Identification of Suitable Sites for Constructed Wetlands to Remove Nitrate

Transcription

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 1

2 Contents Introduction... 3 Criteria Used for Wetland Siting and Design... 5 Data Layers... 6 Locating Suitable Sites Sufficient Watershed Area from Tile-drained Land Wetland may be Located at the Interface between Closed and Open Drains Wetland is on Cropland Topography Lends itself to Wetland Placement Wetland Design Desired Wetland Size is 0.5-2% of its Watershed Area No More than 25% of the Wetland is Greater than Three Feet Deep The Surrounding Buffer Must Extend Four Feet above Wetland Surface, and Should Not Exceed Four Times the Size of the Wetland An Example Wetland Design (Site 8) Applying Wetland Design Criteria to Wetland Designs Nitrate Removal Estimation Conclusions References Appendix I. Locations where Suitable Wetlands are Designed II. Wetland Design Characteristics and Nitrate Removal Efficiencies III. Wetland Designs at Each Site

3 CREP Wetland Final Report August 31, 2009 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 losses in the form of nitrate. The 2008 EPA action plan calls for a reduction of the hypoxic zone to about thirty percent of its five-year running average by 2015 (Gulf Hypoxia Action Plan, 2008) ). Such a reduction will require significant nutrient load reductions from large contributing areas throughout the Midwest. 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 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, which ensures that these wetlands intercept large flows and maximize nitrate reduction in the landscape. This is the concept that t 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 at least 500 acres, to maximize nitrate removal, (Photo from ) 3

4 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 ) used for the GIS analysis. 4

5 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 ( acres of tiledrained 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 5

6 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, ) 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 Cropland Tile drained land (estimate) National Land Cover Dataset (NLCD), selecting the field cultivated crops From SSURGO soils and Cropland (poorly, very poorly, and somewhat poorly drained cropland) Hydric soils Soil Survey Geographic (SSURGO) Database Orthophotos Indiana Framework Data, streamed by University of Indiana locating different wetland sites Used for locating suitable sites for wetland placement and also to approximate tile-drained land in the landscape Used to locate sites that drain a large watershed of tile-drained land To give a general idea of areas that were formerly wetland Used for visualization of sites and determination of locations where closed drains empty into open ones 6

7 Figure 3: Data layers used in the identification of suitable locations for placement of constructed wetlands in the 8-digit watershed. 7

8 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 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. 8

9 (a): Step (1) (b): Step (2) Figure 4: Determining locations that have sufficient watershed area from tile drained land. (a) locations with large ( 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. (c): Step (3) 9

10 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. 10

11 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. Dam location 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. 11

12 Table 2: Ranking Cropland Fields for Wetland Suitability Wetland Suitability Qualitative Definition Ranking 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. 12

13 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). 13

14 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% 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). 14

15 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). Lowest contour would not make large enough wetland Dam (used to create the polygons) Deep wetland (>3 feet deep) Wetland (usual water level) This is the highest contour for the buffer with this particular dam, because it intersects the dam on both sides of the wetland outlet Buffer (4 feet above wetland) 1-foot contours Orthophotos Locations with sufficient watershed area 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. 15

16 Smallest Small Medium Large 0.4% 0.8% 1.2% 1.3% 4 acres 8 acres 11 acres 12 acres 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% 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 2:1 ratio 2:1 ratio 2:1 ratio 4:1 ratio buffer : wetland Dam As small as possible 1200 ft 950 ft 825 ft 775 ft Notes 16

17 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 (m 2 ) K nitrate = nitrate removal rate constant (1/month) We used in winter and -5.7 in summer y = depth of the water in wetland (m) n = porosity of wetland ( ) We used 0.70 Q = inflow (m 3 /month) 17

18 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 Nitrate Concentration (mg/l) Ditch Flow (cm) Month Figure 11: Nitrate concentration and flow data from Hoagland Ditch used in nitrate removal estimates for each wetland design. 18

19 Annual Percent Nitrate Removal (%) Wetland Design 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 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. 19

20 Table 4: Estimated monthly nitrate inflow and outflow concentrations for each wetland design. Inflow Wetland Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 01a a a b a a a a b a b c d a a b c d e a b c a a a b a a a a a b c d

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. 21

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: 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: 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 ( ). 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): USDA, Conversation Reserve Enhancement Program: Iowa enhancement program. Available at 22

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. 23

24 II. Wetland No. Wetland Design Characteristics and Nitrate Removal Efficiencies Watershed Wetland Buffer Deep Dam Average Depth acres acres acres acres ft ft Wetland % of Watershed Buffer: Wetlan ratio Deep Wetland % of Wetland NO 3 Removal 01a a a b a a a a b a b c d a a b c d e a b c a a a b a a a a a b c % NO 3 removal 19d

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. 25

26 Design 1A: Wetland is 1.3% Component Desired Range Design A Wetland 0.5-2% 1.3% Deep wetland < 25% of wetland area 13% Buffer Less than 4:1 ratio 2.3:1 ratio buffer : wetland Dam As small as possible 500 ft Notes Satisfies all desired criteria 26

27 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. 27

28 Design 2A: Wetland is 1.6% Component Desired Range Design A Wetland 0.5-2% 1.6% Deep wetland < 25% of wetland area 0% Buffer Less than 4:1 ratio 4.3:1 ratio buffer : wetland Dam As small as possible 1650 ft Notes Buffer is a bit large, and dam is fairly long. 28

29 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. 29

30 Design 3A: Wetland is 0.58% Design 3B: Wetland is 0.40% Component Desired Range Design A Design B Wetland 0.5-2% 0.58% 0.40% Deep wetland < 25% of wetland area 36% 35% Buffer Less than 4:1 ratio 3.4:1 ratio 4.1:1 ratio buffer : wetland 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 30

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. 31

32 Design 4A: Wetland is 1.9% Component Desired Range Design A Wetland 0.5-2% 1.9% Deep wetland < 25% of wetland area 0% Buffer Less than 4:1 ratio 1.9:1 ratio buffer : wetland Dam As small as possible 508 ft Notes This site appears to be quite suitable for wetland placement 32

33 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. 33

34 Design 5A: Wetland is 1.1% Component Desired Range Design A Wetland 0.5-2% 1.1% Deep wetland < 25% of wetland area 0% Buffer Less than 4:1 ratio 3:1 ratio buffer : wetland Dam As small as possible 550 ft Notes This site appears to be quite suitable for wetland placement 34

35 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. 35

36 Design 6A: Wetland is 1.9% Component Desired Range Design A Wetland 0.5-2% 1.9% Deep wetland < 25% of wetland area 0% Buffer Less than 4:1 ratio 5.2:1 ratio buffer : wetland Dam As small as possible 835 ft Notes The buffer is larger than desired 36

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. 37

38 Design 7A: Wetland is 0.83% Design 7B: Wetland is 2.8% Component Desired Range Design A Design B Wetland 0.5-2% 0.83% 2.8% Deep wetland < 25% of wetland area 0% 0% Buffer Less than 4:1 ratio 3.2:1 ratio 2.7:1 ratio buffer : wetland Dam As small as possible 1381 ft 1688 ft Notes Long dam Long dam, wetland may be larger than desired 38

39 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. 39

40 Design 8A: Wetland is 1.3% Design 8B: Wetland is 1.2% Design 8C: Wetland is 0.84% Design 8D: Wetland is 0.42% 40

41 Component Desired Range Design A Design B Wetland 0.5-2% 1.3% 1.2% Deep wetland < 25% of wetland area 22% 14% Buffer Less than 4:1 ratio 2.4:1 ratio 2.1:1 ratio buffer : wetland Dam As small as possible 1182 ft 946 ft Notes Component Desired Range Design C Design D Wetland 0.5-2% 0.84% 0.42% Deep wetland < 25% of wetland area 2% 0% Buffer Less than 4:1 ratio 2.3:1 ratio 3.9:1 ratio buffer : wetland Dam As small as possible 825 ft 775 ft Notes Wetland is smaller than desired 41

42 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. 42

43 Design 9A: Wetland is 1.1% Component Desired Range Design A Wetland 0.5-2% 1.1% Deep wetland < 25% of wetland area 0% Buffer Less than 4:1 ratio 5.5:1 ratio buffer : wetland Dam As small as possible 1212 ft Notes The buffer is larger than desired 43

44 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. 44

45 Design 10A: Wetland is 3.1% Design 10B: Wetland is 2.1% Design 10C: Wetland is 1.5% Design10D: Wetland is 1.0% 45

46 Design 10E: Wetland is 0.6% Component Desired Range Design A Design B Wetland 0.5-2% 3.1% 2.1% Deep wetland < 25% of wetland area 31% 27% Buffer Less than 4:1 ratio 1.6:1 ratio 2.3:1 ratio buffer : wetland 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% 1.5% 1.0% 0.6% Deep wetland < 25% of wetland area 12% 0% 0% Buffer Less than 4:1 ratio 2.7:1 ratio 3.2:1 ratio 4.6:1 ratio buffer : wetland Dam As small as possible 1045 ft 967 ft 895 ft Notes Buffer is larger than desired 46

47 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. 47

48 Design 11A: Wetland is 0.9% Design 11B: Wetland is 2.2% Design 11C: Wetland is 1.5% Component Desired Range Design A Design B Design C Wetland 0.5-2% 0.9% 2.2% 1.5% Deep wetland < 25% of wetland area 0% 20% 11% Buffer Less than 4:1 ratio 4.4:1 ratio 3.5:1 ratio 3.7:1 ratio buffer : wetland Dam As small as possible 752 ft 925 ft 814 ft Notes Buffer is larger than desired 48

49 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. 49

50 Design 12 A: Wetland is 3.5% Component Desired Range Design A Wetland 0.5-2% 3.5% Deep wetland < 25% of wetland area 0% Buffer Less than 4:1 ratio 3.9:1 ratio buffer : wetland Dam As small as possible 600 ft Notes Wetland is larger than desired 50

51 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. 51

52 Design 13 A: Wetland is 1.1% Component Desired Range Design A Wetland 0.5-2% 1.1% Deep wetland < 25% of wetland area 0% Buffer Less than 4:1 ratio 4.2:1 ratio buffer : wetland 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. 52

53 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. 53

54 Design 14A: Wetland is 0.8% Design 14B: Wetland is 0.5% Component Desired Range Design A Design B Wetland 0.5-2% 0.8% 0.5% Deep wetland < 25% of wetland area 0% 20% Buffer Less than 4:1 ratio 3.3:1 ratio 4.7:1 ratio buffer : wetland Dam As small as possible 814 ft 726 ft Notes Buffer is a bit large 54

55 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. 55

56 Design 15A: Wetland is 3.9% Component Desired Range Design A Wetland 0.5-2% 3.9% Deep wetland < 25% of wetland area 0% Buffer Less than 4:1 ratio 3.7:1 ratio buffer : wetland Dam As small as possible 2146 ft Notes Wetland is much larger than desired, and dam is quite large 56

57 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. 57

58 Design 16A: Wetland is 0.8% Component Desired Range Design A Wetland 0.5-2% 0.8% Deep wetland < 25% of wetland area 0% Buffer Less than 4:1 ratio 4.1:1 ratio buffer : wetland Dam As small as possible 647 ft Notes 58

59 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. 59

60 Design 17A: Wetland is 0.6% Component Desired Range Design A Wetland 0.5-2% 0.6% Deep wetland < 25% of wetland area 0% Buffer Less than 4:1 ratio 3.8:1 ratio buffer : wetland Dam As small as possible 1268 ft Notes 60

61 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. 61

62 Design 18A: Wetland is 1.6% Component Desired Range Design A Wetland 0.5-2% 1.6% Deep wetland < 25% of wetland area 0% Buffer Less than 4:1 ratio 3.9:1 ratio buffer : wetland Dam As small as possible 2470 ft Notes Dam is quite large, and topography makes wetland design difficult. 62

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. 63

64 Design 19A: Wetland is 0.7% Design 19B: Wetland is 1.7% Design 19C: Wetland is 2.4% Design19D: Wetland is 3.3% 64

65 Component Desired Range Design A Design B Wetland 0.5-2% 0.7% 1.7% Deep wetland < 25% of wetland area 0% 0% Buffer Less than 4:1 ratio 4.5:1 ratio 1.9:1 ratio buffer : wetland 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% 2.4% 3.3% Deep wetland < 25% of wetland area 0% 22% Buffer Less than 4:1 ratio 1.6:1 ratio 1.2:1 ratio buffer : wetland Dam As small as possible 532 ft 605 ft Notes Channel would need to be dug to empty wetland 65