Bathymetric and Sediment Survey of Elk City Reservoir, Montgomery County, Kansas Kansas Biological Survey Applied Science and Technology for Reservoir Assessment (ASTRA) Program Report 2010-01 (December 2011)
This work was funded by the Kansas Water Office through the State Water Plan Fund in support of the Reservoir Sustainability Initiative.
SUMMARY In May 2010, the Kansas Biological Survey (KBS) performed a bathymetric survey of Elk City Reservoir in Montgomery County, Kansas. The survey was carried out using acoustic echosounding apparatus linked to a global positioning system. The 2010 bathymetric survey by KBS indicated that the area of the conservation pool at 796 ft was 3515 acres with a capacity of 37,422 acre-feet. Comparison of the 2010 capacity to the 1992 Kansas Water Office data suggests that the capacity of the reservoir at the 796 ft. elevation pool has been reduced from 43,504 acre-feet to 37,422 acre feet, or 6082 acre-feet over 18 years (337.8 acre-feet per year), and a loss of 603 acres in area. Fifteen sediment cores were extracted from the lake to determine accumulated sediment thickness at locations distributed across the reservoir. Sediment samples were taken from the top six inches of each core and analyzed for particle size distributions. Bulk density (g/cm 3 ) of the sediment was computed for samples from the midpoint of each core. Summary Data: Bathymetric Survey: Dates of survey: November 10, 2009 May 28, 2010 Water elevation on date(s) of survey: (see text) Reservoir Statistics: Elevation of pool on reference date (NAIP photography, 2003) Area at 796 conservation pool: Volume at 796 conservation pool: Maximum depth at 796 conservation pool: 796.0 ft. 3515 acres 37,422 acre-feet 35 ft. Year constructed (gates closed): 1966 Datums UTM Zone: UTM datum: Vertical datum, all data: 15N NAD83 NGVD29 Sediment Survey: Date of sediment survey: June 23, 2010
TABLE OF CONTENTS SUMMARY...i TABLE OF CONTENTS...ii LIST OF FIGURES...iii LIST OF TABLES...v LAKE HISTORY AND PERTINENT INFORMATION... 1 BATHYMETRIC SURVEYING PROCEDURE Pre-survey preparation:... 3 Survey procedures:... 3 Establishment of lake level on survey date:... 4 Adjustment of lake levels, November 10, 2009... 4 Adjustment of lake levels, May 28, 2010 data... 5 Post-processing... 8 BATHYMETRIC SURVEY RESULTS Area-volume-elevation tables... 11 PRE-IMPOUNDMENT MAP... 14 Pre-impoundment area-volume-elevation tables... 18 Comparison of pre-impoundment and 2010 area-elevation curves... 21 RESERVOIR CROSS-SECTIONS... 22 SEDIMENT CORING AND SAMPLING Sediment coring and sampling procedures... 26 Sediment coring and sampling results... 27 ii
LIST OF FIGURES Figure 1. Elk CIty Reservoir and Dam... 1 Figure 2. Location of Elk City Reservoir in Montgomery County, Kansas.... 2 Figure 3. Water surface elevation of Elk City Reservoir on November 10, 2009... 6 Figure 4. Water surface elevation of Elk City Reservoir on May 28, 2010... 6 Figure 5. Bathymetric survey transects... 7 Figure 6. Reservoir depth map... 10 Figure 7. Cumulative area-elevation curve.... 13 Figure 8. Cumulative volume-elevation curve.... 13 Figure 9. Digital Raster Graphic (DRG) of Elk City Reservoir..... 15 Figure 10. Digitized preimpoundment contour lines map... 16 Figure 11. Preimpoundment digital elevation model.... 17 Figure 12. Raw and splined preimpoundment cumulative area-elevation curves... 19 Figure 13. Preimpoundment cumulative volume-elevation curve... 19 Figure 14. Changes in lake-bottom elevation, pre-impoundment to 2010... 20 Figure 15. Comparison of splined pre-impoundment and 2010 survey cumulative area-elevation curves... 21 Figure 16. Comparison of splined pre-impoundment and 2010 survey cumulative volume-elevation curves... 21 Figure 17. Siltation range lines map... 23 iii
Figure 18. Cross-sections along range lines: 18a. Cross-section along Rangeline 1... 24 18b. Cross-section along Rangeline 2... 24 18c. Cross-section along Rangeline 3... 25 18d. Cross-section along Rangeline 4... 25 Figure 19. Sediment coring sites in Elk City Reservoir..... 28 Figure 20. Map of sediment thickness in centimeters at coring sites... 29 Figure 21. Sediment particle size analysis... 31 Figure 22. Map of sediment particle size distributions at coring sites... 33 iv
LIST OF TABLES Table 1. Water surface elevations, November 10, 2009... 4 Table 2. Water surface elevation, May 28, 2010... 5 Table 3. Cumulative area in acres by tenth foot elevation increments... 11 Table 4. Table 5. Cumulative volume in acre-feet by tenth foot elevation increments... 12 Preimpoundment cumulative are and volume in acre-feet by one-foot elevation increments... 18 Table 6. Cross-section endpoint coordinates... 22 Table 7. Elk City Reservoir sediment coring site data... 30 Table 8. Elk City Reservoir sediment bulk density data... 32 v
Figure 1. Elk City Reservoir and Dam in Montgomery County, Kansas. The following text was obtained from the US Army Corps of Engineers website: http://www.swt.usace.army.mil/projects/civil/civil_projects.cfm?number=9 HISTORY AND DEVELOPMENT Elk City Lake was authorized by Congress in August 1941 for flood control purposes. The project is one unit of a six-lake system in the Verdigris River Basin. The five other lakes include the Fall River project on Fall River which was completed in 1949, the authorized Neodesha Lake on the Verdigris River, and Toronto Lake, completed in 1960, all in Kansas. Hulah Lake on the Caney River, completed in 1951, and Oologah Lake on the Verdigris River, completed in 1963 are located in Oklahoma. Authorization: Flood Control Act approved August 18, 1941; Public Law 77-228, Project Document HD 440, 76th Congress, 1st Session. Purpose: Flood control, water supply, water quality, recreation, and fish and wildlife. History of Construction: Construction began in February 1962 and the project was completed for full flood control operation in March 1966. Ultimate development was initiated on February 1, 1977; the conservation pool changed from elevation 792.0 to 796.0. A seasonal pool plan is used when requested by the state of Kansas. Type of Structure: The dam is an earthfill embankment 4,840 feet long and rises to a maximum height of 107 feet above the streambed. A rolled earthfill dike 21,712 feet long and rising to a maximum height of 43 feet is located along the right rim of the reservoir south of Table Mound. A rolled earth-fill levee, 13,436 feet long, in two parts, and rising to a maximum height of 29 feet, is located around Elk City, Kansas. 1
Montgomery County, Kansas Elk City Reservoir Parsons Elk City Cherryvale Independence Liberty Havana Dearing Tyro Coffeyville Caney Ü Miles 0 2 4 8 Figure 2. Location of Elk City Reservoir in Montgomery County, Kansas. 2
Reservoir Bathymetric (Depth) Surveying Procedures KBS operates a Biosonics DT-X echosounding system (www.biosonicsinc.com) with a 200 khz split-beam transducer and a 38-kHz single-beam transducer. Latitudelongitude information is provided by a global positioning system (GPS) that interfaces with the Biosonics system. ESRI s ArcGIS is used for on-lake navigation and positioning, with GPS data feeds provided by the Biosonics unit through a serial cable. Power is provided to the echosounding unit, command/navigation computer, and auxiliary monitor by means of a inverter and battery backup device that in turn draw power from the 12-volt boat battery. Pre-survey preparation: Geospatial reference data: Prior to conducting the survey, geospatial data of the target lake is acquired, including georeferenced National Agricultural Imagery Project (NAIP) photography. The lake boundary is digitized as a polygon shapefile from the FSA NAIP georeferenced aerial photography obtained online from the Data Access and Service Center (DASC). Prior to the lake survey, a series of transect lines are created as a shapefile in ArcGIS for guiding the boat during the survey. A transect spacing of 100 meters was used for the main body of the reservoir, narrowing this distance as needed in smaller coves and inlets. Survey procedures: Calibration (Temperature and ball check): After boat launch and initialization of the Biosonics system and command computer, system parameters are set in the Biosonics Visual Acquisition software. The temperature of the lake at 1-2 meters is taken with a research-grade metric electronic thermometer. This temperature, in degrees Celsius, is input to the Biosonics Visual Acquisition software to calculate the speed of sound in water at the given temperature at the given depth. Start range, end range, ping duration, and ping interval are also set at this time. A ball check is performed using a tungsten-carbide sphere supplied by Biosonics for this purpose. The ball is lowered to a known distance (1.0 meter) below the transducer faces. The position of the ball in the water column (distance from the transducer face to the ball) is clearly visible on the echogram. The echogram distance is compared to the known distance to assure that parameters are properly set and the system is operating correctly. On-lake survey procedures: Using the GPS Extension of ArcGIS, the GPS data feed from the GPS receiver via the Biosonics echosounder, and the pre-planned transect pattern, the location of the boat on the lake in real-time is shown on the command/navigation computer screen. Transducer face depth on all dates is 0.25 meters below the water surface. A perimeter run is initially performed to set the immediate off-shore water depth, with this survey track typically placed 50 meters from shore, modified as necessary during the survey if shallow water or other obstructions are encountered. Following the perimeter run, the cross-lake transects are then acquired. The transect pattern is maintained except when modified by obstructions in the lake (e.g., partially submerged trees) or shallow water and mudflats. Data are automatically logged in new files every half-hour (approximately 9000-ping files) by the Biosonics system. 3
Establishment Of Lake Level On Survey Dates: Reservoir shoreline perimeters were digitized off 2003 NAIP aerial photography, and the elevation of the reservoir on the date of aerial photography was used as the water surface elevation in all interpolations from point data to raster data. The water elevation on July 9, 2003 was 796 feet AMSL, NGVD29. Lake levels on the survey dates were obtained from the US Army Corps of Engineers web site for Elk City Reservoir (http://www.swt-wc.usace.army.mil/elkccharts.html) Adjustment of lake levels: November 10, 2009 data Bathymetric surveys were carried out on November 10, 2009 and May 28, 2010. On November 10, large amounts of water were flowing into the lake, causing the water level to rise during the day. Hourly water levels for November 10, 2009 for Elk City Reservoir were obtained from the US Army Corps of Engineers Tulsa District website. A line was fitted to the data to produce a regression equation predicting water elevation as a function of time. Since the Biosonics echosounder includes a time value with each depth measurement, we could then apply the regression equation to the Biosonics data to produce a predicted lake elevation value for each processed depth measurement. Table 1. Recorded and regression-predicted values for water surface elevation as a function of time, November 10, 2009 Time Recorded Elevation Predicted Elevation from equation Notes 8:00:00 801.04 801.04 9:00:00 801.06 801.05 10:00:00 801.07 801.07 Start survey 1045 11:00:00 801.08 801.08 12:00:00 801.09 801.09 13:00:00 801.10 801.10 14:00:00 801.11 801.11 15:00:00 801.12 801.13 16:00:00 801.14 801.14 17:00:00 801.16 801.15 End survey 1628 18:00:00 801.17 801.16 19:00:00 801.18 801.18 20:00:00 801.19 801.19 Regression equation for November 10, 2009 data: water elevation = 0.294287 (time) + 800.943 4
Adjustment of lake levels: May 28, 2010 data Due to water releases from the reservoir by the Corps of Engineers, the water surface elevation for the May 28, 2010 survey data decreased by 0.24 ft, from 797.08 ft at 0700 hours to 796.86 ft. at 2000 hours. As with the November data, a regression line was fitted to hourly data obtained from the Corps of Engineers Tulsa District website to produce a predicted lake elevation value for each processed depth measurement. Table 2. Recorded and regression-predicted values for water surface elevation as a function of time, May 28, 2010 Time Recorded Elevation Predicted Elevation from equation Notes 7:00:00 797.08 797.08 8:00:00 797.06 797.07 Start survey 0840 9:00:00 797.05 797.05 10:00:00 797.03 797.03 11:00:00 797.01 797.01 12:00:00 796.99 796.99 13:00:00 796.98 796.97 14:00:00 796.96 796.95 15:00:00 796.94 796.93 16:00:00 796.91 796.92 17:00:00 796.89 796.90 18:00:00 796.87 796.88 19:00:00 796.87 796.86 End survey 1840 20:00:00 796.86 796.84 Regression equation for May 28, 2010 data: water elevation = -0.44979 (time) + 797.216 5
801.25 801.20 Lake surface elevation (ft) 801.15 801.10 801.05 801.00 800.95 8:00 9:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00 20:00 Time Figure 3. Water surface elevation of Elk City Reservoir on November 10, 2009. 797.10 797.05 Lake surface elevation (ft) 797.00 796.95 796.90 796.85 796.80 796.75 8:00 9:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00 20:00 Time Figure 4. Water surface elevation of Elk City Reservoir on May 28, 2010. 6
Date of Survey 11/10/2009 5/28/2010 0 0.25 0.5 1 Miles Ü Figure 5. Bathymetric survey tracks, Elk City Reservoir. 7
Post-processing (Visual Bottom Typer) The Biosonics DT-X system produces data files in a proprietary DT4 file format containing acoustic and GPS data. To extract the bottom position from the acoustic data, each DT4 file is processed through the Biosonics Visual Bottom Typer (VBT) software. The processing algorithm is described as follows: The BioSonics, Inc. bottom tracker is an end_up" algorithm, in that it begins searching for the bottom echo portion of a ping from the last sample toward the first sample. The bottom tracker tracks the bottom echo by isolating the region(s) where the data exceeds a peak threshold for N consecutive samples, then drops below a surface threshold for M samples. Once a bottom echo has been identified, a bottom sampling window is used to find the next echo. The bottom echo is first isolated by user_defined threshold values that indicate (1) the lowest energy to include in the bottom echo (bottom detection threshold) and (2) the lowest energy to start looking for a bottom peak (peak threshold). The bottom detection threshold allows the user to filter out noise caused by a low data acquisition threshold. The peak threshold prevents the algorithm from identifying the small energy echoes (due to fish, sediment or plant life) as a bottom echo. (Biosonics Visual Bottom Typer User s Manual, Version 1.10, p. 70). Data is output as a comma-delimited (*.csv) text file. A set number of qualifying pings are averaged to produce a single report (for example, the output for ping 31 {when pings per report is 20} is the average of all values for pings 12-31). Standard analysis procedure for all 2008 and later data is to use the average of 5 pings to produce one output value. All raw *.csv files are merged into one master *.csv file using the shareware program File Append and Split Tool (FAST) by Boxer Software (Ver. 1.0, 2006). Post-processing (Excel) The master *.csv file created by the FAST utility is imported into Microsoft Excel. Excess header lines are deleted (each input CSV file has its own header), and the header file is edited to change the column headers #Ping to Ping and E1 to E11, characters that are not ingestable by ArcGIS. Entries with depth values of zero (0) are deleted, as are any entries with depth values less than the start range of the data acquisition parameter (0.49 meters or less) (indicating areas where the water was too shallow to record a depth reading). In Excel, depth adjustments are made. A new field Adj_Depth is created. The value for AdjDepth is calculated as AdjDepth = Depth + (Transducer Face Depth), where the Transducer Face Depth represents the depth of the transducer face below water level in meters (Typically, this value is 0.2 meters; however, if changes were made in the field, the correct level is taken from field notes and applied to the data). Depth in feet is also calculated as DepthFt = Adj_Depth * 3.28084. 8
These water depths are RELATIVE water depths that can vary from day-to-day based on the elevation of the water surface. In order to normalize all depth measurements to an absolute reference, water depths must be subtracted from an established value for the elevation of the water surface at the time of the bathymetric survey. Determination of water surface elevation has been described in an earlier section on establishment of lake levels. To set depths relative to lake elevation, two additional fields are added to the attribute table of the point shapefile: LakeElevM, the reference surface elevation (the elevation of the water surface on the day that the aerial photography from which the lake perimeter polygon was digitized)and Elev_Ft, the elevation of the water surface in feet above sea level (Elev_ft), computed by converting ElevM to elevation in feet (ElevM * 3.28084). Particularly for multi-day surveys, Adj_Depth and Depth_Ft should NOT be used for further analysis or interpolation. If water depth is desired, it should be produced by subtracting Elev_M or Elev_Ft from the reference elevation used for interpolation purposes (for federal reservoirs, the elevation of the water surface on the day that the aerial photography from which the lake perimeter polygon was digitized). Post-processing (ArcGIS): Ingest to ArcGIS is accomplished by using the Tools Add XY Data option. The projection information is specified at this time (WGS84). Point files are displayed as Event files, and are then exported as a shapefile (filename convention: ALLPOINTS_WGS84.shp). The pointfile is then reprojected to the UTM coordinate system of the appropriate zone (14 or 15) (filename convention ALLPOINTS_UTM.shp). Raster interpolation of the point data is performed using the same input data and the Topo to Raster option within the 3D Extension of ArcGIS. The elevation of the reservoir on the date of aerial photography used to create the perimeter/shoreline shapefile was used as the water surface elevation in all interpolations from point data to raster data. Contour line files are derived from the raster interpolation files using the ArcGIS command under 3D Analyst Raster Surface Contour. Area-elevation-volume tables are derived using an ArcGIS extension custom written for and available from the ASTRA Program. Summarized, the extension calculates the area and volume of the reservoir at 1/10-foot elevation increments from the raster data for a series of water surfaces beginning at the lowest elevation recorded and progressing upward in 1/10-foot elevation increments to the reference water surface. Cumulative volume is also computed in acre-feet. 9
Legend 0.00-2 2.01-4 4.01-6 6.01-8 8.01-10 10.01-12 12.01-14 14.01-16 16.01-18 18.01-20 20.01-22 22.01-24 24.01-26 26.01-28 28.01-30 30.01-32 32.01-34 34.01-36 36.01-38 0 0.3 0.6 1.2 Miles Ü Figure 6. Water depth in feet, Elk City Reservoir, based on 2003 NAIP water surface elevation of 796 ft AMSL NAVD29. 10
Table 3 Cumulative area in acres by tenth foot elevation increments Elevation (ft NGVD) 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 760 0 0 0 0 1 1 1 1 1 1 761 1 1 1 2 2 2 3 4 4 5 762 6 7 7 8 9 10 10 11 12 12 763 13 13 14 15 16 16 17 17 18 19 764 19 20 20 21 21 22 23 23 24 25 765 26 27 28 29 30 31 32 33 34 35 766 36 37 38 38 40 41 43 45 47 49 767 51 53 55 57 59 61 63 65 67 69 768 71 73 75 77 79 81 83 86 88 91 769 94 97 100 103 105 108 111 114 117 120 770 123 126 129 132 136 140 143 147 150 153 771 157 161 164 167 171 174 177 181 185 188 772 192 195 198 202 205 208 212 216 220 224 773 228 231 236 240 244 248 253 258 264 269 774 275 280 285 290 295 299 304 308 313 317 775 322 326 331 335 339 344 348 353 358 363 776 368 373 379 384 389 395 400 405 410 415 777 420 425 429 434 439 444 449 454 459 464 778 469 475 482 489 496 504 511 519 527 535 779 543 552 561 570 580 591 603 615 628 640 780 653 669 682 695 708 722 738 753 770 785 781 800 813 827 841 856 873 892 912 931 948 782 966 984 1004 1031 1053 1072 1089 1108 1128 1150 783 1170 1189 1208 1228 1249 1273 1298 1323 1348 1375 784 1403 1430 1455 1481 1503 1527 1552 1577 1599 1621 785 1642 1662 1683 1703 1722 1742 1762 1779 1795 1812 786 1828 1843 1858 1873 1889 1906 1923 1938 1953 1969 787 1984 1999 2015 2033 2051 2067 2084 2101 2118 2134 788 2150 2165 2181 2196 2211 2227 2242 2259 2275 2292 789 2309 2326 2342 2357 2372 2388 2405 2421 2438 2454 790 2471 2487 2505 2522 2539 2554 2570 2585 2600 2615 791 2629 2644 2659 2674 2689 2704 2719 2735 2751 2767 792 2784 2802 2821 2838 2857 2875 2894 2911 2928 2944 793 2961 2979 2997 3015 3033 3053 3074 3098 3122 3144 794 3165 3185 3205 3224 3241 3256 3272 3288 3304 3321 795 3337 3353 3368 3385 3402 3417 3433 3450 3468 3485 796 3515 11
Table 4 Cumulative volume in acre-feet by tenth foot elevation increments Elevation (ft NGVD) 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 760 0 0 0 0 0 0 0 0 1 1 761 1 1 1 1 1 2 2 2 2 3 762 3 4 5 6 6 7 8 9 11 12 763 13 14 16 17 19 20 22 24 25 27 764 29 31 33 35 37 39 41 44 46 49 765 51 54 57 59 62 65 68 72 75 78 766 82 85 89 93 97 101 105 109 114 119 767 124 129 134 140 146 152 158 164 171 177 768 184 192 199 207 214 222 231 239 248 257 769 266 275 285 295 306 316 327 339 350 362 770 374 386 399 412 426 440 454 468 483 498 771 514 530 546 563 579 597 614 632 650 669 772 688 707 727 747 768 788 809 831 853 875 773 897 920 944 967 992 1016 1041 1067 1093 1120 774 1147 1175 1203 1232 1261 1291 1321 1352 1383 1414 775 1446 1479 1511 1545 1579 1613 1647 1682 1718 1754 776 1791 1828 1865 1903 1942 1981 2021 2061 2102 2143 777 2185 2227 2270 2313 2357 2401 2446 2491 2537 2583 778 2630 2677 2725 2774 2823 2873 2924 2975 3027 3081 779 3134 3189 3245 3302 3359 3418 3477 3538 3601 3664 780 3729 3795 3862 3931 4001 4073 4146 4221 4297 4375 781 4454 4535 4617 4700 4785 4872 4960 5050 5143 5237 782 5332 5430 5529 5631 5736 5842 5950 6060 6172 6286 783 6402 6520 6640 6762 6886 7012 7140 7271 7405 7541 784 7680 7822 7966 8113 8263 8414 8568 8725 8884 9045 785 9208 9374 9541 9711 9882 10055 10231 10408 10587 10767 786 10949 11133 11318 11505 11693 11883 12074 12268 12462 12659 787 12856 13056 13256 13459 13663 13869 14077 14287 14498 14710 788 14925 15141 15358 15577 15798 16020 16243 16468 16695 16924 789 17154 17386 17620 17855 18091 18330 18570 18811 19054 19299 790 19545 19794 20043 20295 20548 20803 21059 21317 21577 21838 791 22100 22364 22629 22896 23164 23434 23706 23978 24253 24529 792 24807 25086 25368 25651 25936 26223 26511 26802 27094 27388 793 27683 27980 28280 28580 28883 29188 29494 29803 30114 30428 794 30743 31061 31381 31703 32026 32351 32678 33006 33336 33668 795 34001 34336 34672 35010 35350 35691 36034 36378 36724 37072 796 37422 12
4000 3500 3000 Cumulative Area (acres) 2500 2000 1500 1000 500 0 760 762 764 766 768 770 772 774 776 778 780 782 784 786 788 790 792 794 796 Elevation (feet) Figure 7. Cumulative area-elevation curve 40000 35000 Cumulative Volume (acre-feet) 30000 25000 20000 15000 10000 5000 0 760 762 764 766 768 770 772 774 776 778 780 782 784 786 788 790 792 794 796 Elevation (feet) Figure 8. Cumulative volume-elevation curve 13
PRE-IMPOUNDMENT MAP Caution should be exercised in drawing conclusions based on comparison between two maps of different scales, dates, and production methods. Pre-impoundment contour lines with a contour interval of ten feet (10 ) were digitized from a US Geological Survey georeferenced Digital Raster Graphic (DRG) based on 1:24,000 topographic map sheets. Contour lines were manually digitized to a polyline shapefile and attributed (Figure 9). All contour intervals at elevations 700 to 810 feet were digitized (every ten feet of vertical)(figure 10). The ArcGIS TopotoRaster tool was then used to generate a raster file (Digital Elevation Model) with a horizontal resolution of 10 meters (Figure 11). Area and volume were computed from the pre-impoundment DEM (Table 5; Figure 12; Figure 13). The pre-impoundment cumulative area-elevation curve exhibited a stair-step effect as a result of the 10-foot contour interval used to create the pre-impoundment digital elevation model (Figure 12, orange line). A cubic spline function was applied to the cumulative area-elevation curve, using the contour line intervals (e.g., 745, 750, 755, etc.) as input and splining to one-foot intervals to eliminate the stair-step effect (Figure 12, blue line). No spline function was applied to the cumulative volume-elevation curve data. Changes in lake bottom elevation between pre-impoundment and 2010 were computed by digitally subtracting the pre-impoundment digital elevation model from the 2010 digital elevation model. Negative numbers on the resulting output indicate 2010 elevation lower than pre-impoundment elevation (loss of material during the intervening period); positive numbers indicate 2010 lake bottom higher than pre-impoundment (accumulated material, or likely siltation) (Figure 14). As the contour interval is ten (10) feet, areas of ± 5 feet difference are not shown on the difference map. The difference map suggests that the greatest sedimentation has occurred in the former river channel, as might be expected; furthermore, the majority of the non-river channel silt accumulation has occurred in the upper part of the reservoir (Figure 14; orange and tan colors). 14
Legend Perimeter from 2003 NAIP 0 0.25 0.5 1 Miles Ü Figure 9. US Geological Survey 1:24.000 Digital Raster Graphic (DRG). 15
Legend Streams Contour lines Perimeter from 2003 NAIP 0 0.25 0.5 1 Miles Ü Figure 10. Pre-impoundment contours, Elk City Reservoir. Contours were digitized from a US Geological Survey 1:24.000 Digital Raster Graphic (DRG). 16
Elevation (Ft) 746.49-750 750.01-755 755.01-760 760.01-765 765.01-770 770.01-775 775.01-780 780.01-785 785.01-790 790.01-795 795.01-800 800.01-805 805.01-810 810.01-815 815.01-820 0 0.375 0.75 1.5 Miles Ü Figure 11. Digital elevation model (DEM) created from pre-impoundment contours. 17
Table 5 Cumulative pre-impoundment area and volume by one-foot elevation increments Elevation (ft NGVD) Splined pre-impoundment cumulative area (acres) Volume (acre-feet) 747 6 0 748 9 0 749 12 4 750 16 14 751 20 32 752 24 58 753 29 89 754 35 125 755 42 164 756 50 206 757 59 254 758 66 308 759 73 370 760 77 442 761 80 524 762 83 614 763 88 712 764 101 817 765 122 934 766 155 1062 767 199 1212 768 253 1396 769 317 1630 770 389 1943 771 468 2420 772 552 3011 773 638 3675 774 725 4401 775 810 5181 776 893 6016 777 976 6908 778 1065 7870 779 1166 8912 780 1283 10076 781 1421 11505 782 1573 13110 783 1736 14859 784 1902 16742 785 2066 18750 786 2223 20875 787 2375 23125 788 2525 25507 789 2676 28023 790 2832 30697 791 2995 33733 792 3164 36949 793 3338 40316 794 3515 43815 795 3693 47446 796 3830 51210 18
4000 3500 3000 Preimpoundment data (splined) Unsplined data Cumulative Area (acres) 2500 2000 1500 1000 500 0 745 750 755 760 765 770 775 780 785 790 795 Elevation (feet) Figure 12. Raw and splined pre-impoundment cumulative area-elevation curve 50000 45000 40000 Cumulative Volume (acre-feet) 35000 30000 25000 20000 15000 10000 5000 0 745 750 755 760 765 770 775 780 785 790 795 Elevation (feet) Figure 13. Pre-impoundment cumulative volume-elevation curve 19
Difference in feet -20.00 - -15-14.99 - -10-9.99 - -5-4.99 - +5 +5.01 - +10 +10.01 - +15 +15.01 - +20 +20.01 - +50 +0.01 - +5 Negative values indicate 2009 elevation lower than preimpoundment elevation; Positive values indicate 2009 lake bottom higher than preimpoundment elevation. Legend Pre-impoundment 796' contour Area of difference between 796' elevations 2003 NAIP 796' water elevation 0 0.25 0.5 1 Miles Ü Figure 14. Difference between pre-impoundment and 2010 reservoir bottom surface. Light blue area indicates lake in 2003 NAIP photography; red line indicates 796' perimeter computed from pre-impoundment DRG DEM; darker blue-tinted area indicates difference between two areas (below 796 ft preimpoundment, above 796 in 2010). 20
4000 3500 3000 Preimpoundment data (splined) 2010 data Cumulative Area (acres) 2500 2000 1500 1000 500 0 745 750 755 760 765 770 775 780 785 790 795 Elevation (feet) Figure 15. Comparison of splined pre-impoundment and 2010 survey cumulative areaelevation curve 50000 45000 40000 Preimpoundment data 2010 data Cumulative Volume (acre-feet) 35000 30000 25000 20000 15000 10000 5000 0 745 750 755 760 765 770 775 780 785 790 795 Elevation (feet) Figure 16. Comparison of pre-impoundment and 2010 survey cumulative volume-elevation curve 21
Reservoir Cross-sections: A scanned image of a coarse-scale blueprint map dated 1994 and titled Elk City Lake Sedimentation and Degradation Ranges was obtained by the Kansas Water Office from the US Army Corps of Engineers Tulsa District office (Figure 7). The scanned blueprint was georeferenced to the UTM-15N coordinates system using the road and section corners drawn on the map. Rangelines were digitized from the coarse-scale map, maintaining the original Corps rangeline numbering system. Only four (4) rangelines co-occurred with areas covered by this 2010 bathymetric survey. No formal rangeline endpoint coordinates were provided by either KWO or USACOE to KBS to aid in determining the location of the rangeline endpoints. Table 6. Cross-section endpoint Coordinates (UTM Zone 15) Line West Endpoint East Endpoint UTM X UTM Y UTM X UTM Y 1 251991 4129048 253754 4128802 2 251074 4128636 253222 4127610 3 250463 4127771 254932 4125231 4 248923 4126481 250278 4127711 Each line representing a shapefile was converted into a point shapefile with points at 10-meter intervals. The ArcGIS program Extract Values to Points was used to extract the elevation value for each point from the reservoir bottom elevation DEM previously described. Points were then imported to Excel for plotting as charts (Figure 18a - 9d). No data was extracted for the non-water areas outside the perimeter of the lake digitized from the 2003 NAIP photography; these values were set to 796 ft. AMSL, NGVD29. 22
1 2 4 3 0 0.25 0.5 1 Miles Ü Figure 17. Siltation range lines in Elk City Reservoir. 23
Range Line 1 800 795 790 Elevation (feet) 785 780 775 770 765 760 0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 Meters along cross-section, west-east Figure 18a. Cross-section along Rangeline 1. Reservoir reference elevation = 796.0 ft. Range Line 2 800 795 790 Elevation (feet) 785 780 775 770 765 760 0 250 500 750 1000 1250 1500 1750 2000 2250 Meters along cross-section, west-east Figure 18b. Cross-section along Rangeline 2. Reservoir reference elevation = 796.0 ft. 24
Range Line 3 800 795 790 Elevation (feet) 785 780 775 770 765 760 0 250 500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000 Meters along cross-section, west-east Figure 18c. Cross-section along Rangeline 3. Reservoir reference elevation = 796.0 ft. Range Line 4 800 795 790 Elevation (feet) 785 780 775 770 765 760 0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 Meters along cross-section, west-east Figure 18d. Cross-section along Rangeline 4. Reservoir reference elevation = 796.0 ft. 25
SEDIMENT CORING/SAMPLING PROCEDURES KBS operates a Specialty Devices Inc. sediment vibracorer mounted on a dedicated 24 pontoon boat. The vibracorer uses 3 diameter aluminum thinwall pipe in userspecified lengths. The system uses an 24-v electric motor with counter-rotating weights in the vibracorer head unit to create a highfrequency vibration in the pipe, allowing the pipe to penetrate sediments and substrate as it is lowered into the lake using a winch. Once the open end of the core pipe has penetrated to the substrate, the unit is turned off and the unit is raised to the surface using the winch. At the surface, the pipe containing the sediment core is disconnected from the vibracore head and the sediment extruded from the pipe and measured. KBS vibe-core system. At each site, determined using GPS, the core boat is anchored and the vibracore system used to extract a sediment core down to and including the upper several inches of pre-impoundment soil (substrate). The location of each core site is recorded using a GPS. Cores are carefully extruded from the core pipe, and the interface between sediment and substrate identified. Typically, this identification is relatively easy, with the interface being identifiable by changes in material density and color, and the presence of roots or sticks in the substrate. The top 15 cm of sediment are collected and sealed in a sampling container. The samples are then shipped to the Kansas State University Soil Testing Laboratory (Manhattan, KS), for texture and other analyses. To assess bulk density, the syringe method described by Hilton et al (1986) 1 was used, employing a cutoff 35-ml syringe inserted into the exposed core to extract a 15-cc sample of the sediment. Where permitted by core length, samples were taken from the lower, midpoint, and upper parts of the core (e.g., 10-cm above sediment-substrate interface; midpoint of core length; 10 cm below sediment top). Shorter cores (30-50 cm) were sampled only at the upper and lower end, and very short (length < 20 cm) were sampled only at the midpoint. Samples were ejected from the syringe using the plunger and sealed in sample canisters. In the lab, samples were weighed, dried at 100ºC for 48 hours, and weighed again. At several sites, a bulk density sample was taken from the substrate as well for comparison to sediment bulk density. 1 J. Hilton, J., Lishman, P., and Millington, A. 1986. A comparison of some rapid techniques for the measurement of density in soft sediments. Sedimentology (33):777-781. 26
Sediment Coring and Sampling Results: Fifteen coring sites were distributed across the reservoir (Figure 19). An effort was made to avoid the original stream channel, which would have likely yielded higher sediment thicknesses not representative of the overall reservoir bottom sediment thickness. Highest sediment thicknesses were recorded at two areas near the inflow of the Elk River at the western side of the reservoir (sites ELK-4 and ELK-6, 100 cm each), and the two sites closest to the dam (ELK-12 and ELK-13). Sediment thicknesses in the main body of the reservoir were low, ranging from 0 cm (ELK-14) to 82 cm (ELK-15) (Figure 20). Texture analysis indicated that sediment in the reservoir is predominately clay, with a secondary fraction of silt (Table 7; Figure 21). Again, typical of large reservoirs sampled in this area, silt predominates in the samples taken from the upper (inflow) end, and clay predominates in the samples taken from the lower (dam) end. Sand is not a significant constituent in the majority of samples, with the exception of site ELK-6, near the inflow of the Elk River (Figure 22). 27
ELK-12 ELK-11 ELK-13 ELK-5 ELK-6 ELK-4 ELK-7 ELK-8 ELK-10 ELK-9 ELK-14 ELK-15 ELK-1 ELK-3 ELK-2 0 0.25 0.5 1 Miles Ü Figure 19. Location of coring sites in Elk City Reservoir. 28
240 44 125 n.d. 100 100 10 10 20 10 0 82 33 27 44 0 0.25 0.5 1 Miles Ü Figure 20. Sediment thickness, in centimeters, at coring sites in Elk City Reservoir. (n.d. = No sediment thickness recorded for site ELK-5 - indefinite bottom) 29
Table 7 Elk City Reservoir Sediment Coring Site Data Code UTMX UTMY Sediment Thickness (cm) Mean Bulk Density Sand % Silt % Clay % ELK-1 253125 4126258 33 0.65 0 28 72 ELK-2 252594 4125590 44 0.73 0 38 62 ELK-3 250720 4125701 27 0.63 0 34 66 ELK-4 250145 4126476 100 0.93 0 52 48 ELK-5 249294 4126821 (b) 1.15 0 66 34 ELK-6 249974 4127435 100 1.40 8 68 24 ELK-7 250931 4127521 10 0.68 0 50 50 ELK-8 250921 4126814 10 (a) 0 44 56 ELK-9 251685 4126718 10 (a) 0 34 66 ELK-10 251699 4127657 20 0.57 0 40 60 ELK-11 251499 4128433 44 0.61 0 28 72 ELK-12 252788 4128937 240 0.54 0 24 76 ELK-13 253083 4128467 125 0.58 0 26 74 ELK-14 252520 4127945 0 (a) 0 0 0 ELK-15 252778 4127142 82 0.68 2 32 66 Notes: a. Bulk density was not collected for samples due to insufficient core size. b. Sediment thickness indeterminate; substrate-sediment interface indeterminate. 30
Elk City Reservoir 2010 Sediment Particle Size Analysis 100% 90% 80% 70% 60% 50% CLAY SILT 40% SAND 30% 20% 10% 0% ELK-1 ELK-2 ELK-3 ELK-4 ELK-5 ELK-6 ELK-7 ELK-8 ELK-9 ELK-10 ELK-11 ELK-12 ELK-13 ELK-14 ELK-15 Sample Site Figure 21. Sediment particle size analysis. 31
Table 8 Elk City Reservoir Sediment Bulk Density Data Sample Site Position Volume (cc) Density (g/cc) Mean density, (g/cm 3 ) (excluding substrate) ELK-1 mid-core 15 0.65 0.65 substrate 15 1.33 ELK-2 top 15 0.59 0.73 bottom 15 0.87 ELK-3 mid-core 15 0.63 0.63 ELK-4 top 15 1.00 0.93 middle 15 0.93 bottom 15 0.87 substrate 15 1.63 ELK-5 top 15 1.15 1.15 bottom 15 1.15 ELK-6 top 15 1.27 1.40 mid-core 15 1.47 bottom 15 1.47 substrate 15 1.42 ELK-7 mid-core 15 0.68 0.68 ELK-8* ELK-9* ELK-10 mid-core 15 0.57 0.57 substrate 15 1.50 ELK-11 top 15 0.53 0.61 bottom 15 0.68 ELK-12 top 15 0.47 0.54 upper 15 0.51 upper-mid 15 0.53 lower-mid 15 0.61 lower 15 0.57 bottom 15 0.57 ELK-13 top 15 0.46 0.58 mid-core 15 0.62 bottom 15 0.66 ELK-14* ELK-15 top 15 0.43 0.68 mid-core 15 0.62 bottom 15 0.99 substrate 15 1.71 32
ELK-12 ELK-11 ELK-13 ELK-6 ELK-7 ELK-10 ELK-14 ELK-15 ELK-5 ELK-8 ELK-9 ELK-4 ELK-1 ELK-3 ELK-2 Particle Size Distributions Sand Silt Clay 0 0.25 0.5 1 Miles Ü Figure 22. Particle size distributions of samples from coring sites in Elk City Reservoir. (No sample taken from site ELK-14). 33