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Development of Remote Sensing Techniques
This project tested remote sensing techniques for mapping agricultural drainage tiles in the Prairie Pothole Region of Iowa. Optimal conditions required over 4 inches of rainfall accumulation over 10 days followed by imagery 3-4 days later, when tile drainage effects would be visible. Completely mapping a multi-county area could take 2-5 years due to variability in rainfall patterns and aircraft availability. A photo interpretation guide was created to identify and map tile patterns.
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Development of Remote Sensing Techniques
- 1. Development of RemoteSensing Techniques to Map Drainage Tiles in the Prairie Pothole Region of Iowa Jim Giglierano Wisconsin Dept of Administration jim.giglierano@wi.gov
- 2. Final Contractor Report:Development of Remote Sensing Technologies to Characterize Drained (Farmed) Wetlands in the Prairie Pothole Region of Iowa EPA WPDG CD97731601 James D Giglierano (principal investigator), Emily Milton, Ligia de Oliveira Serrano, Amy Logan, Robin McNeeley, Kevin Kane - Iowa State University Sherry Torres, Xiaodan Chen - University of Iowa Michelle Fields, Greene County Drainage Clerk/GIS Chris Ensminger, Pete Kollasch, Matt Swanson, Calvin Wolter, Andy Asell - Iowa Department of Natural Resources Aerial Contractors: Aerial Services, Inc. and GeoVantage, Inc. December 20, 2015 IOWA STATE UNIVERSITY, GIS SUPPORT AND RESEARCH FACILITY IOWA GEOLOGICAL AND WATER SURVEY, IOWA DNR US EPA REGION 7, WETLAND PROGRAM DEVELOPMENT GRANT
- 6. Water table undernormal conditions Water table after heavy rainfall
- 7. Color infrared ortho-photoacquired on 4/29/2007, 3 days after 3+” rain.
- 8. Previous research byNaz and Bowling (2008) in central Illinois “tiles were visible after rainfall events greater than 1 inch in 24 hours. The optimum time for flights was 2-3 days after such events, in the spring season when the ground is most free from vegetation and residue cover.”
- 9. Locations of projecttest areas in Greene, Wright and Hamilton Counties, Iowa.
- 10. Locations of smalltest sites
- 11. Wright County testarea repeatability test. April 29, 2007 CIR Ortho May 31, 2013 Color Ortho Tiles mapped from 2013 image
- 14. Lyons Creek testarea in Hamilton County, flown on 5/31/13
- 15. Lyons Creek testarea in Hamilton County, flown on 5/31/13
- 16. Close up viewof Lyons Creek test area in Hamilton County, image collected 5/31/13 by ASI, 4 days after 1.67” rainfall event, with a 10 day rainfall accumulation of 4.28”.
- 17. Aerial image collected4/20/13 over Greene County test area. Taken 2 days after a 1.82” rainfall event which meets the initial flight criteria > 1” rain, but <50% of tiles visible. Ten day rainfall total 2.6”. Ground not saturated enough for tiles to show up.
- 18. Aerial image collected5/31/13 over Greene County test area showing light and dark cloud shadow patterns. Plane flew under clouds one day after 1.56” rainfall to collect imagery. Ten day accumulation was 6.94” which was too wet.
- 19. Final aerial imagecollected 6/18/13 over Greene County test area. This flight was 3 days after a 1.74” rainfall event which should have met the original flight criteria of 3 days after 1” plus event. Ten day rainfall accumulation was only 2.29”. All the tiles visible from all three flights are shown in red on this slide.
- 20. Greene County testarea with imagery from 4/29/13. Comparison of mapped tile patterns with actual GPS locations of installed tiles. Overall, tile pattern and location are very similar. April 20, 2013 Color Ortho showing tile patterns. Mapped tile patterns. GPS locations of installed tiles from drainage contractor. Comparison of mapped tile patterns with GPS locations.
- 22. Basic Mapping Criteriafor Tile Mapping on the PPR 1. Tiles can be fully mapped with 7-10 day total rainfall accumulations of 4-8 inches and flights 3-5 days after the last significant rainfall. Conditions may also be good for 7-10 day total accumulations of 3-4 inches and flights 2-3 days after last significant rainfall over 1 inch. 2. Tiles can be partially mapped with 7-10 day total rainfall accumulations of 2-3 inches and flights 2-3 days after last significant rainfalls over 1 inch. 3. Tiles cannot be mapped with 7-10 day accumulations less than 2 inches, even with a 1 inch plus event and a flight 2-3 days afterward.
- 23. May 18th, 2014 10day accumulations
- 24. June 24th, 2014 10day accumulations
- 25. Figure 3.1a 2000-2015(up to July 1, 2015) rain gage data from the Algona, Iowa NWS COOP station in the northern part of the PPR. Daily rainfall totals were added up over 10 days. Chart shows very few 10 day accumulations over 4 inches each year, with some years having no events and some have 2-3 events. 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015
- 26. Figure 3.1b 2000-2015(up to July 1, 2015) rain gage data from the Webster City, Iowa NWS COOP station in the middle part of the PPR. Daily rainfall totals were added up over 10 days. Chart shows very few 10 day accumulations over 4 inches each year, with some years having no events and some have 2-3 events. 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015
- 27. Figure 3.1c 2000-2015(up to July 1, 2015) rain gage data from the Perry, Iowa NWS COOP station in the southern part of the PPR. Daily rainfall totals were added up over 10 days. Chart shows very few 10 day accumulations over 4 inches each year, with some years having no events and some have 2-3 events. 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015
- 29. Estimates for TileMapping the PPR Based on imagery costs of $50 per square mile for 30cm imagery 1. Worst case: five years to map entire PPR, double coverage of imagery, labor for mapping and contract administration, total of about $1.6M 2. Best case: three years, single coverage of imagery, labor for mapping and contract administration, total of about $800k
- 30. A PHOTO INTERPRETATIONMANUAL FOR MAPPING AGRICULTURAL DRAINAGE TILES EPA WPDG CD97731601 Emily Milton and Ligia de Oliveira Serrano Iowa State University GIS Support and Research Facility Sherry Torres, Xiaodan Chen and Jim Giglierano (principal investigator) Iowa Geological and Water Survey, Iowa Department of Natural Resources
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- 38. Close up imageshowing a pothole with a tile intake in the center (lighter orange pixels). Tile Intakes
- 39. Another close up imageshowing a pothole with a tile intake in the center (lighter orange pixels).
- 40. Close up image showing tile outletinto drainage ditch
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- 44. Development of RemoteSensing Techniques to Map Drainage Tiles in the Prairie Pothole Region of Iowa Previous research in the Midwest indicated that agricultural drainage tiles could be mapped through traditional remote sensing techniques. Photo- interpretation of color infrared aerial photographs could be used to map tiles 2 to 3 days after a 1 inch rainfall or more. This scenario was extensively tested between 2012 to 2015 in the Prairie Pothole Region (PPR) of Iowa by staff and students at the Iowa Geological and Water Survey and Iowa State University GIS Facility. Results from several flights over target areas in the PPR showed that optimal conditions there were more stringent, and required a 10 day rainfall accumulation of more than 4" in order to completely saturate the soil profile. After waiting 3 to 4 days for stream levels to recede, the effects of tile drainage became visible at the land surface and were easily photographed from the air with 1 meter or better color or color- infrared imagery. The chance of occurrence of these >4 inch rainfall periods in the spring is small in any one year for a particular target area. Arranging for aerial coverage in advance was not difficult, though planes were not be always available on one or two day notice when actual conditions were met. In addition, identifying where local soil moisture conditions were optimal was extremely challenging using rainfall accumulation databases and models available on the Internet from NOAA and university researchers. Overall, this effort showed that tile mapping projects are possible over a multi county area in the PPR, but 2 to 5 years may be required to fully cover all areas within the project area of interest due to local variations in rainfall patterns, aircraft availability and other unforeseen circumstances. A photo-interpretation guide for identifying and mapping tile patterns was also assembled during this project.
Editor's Notes
- #4 Prairie Pothole Region of Iowa (PPR), also known as the Des Moines Lobe based on glacial feature terminology. Represents the area of last glacial advance into the state. Topography is generally flat with poorly integrated drainage. Soils are mostly derived from weathered glacial till and outwash. Total area is about 12,000 square miles or 31,000 square kilometers.
- #5 Map showing estimated extent of tiling present in Iowa based on soil survey attributes. From Iowa Nutrient Reduction strategy.
- #7 Effects of tile on water table. (“Design of Subsurface Drains in Humid Areas,” 2005).
- #8 Color infrared ortho-photo acquired on 4/29/2007, 3 days after 3+” rain. Areas with tiles are lighter toned than surrounding soils due to removal of water from soil profile above tile. Image on the right shows mapped tiles in blue, with drainage district tile mains mapped in green. From Iowa statewide orthophoto program, 2007-2010, on the PPR.
- #10 Figure 1.5 Locations of project test areas in Greene, Wright and Hamilton Counties, Iowa. Greene County test area chosen for availability of GPS locations of installed tiles. Wright County area chosen based on availability of 2007 imagery showing extensive tiling. Lyons Creek in Hamilton County chosen based on DNR water quality testing project, and as a backup site because of difficulty collecting imagery over Greene County in 2012 and 2013. Wright and Lyons Creek were successfully flown on 5/31/13 with imagery showing extensive tile patterns. Greene County flown a total of three times, collecting imagery but were unable to completely map tiles. Area was either too dry or too wet.
- #11 Figure 1.12 Map of small test sites selected to test tile mapping methodologies developed in the first half of the project. These sites were selected in order to match Iowa DNR water quality project sites. It was hoped that these would provide some background information on tiling around the testing sites. Unfortunately, only six of the eight sites were flown, and little useable imagery was gathered and could be used for tile mapping. The Ellsworth, Beaver, Gowrie, and Twin Lakes sites were flown but in all cases the soils conditions were too dry for tiles to be completely visible, and therefore mappable. Several flights were after >1” rain events, but generally 10 day accumulations were less that 3”.
- #12 Wright County test area repeatability test. On left color infrared photo taken on 4/29/07 showing extensive light and dark tile patterns, Flown 3 days after 1.13” rain with a 10 day accumulation of 4.4”. Middle image taken 5/31/13 by ASI, 4 days after 1.67” rain and ten day accumulation of 4.28”. Tiles appear in same place on two both dates, except for newly installed tiles. Dark areas on 2013 imagery are cloud shadows. Plane had to fly underneath clouds to get imagery. Map on right shows extent of mapped tiles as red lines. Compared to Greene County test area on previous slide, 75-100% of tiles present were mapped.
- #13 1.7b Close up view of area in Figure 1.7a, better showing lighter pattern of tiles (soil profile drying out) against darker field pattern (wetter soils). Some fields are nearly completely dry which makes it difficult to see their extensive tiling patterns. Heavier residues left on fields in middle image also make interpretation more difficult. Linear patterns of tillage, residue and harvesting all potentially confuse linear tile patterns. Overall, there was little additional benefit from using color infrared imagery over plain color RGB imagery.
- #14 1.7b Close up view of area in Figure 1.7a, better showing lighter pattern of tiles (soil profile drying out) against darker field pattern (wetter soils). Some fields are nearly completely dry which makes it difficult to see their extensive tiling patterns. Heavier residues left on fields in middle image also make interpretation more difficult. Linear patterns of tillage, residue and harvesting all potentially confuse linear tile patterns. Overall, there was little additional benefit from using color infrared imagery over plain color RGB imagery.
- #15 Color imagery collected over the Lyons Creek test area in Hamilton County on 5/31/13 by ASI. This was the same day as the flights over Wright test area and Greene test area. Rainfall conditions similar to Wright test area; 4 days after 1.67” event, with 10 day accumulation of 4.28”. Extensive cloud shadows are evident on this set of imagery, making interpretation difficult but not impossible.
- #16 Figure 1.8b Mapped tiles in red over 5/31/13 imagery for Lyons Creek test area in Hamilton County. This map reveals different tiling patterns than the Wright County test area shown in Figure 1.6a and b. In this area there are less parallel tile patterns, and more irregular and random connections between potholes.
- #17 Close up view of Lyons Creek test area in Hamilton County, image collected 5/31/13 by ASI, 4 days after 1.67” rainfall event, with a 10 day rainfall accumulation of 4.28”. Many of the potholes are still flooded from the heavy rainfall, but with more tiles visible than the Greene Co. areas flown on same day. Image on the right has tile lines mapped in red, and locations of tile intakes represented by red triangles. Red, yellow or white intakes are sometimes visible as one or two bright pixels on the 30 cm resolution imagery flown by ASI. They can be observed and mapped by close inspection of potholes and ditches. One meter Geovantage and NAIP imagery was too coarse to see tile intakes.
- #18 Aerial image collected 4/20/13 over Greene County test area by Geovantage, Inc. The image was taken 2 days after a 1.82” rainfall event which meets the initial flight criteria > 1” rain, but less than 50% of tiles present were actually visible. Ten day rainfall total was only 2.6”. Ground wasn’t saturated enough for tiles to show distinctive drying patterns.
- #19 Aerial image collected 5/31/13 over Greene County test area by ASI, showing light and dark cloud shadow patterns. Plane flew under clouds one day after 1.56” rainfall to collect imagery. Ten day accumulation was 6.94” which combined with a quick flight one day after the 1.56” rainfall, produced imagery with too wet ground conditions. Most low lying areas were flooded and less than 50% of tiles present were visible. It is possible that if the imagery was taken a little later, 3 or 4 days after the last event, there would have been less flooding and more tiles would have been visible.
- #20 Final aerial image collected 6/18/13 over Greene County test area by ASI. This flight was 3 days after a 1.74” rainfall event which should have met the original flight criteria of -3 days after 1” plus event. Later analysis showed the ten day rainfall accumulation was only 2.29”, indicating that conditions were too dry again. All the tiles visible from all three flights are shown in red on this slide.
- #21 Greene County test area with Geovantage imagery from 4/29/13. Comparison of mapped tile patterns with actual GPS locations of installed tiles. Overall, tile pattern and location are very similar. Rotated 90 degrees, north to right.
- #29 Table 2 - Compilation of number of >4 inch accumulation “events” over 10 days from 2000-2015 for three rain gage sites on the PPR. (See Figures 3.1a, b and c for graph of ten day accumulations for each site). These rain gage records were chosen to represent northern PPR (Algona), central (Webster City) and southern PPR (Perry). Green indicates “wet” years and tan being “dry” years. Note - this project was started in 2012, the year of the flash drought over much of Iowa. An examination of 16 years of daily rainfall from 2000-2015 (Table 2) from three sites on the PPR (Algona, Webster City and Perry) can be found in figures 3.1a, b and c. These figures show graphs of the daily rainfall for each station. By counting up the >4 inch 10-day accumulation “events” between April and July, there are a total of 36 events with 10-day rainfall accumulations over 4 inches, with a maximum of 6 events in one year (2013) and 6 years with one or no events (very dry years). Table 2 shows that there are patterns of wet years and dry years grouped together. There were several times during this project when it wasn’t feasible to get the aircraft over the target area two days after the last heavy rainfall, either due to clouds or other technical problems. Implications for a systematic mapping program over the PPR include the need for a multiyear program, maybe as many as four to five years to completely cover the PPR. A one or two year dry period would extend the time needed for completion.
- #32 Figure 7: Parallel tiles usually cover a large extent of an individual field. In this image the tiles (N-S and E-W linear features) primarily parallel the field edges, but this doesn’t always have to be the case. The smaller, more closely spaced lighter toned lines at a slight angle to the field boundary are either tillage or harvesting patterns. Fall or spring tillage can leave a small ridge of built-up soils that dries out more than the surrounding soils. The other possibility is a greater accumulation of crop residue left by harvesting at a slight angle in the field.
- #33 Figure 8: Herringbone or fan shaped tile patterns usually cover wetter spots in fields, like potholes, and not usually cover the whole field as in this example.
- #34 Figure 10: Random tile patterns usually are singular linear patterns that connect wet spots and potholes, or follow natural drainage within fields. Older tiling systems, especially the original drainage district mains installed in the late 19th and early 20th centuries follow this pattern.
- #35 Figure 11: Color infrared aerial imagery showing examples of at least three tiling patterns in one area: random, herringbone and parallel.
- #36 Figure 13: Color image taken in fall showing newly installed tiles. Dark linear patterns of disturbed soil on background of lighter toned crop residue. Note harvest pattern at slight angle to field boundaries.
- #37 Figure 13: Color aerial imagery taken in mid-spring showing early crops or weeds starting to grow above tiles. Also visible here is the north-south row crop pattern, made from lighter tone residue on darker toned soils. The lack of residues on the pothole at the lower left and upper right indicates heavy rains have earlier washed away the residues, and deposited some amount on the “beach” on the north and west sides of the potholes. Also visible at the top of the image are half circles in the field patterns. These indicate whether the tractor or combine turned for another pass of the field. If one is not sure if a linear feature is related to the presence of a tile, if the feature includes these half circles the pattern is probably not tile related. Figure 14: On this July 2014 NAIP image from Howard County, Iowa, tiles are indicated by both the tile drying patterns in the bare fields and crops growing over the tiles in the already planted corn fields. In this case, the wet spring weather permitted the corn to be planted, but inhibited the growth of corn away from the tiles. The soybean fields that were planted later and have yet to germinate, still show the tile drying patterns.
- #38 Figure 15: Black and white aerial imagery showing two harvesting pattern on top half of image. Corn crop harvested at slight angle to field boundary (a). Within the pothole (b), corn did not germinate so another crop, probably soybeans was planted and harvested at a different time and with different equipment. Lower half of image shows large squares around edge of field with diagonal fall tillage patterns within the squares (c). East-west harvest patterns still visible in spots beneath tilled areas.
- #39 Close up showing a pothole with a tile intake in the center (lighter orange pixels). While tiles were not visible on these images, because of the 30 cm pixel resolution, intakes were visible and could be mapped. Irregular squiggly double patterns are tractor tracks where fertilizer was applied. Tracks of tractor tend to avoid the intakes, so they can be used to indicate their presence.