also to approximate tile-drained
land in the landscape
Tile drained
land
(estimate)
From SSURGO soils and Cropland
(poorly, very poorly, and somewhat
poorly drained cropland)
Used to locate sites that drain a large watershed of
tile-drained land
Hydric soils Soil Survey Geographic (SSURGO)
Database
To give a general idea of areas that were formerly
wetland
Orthophotos Indiana Framework Data, streamed
by University of Indiana
Used for visualization of sites and determination of
locations where closed drains empty into open
ones
CREP Wetland Final Report August 31, 2009
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Figure 3: Data layers used in the identification of suitable locations for placement of constructed wetlands
in the 8-digit watershed.
CREP Wetland Final Report August 31, 2009
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Locating Suitable Sites
1. Sufficient Watershed Area from Tile-drained Land
To make the greatest impact in the landscape, each wetland should be placed strategically so that it
intercepts a large flow of water from tile-drained land, which is the source of much of the nitrate in
Indiana landscapes. We targeted these locations through the following three steps: (1) finding locations
that have watersheds between 500 and 2000 acres in size; (2) narrowing these locations to only those
that drain at least 500 acres of tiled land; and (3) excluding those locations that are in streams, rivers, or
open ditches to reduce permitting issues.
Step (1) was completed by processing 30-foot grid elevation data in Arc Hydro to determine flow
accumulation, or the paths where water should flow in a landscape. Locations with very large
watersheds appear like line segments or paths because water flow is channelized. Step (2) was similar
to step (1), except a weighted flow accumulation was used that only takes into account flow originating
from tile drained land. In Step (3) the NHD Streams dataset was buffered 100 meters to account for
discrepancies between stream and flow accumulation datasets, and all locations within this region were
excluded from the analysis. The results of each step are shown in Figure 4.
After Step (1), there were 1029 paths that had watersheds of 500-2000 acres. Step (2) narrowed the
sites considerably, with only 431 paths remaining, generally located near headwaters at the edges of the
watershed, and not in the Wabash River valley. The portion of the 8-digit watershed in Illinois was not
considered for wetland placement. Step (3) narrowed the number of sites to 105, about 10% of those
from Step (1), which were located almost exclusively in the northern portion of the watershed. It
appears that in the south (Parke and adjacent counties) the stream network is denser, perhaps because
of hillier terrain or decreased tile drainage of this land.
CREP Wetland Final Report August 31, 2009
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(a): Step (1) (b): Step (2)
(c): Step (3)
Figure 4: Determining
locations that have sufficient
watershed area from tile
drained land. (a) locations
with large (500-2000 acre)
watersheds, (b) use of an
estimate of tile drained land to
narrow these locations to
target high nitrate flows, and
(c) use of the NHD streams
data to eliminate locations
that are found in open
waterways.
CREP Wetland Final Report August 31, 2009
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2. Wetland may be Located at the Interface between Closed and Open Drains
For each flow path found in the previous step there is a location where the path meets an open
waterway. Results of our analysis in the pilot watershed in Tippecanoe County using the county’s
Regulated Drains data layer showed that this is typically where a large underground tile main (“closed
drain”) empties into a stream or open ditch (“open drain”). Placing wetlands at the interface between
closed and open drains is the preferred location, rather than interrupting a closed drain, since the water
leaving the wetland is a combination of flows above and below ground and is potentially difficult to
route back through a closed tile. Locating the wetland downstream in an open drain (ditch or stream)
would require permitting from various regulatory agencies and therefore is not desired.
3. Wetland is on Cropland
CREP constructed wetlands must be placed on cropland. To determine suitable cropped fields for
wetland placement, we delineated the watersheds of desirable outlet points and intersected these
watersheds with the cropland. Then we selected those fields that contain a location with sufficient
watershed area. The final output looks like the example shown in Figure 5, where the bright green field
is the only site where a wetland could be placed. A total of 113 crop fields were found, though not all
were truly suitable and were narrowed further in the next steps.
Figure 5: The output of the methods for siting wetlands. First an outlet point is found where the locations with
sufficient watershed area (red line) empty into an open stream (blue line). Next the watershed for this outlet
point is delineated (blue and dark green areas). Then the watershed and cropland layers are combined, and any
crop field that contains a location with sufficient watershed area is selected as potentially suitable for wetland
placement.
CREP Wetland Final Report August 31, 2009
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Note: The three steps described above were completely automated, using ArcGIS and Arc Hydro tools.
The remaining steps required human judgement, and thus cannot be completely automated.
4. Topography Lends itself to Wetland Placement
We looked carefully at each potentially suitable cropland field to determine, qualitatively, if topography
lends itself to wetland placement. We created 1-foot elevation contours and used them to visualize
wetland designs. Orthophotos and the streams data layer were used to more accurately determine the
interface between closed and open drains. The keys to good topography are a small dam, indicated by
dense contours, and a large and steep topographic rise of over 4 feet for buffer placement. Another
way to think of it is that the wetland and buffer should form a bowl-shape, where the wetland is
relatively flat and the surrounding buffer is steep. An example of a good site is shown in Figure 6.
Figure 6: An example of topography that lends itself to wetland placement. The orthophotos are used to
confirm that land is indeed cropland, and also to find the actual interface between closed and open drains. The
wetland and buffer shapes are determined by dam placement and topography.
We ranked each of the 113 sites qualitatively for wetland suitability, using the ranking scheme shown in
Table 2. We also noted whether or not the wetland could be placed at the interface between closed
and open drains. Results of the suitability ranking are shown in Figure 7. There were 11 sites given rank
5, 21 given rank 4, and 17 were ranked 3. The 49 sites ranked 3-5 were taken to the next stage of
placing preliminary wetland designs where possible.
Dam location
CREP Wetland Final Report August 31, 2009
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Table 2: Ranking Cropland Fields for Wetland Suitability
Wetland Suitability
Ranking
Qualitative Definition
5: Quite suitable Topography easily defines wetland and buffer with a relatively small dam, where
buffer does not appear more than 4 times the size of the wetland
4 A dam can be placed that allows for wetland and buffer features
3 Some element of topography or surrounding features make wetland placement
difficult, but not impossible
2 Wetland placement is impossible without considerable terrain alteration
1: Least suitable There is absolutely no possibility of a wetland at this location (probably due to
small size of field or surrounding features)
0: Invalid This plot of land does not meet wetland siting criteria, and was selected
erroneously in the automated method
Figure 7: Suitability Rankings on all potential sites found in part 3 of the analysis.
CREP Wetland Final Report August 31, 2009
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Wetland Design
We created preliminary wetland designs on all sites with suitability rankings of 3-5 where wetland
placement was possible. For each site, we created hypothetical “dams” to indicate the outlet of the
wetland, and then used contours to create the shape of wetland features for various heights of the dam.
A design was not considered valid unless the wetland and buffer contours intersect the dam to form
closed polygons. Topography and other features limited the number of feasible designs to one or two at
most sites. We made designs at a total of 31 sites. After creating all possible designs for each site, we
compared these designs quantitatively based on the wetland placement criteria discussed below, and
narrowed the suitable locations to 19 sites (Figure 8; Appendix).
Figure 8: Left: Suitable wetland designs were created at 19 sites. See Appendix for numbered sites. Right: The
watersheds of each potential wetland shows the drainage area that would be treated by the wetlands, which
account for three percent of the entire tile-drained portion of the 8-digit watershed.
5. Desired Wetland Size is 0.5-2% of its Watershed Area
Wetlands must be large enough to treat the volume of water they receive, but larger wetlands have
higher costs. The size of the wetland depends on the size of its watershed, the amount of drainage
water, and the degree of treatment desired. In Iowa, the desired size for these wetlands is 0.5-2% of its
watershed area. Yet Indiana generally has higher rainfall, which could produce higher flows in Indiana,
and wetlands should be designed accordingly. For this analysis we aimed for the desired wetland range
of 0.5-2% of its watershed area. This means a wetland with a 1,000 acre watershed should be 5 to 20
acres in size, with a buffer surrounding it up to 80 acres. However, designs with a higher percentage are
included as well for they may still hold value as they would result in a higher level of treatment
(although at a greater cost).
CREP Wetland Final Report August 31, 2009
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6. No More than 25% of the Wetland is Greater than Three Feet Deep
The primary process of nitrate reduction in a wetland is usually denitrification by bacteria, which takes
place most efficiently under oxygen depleted conditions (usually less than 3 ft deep). At the same time
water should be shallow enough in parts of the wetland for the wetland plants to establish. Therefore,
most of a wetland should be less than three feet deep to achieve nitrate treatment efficiency. We used
the criteria that no more than 25% of the pond should be greater than three feet deep, the same as in
the Iowa CREP program. As described above, this means that the ideal site would be fairly flat in the
specific area where the wetland pool is located, but sloping fairly steeply just outside the wetland pool
to minimize buffer size.
7. The Surrounding Buffer Must Extend Four Feet above Wetland Surface, and Should Not
Exceed Four Times the Size of the Wetland
When a wetland is installed, the local water table level will be the wetland surface elevation. If the
surface of a wetland is above a nearby tile then the tile will be submerged, hindering proper drainage.
Therefore the land surrounding the wetland surface should not be farmed, but rather converted to a
buffer of vegetation that is tolerant to wet conditions. In Indiana, tiles are usually located about three
feet below grade, so we aimed to design wetlands that are about four feet below the surrounding land.
This means that the buffer strip extends from the edge of the wetland to the farmable land, which is a
four-foot rise.
A four-foot rise in elevation around a wetland basin is a rather large topographic feature in the
landscape in this part of Indiana. Many locations do not even have such a rise, and others may rise so
gradually that the buffer strip is excessively large relative to the size of the wetland. In Iowa the desired
size of a buffer strip was no more than four times the size of the wetland, and this is also the criterion
we used. Note that if the farmer wishes to square off the buffer strip to give it a regular and more
farmable shape, then the buffer will be larger than the minimum necessary buffer region that we
estimated in these designs.
An Example Wetland Design (Site 8)
The goal of the wetland design process was to determine ways to place the wetland in the landscape to
meet the three design criteria of (5) wetland size of 0.5 to 2% of watershed area, (6) no more than 25%
greater than 3 feet deep, and (7) 4-foot elevation buffer with area no more than 4 times the wetland
size. We created each design by selecting the contour that defines the wetland surface, then selecting
the contour four feet above this which is the necessary buffer, and finally selecting the contour three
feet below the wetland (if one exists) that will become deep wetland (see Figure 9). The first contour
considered was one of the lowest contours that intersected the dam. This contour probably would not
allow for a large enough wetland, and in this case we move on to the next lowest contour (Figure 9).
The design is considered “valid” if the contour four feet above the wetland wraps around the wetland
and intersects the dam on both sides on the outlet. The next design we create has the wetland
extending to the contour one foot above the previous design, and if a buffer can be made, this design is
considered valid as well. After a few designs there will be a point where the buffer no longer surrounds
the wetland and a wetland of the proposed size can be not be placed at the site (see Figure 9, Figure
10).
CREP Wetland Final Report August 31, 2009
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All valid designs were compared against the wetland design criteria. We have documented those
designs that met (or nearly met) the design criteria (see Appendix).
Figure 9: The process of creating preliminary wetland designs based on 1-foot contours and a hypothetical dam
location.
Applying Wetland Design Criteria to Wetland Designs
The design criteria were then applied to the example wetland designs (Table 3). All but the smallest
wetland are within the desired range of wetland size; all wetlands have a small enough portion of deep
wetland, and all have a reasonable buffer. The dam length and the associated cost increases with the
larger designs. This shows that this example wetland truly has some flexibility in its design, which is not
characteristic of most wetland sites, which have one or two possible designs. Therefore, this location is
one of the most suitable for wetland placement in the entire watershed. A similar analysis for each of
the 19 suitable locations for wetland placement is presented in the Appendix, along with maps of each
design.
“Wetland” (usual water level)
“Deep wetland” (>3 feet deep)
“Buffer” (4 feet above wetland)
“Dam” (used to create the polygons)
Locations with sufficient
watershed area
Orthophotos
1-foot contours
Lowest contour would
not make large
enough wetland
This is the highest
contour for the buffer
with this particular
dam, because it
intersects the dam on
both sides of the
wetland outlet
CREP Wetland Final Report August 31, 2009
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Figure 10: All possible designs for this example site. The large design is only possible when the dam is adjusted
to intercept the buffer contour.
Table 3: Applying the Wetland Placement Criteria to the example wetland, designed in Figure 10.
Component Desired Range Smallest Small Medium Large
Wetland 0.5-2% of watershed 0.4% of
watershed
0.8% of
watershed
1.2% of
watershed
1.3% of
watershed
Deep wetland < 25% of wetland area 22% 14% 2% 0%
Buffer Less than 4:1 ratio
buffer : wetland
2:1 ratio 2:1 ratio 2:1 ratio 4:1 ratio
Dam As small as possible 1200 ft 950 ft 825 ft 775 ft
Notes
Smallest Small Medium Large
0.4% of watershed 0.8% of watershed 1.2% of watershed 1.3% of watershed
4 acres 8 acres 11 acres 12 acres
CREP Wetland Final Report August 31, 2009
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Nitrate Removal Estimation
Nitrate removal takes place by plant uptake and microbial processes in oxygen-poor environments such
as wetlands. A number of factors affect the rate of nitrate removal, including hydraulic loading
rate/hydraulic retention time, the concentration of nitrate in the inflow water, the temperature of the
water, soil conditions, vegetation processes, and flow characteristics in the wetland.
Because so many variables affect nitrate removal in a wetland, we chose to use two wetland nitrate
removal models developed in climates and conditions similar to Indiana. The first model is an annual
model developed on Iowa CREP wetlands (Crumpton et al., 2006), in which nitrate removal depends on
annual hydrulic loading rate and the average concentration of nitrate in the wetland. This regression
was shown to predict nitrate removal quite well in Iowa CREP wetlands. The second model was
developed in North Carolina to predict how large constructed wetlands should be to achieve a certain
nitrate reduction (Burchell et al., 2007). We used this model to predict nitrate reduction on a monthly
timescale, and then determined annual reduction. The model estimates effluent nitrate concentration
as a function of inflow concentration, surface area of the wetland, an empirically determined nitrate
removal constant that varies with water temperature, the depth of water in the wetland, the wetland
sediment porosity, and the volume of inflow. See equations in box below.
Annual Model (Crumpton et al., 2006): � ������� �� �����.��
N Removed = annual percent of nitrate removed from wetland (%)
HLR = annual hydraulic loading rate to the wetland (m/yr)
Monthly Model (Burchell et al., 2007): �� ������ �� ���� !�� " �
#
Ce = effluent nitrate concentration (mg/L)
Co = influent nitrate concentration (mg/L)
As = surface area of wetland (m2)
Knitrate = nitrate removal rate constant (1/month)
We used -0.45 in winter and -5.7 in summer
y = depth of the water in wetland (m)
n = porosity of wetland (0.65-0.75)
We used 0.70
Q = inflow (m3/month)
CREP Wetland Final Report August 31, 2009
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Applying these models to hypothetical wetland designs required estimates of annual and monthly flow
and average nitrate concentrations of the flow entering the wetland. Actual flow and nitrate
concentration data from these locations are not available. We used data from 2000 to 2002 in Hoagland
Ditch, located in White County, Indiana, which has similar land use and drainage characteristics to the
wetland watersheds analyzed in this project. Monthly data on nitrate concentration and ditch flow are
shown in Figure 11. The annual flow weighted average nitrate concentration in Hoagland Ditch was
approximately 10 ppm, so the results shown are for this concentration. It should be noted that the
actual nitrate removal efficiency will be different by these wetlands as some wetlands may receive a
higher nitrate concentration than 10 ppm, and in this case they will show greater efficiency than those
reported here.
The estimated annual wetland efficiency for all suitable wetland designs is shown in Figure 12, and the
estimated monthly effluent nitrate concentration is shown in Table 4. All designed wetlands are
predicted to remove approximately 25 to 45 percent of the nitrate they receive each year. Yet nitrate
removal depends heavily on the time of year, with high removal rates in the warm months (April
through September) and low removal rates in the winter. Therefore, the removal efficiency will vary
based on timing of nutrient application as well as timing of flow events in the watershed.
Figure 11: Nitrate concentration and flow data from Hoagland Ditch used in nitrate removal estimates for each
wetland design.
0.00
5.00
10.00
15.00
20.00
1 2 3 4 5 6 7 8 9 10 11 12
Month
Nitrate Concentration (mg/L)
Ditch Flow (cm)
CREP Wetland Final Report August 31, 2009
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Figure 12: Estimated nitrate removal efficiency for each wetland design using the annual model. Efficiencies
range between about 25 and 45%. Bars are colored only to show the difference between adjacent wetland
design sites.
0.00 10.00 20.00 30.00 40.00 50.00
01a
02a
03a
03b
04a
05a
06a
07a
07b
08a
08b
08c
08d
09a
10a
10b
10c
10d
10e
11a
11b
11c
12a
13a
14a
14b
15a
16a
17a
18a
19a
19b
19c
19d
Annual Percent Nitrate Removal (%)
We
tla
nd
De
sig
n
CREP Wetland Final Report August 31, 2009
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Table 4: Estimated monthly nitrate inflow and outflow concentrations for each wetland design.
Inflow 11.6 12.8 15.2 13.6 15.1 17.3 11.8 0.9 0.7 3.4 7.4 11.1
Wetland
No. Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
01a 10.8 12.5 14.6 9.5 7.4 10.5 0.1 0.0 0.4 3.4 6.6 10.7
02a 10.8 12.6 14.7 9.8 7.8 10.9 0.1 0.0 0.4 3.4 6.6 10.7
03a 11.0 12.6 14.8 10.5 9.0 12.1 0.3 0.0 0.4 3.4 6.8 10.8
03b 11.2 12.7 14.9 11.5 10.8 13.7 1.0 0.0 0.5 3.4 7.0 10.9
04a 10.8 12.6 14.6 9.7 7.7 10.8 0.1 0.0 0.4 3.4 6.6 10.7
05a 10.9 12.6 14.7 10.3 8.5 11.6 0.2 0.0 0.4 3.4 6.7 10.8
06a 10.8 12.5 14.6 9.6 7.5 10.6 0.1 0.0 0.4 3.4 6.6 10.7
07a 11.2 12.7 15.0 11.8 11.2 14.1 1.4 0.0 0.5 3.4 7.0 10.9
07b 10.7 12.5 14.5 9.0 6.6 9.7 0.0 0.0 0.3 3.4 6.5 10.6
08a 10.5 12.5 14.4 8.2 5.4 8.5 0.0 0.0 0.3 3.4 6.3 10.5
08b 10.7 12.5 14.6 9.3 6.9 10.1 0.0 0.0 0.3 3.4 6.5 10.7
08c 11.1 12.6 14.9 11.3 10.3 13.2 0.7 0.0 0.5 3.4 6.9 10.9
08d 11.4 12.7 15.1 12.7 13.0 15.6 4.1 0.1 0.6 3.4 7.2 11.0
09a 11.0 12.6 14.8 10.7 9.3 12.3 0.3 0.0 0.4 3.4 6.8 10.8
10a 9.0 12.0 13.2 3.9 1.2 3.0 0.0 0.0 0.1 3.2 4.9 9.8
10b 9.9 12.3 13.9 6.1 3.0 5.6 0.0 0.0 0.2 3.3 5.7 10.2
10c 10.6 12.5 14.5 8.6 6.0 9.1 0.0 0.0 0.3 3.4 6.4 10.6
10d 11.1 12.6 14.8 10.8 9.5 12.5 0.4 0.0 0.5 3.4 6.8 10.8
10e 11.4 12.7 15.1 12.5 12.6 15.2 3.2 0.1 0.6 3.4 7.2 11.0
11a 11.1 12.6 14.9 11.1 10.1 13.0 0.6 0.0 0.5 3.4 6.9 10.9
11b 10.0 12.3 14.0 6.4 3.3 6.0 0.0 0.0 0.2 3.3 5.8 10.3
11c 10.6 12.5 14.5 8.9 6.4 9.5 0.0 0.0 0.3 3.4 6.4 10.6
12a 11.3 12.7 15.0 11.9 11.5 14.3 1.6 0.0 0.5 3.4 7.1 10.9
13a 11.1 12.6 14.8 11.0 9.8 12.8 0.5 0.0 0.5 3.4 6.9 10.9
14a 11.2 12.6 14.9 11.3 10.3 13.3 0.8 0.0 0.5 3.4 6.9 10.9
14b 11.4 12.7 15.1 12.7 13.1 15.6 4.1 0.1 0.6 3.4 7.2 11.0
15a 10.7 12.5 14.5 9.0 6.5 9.6 0.0 0.0 0.3 3.4 6.5 10.6
16a 11.3 12.7 15.0 11.8 11.4 14.2 1.5 0.0 0.5 3.4 7.0 10.9
17a 11.4 12.7 15.1 12.8 13.3 15.8 4.6 0.2 0.6 3.4 7.2 11.0
18a 11.2 12.7 14.9 11.5 10.7 13.6 0.9 0.0 0.5 3.4 7.0 10.9
19a 11.5 12.7 15.1 13.1 13.9 16.3 6.6 0.3 0.6 3.4 7.3 11.1
19b 11.0 12.6 14.8 10.6 9.0 12.1 0.3 0.0 0.4 3.4 6.8 10.8
19c 10.2 12.4 14.2 7.2 4.2 7.1 0.0 0.0 0.2 3.3 6.0 10.4
19d 9.2 12.1 13.4 4.2 1.4 3.4 0.0 0.0 0.1 3.2 5.1 9.9
CREP Wetland Final Report August 31, 2009
21
Conclusions
Using publicly available data and GIS analysis, we found 31 locations in the 8-digit watershed where
wetlands may be placed to intercept high nitrate loads. In all, 64 designs were created at these 31 sites.
Of these 31 locations, 19 have at least one reasonable wetland design based on the wetland placement
criteria, and 34 wetlands are designed at these 19 sites. Many of these sites are located at the interface
between open and closed drainage.
All suitable sites are located in the northern part of the watershed, which is flatter and more extensively
tiled than the south, which has a denser stream network. The best locations for wetlands are in the
headwaters of streams, often near the outer edges of the 8-digit watershed. Topography greatly limits
wetland placement on a given site, because the four-foot elevation drop in the buffer is difficult to find
in the relatively flat landscapes.
The total watershed of these 19 locations is 21,650 acres, with 16,081 acres estimated to be tile drained
land. If wetlands are placed at all of these 19 locations, they will intercept three percent of the entire
tile drained portion of the watershed.
The estimated nitrate removal efficiency of these 34 wetlands varies from about 25 to 45 percent, with
an average of 35 percent. Efficiencies may be greater if the average incoming nitrate concentration is
higher than 10 ppm, which is likely in heavily tile drained watersheds.
The most critical step in this analysis is to target locations with a large watershed area draining into the
wetland, to maximize nitrate reduction. Any GIS analysis must consider wetland placement from a
watershed-scale perspective, and the use of GIS in the placement of these wetlands is an important part
of a strategy to reduce nitrate loads in the agricultural Midwest.
CREP Wetland Final Report August 31, 2009
22
References
Burchell, M.R., Skaggs, R.W., Lee, C.R., Broome, S., Chescheir, G.M., Osborne, J. (2007). Substrate
organic matter to improve nitrate removal in surface-flow constructed wetlands. Journal of
Environmental Quality, 36:194-207.
Crumpton, W.G. (2001). Using wetlands for water quality improvement in agricultural watersheds: The
importance of a watershed scale approach. Water Science and Technology, 44:559-564.
Crumpton, W.G., Stenback, G.A., Miller, B.A., Helmers, M.J. (2006). Potential benefits of wetland filters
for tile drainage systems: Impacts on nitrate loads to Mississippi River subbasins. Report to USDA.
ESRI (1999-2006). ArcGIS 9.2. ArcInfo license.
ESRI (2007). Arc Hydro for ArcGIS 9 Version 1.2. Environmental Systems Research Institute, Redlands,
California, USA.
Mississippi River/Gulf of Mexico Watershed Nutrient Task Force (2008). Gulf Hypoxia Action Plan 2008
for Reducing, Mitigating, and Controlling Hypoxia in the Northern Gulf of Mexico and Improving Water
Quality in the Mississippi River Basin. Washington, DC.
Tomer, M.D., D.E. James, and T.M. Isenhart (2003). Optimizing the placement of riparian practices in a
watershed using terrain analysis. J. Soil Water Conservation, 58(4): 198-206.
USDA, 2001. Conversation Reserve Enhancement Program: Iowa enhancement program. Available at
http://www.agriculture.state.ia.us/waterResources/pdf/LandownerGuide.pdf.
CREP Wetland Final Report August 31, 2009
23
Appendix
I. Locations where Suitable Wetlands are Designed
Potentially suitable wetland designs were created at the sites shown above. Designs for each of these
sites are shown in the following pages.
CREP Wetland Final Report August 31, 2009
24
II. Wetland Design Characteristics and Nitrate Removal Efficiencies
Wetland
No. Watershed Wetland Buffer Deep Dam
Average
Depth Wetland
Buffer:
Wetlan
d
Deep
Wetland
NO3
Removal
acres acres acres acres ft ft % of
Watershed ratio
% of
Wetland
% NO3
removal
01a 619 8.32 18.84 1.10 502 1.4 1.34 2.3 13.2 31
02a 1640 26.90 116.65 0.00 1646 1.1 1.64 4.3 0.0 45
03a 1604 9.32 32.14 3.34 637 2.4 0.58 3.4 35.8 32
03b 1604 6.47 26.63 2.16 617 2.2 0.40 4.1 33.4 28
04a 1119 21.60 41.95 0.00 508 0.9 1.93 1.9 0.0 42
05a 788 9.01 26.63 0.00 554 1.3 1.14 3.0 0.0 31
06a 889 16.99 88.14 0.00 835 1.0 1.91 5.2 0.0 39
07a 1056 8.81 28.18 0.00 1381 0.9 0.83 3.2 0.0 31
07b 993 27.67 74.31 0.00 1688 0.8 2.79 2.7 0.0 45
08a 944 12.60 30.49 2.78 1182 2.0 1.33 2.4 22.1 35
08b 944 11.26 23.72 1.56 946 1.7 1.19 2.1 13.8 34
08c 944 7.97 17.97 0.19 825 1.2 0.84 2.3 2.4 30
08d 944 3.97 15.66 0.00 775 0.9 0.42 3.9 0.0 24
09a 1407 15.96 87.45 0.00 1212 1.1 1.13 5.5 0.0 38
10a 694 21.84 34.52 6.76 1169 2.1 3.15 1.6 30.9 42
10b 694 14.42 32.83 3.88 1102 2.1 2.08 2.3 26.9 37
10c 694 10.51 28.14 1.27 1045 1.6 1.52 2.7 12.1 33
10d 694 6.76 21.56 0.00 967 1.3 0.97 3.2 0.0 29
10e 694 3.88 17.96 0.00 895 0.9 0.56 4.6 0.0 24
11a 1191 11.03 48.60 0.00 752 1.2 0.93 4.4 0.0 34
11b 1191 26.30 91.23 5.21 925 1.8 2.21 3.5 19.8 45
11c 1191 17.61 64.59 1.98 814 1.5 1.48 3.7 11.2 39
12a 1023 6.29 20.30 0.00 666 1.2 0.61 3.2 0.0 28
13a 931 9.90 41.22 0.00 1959 1.1 1.06 4.2 0.0 32
14a 1590 12.55 41.49 0.00 814 1.3 0.79 3.3 0.0 35
14b 1590 7.40 34.63 0.00 726 0.8 0.47 4.7 0.0 29
15a 672 26.01 96.48 0.00 2146 0.6 3.87 3.7 0.0 45
16a 1251 10.18 41.28 0.00 647 0.9 0.81 4.1 0.0 33
17a 1551 9.07 34.40 0.00 1268 0.6 0.58 3.8 0.0 31
18a 1033 17.05 66.53 0.00 2470 0.6 1.65 3.9 0.0 39
19a 654 4.81 21.59 0.00 383 0.3 0.73 4.5 0.0 25
19b 654 11.14 21.42 0.00 469 0.8 1.70 1.9 0.0 34
19c 654 15.53 24.27 0.00 532 1.4 2.37 1.6 0.0 38
19d 654 21.37 26.69 4.81 605 1.9 3.27 1.2 22.5 42
CREP Wetland Final Report August 31, 2009
25
III. Wetland Designs at Each Site
Site 1 Wetland Designs
Watershed of the Site 1
wetland
Site 1 is located in Fountain
County.
95% of the watershed is
estimated to be tile
drained.
Site of wetland placement
The best location for a
wetland is shown by the
black proposed dam. This
location DOES appear to be
located near the interface
between closed and open
drains. The interface of
closed and open drains lies to
the north. The dam could be
placed anywhere along the
red line or the blue line to
alter the designs.
CREP Wetland Final Report August 31, 2009
26
Component Desired Range Design A
Wetland 0.5-2% of watershed 1.3% of watershed
Deep wetland < 25% of wetland area 13%
Buffer Less than 4:1 ratio
buffer : wetland
2.3:1 ratio
Dam As small as possible 500 ft
Notes Satisfies all desired criteria
Design 1A:
Wetland is 1.3%
of watershed
CREP Wetland Final Report August 31, 2009
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Site 2 Wetland Designs
Watershed of the Site 2
wetland
Site 2 is located in Fountain
County.
86% of the watershed is
estimated to be tile
drained.
Site of wetland placement
The best location for a
wetland is shown by the
black proposed dam. This
location DOES appear to be
located near the interface
between closed and open
drains. The dam could be
placed anywhere along the
red line or along the blue
line between the red line
and the dam to alter the
designs.
CREP Wetland Final Report August 31, 2009
28
Component Desired Range Design A
Wetland 0.5-2% of watershed 1.6% of watershed
Deep wetland < 25% of wetland area 0%
Buffer Less than 4:1 ratio
buffer : wetland
4.3:1 ratio
Dam As small as possible 1650 ft
Notes Buffer is a bit large, and dam
is fairly long.
Design 2A:
Wetland is 1.6%
of watershed
CREP Wetland Final Report August 31, 2009
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Site 3 Wetland Designs
Watershed of the Site 3
wetland
This site is located in
Vermillion County.
69% of the watershed is
estimated to be tile
drained.
Site of wetland placement
The best location for a
wetland is shown by the
black proposed dam. This
location appears to be
located near the interface
between closed and open
drains, but intercepts open
drainage. The dam could
be placed anywhere along
the red line or along the
blue line between the red
line and the dam to alter
the designs.
CREP Wetland Final Report August 31, 2009
30
Component Desired Range Design A Design B
Wetland 0.5-2% of watershed 0.58% of watershed 0.40% of watershed
Deep wetland < 25% of wetland area 36% 35%
Buffer Less than 4:1 ratio
buffer : wetland
3.4:1 ratio 4.1:1 ratio
Dam As small as possible 637 ft 617 ft
Notes Wetland is a bit too deep Wetland is smaller than
desired, and a bit too deep
Design 3A:
Wetland is 0.58%
of watershed
Design 3B:
Wetland is 0.40%
of watershed
CREP Wetland Final Report August 31, 2009
31
Site 4 Wetland Designs
Watershed of the Site 4
wetland
This site is located in
Montgomery County.
63% of the watershed is
estimated to be tile
drained.
Site of wetland placement
The best location for a
wetland is shown by the
black proposed dam. This
location DOES appear to be
located near the interface
between closed and open
drains. The dam could be
placed anywhere along the
red line to alter the designs.
The topography lends itself
to wetland placement.
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32
Component Desired Range Design A
Wetland 0.5-2% of watershed 1.9% of watershed
Deep wetland < 25% of wetland area 0%
Buffer Less than 4:1 ratio
buffer : wetland
1.9:1 ratio
Dam As small as possible 508 ft
Notes This site appears to be quite
suitable for wetland
placement
Design 4A:
Wetland is 1.9%
of watershed
CREP Wetland Final Report August 31, 2009
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Site 5 Wetland Designs
Watershed of the Site 5
wetland
This site is located in
Benton County.
76% of the watershed is
estimated to be tile
drained.
Site of wetland placement
The best location for a
wetland is shown by the
black proposed dam. This
location DOES NOT appear
to be located near the
interface between closed
and open drains. The dam
could be placed anywhere
along the red line to alter
the designs.
The topography lends itself
to wetland placement.
CREP Wetland Final Report August 31, 2009
34
Component Desired Range Design A
Wetland 0.5-2% of watershed 1.1% of watershed
Deep wetland < 25% of wetland area 0%
Buffer Less than 4:1 ratio
buffer : wetland
3:1 ratio
Dam As small as possible 550 ft
Notes This site appears to be quite
suitable for wetland
placement
Design 5A:
Wetland is 1.1%
of watershed
CREP Wetland Final Report August 31, 2009
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Site 6 Wetland Designs
Watershed of the Site 6
wetland
This site is located in
Tippecanoe County.
69% of the watershed is
estimated to be tile
drained.
Site of wetland placement
The best location for a
wetland is shown by the
black proposed dam. This
location DOES appear to be
located near the interface
between closed and open
drains. The dam could be
placed anywhere along the
red line to alter the designs.
CREP Wetland Final Report August 31, 2009
36
Component Desired Range Design A
Wetland 0.5-2% of watershed 1.9% of watershed
Deep wetland < 25% of wetland area 0%
Buffer Less than 4:1 ratio
buffer : wetland
5.2:1 ratio
Dam As small as possible 835 ft
Notes The buffer is larger than
desired
Design 6A:
Wetland is 1.9%
of watershed
CREP Wetland Final Report August 31, 2009
37
Site 7 Wetland Designs
Watershed of the Site 7
wetland
This site is located in
Fountain County, though
the watershed extends into
Tippecanoe.
69% of the watershed is
estimated to be tile
drained.
Site of wetland placement
The best locations for a
wetland are shown by the
black proposed dam. These
locations DO appear to be
located near the interface
between closed and open
drains. The dam could be
placed anywhere along the
red line or along the blue
line between the red line
and the dam on the left to
alter the designs.
CREP Wetland Final Report August 31, 2009
38
Component Desired Range Design A Design B
Wetland 0.5-2% of watershed 0.83% of watershed 2.8% of watershed
Deep wetland < 25% of wetland area 0% 0%
Buffer Less than 4:1 ratio
buffer : wetland
3.2:1 ratio 2.7:1 ratio
Dam As small as possible 1381 ft 1688 ft
Notes Long dam Long dam, wetland may be
larger than desired
Design 7A:
Wetland is 0.83%
of watershed
Design 7B:
Wetland is 2.8%
of watershed
CREP Wetland Final Report August 31, 2009
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Site 8 Wetland Designs
Watershed of the Site 8
wetland
This site is located in
Tippecanoe County.
78% of the watershed is
estimated to be tile
drained.
Site of wetland placement
The best locations for a
wetland are shown by the
black proposed dams.
These locations DO appear
to be near the interface
between closed and open
drains. The dam could be
placed anywhere along the
red line.
Topography lends itself to
wetland placement. This
may be one of the most
promising sites.
CREP Wetland Final Report August 31, 2009
40
Design 8A:
Wetland is 1.3%
of watershed
Design 8B:
Wetland is 1.2%
of watershed
Design 8C:
Wetland is 0.84%
of watershed
Design 8D:
Wetland is 0.42%
of watershed
CREP Wetland Final Report August 31, 2009
41
Component Desired Range Design A Design B
Wetland 0.5-2% of watershed 1.3% of watershed 1.2% of watershed
Deep wetland < 25% of wetland area 22% 14%
Buffer Less than 4:1 ratio
buffer : wetland
2.4:1 ratio 2.1:1 ratio
Dam As small as possible 1182 ft 946 ft
Notes
Component Desired Range Design C Design D
Wetland 0.5-2% of watershed 0.84% of watershed 0.42% of watershed
Deep wetland < 25% of wetland area 2% 0%
Buffer Less than 4:1 ratio
buffer : wetland
2.3:1 ratio 3.9:1 ratio
Dam As small as possible 825 ft 775 ft
Notes Wetland is smaller than
desired
CREP Wetland Final Report August 31, 2009
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Site 9 Wetland Designs
Watershed of the Site 9
wetland
This site is located in
Tippecanoe County.
67% of the watershed is
estimated to be tile
drained.
Site of wetland placement
The best location for a
wetland is shown by the
black proposed dam. This
location DOES appear to be
located near the interface
between closed and open
drains. The dam could be
placed anywhere along the
red line to alter the designs.
CREP Wetland Final Report August 31, 2009
43
Component Desired Range Design A
Wetland 0.5-2% of watershed 1.1% of watershed
Deep wetland < 25% of wetland area 0%
Buffer Less than 4:1 ratio
buffer : wetland
5.5:1 ratio
Dam As small as possible 1212 ft
Notes The buffer is larger than
desired
Design 9A:
Wetland is 1.1%
of watershed
CREP Wetland Final Report August 31, 2009
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Site 10 Wetland Designs
Watershed of the Site 10
wetland
This site is located in
Montgomery County.
71% of the watershed is
estimated to be tile
drained.
Site of wetland placement
The best locations for a wetland
are shown by the black proposed
dams. These locations DO appear
to be near the interface between
closed and open drains. There
may be no other possible dam
location.
There may be features preventing
the placement of wetlands. A site
visit may be necessary. Otherwise
this is a promising site.
CREP Wetland Final Report August 31, 2009
45
Design 10A:
Wetland is 3.1%
of watershed
Design 10B:
Wetland is 2.1%
of watershed
Design 10C:
Wetland is 1.5%
of watershed
Design10D:
Wetland is 1.0%
of watershed
CREP Wetland Final Report August 31, 2009
46
Component Desired Range Design A Design B
Wetland 0.5-2% of watershed 3.1% of watershed 2.1% of watershed
Deep wetland < 25% of wetland area 31% 27%
Buffer Less than 4:1 ratio
buffer : wetland
1.6:1 ratio 2.3:1 ratio
Dam As small as possible 1169 ft 1102 ft
Notes Wetland is larger than
desired, with more deep
wetland than desired
Component Desired Range Design C Design D Design E
Wetland 0.5-2% of watershed 1.5% of watershed 1.0% of watershed 0.6% of watershed
Deep wetland < 25% of wetland area 12% 0% 0%
Buffer Less than 4:1 ratio
buffer : wetland
2.7:1 ratio 3.2:1 ratio 4.6:1 ratio
Dam As small as possible 1045 ft 967 ft 895 ft
Notes Buffer is larger
than desired
Design 10E:
Wetland is 0.6%
of watershed
CREP Wetland Final Report August 31, 2009
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Site 11 Wetland Designs
Watershed of the Site 11 wetland
This site is located in Tippecanoe
County.
92% of the watershed is
estimated to be tile drained.
Site of wetland placement
The best locations for a wetland
are shown by the black proposed
dams. These locations DO NOT
appear to be near the interface
between closed and open drains.
The dam could be placed
anywhere along the red line.
CREP Wetland Final Report August 31, 2009
48
Component Desired Range Design A Design B Design C
Wetland 0.5-2% of watershed 0.9% of watershed 2.2% of watershed 1.5% of watershed
Deep wetland < 25% of wetland area 0% 20% 11%
Buffer Less than 4:1 ratio
buffer : wetland
4.4:1 ratio 3.5:1 ratio 3.7:1 ratio
Dam As small as possible 752 ft 925 ft 814 ft
Notes Buffer is larger
than desired
Design 11A:
Wetland is 0.9%
of watershed
Design 11B:
Wetland is 2.2%
of watershed
Design 11C:
Wetland is 1.5%
of watershed
CREP Wetland Final Report August 31, 2009
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Site 12 Wetland Designs
Watershed of the Site 12
wetland
This site is located in
Tippecanoe County.
78% of the watershed is
estimated to be tile
drained.
Site of wetland placement
The best location for a
wetland is shown by the
black proposed dam. This
location DOES NOT appear
to be located at the
interface between closed
and open drains, but
instead intercepts closed
drainage. The dam could
be placed anywhere along
the red line to alter the
designs.
CREP Wetland Final Report August 31, 2009
50
Component Desired Range Design A
Wetland 0.5-2% of watershed 3.5% of watershed
Deep wetland < 25% of wetland area 0%
Buffer Less than 4:1 ratio
buffer : wetland
3.9:1 ratio
Dam As small as possible 600 ft
Notes Wetland is larger than
desired
Design 12 A:
Wetland is 3.5%
of watershed
CREP Wetland Final Report August 31, 2009
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Site 13 Wetland Designs
Watershed of the Site 13
wetland
This site is located in
Tippecanoe County, though
the watershed enters
Montgomery County.
56% of the watershed is
estimated to be tile
drained.
Site of wetland placement
The best location for a
wetland is shown by the
black proposed dam. This
location appears to be
somewhat near the
interface between closed
and open drains, which is
to the north of the site.
The dam could be placed
anywhere along the red line
to alter the designs.
CREP Wetland Final Report August 31, 2009
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Component Desired Range Design A
Wetland 0.5-2% of watershed 1.1% of watershed
Deep wetland < 25% of wetland area 0%
Buffer Less than 4:1 ratio
buffer : wetland
4.2:1 ratio
Dam As small as possible 1959 ft
Notes Buffer is larger than desired,
dam is quite long, a patch of
trees interferes with
preliminary design. This site
may be more promising than
it appears from this design.
Design 13 A:
Wetland is 1.1%
of watershed
CREP Wetland Final Report August 31, 2009
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Site 14 Wetland Designs
Watershed of the Site 14 wetland
This site is located in Tippecanoe
County.
78% of the watershed is
estimated to be tile drained.
Site of wetland placement
The best locations for a wetland
are shown by the black proposed
dams. This location DOES appear
to be near the interface between
closed and open drains. The dam
could be placed anywhere along
the red line.
CREP Wetland Final Report August 31, 2009
54
Component Desired Range Design A Design B
Wetland 0.5-2% of watershed 0.8% of watershed 0.5% of watershed
Deep wetland < 25% of wetland area 0% 20%
Buffer Less than 4:1 ratio
buffer : wetland
3.3:1 ratio 4.7:1 ratio
Dam As small as possible 814 ft 726 ft
Notes Buffer is a bit
large
Design 14A:
Wetland is 0.8%
of watershed
Design 14B:
Wetland is 0.5%
of watershed
CREP Wetland Final Report August 31, 2009
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Site 15 Wetland Designs
Watershed of the Site 15 wetland
This site is located in Tippecanoe
County.
83% of the watershed is
estimated to be tile drained.
Site of wetland placement
The best locations for a wetland
are shown by the black proposed
dams. This location DOES NOT
appear to be near the interface
between closed and open drains.
The dam could be placed
anywhere along the red line.
CREP Wetland Final Report August 31, 2009
56
Component Desired Range Design A
Wetland 0.5-2% of watershed 3.9% of watershed
Deep wetland < 25% of wetland area 0%
Buffer Less than 4:1 ratio
buffer : wetland
3.7:1 ratio
Dam As small as possible 2146 ft
Notes Wetland is much
larger than
desired, and dam
is quite large
Design 15A:
Wetland is 3.9%
of watershed
CREP Wetland Final Report August 31, 2009
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Site 16 Wetland Designs
Watershed of the Site 16 wetland
This site is located in Tippecanoe
County.
72% of the watershed is
estimated to be tile drained.
Site of wetland placement
The best locations for a wetland
are shown by the black proposed
dams. This location DOES NOT
appear to be near the interface
between closed and open drains.
The dam could be placed
anywhere along the red line.
CREP Wetland Final Report August 31, 2009
58
Component Desired Range Design A
Wetland 0.5-2% of watershed 0.8% of watershed
Deep wetland < 25% of wetland area 0%
Buffer Less than 4:1 ratio
buffer : wetland
4.1:1 ratio
Dam As small as possible 647 ft
Notes
Design 16A:
Wetland is 0.8%
of watershed
CREP Wetland Final Report August 31, 2009
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Site 17 Wetland Designs
Watershed of the Site 17 wetland
This site is located in Tippecanoe
County.
63% of the watershed is
estimated to be tile drained.
Site of wetland placement
The best locations for a wetland
are shown by the black proposed
dams. This location DOES appear
to be near the interface between
closed and open drains. The dam
could be placed anywhere along
the red line.
CREP Wetland Final Report August 31, 2009
60
Component Desired Range Design A
Wetland 0.5-2% of watershed 0.6% of watershed
Deep wetland < 25% of wetland area 0%
Buffer Less than 4:1 ratio
buffer : wetland
3.8:1 ratio
Dam As small as possible 1268 ft
Notes
Design 17A:
Wetland is 0.6%
of watershed
CREP Wetland Final Report August 31, 2009
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Site 18 Wetland Designs
Watershed of the Site 18 wetland
This site is located in Montgomery
County.
73% of the watershed is
estimated to be tile drained.
Site of wetland placement
The best locations for a wetland
are shown by the black proposed
dams. This location DOES appear
to be near the interface between
closed and open drains. The dam
could be placed anywhere along
the red line.
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62
Component Desired Range Design A
Wetland 0.5-2% of watershed 1.6% of watershed
Deep wetland < 25% of wetland area 0%
Buffer Less than 4:1 ratio
buffer : wetland
3.9:1 ratio
Dam As small as possible 2470 ft
Notes Dam is quite large,
and topography
makes wetland
design difficult.
Design 18A:
Wetland is 1.6%
of watershed
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63
Site 19 Wetland Designs
Watershed of the Site 19
wetland
This site is located in
Tippecanoe County.
93% of the watershed is
estimated to be tile
drained.
Site of wetland placement
The best locations for a wetland
are shown by the black proposed
dams. This location DOES NOT
appear to be near the interface
between closed and open drains.
The dam could be placed
anywhere along the red line.
There may be features preventing
the placement of wetlands. A site
visit may be necessary. Otherwise
this is a promising site.
CREP Wetland Final Report August 31, 2009
64
Design 19A:
Wetland is 0.7%
of watershed
Design 19B:
Wetland is 1.7%
of watershed
Design 19C:
Wetland is 2.4%
of watershed
Design19D:
Wetland is 3.3%
of watershed
CREP Wetland Final Report August 31, 2009
65
Component Desired Range Design A Design B
Wetland 0.5-2% of watershed 0.7% of watershed 1.7% of watershed
Deep wetland < 25% of wetland area 0% 0%
Buffer Less than 4:1 ratio
buffer : wetland
4.5:1 ratio 1.9:1 ratio
Dam As small as possible 383 ft 469 ft
Notes Channel would need to be
dug to empty wetland
Channel would need to be
dug to empty wetland
Component Desired Range Design C Design D
Wetland 0.5-2% of watershed 2.4% of watershed 3.3% of watershed
Deep wetland < 25% of wetland area 0% 22%
Buffer Less than 4:1 ratio
buffer : wetland
1.6:1 ratio 1.2:1 ratio
Dam As small as possible 532 ft 605 ft
Notes Channel would need to be
dug to empty wetland