J.C. Headwaters, Inc.
Bathymetry and Sediment Classification of the Klamath Hydropower Project Impoundments
Prepared for PacifiCorp
By
J.M. Eilers And C. P. Gubala
JC Headwaters, Inc.
April 2003 Klamath Hydropower Impoundment Bathymetry April 2003 J.C. Headwaters, Inc., 1972 NE 3rd Street, PMB 341, Bend, OR 97701
ABSTRACT
Bathymetric surveys were conducted on Lake Ewauna, Keno Reservoir, JC Boyle Reservoir, Copco Reservoir, and Irongate Reservoir. A supervised sediment classification was also conducted on each of these impoundments. A general assessment of the magnitude of accumulated sediment in the impoundments was conducted by comparing the current bathymetry of the impoundments with available information on pre-impoundment topography. The results indicate the sediment accumulation in the impoundments is relatively modest, generally ranging from 5 to 15 percent of the current volumes.
INTRODUCTION
Knowledge of lake morphometry provides critical information for understanding and managing lakes and impoundments. The information provides data on maximum depth and mean depth which are necessary for understanding lake stratification and functioning of biological and chemical dynamics in stratified and mixed systems. The information on lake area combined with depth provides knowledge of lake volume, which when combined with hydrological data, allows for calculation of hydraulic residence time.
Another important factor in managing lakes and impoundments is knowledge of the sediments. Sediments have the potential to strongly influence the chemistry of the water column through various diagenetic processes. Sediments can be especially important in impoundments because of the high trapping efficiency of lakes and their obvious location on riverine systems. High rates of sediment accumulation can lead to premature in-filling of impoundments with considerable loss in usable capacity for storage and hydropower production.
The primary purpose of this project was to provide information on the current bathymetry of the impoundments in the Klamath Hydropower Project Area (Figure 1). A second objective was to provide information on the nature and distribution of the sediments in the impoundments.
2 Klamath Hydropower Impoundment Bathymetry April 2003
1400 80
60 Keno Ewauna 40 1200 20
) JC Boyle m
( 0
Ig Co JC Ke Ew n o i
t 1000 a v e l E
800 Copco
Irongate 600 120000 80000 40000 0 Distance from Start of Lake Ewauna (m)
Figure 1. Diagram of Klamath Hydropower Project area illustrating the position of the impoundments and relative distances. The X axis is distance from the start of Lake Ewauna (m) and the Y axis is elevation (m). The inset bar chart shows the volume of the reservoirs (x 107 m3).
METHODS
Bathymetry of the study impoundments was collected using a Simrad EK 120 KHz split-beam hydroacoustic echo sounder mounted on the bow of a 19 ft Workskiff vessel. A DGPS unit with a reported precision of < 1m was placed directly over the transducer. The operational error in the DGPS during the course of the survey was substantially less than the reported error, averaging closer to 20-30 cm. The acqusition rate for the hydroacoustics was set at six pings per second with a nominal boat speed of 10 kph. Data from the hydroacoustic unit was interlaced with the DGPS into a real-time Access database. Field acquisition work for the bathymetry was conducted October 21-27, 2001. Supplemental work on the laser edge-of water was
3 Klamath Hydropower Impoundment Bathymetry April 2003 conducted March 10-13, 2002. Substrate sampling was conducted March 10-15, 2002.
Transect distances were originally set at 75 m intervals. However, based on inspection of the study sites, a uniform transect density of 50 m was employed. The transect paths were superimposed on a digital outline of the study sites and the boat operator followed the prescribed paths, except where navigation impediments required adjustments.
The location of the shoreline was measured with a Laser Advantage laser rangefinder linked with the same DGPS used for the bathymetry. The laser measures distance and bearing, allowing the position of each recorded measurement to be determined, generally within about 1m. The laser edge-of-water data were edited to remove spurious measurements and the resulting digital shoreline was check against the USGS 10m digital elevation models (DEM) for fit.
In addition to recording depth to substrate, the hydroacoustic signal provides two echoes which can be interpreted to yield information regarding the bottom roughness and bottom hardness. These two echoes were used to generate unsupervised sediment classification maps of the impoundments. Based on the nature of the sediments indicated from the unsupervised sediment classification, sites in each impoundment were selected for sediment sampling. Sediments in each impoundment were sampled using a mini-Glew gravity corer. The upper sediments (defined as less than or equal to 10 cm) were collected and extruded into WhirlPac® bags, labeled, and stored in a cooler. The appearance of the sediment samples was documented with digital images (Appendix A). The sediment samples were sent to the Crop and Soil Science Laboratory at Oregon State University, Corvallis for analysis of percent water, carbon (C), nitrogen (N), phosphorus (P), and particle size analysis (Table 1).
Additional information on the nature of the sediments was derived from direct images of the sediment obtained with a Sea Viewer® infrared underwater camera. The camera was lowered to the sediments and in the case of soft sediments, was lowered into the sediments. An on-board monitor was used to follow deployment of the camera.
The data on particle size analysis and other observations were integrated with the unsupervised hydroacoustic analysis of the sediments by combining hydroacoustic images of similar type to yield a supervised mapped of sediment composition.
Table 1. Sediment analytical methods at the OSU Crop and Soil Science Laboratory. Analyte Method Description Reference Carbon CNS Analyzer Leco mode CNS-2000 elemental analyzer Nitrogen CNS Analyzer Leco mode CNS-2000 elemental analyzer Phosphorus RFA methodology Alpkem Corporation (1986) using the Kjeldahl
4 Klamath Hydropower Impoundment Bathymetry April 2003 digestion method (Bremner and Mulvaney, 1982)
RESULTS
1. Bathymetry
Bathymetric maps for the Project area are presented in Figures 2-6. Maps of reservoir slopes derived from the bathymetric maps are presented in Figures 7-11.
4674500
4674000
0 ft 4673500 -2 ft -4 ft -6 ft -8 ft -10 ft -12 ft 4673000 -14 ft -16 ft -18 ft -20 ft -22 ft -24 ft 4672500 -26 ft -28 ft -30 ft -32 ft
4672000 Upper Ewauna FOR RESEARCH & MANAGEMENT NOT FOR NAVIGATION (1247.53m elevation datum for 0 depth)
600000 600500 601000
5 Klamath Hydropower Impoundment Bathymetry April 2003 Figure 2. Bathymetric map of Lake Ewauna, Oregon.
4665800
0 ft -1 ft -2 ft 4665600 -3 ft -4 ft -5 ft -6 ft -7 ft -8 ft 4665400 -9 ft -10 ft -11 ft -12 ft -13 ft 4665200 -14 ft -15 ft -16 ft -17 ft -18 ft -19 ft 4665000 -20 ft
4664800 Keno Reservoir
FOR RESEARCH & MANAGEMENT NOT FOR NAVIGATION 4664600 (1245.27m elevation datum for 0 depth)
586600 586800 587000 587200 587400 587600 587800 588000 588200 588400
Figure 3. Bathymetric map of Keno Lake, Oregon up to the bridge at Highway 66.
6 Klamath Hydropower Impoundment Bathymetry April 2003
4667000
4666500
0 ft 4666000 -2 ft -4 ft -6 ft -8 ft -10 ft -12 ft -14 ft 4665500 -16 ft -18 ft -20 ft -22 ft -24 ft -26 ft -28 ft 4665000 -30 ft -32 ft -34 ft -36 ft -38 ft -40 ft 4664500
JC Boyle Reservoir 4664000 FOR RESEARCH & MANAGEMENT NOT FOR NAVIGATION
(1155.75m elevation datum for 0 depth)
579000 579500 580000 580500 581000
Figure 4. Bathymetric map of JC Boyle Reservoir. The shallow areas in the north half of the lake were not navigable during the survey and the depth in this region is estimated between 0 to 2 ft.
7 Klamath Hydropower Impoundment Bathymetry April 2003
0 ft -5 ft 4649000 -10 ft -15 ft -20 ft -25 ft -30 ft 4648500 -35 ft -40 ft -45 ft -50 ft 4648000 -55 ft -60 ft -65 ft -70 ft -75 ft 4647500 -80 ft -85 ft -90 ft -95 ft -100 ft 4647000 -105 ft Copco Reservoir -110 ft
4646500 FOR RESEARCH & MANAGEMENT NOT FOR NAVIGATION
(793.09m elevation datum for 0 depth) 4646000 555000 556000 557000 558000 559000 560000 561000 Figure 5. Bathymetric map of Copco Reservoir up to bridge crossing.
4647000
4646000 0 ft -10 ft -20 ft -30 ft -40 ft 4645000 -50 ft -60 ft -70 ft -80 ft -90 ft 4644000 -100 ft -110 ft -120 ft Irongate Reservoir -130 ft FOR RESEARCH & MANAGEMENT -140 ft NOT FOR NAVIGATION 4643000 -150 ft (708.782m elevation datum for 0 depth) -160 ft
547000 548000 549000 550000 551000 552000 553000
Figure 6. Bathymetric map of Irongate Reservoir.
8 Klamath Hydropower Impoundment Bathymetry April 2003
4674500
4674000
4673500
9%
8%
7%
4673000 6%
5%
4%
3%
4672500 2% 1%
0%
Bottom Slope
4672000 Upper Ewauna FOR RESEARCH & MANAGEMENT NOT FOR NAVIGATION (1247.53m elevation datum for 0 depth)
600000 600500 601000
Figure 7. Slope map for Lake Ewauna based on bathymetric map presented in Figure 2.
9 Klamath Hydropower Impoundment Bathymetry April 2003
4665800
9%
4665600 8%
7%
6%
4665400 5% 4%
3%
2% 4665200 1%
0% Bottom Slope 4665000
4664800 Keno Reservoir
FOR RESEARCH & MANAGEMENT NOT FOR NAVIGATION 4664600 (1245.27m elevation datum for 0 depth)
586600 586800 587000 587200 587400 587600 587800 588000 588200 588400 Figure 8. Slope map for Keno Reservoir.
4667000
4666500
4666000 30% 28% 26% 24% 4665500 22% 20% 18% 16% 14% 4665000 12% 10% 8% 6% 4% 4664500 2% 0% Bottom Slope JC Boyle Reservoir 4664000 FOR RESEARCH & MANAGEMENT NOT FOR NAVIGATION
(1155.75m elevation datum for 0 depth)
579000 579500 580000 580500 581000
Figure 9. Slope map for JC Boyle Reservoir.
10 Klamath Hydropower Impoundment Bathymetry April 2003
4649000 48%
44% 4648500 40% 36%
32% 4648000 28% 24%
20%
4647500 16%
12%
8%
4647000 4%
Copco Reservoir 0% Bottom Slope 4646500 FOR RESEARCH & MANAGEMENT NOT FOR NAVIGATION
(793.09m elevation datum for 0 depth) 4646000 555000 556000 557000 558000 559000 560000 561000
Figure 10. Slope map for Copco Reservoir.
4647000
4646000
38% 36% 34% 32% 30% 28% 4645000 26% 24% 22% 20% 18% 16% 14% 4644000 12% 10% 8% 6% 4% Irongate Reservoir 2% FOR RESEARCH & MANAGEMENT 0% NOT FOR NAVIGATION Bottom Slope 4643000 (708.782m elevation datum for 0 depth)
547000 548000 549000 550000 551000 552000 553000
Figure 11. Slope map for Irongate Reservoir.
11 Klamath Hydropower Impoundment Bathymetry April 2003
Although the channel between Lake Ewauna and Keno Reservoir was not surveyed in a manner comparable to that of the impoundments, we did conduct a bottom survey between the two systems to assess the general nature of the study area. The results show that the average depth of water is about 10 to 12 ft. The large fluctuations in depth down the length of the channel are associated with movement of the vessel across the thalweg and pools present near bends in the system (Figure 12).
Approximate Water Surface Elevation 4090 ) t f ( 4080 n o i t a v e l E
Bed Elevation 4070
Fit : Polynomial Equation Y = 4083.78 - 1.10394 * X + 0.023965 * pow(X,2) Degree = 2 4060 Number of data points used = 1730 0 4 8 12 16 20 Distance from North End of Lake Ewauna (mi)
Figure 12. Bed elevation between Lake Ewauna and Keno Reservoir based on a single transect run. The average bed elevation is shown as a polynomial fit (curved line) of the observed data and the water surface elevation is depicted as a linear fit between maximum pool elevations for Lake Ewauna and Keno Reservoir.
12 Klamath Hydropower Impoundment Bathymetry April 2003
2. Unsupervised Sediment Classification
The hydroacoustic signature produces two echoes which can be analyzed separately to yield information on sediment regularity (E1; bottom smoothness) and reflectivity (E2; bottom hardness). The images below for Lake Ewauna illustrate obvious differences in sediment composition in the original thalweg compared to the shallows extending up to the northeastern portion of the impoundment (Figure 13). The surprisingly high degree of reflectivity for much of the shallow area in Lake Ewauna may be associated with the high incident of wood fiber observed in these sediments.
In Keno Reservoir, much of the impoundment was characterized by reflective, irregular substrate which would be indicative of rock, possibly interspersed with some depositional material (Figure 14). Only in the forebay was there any indication of significant quantities of a high percentage of soft, flocculent material.
Figure 13. Unsupervised sediment classification for Lake Ewauna based on E1 and E2 hydroacoustic responses.
13 Klamath Hydropower Impoundment Bathymetry April 2003
Figure 14. Unsupervised sediment classification based for Keno Reservoir based on E1 and E2 hydroacoustic responses.
14 Klamath Hydropower Impoundment Bathymetry April 2003
Figure 15. Unsupervised sediment classification for JC Boyle Reservoir based on E1 and E2 hydroacoustic responses.
The hydroacoustic signals in JC Boyle Reservoir indicated the presence of a high percentage of rock substrate (Figure 15). However, this does not include the very shallow material in the upper half of the reservoir which was not navigable during the survey work. Thus, much of the deeper portions of the impoundment is comprised of the original river channel which has retained much of its recognizable shape.
Copco Reservoir shows considerable contrasts in substrate types ranging from highly reflective materials on the upper portion, indicative of exposed rock, to dispersive material in the deep areas indicative of soft sediment (Figure 16). This is a typical pattern observed in many reservoirs where higher velocities in the upper areas associated with inflows and exposed shorelines during lake-stage fluctuations provide little opportunity for deposition of fine particles. However, the deep, lower ends of elongate impoundments provide considerable opportunity for deposition of all but the smallest particles. A somewhat similar pattern is achieved in Irongate Reservoir, although the bend in the upper northeast arm of the impoundment appears to offer an intermediate depositional zone prior to the main deep basin approaching the forebay (Figure 17).
15 Klamath Hydropower Impoundment Bathymetry April 2003
Figure 16. Unsupervised sediment classification of Copco Reservoir based on E1 and E2 hydroacoustic responses.
16 Klamath Hydropower Impoundment Bathymetry April 2003
Figure 17. Unsupervised sediment classification of Irongate Reservoir based on E1 and E2 hydroacoustic responses.
17 Klamath Hydropower Impoundment Bathymetry April 2003
2. Sediment Composition
Sediment sample sites are described in Table 2 and analytical results for all 39 sediment samples collected are presented in Table 3. Histograms of all results are presented in Figures 18-20. The water content of the sediment samples ranged from 68 to 90 percent, with a median value of 82 percent. The water content of the sediments in these impoundments is considerably lower than those in Upper Klamath Lake (Eilers et al., unpublished data). Low water content is indicative of a higher proportion of inorganic material in the sediments. The carbon content for the sediments ranged from 4.3 to 16.9 percent with a median of 6.3 percent. The highest values were associated with samples collected in Lake Ewauna obtained with an anchor. These samples had large wood chips imbedded in the sediment, which greatly affected the carbon and nitrogen results (Appendix). Excluding these wood-fiber samples, the sediments had relatively low carbon content, which is consistent with a higher proportion of inorganic inputs or high rates of decomposition and loss of carbon through sediment diagenesis. The samples with low concentrations of nutrients were associated with sediment samples with a high percentage of sand. Nitrogen and phosphorus concentrations in the sediment are also comparatively low even when compared to carbon concentrations. The ratio of C:N on a percentage basis averaged 10.2 (sd 2.2), which is almost twice as great as the Redfield ratio (5.56) expected for phytoplankton (Chapra 1997). The N:P ratio averaged 10.1 (sd 3.2), which is also considerably greater than the Redfield ratio of 7.2.
Table 2. Sediment site location and sediment descriptions. Lake/ Latitude Depth Sample Description Site ID Longitude (m) Type Ewauna ewa-01 42 13 00.8 8.5 No sample; rock and gravel 121 47 14.7 ewa-02 42 12 57.0 5.9 No sample; gravel 121 47 09.0 ewa-03 42 12 55.2 3.6 No sample; rock and gravel 121 47 07.4 ewa-04 42 12 37.6 2.6 Core; 12 bark chips up to 10 cm long on 121 46 cm anchor; mollusk shells, sulfur smell, 46.8 light to med brown ewa-05 42 11 54.9 3 Core; 2 distinct layers in core; large wood 121 46 anchor chips on anchor
18 Klamath Hydropower Impoundment Bathymetry April 2003 28.8 ewa-06 42 11 43.2 3.3 No sample; too hard 121 46 40.5 ewa-07 42 12 56.6 1.6 Core; 12 2 distinct bands in core, upper 121 46 cm; anchor organic ooze; wood chips abundant 48.0 on anchor ewa-08 42 12 10.9 3.3 No sample; 2 cm sediment over rock 122 46 31.1 ewa-09 42 12 25.2 2.1 Core; 2 bands in core; wood chips on 121 46 anchor anchor and sawdust in sediment 28.0 Keno keno-01 No sample; Dredging in progress at site keno-02 42 08 13.1 5.2 No sample; too hard 121 56 58.3 keno-03 42 08 17.7 1.7 No sample; gravel under silt 121 56 50.2 keno-04 42 08 17.3 1.7 Core Upper has high water content; 121 56 medium to dark brown 40.0 keno-05 42 08 10.6 4.8 No sample; too hard 121 56 27.2 keno-06 42 08 26.4 4.7 No sample; too hard 121 56 31.9 keno-07 42 07 50.3 4.5 No sample; too hard 121 55 53.6 JC Boyle jcb-01 42.149081 2 No sediment sample; bent core 122.026550 tube;collected Potomogeton sample; 2 cm flocculent material over imbedded gravel jcb-02 42.149114 3.1 No sample; 1-2 cm of floc over hard 122.031080 substrate jcb-03 42.149586 6.7 Core; 15 Upper med brown grading to dark 122.036004 cm brown; soft, sulfur odor; chironomid tube jcb-04 42.142376 4 Core; 18 Similar appearance to JCB-03; 122.035658 cm chironomid tube; no sulfur odor
19 Klamath Hydropower Impoundment Bathymetry April 2003 jcb-05 42.135477 4.6 No sample; 2-3 cm of floc over 122.031855 cobble jcb-06 42 07 50.9 7.5 No sample; rocky 122 02 08.5 jcb-07 42 07 40.1 10.7 Core; 15 Med brown grading to dark brown; 122 02 cm mild organic odor; very flocculent 28.5 jcb-08 42 07 22.7 11.5 Core; 20 Similar to JCB-07; chironomid tubes 122 02 cm 44.3 Copco copco-01 41 58 57.6 27 Core; 19 6 layers, distinct bands (grey/black); 122 19 cm top/bot samples 37.7 copco-02 41 58 59.6 23.9 Core Similar to Copco-01 122 19 27.8 copco-03 41 58 59.2 25.8 Minimal sample from core sidewall 122 19 18.2 copco-04 41 59 01.5 21 Core Very flocculent sed; poor settling 122 18 properties; top/bottom samples 31.2 copco-05 41 58 46.4 14.1 Core More cohesive sediments than 122 17 Copco-04 52.0 copco-06 41 58 36.4 13.1 Cores Duplicate cores collected; 122 17 top/bottom samples 30.8 copco-07 41 59 08.9 14.2 Core Top/bottom samples 122 18 55.9 copco-08 41 58 16.6 8.5 Core Top/bottom samples 122 17 02.9 copco-09 41 58 15.9 7.5 Core Top/bottom samples 122 16 52.0 Irongate Iron-01 41 58 13.1 3.4 Cores Duplicate cores; macrophytes on 122 22 anchor 22.8 Iron-02 41 58 09.9 16.5 Core; 28 Chironomids at bottom of core 122 23 cm 52.9
20 Klamath Hydropower Impoundment Bathymetry April 2003 Iron-03 41 58 12.7 24.7 Core 122 24 30.1 Iron-04 41 58 06.4 17 Corer broke; fine black organic 122 26 sediment 12.8 Iron-05 41 57 37.5 37 No sample; corer malfunctioned 122 25 41.0 Iron-06 41 56 17.5 47.6 Core; 16 Grey/black bands 122 25 cm 55.9 Iron-07 41 56 41.1 44.7 No sample; two attempts 122 26 02.6 Iron-08 41 57 10.5 41 Core High water content; black ooze 122 26 present on top 08.9 Iron-09 41 56 40.2 24 No sample; substrate too hard 122 25 43.5
Table 3. Analytical results for sediment samples collected from the Klamath Hydropower impoundments. Lake Sample Lab TP C N Water C_N N_P Number Number ppm % % % Ewauna EWA-04 2377.24 734 10.6 0.95 88.3 11.13 12.96 Ewauna EWA-05 2377.25 754 8.2 0.90 90.2 9.15 11.90 Ewauna EWA-05 bottom 2377.26 269 4.8 0.52 86.7 9.38 19.17 Ewauna EWA-07 2377.27 846 10.5 0.74 87.7 14.11 8.78 Ewauna EWA-09 2377.28 815 11.2 0.95 89.1 11.73 11.71 Ewauna EWA-09 bottom 2377.29 379 7.4 0.64 87.2 11.71 16.76
21 Klamath Hydropower Impoundment Bathymetry April 2003 Ewauna EWA-05 anchor 2377.3 349 6.6 0.56 82.0 11.92 15.94 Ewauna EWA-07 anchor 2377.31 542 13.6 0.76 84.2 17.97 14.02 Ewauna EWA-09 anchor 2377.32 534 13.5 0.75 80.4 17.92 14.05 Keno Keno-04 2377.23 639 5.6 0.56 80.5 10.14 8.70 Boyle JCB-03 2377.19 1042 9.6 1.16 87.4 8.30 11.16 Boyle JCB-04 2377.2 604 4.3 0.46 73.6 9.35 7.57 Boyle JCB-07 2377.21 686 6.8 0.72 81.7 9.42 10.50 Boyle JCB-08 2377.22 902 8.1 0.97 88.3 8.40 10.71 Copco Copco-01 2377.01 615 5.3 0.62 82.7 8.57 10.00 Copco Copco-01 bottom 2377.02 605 5.6 0.68 78.6 8.21 11.21 Copco-02 Copco duplicate 2377.03 645 5.5 0.63 83.7 8.72 9.74 Copco Copco-01 bottom 2377.04 663 5.4 0.60 79.0 9.00 9.08 Copco Copco-04 2377.05 989 6.1 0.67 85.6 9.02 6.81 Copco Copco-04 bottom 2377.06 778 6.0 0.66 80.4 9.08 8.43 Copco Copco-05 2377.07 787 6.7 0.75 85.2 8.98 9.52 Copco Copco-05 bottom 2377.08 705 6.4 0.71 80.2 9.08 10.02 Copco Copco-06 2377.09 733 6.6 0.69 83.8 9.60 9.35 Copco Copco-06 bottom 2377.1 774 6.2 0.65 77.5 9.51 8.36 Copco-06 Copco duplicate 2377.11 738 6.8 0.72 85.0 9.43 9.77 Copco-06 Copco duplicate bottom 2377.12 696 6.7 0.73 80.5 9.26 10.47 Copco Copco-07 2377.13 665 5.6 0.60 84.2 9.31 8.98 Copco Copco-07 bottom 2377.14 637 5.7 0.63 79.8 9.09 9.88 Copco Copco-08 2377.15 899 6.9 0.76 84.1 9.17 8.40 Copco Copco-08 bottom 2377.16 723 6.3 0.62 76.8 10.08 8.60 Copco Copco-09 2377.17 825 5.9 0.59 78.9 9.92 7.15 Copco Copco-09 bottom 2377.18 690 5.0 0.48 67.9 10.39 6.95 Irongate Iron-01 2377.33 730 6.6 0.55 69.7 11.97 7.52 Irongate Iron-02 2377.34 1039 6.1 0.64 83.6 9.47 6.18 Irongate Iron-02 bottom 2377.35 712 4.5 0.44 73.7 10.21 6.20 Irongate Iron-06 2377.36 875 5.2 0.64 80.3 8.20 7.29 Irongate Iron-06 bottom 2377.37 822 5.8 0.71 78.5 8.19 8.64 Irongate Iron-01 anchor 2377.38 915 16.9 1.46 74.3 11.60 15.94 Irongate Iron-03 2377.39 970 4.6 0.39 75.8 11.84 3.98
22 Klamath Hydropower Impoundment Bathymetry April 2003 16 12
12
8 y c y n c e n e u 8 u q q e e r r F F 4 4
0 0 64 68 72 76 80 84 88 92 4 6 8 10 12 14 16 18 Water (%) Carbon (%)
12 25
20
8 y y c
c 15 n n e e u u q q e e r r
10 F F 4
5
0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 200 400 600 800 1000 Nitrogen (%) Total Phosphorus (ppm)
Figure 18. Histograms of water, carbon, nitrogen, and phosphorus content in sediment samples from the Klamath Hydropower Project area.
23 Klamath Hydropower Impoundment Bathymetry April 2003 16 8
12 6 y y c c n n e e u u 8 4 q q e e r r F F
4 2
0 0 8 10 12 14 16 18 2 4 6 8 10 12 14 C:N (% basis) N:P (% basis)
Figure 19. Histograms of C:N and N:P ratios (on a percent dry weight basis) for sediment samples from the Klamath Hydropower Project area.
100 Clay
80
t 60
n Silt e c r e P 40
20
Sand
0 Ewauna Boyle Copco Irongate Keno
Figure 20. Textural classes of sediment samples from the Klamath Hydropower Project. The samples are arranged in the same order as shown in Table 3. Samples identified with a cross-filled circle were collected with an anchor.
24 Klamath Hydropower Impoundment Bathymetry April 2003
The textural analysis of the samples illustrates that the sediments in the upper impoundments (Ewauna thru JC Boyle) typically have a greater percentage of sand based on the sites sampled. This spatial trend is reversed somewhat in Irongate Reservoir where percentages of sand again increase over those found in Copco Reservoir. Percentages of clay are greatest in the samples from Copco and Irongate Reservoirs. A comparison of sediment samples from the upper 10 cm with those below 10 cm shows that the upper sediments have higher values of nutrients and water content (Table 4).
Table 4. Comparison of analytical results (mean and standard deviation) for sediment samples collected from depths of 0-10 cm (Top) versus 10-20 cm (Bottom) for eleven paired samples from the Klamath impoundments. The P value is presented for a one- way ANOVA comparing top and bottom sample results. Variable Top Bottom P Value Carbon (%) 6.70 (1.7) 5.79 (0.82) 0.128 Nitrogen (%) 0.71 (0.121) 0.61 (0.911) 0.045 Phosphorus (ppm) 818 (128) 645 (172) 0.015 Water (%) 84.3 (3.3) 78.8 (5.4) 0.009
Supervised sediment classifications were derived by integrating the hydroacoustic signals (E1 and E2) with the sediment sampling results. The resulting maps for the 50 meter grid nodes (Ewauna and Keno were prepared at 25 meter grid nodes) illustrate major differences in sediment composition of the upper impoundments (Ewauna, Keno, JC Boyle) with the lower impoundments (Copco and Irongate). The upper systems are characterized by higher proportions of rock, sand, and silt, whereas the lower impoundments have higher proportions of silt and clay (Figures 21-25).
25 Klamath Hydropower Impoundment Bathymetry April 2003
4674500
4674000
4673500 Sand & Rock Silt Clay
0 % to 20 % 4673000 20 % to 30 % 30 % to 40 % 40 % to 50 % 50 % to 100 %
4672500
4672000
600000 600500 601000 600000 600500 601000 600000 600500 601000
Figure 21. Acoustically classed sediments for Lake Ewauna.
26 Klamath Hydropower Impoundment Bathymetry April 2003
4665600
4665400
4665200 Sand & Rock
4665000 0 % to 20 % 20 % to 30 % 30 % to 40 % 4664800 40 % to 50 % 50 % to 100 %
4664600
4665600
4665400
4665200 Silt
4665000
4664800
4664600
4665600
4665400
4665200 Clay
4665000
4664800
4664600 586800 587000 587200 587400 587600 587800 588000 588200 588400
Figure 22. Acoustically classed sediments for Keno Reservoir
27 Klamath Hydropower Impoundment Bathymetry April 2003
4667000
4666500
4666000
4665500 Sand & Rock Silt Clay
0 % to 20 % 20 % to 30 % 30 % to 40 % 40 % to 50 % 4665000 50 % to 100 %
4664500
4664000
579000 579500 580000 580500 579000 579500 580000 580500 579000 579500 580000 580500
Figure 23. Acoustically classed sediments for JC Boyle Reservoir.
28 Klamath Hydropower Impoundment Bathymetry April 2003
4649000 Sand & Rock
4648500 0 % to 20 % 20 % to 30 % 4648000 30 % to 40 % 40 % to 50 % 4647500 50 % to 100 %
4647000
4646500
4646000
4649000
4648500 Silt
4648000
4647500
4647000
4646500
4646000
4649000
4648500 Clay
4648000
4647500
4647000
4646500
4646000 556000 557000 558000 559000 560000 561000
Figure 24. Acoustically classed sediments for Copco Reservoir.
29 Klamath Hydropower Impoundment Bathymetry April 2003
4647000
4646000
4645000 Sand & Rock
0% to 20% 4644000 20% to 30% 30% to 40% 40% to 50% 50% to 100% 4643000
4647000
4646000
Silt 4645000
4644000
4643000
4647000
4646000
4645000 Clay
4644000
4643000
547000 548000 549000 550000 551000 552000
Figure 25. Acoustically classed sediments for Irongate Reservoir.
30 Klamath Hydropower Impoundment Bathymetry April 2003
3. Comparison with Historic Topography
An indication of the amount of sediment accumulated in the impoundments was derived by comparing the current bathymetry with the pre-dam topography of the study sites. Pre-construction topography of the study sites provided by Pacificorp was used to generate a surface which was compared with the current bathymetry. No historic topographic map was provided for Lake Ewauna and thus this site was not included in the historical comparison.
The estimates for loss of lake volume calculated using historic topography for the four impoundments is presented in Figure 26. Pre-construction topography for the study sites is presented in Figures 27-30. The hypsographic curves of the lakes and the historic volumes for the same area were plotted and compared (Figures 31-34).
16
e 12 m u l o V
n i
s 8 s o L
t n e c r e
P 4
0 Keno JC Copco Iron Boyle Gate Figure 26. Estimates of loss in reservoir volume based on comparison of current bathymetry with historic topography for four of the five study sites.
31 Klamath Hydropower Impoundment Bathymetry April 2003
There is a considerable disparity in the estimates for volume loss ranging from 0.6 percent in JC Boyle Reservoir to 14.6 percent in Copco Reservoir. The greatest loss in volume, that calculated for Copco Reservoir, appears realistic considering that this is the oldest impoundment in the system, it is deep with a high trapping efficiency, and is situated in a portion of the study area with considerable topographic relief. Irongate Reservoir would be expected to have experienced a considerably lower degree of in- filling because it is relatively recent and it is located immediately below Copco Reservoir. The values computed for Keno Reservoir are also consistent with a shallow, narrow system that would likely have comparatively low trapping efficiency. The values computed for Keno Reservoir are based on the bathymetry of the impoundment prior to dredging in the forebay conducted in 2002. The change in volume estimates for JC Boyle Reservoir are extremely low, well below what would be expected for a system of this type.
For three of the impoundments, JC Boyle, Copco, and Irongate, the historical topography does not include elevation data below the original river channel. This results in underestimating the total loss of volume from sedimentation. For Copco and Irongate Reservoirs, this bias is small because the volume of the historic river channel is small relative to the volume of these large impoundments. For JC Boyle Reservoir, the volume of the original river channel is much greater relative to the volume of the impoundment. The degree to which the loss of lake volume is underestimated in JC Boyle is difficult to assess. However, the sediment sampling in JC Boyle Reservoir showed that much of the original thalweg remained sediment-free through site #7 (mid-way through the lower half of the impoundment), suggesting that the magnitude of the sedimentation bias estimate for this reservoir may not be large.
32 Klamath Hydropower Impoundment Bathymetry April 2003
Figure 27. Historic topographic information for the Keno Reservoir area.
Figure 28a. Historic topography for upper JC Boyle Reservoir area.
33 Klamath Hydropower Impoundment Bathymetry April 2003
Figure 28b. Historic topography for the middle portion of the JC Boyle Reservoir area.
Figure 28c. Historic topography for the lower portion of the JC Boyle Reservoir area. 34 Klamath Hydropower Impoundment Bathymetry April 2003
Figure 29a. Historic topography for the Copco Reservoir study area.
Figure 29b. Historic topography for the central portion of the Copco Reservoir area, shown at a larger scale.
35 Klamath Hydropower Impoundment Bathymetry April 2003
Figure 30a. Historic topography for the Irongate Reservoir study area.
Figure 30b. Expanded scale of the historic topography for the forebay of the Irongate Reservoir area. 36 Klamath Hydropower Impoundment Bathymetry April 2003
Keno Reservoir Volume Analyses
4088 4088
4084 t t
e 4084 e e e f f
, , n n 4080 o o i i t t a a v v e e l l E E
4080
4076 e e c c a a f f r r u u S S
r r
4072 e e t t
Volume Analyses a a W
W 4076 3.644E+07 ft3 Current (2001) 4068 4.033E+07 ft3 Historical
Change in volume = 3.9E+06 ft3 (~9.6%) Maximum change in mid to lower strata 4064 4072
0 10000000 20000000 30000000 40000000 50000000 0.00E+000 4.00E+005 8.00E+005 Volume below strata, cubic feet Change in Reservoir Volume, cubic feet Figure 31. Current and historical hypsographic curves for Keno Reservoir and an estimate of the distribution of the change in lake volume as a function of lake depth.
JC Boyle Reservoir Volume Analyses
3800 3800
3790 3790 t t e e e e f f
, , n n o o i i t t a 3780 a 3780 v v e e l l E E
e e c c a a f f r 3770 r u 3770 u S S
Volume Analyses r r e e t t a 9.874E+07 ft3 Current (2001) a W 3 W 3760 9.934E+07 ft Historical 3760 Change in volume = 6.0E+05 ft3 (~0.6%) N.B. Historical Bathymetry appears to have omitted stream channel shape and volume 3750 3750
0 20000000 40000000 60000000 80000000100000000 -8.00E+006 0.00E+000 8.00E+006 Volume below strata, cubic feet Change in Reservoir Volume, cubic feet
37 Klamath Hydropower Impoundment Bathymetry April 2003
Figure 32. Current and historical hypsographic curves for JC Boyle Reservoir and an estimate of the changeC ino plakeco volume Rese rasv oa ifunctionr of depth. Volume Analyses
2640 2640 t t
e 2600 e 2600 e e f f
, , n n o o i i t t a a v v e e l l E E 2560 2560 e e c c a a f f r r u u S S
r r e e
t Volume Analyses t a a
W 2520 W 2520 1.469E+09 ft3 Current (2001) 1.725E+09 ft3 Historical
Change in volume = 2.6E+08 ft3 (~17.4%) Maximum change in middle depth strata 2480 2480
0 800000000 1600000000 0.00E+000 4.00E+007 8.00E+007 Volume below strata, cubic feet Change in Reservoir Volume, cubic feet Figure 33. Current and historical hypsographic curves for Copco Reservoir and estimate of change in lake volume as a function of depth.
Irongate Reservoir Volume Analyses
2360 2360 t t 2320 2320 e e e e f f
, , n n o o i i t t
a 2280 a 2280 v v e e l l E E
e e c c a a f f r r 2240 2240 u u S S
r r
e Volume Analyses e t t a a
W 3 W 2200 2.219E+09 ft Current (2001) 2200 2.349E+09 ft3 Historical
Change in volume = 1.3E+08 ft3 (~5.5%) Maximum change in middle depth strata 2160 2160
0 1000000000 2000000000 -20000000 0 20000000 40000000 Volume below strata, cubic feet Change in Reservoir Volume, cubic feet
Figure 34. Current and historical hypsographic curves for Irongate Reservoir and an estimate of a change in lake volume based on depth.
38 Klamath Hydropower Impoundment Bathymetry April 2003
DISCUSSION
Bathymetry for all of the impoundments was conducted and the results showed that the current bathymetry of the impoundments does not differ greatly from the historical topography. The estimated maximum loss of lake volume was calculated for Copco Reservoir, the oldest and most likely impoundment in the system to have accumulated the greatest amount of sediment. The least loss of volume was calculated for JC Boyle Reservoir, although anomalies in the historical topography for the upper portion of the reservoir cast doubt on the estimate for this system. Sediment composition in the impoundments consisted of a relatively high proportion of hard substrate, although deep sediments had a high proportion of silt and clay. Deltaic formation at the mouths of tributaries entering the impoundments was relatively sparse, reflecting the low rates of sediment production in the Project area.
Sediment classification using hydroacoustic analysis in some portions of the impoundments appeared to be affected by somewhat unusual sediment conditions. For example, in the northeastern portion of Lake Ewauna, buried wood fiber in the sediments appeared to promote reflectivity of the sediments to a degree greater than expected based on the soft matrix of the material in the area. In Keno Reservoir, the presence of shallow accumulations (~ 2cm) of soft sediment over the hard basaltic base rock appeared to dampen the hydroacoustic signal to a significant degree. Regardless of these minor anomalies, the bathymetric analysis provides managers with a reasonable basis for assessing current and future conditions in the study impoundments.
The chemical analysis of the sediments indicated that carbon content was relatively low throughout the system, with the exception of sites in and below Lake Ewauna that had high wood-fiber content. Thus despite the influx of lake water with high phytoplankton densities, the sediment in the Project area are principally inorganic.
39 Klamath Hydropower Impoundment Bathymetry April 2003
ACKNOWLEDGEMENTS
This project was funded by PacifiCorp under contract #3000011432 to JC Headwaters, Inc. Technical assistance in the field was provided by Scott Milne and assistance in data processing was provided by Benn Eilers.
LITERATURE CITED
Alpkem Corporation. 1986. Ortho Phosphate and Total Phosphate RFA Methodology – A303-S635-01. In Methods of Soil Analysis Used in the Soil Testing Laboratory at Oregon State University. 1989. Agricultural Experiment Station, Oregon State University, Corvallis, Oregon.
Bremner, J.M. and C.S. Mulvaney.1982. Total Nitrogen. In Methods of Soil Analysis, Part 2. Pp 595-624. A.L. Page, R.H. Miller, and D.R. Kenney (eds). Agron. Monogr. 9, Amer. Soc. Agron., Madison, Wisconsin.
Chapra, S.C. 1997. Surface Water-Quality Modeling. McGraw-Hill, New York. 844 pp.
APPENDICES
Data files provided in attached CD.
40