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Home My WebLink AboutDillingham Hydrology Studies 20132011-2013 HYDROLOGY STUDIES DILLINGHAM AREA HYDROELECTRIC PROJECT (FERC. No. 14356) Prepared by: Civil Science Prepared for: Nusbagak Electric and Telephone Cooperative December 2013 Table of Contents INTRODUCTION AND BACKGROUND ....................................................................... 1 STUDY OBJECTIVES ....................................................................................................... 2 FIELD STUDY LOCATIONS, METHODS AND TIMEFRAME .................................... 3 STAGE AND DISCHARGE MEASUREMENT METHODS ........................................ 10 OFFICE ANALYSIS METHODS .................................................................................... I 4 RESULTS ......................................................................................................................... I4 REFERENCE DATA & LITERATURE .......................................................................... 24 List of Figures Figure I. Grant Lake System Watershed and Gaging Stations .......................................... 4 Figure 2. Lake Elva System Watershed and Gaging Stations ........................................... 5 Figure 3. Grant Lake Outlet Station Location ................................................................... 6 Figure 4. Grant River Gaging Station Location ................................................................. 7 Figure 5. Aerial View of Lake Elva showing gaging station location ............................... 8 Figure 6. Lower Elva Creek and Lake Nerka showing Elva Creek Station Location ....... 9 Figure 7. Elva Creek Station Location and RM 1 .............................................................. 9 Figure 8. Grant River Gage showing staff gage and protective conduit anchored to boulder. Conduit leads shoreward from submerged well point or suspended tranducer to enclosure on bank ..................................................... II Figure 9. Grant Lake Outlet Gage showing staff gage and protective conduit pinned to stream bed with driven steel bars .................................................... 11 Figure 10. Rating Curve for Grant Lake Outlet Station ................................................... 15 Figure 11. Rating Curve for Grant River Station ............................................................. 16 Figure 12. Rating Curve for Lake Elva Outlet Station .................................................... 17 Figure I 3. Rating curve for Elva Creek Station ............................................................... 1g Figure 14. Synthesized Monthly 20t 11, 50th, Average and goth Percent Exceedance Flows for Grant Lake Outlet Gaging Station .................................................. 22 Figure 15. Synthesized Monthly 20th, 50th, Average and goth Percent Exceedance Flows for Lake Elva Outlet Gaging Station ............................................... ; .... 23 List of Tables Table 1. Minimum, Maximum and Average Daily Grant Lake Outlet Flows by Month .............................................................................................................. I9 Table 2. Minimum, Maximum and Average Daily Grant River Flows by Month .......... 20 Table 3. Minimum, Maximum and Average Daily Lake Elva Outlet Flows by Month .............................................................................................................. 20 Table 4. Minimum, Maximum and Average Daily Elva Creek Flows by Month ........... 21 Table 5. Synthesized Monthly 20 1h, 50th, Average and 80th Percent Exceedance Flows for Grant Lake Outlet Gaging Station .................................................. 22 Table 6. Synthesized Monthly 20th, 50 1\ Average and 80th Percent Exceedance Flows for Lake Elva Outlet Gaging Station .................................................... 23 Appendices APPENDIX I -Station Descriptions APPENDIX II -Stage/Discharge Measurements Summary APPENDIX Ill-ADCP Trials DRAFT REPORT 2011 HYDROLOGY STUDIES DILLINGHAM AREA HYDROELECTRIC PROJECT (FERC. No. 14356) Prepared by: Civil Science Prepared for: Nushagak Electric and Telephone Cooperative December, 2013 INTRODUCTION AND BACKGROUND INTRODUCTION Nushagak Electric & Telephone Cooperative, Inc., ("NETC"), is evaluating a multiple- development hydroelectric Project, the Dillingham Area Hydroelectric Project ("DAHP", "Project"), as described in this document. The DAHP would consist of the Grant Lake and Lake Elva hydroelectric projects ("Projects", "Grant Lake Project", "Lake Elva Project"). Both Projects and portions of their transmission systems would be located in Wood-Tikchik State Park (WTSP) administered by the State of Alaska Department of Natural Resources (ADNR). The proposed 1.0 megawatt (MW) installed capacity Lake Elva Project would be located 36 miles north by northwest of Dillingham, Alaska. The proposed 2.0 MW Grant Lake Project would be located 43 miles north of Dillingham. The purpose of the Projects would be to displace costs of diesel fuel electrical generation which is currently NETC's only generation alternative. The Grant Lake Project electrical generation would meet NETC's current base load and would equal the average generation of NETC's diesel power plant. Lake Elva Project generation would meet existing NETC's peak loads. In order to gain approval to construct and operate the project, NETC is required by various state and federal requirements to conduct environmental, engineering and 20/1-2013 Hydrology Report NETC DAHP December, 2013 economic studies to determine project feasibility in light of constraints relative to each of these elements. Among the most important resources in the development and operation of a hydroelectric project is hydrology, most notably the magnitude and timing of stream flows and lake levels in the associated water bodies. This study report documents the first year of a series of hydrology studies (20 II) and subsequent years (20 12 and 20 13) which have served as the basis for numerous other evaluations and analyses of the Projects feasibility. BACKGROUND AND CONSULTATION NETC began work in 2010 on DAHP hydrology studies by developing a draft hydrology study plan which was reviewed by agencies (NETC, 20 1 0). The plan, developed by Oasis Environmental, noted general proposed locations for stream gaging stations as well as methods for discharge measurements. The 2010 plan was reviewed by resource agencies and comments were received from US Fish and Wildlife Service. The plan was not revised in 2010, and subsequent difficulties with access and weather conditions led to suspension of the hydrology field efforts that year. In 2011, Civil Science of Klawock, Alaska was requested to continue the hydrology studies, beginning in May. Civil Science used the Oasis plan as a basis for their studies, but implemented some different methods in their 2011 surveys. This report documents those methods and all field work accomplished between March 20 11 and September, 2012. While it is desirable to obtain and incorporate comments on draft study plans, the need to access the measurement stations and conduct measurements in 2011 precluded refinement of the study plan for the 201 I studies. Concurrent with this report, however, Civil Science and NETC developed a more detailed study plan for 20 12, based on work completed in 20 I 1 and documented in this report. We have requested comments on this plan and will address all comments and produce a final study plan prior to the onset of work in 2012. STUDY OBJECTIVES The overall objective for the 2011 field studies was to install continuous monitoring stream gages at two locations (stations) in both the Grant Lake and Lake Elva systems. These monitoring stations would be located in such a way as to document stream discharge at the two lake outlets to analyze energy generation potential and another station at a downstream location selected to support analysis of environmental (primarily fish) impacts. A further objective during 20 I I was to make stage-discharge measurements at the four stations sufficient to establish a "rating curve", or stage-discharge relationship at each station. Development of these rating curves, used in association with applicable long- term stream gages in the near-project vicinity would allow for synthesis of flow regimes 20 I I-20 I 3 Hydrology Report NETC 2 DAHP December. 20I 3 on which to base estimates of both energy generation and the corresponding environmental effects. 2012 objectives included the refinement of the ratings as well as the development of hydrologic time series data and computation of characteristic flows, e.g. mean monthly flows, average annual flow, etc. for each station. In addition, the records of the Grant Lake outlet and Lake Elva outlet station were extended via a hydrologic correlation with the Nuyakuk River station (USGS Station 15302000). FIELD STUDY LOCATIONS, METHODS AND TIMEFRAME As described in detail in the following sections, discharge measurement at the four selected stations entailed: l) Installation of the continuous stage monitoring device and associated equipment at a permanent location (stream gaging station); 2) Discreet measurements of concurrent stream stage and discharge at the station made over a broad range of streamflow conditions. Data from these stage/discharge measurements was used to construct and refine rating curves (predictive stage-discharge relationships). In descriptions of the study locations below, we describe the stations where the stream gages were installed and those at which the successive discharge measurements were taken. STUDY LOCATIONS Based on preliminary work done by Oasis in 2010, and early reconnaissance by Civil Science, four stations were selected for installation of the continuous recording gages. The two stations on Lake Elva/Elva Creek and on Grant River/Grant Lake are shown in the following Figures 1 and 2. 20/1-2013 Hydrology Report NETC 3 DAHP December. 2013 Flpro 1. G-t Loke System Watenhod atMI Gapa1 Statie111 4 Figure 2. Lake Elva System Watershed and Gaging Stations. 2011-2013 Hydrology Report NETC 5 DAHP Dece mbe r, 2013 Grant Lake/Grant River Stations Grant Lake Outlet Station This station was in the outlet channel of Grant River, approximately 150 yards downstream ofthe lake's outlet below in Figure 3. The stream gage was installed in a 1- 118" stainless steel wellpoint driven into the streambed at the right bank which offered reasonable protection from freezing during winter and ice forces at breakup. Figure 3. Grant Lake Outlet Station Location. (Note: A United States Geological Survey(USGS) Gaging Station 15302800, "Grant Lake Outlet near Aleknagik" was operated in Grant Lake outlet area between July 16, 20//-20/3 Hydrology Report NETC 6 DAHP December, 20/3 1959 and July 31, 1965. NETC's Grant Lake Outlet station location was influenced by knowledge of this former gaging station with hopes of using the same gage datum through the recovery ofthe USGS reference marks. To date these reference marks have not been found. Grant River Station This station was located approximately Y2-mile upstream of the Grant River confluence with Lake Kulik as illustrated by Figure 4. The stream gaging station was selected at a large boulder in a deep pool at the toe of the steep right bank which offers protection from ice and was more difficult to access by bears, which often can be quite destructive of such installations. Figure 4. Grant River Gaging Station Location. Lake Elva/Elva Creek Stations Lake Elva Outlet Station This station is located in Lake Elva approximately 150-200 yards upstream of the lake outlet. The station was located along the left shore of the lake below a small patch of Alder which would help shield the gage from avalanches from the mountainsides above. Avalanche danger was noted in the entire outlet area of Lake Elva. The Lake Elva station's location is illustrated in Figure 5. 2011-2013 Hydrology Report NETC 7 DAHP December, 2013 Figure 5. Aerial View of Lake Elva showing gaging station location. (Note: The USGS operated a gaging station at Lake Elva from October I . 1979 through June 30. I982. The original station was destroyed by avalanche shortly after gaging began and the station was subsequently relocated downstream were it was operated until the station was discontinued. An effort was made to find remnants of the Lake Elva outlet station but no signs of the station were found. The new gaging station measures the level of Lake Elva and is not located in the stream. As such. the ratings would not coincide since they do not share the same hydraulic control. Elva Creek Station This station was located about %-mile upstream ofthe Elva Creek confluence with Lake Nerka where an exposed outcropping ofbedrock on the right stream bank created a deep pool and provided a good location to mount and anchor the gage hardware. Additionally, a large instream boulder at this station provided a natural benchmark. designated RM I . for stage measurement as well as a prominent feature to aid in aerial location ofthe gage. Lower Elva Creek and the location of the Elva Creek Station in relation to Lake Nerka are shown in Figure 6. An aerial view of the station location showing the prominent boulder benchmark. designated RM I , is shown in Figure 7. 2011-2013 Hydrology Report NETC 8 DAHP December, 201 3 Figure 6. Lower Elva Creek and Lake Nerka showing Elva Creek Station Location. Figure 7. Elva Creek Station Location and RM 1. 201 I-2013 Hydrology Report NETC 9 DAHP Decem ber, 2013 STAGE and DISCHARGE MEASUREMENT METHODS Stage Measurements Continuous stream stage measurements were made at all four gaging stations using (brand and model number of transducer) stage recorders ("transducers"). The transducers can continuously record stream water surface elevations ("stages") for as long as 3 years with proper operation. In all cases, the stream gage instruments were programmed to measure and record stage every 15 minutes (0.25 hours). Each gage consisted ofthe following elements: • Two submersible, recording pressure/temperature transducers, emplaced inside a 1-1/4" wellpoint driven into the streambed (Grant Lake Outlet and Grant River) or emplaced in suspended conduit to measure and record absolute and gage water pressure and water temperature. • A data cable, housed in a 2" galvanized steel conduit. This cable is used to communicate with the recording instrument to calibrate the gage and program the data logger as well as to receive data from the transducers via a data retrieval terminal, located on the bank in a protected enclosure mounted to the shoreward end of the conduit. Data is retrieved with a mobile device designed for rugged conditions. • A barometric pressure and air temperature recording device mounted in the enclosure; and, • A staff gage, graduated in feet and hundredths of a foot, mounted on an untreated 2 x 6" dimensioned lumber secured with steel pins driven into the stream or lake bed (Grant Lake Outlet and Lake Elva) or rock bolts and angle brackets secured steep exposed bedrock (Elva Creek) or a large instream boulder (Grant River). Examples of the general locations and configuration for these components are shown below in Figure 8 showing the Grant Lake Outlet Gage and Figure 9 showing the Grant River Gage. 2011-20/3 Hydrology Report NETC 10 DAHP December, 2013 Figure 8. Grant River Gage showing staff gage and protective conduit anchored to boulder. Conduit leads shoreward from submerged wellpoint or suspended tranducer to enclosure on bank. Figure 9. Grant Lake Outlet Gage showing staff gage and protective conduit pinned to stream bed witb driven steel bars. 2011-2013 Hydro logy Report NETC I I DAHP December, 2013 After each stream gage was installed, standard land surveying techniques were used to determine the elevation of the stream gage components relative to a station-specific benchmark (See Elevation Determination, below). Stage Measurement Recording Instrumentation Submersible pressure transducers used in this study were In-Situ® Leveltroll Model 500 (2 units per station) for water temperature and pressure (stage) measurements. In-Situ® Barotroll instruments were used to measure and record air temperature and barometric pressure. In each gage, both vented (absolute pressure) and unvented (gage pressure) transducer assemblies were emplaced to provide redundancy in stage measurements in case of equipment failure. More detailed descriptions of these gaging stations are included in Appendix I. The Grant Lake Outlet Station was visited eight times since its installation and the Grant River station was visited once since its installation in July. Data was downloaded and data loggers were re-programmed with new logs on these visits. The Lake Elva system gages were installed on the final trip of the season in September 2011. These stations were visited 3 times in 2012 to retrieve data and make station stage-discharge measurements. Because it was foreseen that these gages would not be seen for several months, an extra large amount of desiccant was used in the venting apparatus on the terminus of the vented instrument's breathing tube/data cable to accommodate this long period. Discharge Measurements Stream stage/discharge measurements were made at all four stations using standard USGS techniques. Under these guidelines, measurement cross-sections were selected which were influenced by backwater from a downstream flow control feature in the stream channel. These channel controls are typically knickpoints (Lake Elva Stations and Grant Lake Outlet Station) or tailout controls below a stream pool (Grant River and Elva Creek stations). Cross-sections where discharge measurements were made varied with flow to assure measurement at the best locations for accurate measurements. While discharge measurement location may vary within a reasonable distance from the gaging station, the stage measurements, both those of the recording instruments and stage measured by surveying techniques, always correspond to the stage at the precise location of the gaging station. Water velocity was measured using USGS Price (AA and Pygmy) current meters under USGS operational guidelines. These meters were spin tested before each field trip. During observations made for discharge measurements, the operator counted rotations of the current meter via an audible counter or with a digital data collector for a minimum of 40 seconds for each velocity reading. Depths at each velocity observation location were measured directly using a top-setting wading rod. Velocity observation locations 2011-2013 Hydrology Report NETC 12 DAHP December, 2013 (verticals) along each measurement cross-section were established based on stream channel characteristics and measurement precision. Locations across the cross-section were measured using a graduated tagline. In addition to conventional Price meters, we also used an Acoustic Doppler Current Pro filer (ADCP) in 2011. Measurements were made using Teledyne RDI Stream Pro ADCP units (two separate instruments were used) on two separate trips in June and July. ADCP measurements were made at all four stations under both high early runoff conditions and moderated summer levels. We conducted extensive tests to demonstrate comparability between results using the ADCP and the Price AA measurement techniques. ADCP measurements are differentiated from conventional measurements in subsequent rating curve figures in this report. ADCP measurements and are presented along with conventional measurements in the measurement summary in Appendix II. A brief summary comparison of ADCP measurements and conventional measurement techniques is in included in Appendix III. Stage Measurement Determination At each station, certain actions were taken to ensure reproducible elevation control. This consisted on establishing a datum referenced to physical benchmarks. The staff gage is then set so that the water surface can be read on its graduated plates. Pressure transducers, after being securely mounted, are calibrated so that their reading matches the water level observed on the staff gage through the addition or subtraction of an offset (a constant measured in the same units as the gage, in our case feet and hundredths of a foot). Datum and Benchmarks All measurements at individual stations were made relative to the elevation of a physical benchmark consisting of a permanent existing feature, (usually exposed bedrock or a large stable boulder) or a temporary benchmark consisting of a spike, rock bolt or lag bolt, or other device driven into a rock or large tree. See the station descriptions in Appendix I for further description of each gage's datum and associated reference marks. Differential Leveling Relative elevations of the benchmarks, staff gages, monitoring equipment components and water stage during discharge measurements were assured by using standard differential leveling techniques. In all surveys, backsights were made on established benchmarks, and foresights were made to the staff gages, water surfaces and gage components to an accuracy of 0.0 l foot. In all cases, a "level loop" was run and closed to assure accuracy of results. Instruments used for leveling were regularly peg tested to insure accuracy. 2011-2013 Hydrology Report NETC l3 DAHP December, 2013 OFFICE ANALYSIS METHODS Raw field data consisted of: I) Specifications for the various stream gage installations (locations and surveying details to note gage heights, staff gage relationships, etc.) 2) Level notes; 3) Depth, Distance (across the tag line) and velocity measurement notes; 4) Weather, ice, and other conditions, as noted by field workers. For each station, survey notes, stream gage and staff gage elevation associations were made and standardized. Water depth, velocity and distance measurements were used to calculate stream discharge. Finally, stream stage from the staff gage and/or from surveyed water surface elevations was associated with the discharge measurements to begin development of the rating curves. RESULTS DATA OUTPUT At each station, individual measurements and instrument data logs resulted in an extensive output package, too large to be transmitted in either the body of this report or its appendices. Summarized results from all stage/discharge measurements are presented in Appendix II of this report. Raw data of individual measurements, e.g., tag line distances, current meter revolutions, etc., are available from NETC, who will forward requests for raw data to Civil Science. Generally, we will demonstrate how the data were used to construct rating curves for the stations. RATING CURVE DEVELOPMENT Sufficient measurements have been made to construct a preliminary rating curve for all stations. Further measurements will be required to maintain ratings and adjust for shifts, that occur, if any, in the rating due to aggredation or degradation ofthe streambed. Grant Lake Outlet The Grant Lake outlet station, having been visited on eight occasions by the Civil Science team has the most data from which to make ratings. Stage/discharge 2011-2013 Hydrology Report NETC 14 DAHP December. 2013 measurements for the Grant River above Lake Kulik Station are summarized in the measurement summary. The stage-discharge measurements showed a good fit to the predicted values with a correlation coefficient of 0.984 (Figure X). .. Gl 4.00 3.50 3.00 .! ~' 2.50 1111 Qj % 2.00 Gl : C) 1.50 1.00 0.50 0.00 Grant Lake Outlet Station ------• Not Used in Rating --- ~ter malfuncdon) ~-.f!:lrA------~· ~-----~----~ .<{ , "-a= 12.669(GH-0.70)3·64 , , , , ~ , , I I / GZF = 0. 70 feet v 6 New Comenlional MNS~rements 0 100 200 300 400 Discharge, cfs Figure 10. Rating Curve for Grant Lake Outlet Station. Grant River above Lake Kulik Station. 500 Stage/discharge measurements for the Grant River above Lake Kulik Station are summarized in the measurement summary. The stage-discharge measurements showed a good fit to the predicted values with a correlation coefficient of 0.984 (Figure 1 0). 2011-2013 Hydrology Report NETC 15 DAHP December, 2013 Grant River above lake Kulik Station 6.50 6.00 5.50 ... 5 .00 Ql Ql -:i 4.50 Q6 'Qj % 4.00 Ql Ill .---- ------ .... ~--' --,JA "" .... -/!,.- ,liE '\ Q = 58.583(GH-3.76)2-50t ;' , R2 = 0.984 " / L GZF =3 .76feet v ,. ~ 3.50 {!,. New Conventional 3.00 2.50 l!J. ADCP Measurements 2 .00 0 100 200 300 400 500 600 Discharge.cfs Figure 11. Rating Curve for Grant River Station. Lake Elva Outlet Station Stage/discharge measurements for the Lake Elva Station are summarized in the measurement summary. The stage-discharge measurements showed a good fit to the predicted values with a high correlation coefficient of 0.997 (Figure 11 ). '101 /-'101 3 Hydrology Report NETC 16 DAHP Dece mber, '10/ 3 Lake Elva Outlet Station 5.00 4.50 4.00 3.50 ... Ql Ql .1:!.------- -r:r ----------------~, -----, L!if "' , , , 3.00 -i QO 2.50 I "" Q = 47.13{GH-2.50}2428 I ·; % Ql 2 .00 QO 111 ~ ~ R2 =0.997 " GZF = 2.5 feet 1.50 1.00 t,. New Conventional 0.50 Measurements 0.00 0 so 100 150 200 250 300 350 Discharge, cfs Figure 12. Rating Curve for Lake Elva Outlet Station. Elva Creek Station Stage/discharge measurements for the Elva Creek Station are summarized in the measurement summary. The stage-discharge measurements showed a good fit to the predicted values with a correlation coefficient of 0.985 (Figure 13). 2011-2013 Hydrology Report NETC 17 DAHP December, 2013 10.00 9 .50 9.00 ... Ql 8.50 Ql -.; .r: .!!1 8.00 Cll % Ql IIIII rl 7.50 CJ 7.00 6.50 6.00 Elva Creek above Lake Nerka Station -----· -----_ .. •. :~----- 4/)t(r _ .. - ,- --l:). "\ n-11:n ,., tr.:L -, c:\1.11 , .. ,~ -RZ,. 0.985 , ~, ~ {_.----GZF= 7.5 feet 0 6. New Conventional Measurements 100 200 300 400 Discharae, ds 500 600 Figure 13. Rating curve for Elva Creek Station. TIME SERIES DATA 700 Time series daily discharge data are available for the Grant Lake Outlet station from June 8, 20 ll through September. This the lake outlet is generally open in all but the coldest temperatures throughout the year and thus data are good with only intermittent exceptions during more severe cold weather events. The Lake Elva outlet showed ice effects from February through May. Avalanches have significant effects on this station and can both disturb the instrument or dam the lake outlet causing erroneous sensor readings or, in the case of damming the stream, making the rating inapplicable. Time series data for the two stations on the lower streams are ice-affected for significant portions of the year. These stations had ice effects present for portions ofNovember through April. Additional measurements in winter and installation of time-lapse cameras will improve the accuracy of the records by providing clear evidence of the presence ice effects and reveal periods in winter when ice effects are negligible or non-existent. Daily time series data are available by request from NETC who will forward the request to Civil Science. 2011-2013 Hydrology Report NETC 18 DAHP December, 2013 Monthly Data Monthly time series data for the four gaging stations are show a typical Alaskan hydrologic patter with highest flows in June and a gradual recession of flow through the summer months. Fall storms cause isolated high-water events before cold fall temperatures cause flows to drop into the winter low flow period. Minimum flows occur in March or April before a slight increase in flow preceding a rapid rise in levels at spring breakup. Minimum, Maximum and average daily flows for Grant Lake outlet, Grant River, Lake Elva outlet and Elva Creek for each month follow in Tables I through 4 respectively. Table 1. Minimum, Maximum and Average Daily Grant Lake Outlet Flows by Month. Month Minimum June2011" 96.8 July 2011 89.0 August 2011 66.4 September 2011 69.6 October 20 1 I 87.6 November 20 II 50.4 December 2011 50.4 January 2012 26.9 February 20 12 13.4 March 2012 22.1 April2012 22.8 May 2012 36.8 June 2012 151 July 2012 125 August 2012 70.4 # Part1al Record. June 8-June 30. 2011-2013 Hydrology Report NETC Avera2e 186 120 80.7 110 114 75.2 78.8 40.6 38.8 26.7 25.5 260 431 248 109 19 Maximum 396 171 91.7 164 137 103 104 53.2 51.9 34.6 33.4 711 740 470 165 DAHP December, 2013 Table 2. Minimum, Maximum and Average Daily Grant River Flows by Month Month Minimum July2011 46.1 August 2011 30.4 September 2011 35.6 October 2011 120 November 2011 * December 20 11 * January_ 2012 * February 2012 * March 2012 * April2012 * May 2012 93.3 June 2012 164 July 2012 144 August 2012 93.4 #, Parttal Record. July 3 July 31. *Ice affects. Avera2e Maximum 98.2 197 45.7 64.5 144 221 165 218 * * * * * * * * * * * * 417 900 474 835 287 510 193 291 Table 3. Minimum, Maximum and Average Daily Lake Elva Outlet Flows by Month Month Minimum September 20 11" 37.6 October 2011 33.7 November 20 It 25.0 December 2011 15.0 January 2012 8.7 February 2012 I 0.4 March 2012 * April2012 * May 2012 * June 2012 * July 2012 64.4 August 2012 47.8 "' Parttal Record. September 10 30. *Ice affects. 2011-2013 Hydrology Report NETC Average 67.7 41.9 29.7 25.2 12.6 * * * * * 139 124 20 Maximum 108 54.8 38.5 37.1 17.0 * * * * * 535 299 DAHP December. 2013 Table 4. Minimum, Maximum and Average Daily Elva Creek Flows by Month. Month Minimum September 2011 11 49.2 October 2011 46.2 November 2011 39.8 December 20 11 27.6 January 2012 * February 20 12 * March 2012 * April2012 * May 2012 34.2 June 2012 99.8 July 2012 76.6 August 2012 49.0 #, Parttal Record. September 9 30. *Ice affects. Avera2e Maximum 94.4 154 59.3 81.9 128 393 126 * * * * * * * * * 97.3 279 224 295 159 488 69.1 102 EXTENDED MONTHLY DATA VIA HYDROLOGICAL SYNTHESIS Hydrological correlation analyses were performed between both the USGS monthly records for the Grant Lake outlet station and Lake Elva outlet station as a function of the USGS Nuyakuk River Station. This correlation was performed to extend the records for the two lake outlet stations to develop long-term synthetic records for energy generation modeling. Details of the correlation are presented in the Conceptual Feasibility Study for the DAHP. Results of the hydrological synthesis, showing 20 1h percentile, average, 501h (median) and 80 1h percentile monthly flows are illustrated below in Figures 14 and 15 and summarized in Tables 5 and 6 for the Grant Lake and Lake Elva outlet stations respectively. 2011-2013 Hydrology Report NETC 21 DAHP December, 2013 300 250 il .; 200 1!!1 .2 u i5 1 50 > l! 1100 50 0 - -= • 20th Percentile Monthly Flow • 50th Per ce ntile Monthly Flow • Ave r age Monthly Flow • 80th Percentile Monthly Flow - ---... ] -- ---1-1- ltlJ1 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Figure 14. Synthesized Monthly 20th, 50th, Average and 80th Percent Exceedance Flows for Grant Lake Outlet Gaging Station. Table 5. Synthesized Monthly 20th, 50th, Average and 80th Percent Exceedance Flows for Grant Lake Outlet Gaging Station. Jan Feb Mar Q2o 46.3 43.3 30.2 Q50 58.2 53.2 35 .3 QAnrage 60.9 54.9 35.2 Qso 73.8 68.6 39.7 201 1-20/3 Hydrology Report NETC Apr May Jun 30 .3 123 192 36.0 162 202 35 .9 198 203 42.9 2 77 2 16 22 Jul Aug Sep 94.9 70.9 85.0 104 87.6 11 2 108 94.5 125 121 117 173 Oct Nov Dec 102 13 7 144 2 15 59.1 48.2 84.4 52.3 93.1 55.1 117 60.9 DAHP December, 20/3 140 r---------------------------------------------------~ 120 +------------------------;.-------------------------~ 100 • 20th Pe rrentile Monthly Flo •. 1------._--t ...... -------------:=---------1 • 50th Perrentile Monthly Flo • Average Monthly Flow • 80th PerrenUeMonthlyFio 80 ai e!' 60 +----------------------.2 u "' i5 40 +---------------------- 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Figure 15. Synthesized Monthly 20th, 50th, Average and 80th Percent Exceedance Flows for Lake Elva Outlet Gaging Station. Table 6. Synthesized Monthly 20th, 50th, Average and 80th Percent Exceedance Flows for Lake Elva Outlet Gaging Station. Jan Feb Mar Q2o 13.1 12.6 12.2 Qso 14.0 13.3 12.9 QAverage 14.2 13.4 12.9 Qso 15.1 14.1 13.4 2011-2013 Hydrology Report NETC Apr May 12.1 15.8 12.8 17.3 12.8 18.5 13.5 21.2 Jun Jul Aug 94.8 80.1 55.1 111 96.5 66.3 112 101 70.2 131 116 82.8 23 Sep 49.6 60.5 63.8 76.6 Oct Nov Dec 46.7 16.2 0.25 72.6 33.8 8.75 77.1 39.1 13.7 120.7 54.0 21.1 DAHP December, 2013 REFERENCE DATA & LITERATURE Gaging Station Records. USGS Station No. 15302800. Grant Lake Outlet near Aleknagik, Alaska.http://waterdata.usgs.gov/nwis/nwisman/?site no=15302800&agency cd=USGS Streamflow Measurement Records. USGS Station No. 15302800. Grant Lake Outlet near Aleknagik, Alaska. http://waterdata.usgs.gov/nwis/measurements/?site no= 15302800 Gaging Station Records. USGS Station No. 15302800. Elva Lake Outlet near Aleknagik, Alaska. http://waterdata.usgs.gov/nwis/nwismanl?site _no= 15302840&agency _ cd=USGS Streamflow Measurement Records. USGS Station No. t 5302800. Elva Lake Outlet near Aleknagik, Alaska.http://waterdata.usgs.gov/nwis/measurements/?site no= t 5302840 Nushagak Electric and Telephone Cooperative. Dillingham Area Hydroelectric Project. Conceptual Feasibility Study. Grant Lake and Lake Elva Projects. October 2013. Rantz, S.E., et al. 1982. Measurement and computation of streamflow. U.S. Geological Survey Water-Supply Paper 2175, 2 v., 631 p. United States Geological Survey. Techniques of Water-Resources Investigations Reports. Book 3: Applications of Hydraulics, Section A: Surface-water techniques. United States Geological Survey. Techniques ofWater-Resources Investigations Reports. Book 3, Chapter A6: General procedure for gaging streams. R.W. Carter and Jacob Davidian. I 968. United States Geological Survey. Techniques of Water-Resources Investigations Reports. Book 3, Chapter A7: Stage measurement at gaging stations. T.J. Buchanan and W.P. Somers. 1968. United States Geological Survey. Techniques of Water-Resources Investigations Reports. Book 3,Chapter A8: Discharge measurements at gaging stations. T.J. Buchanan and W.P. Somers. 1969. United States Geological Survey. Techniques of Water-Resources Investigations Reports. Book 3, Chapter A 19: Levels at streamflow gaging stations. E.J. Kennedy. 1990. United States Geological Survey. Techniques of Water-Resources Investigations Reports. Book 3, Chapter A21: Stream-gagingcableways, by C.R. Wagner. 1995. United States Geological Survey. Techniques of Water-Resources Investigations Reports. Book 8: Instrumentation Section B: Instruments for measurement of discharge 2011-2013 Hydrology Report NETC 24 DAHP December, 2013 Chapter B2: Calibration and maintenance of vertical-axis type current meters, by G.F. Smoot and C. E. Novak: USGS-TWRI Book 8, Chapter B2. 1968. 2011-2013 Hydrology Report NETC 25 DAHP December, 2013 APPENDIX I Station Descriptions Grant Lake Outlet near Aleknagik, Alaska Gaging Station Description/Notes Location 59°47'42"N, 158°33'11 "W per Google Earth (WGS 84). Gage is located on the right bank of Grant River appx l 00 feet below the outlet of Grant Lake at the site of discontinued USGS Station No. 15302800. Elev. approx. 400 feet. Station was re-established (new datum) on March 26, 20 ll. Station was rebuilt on June 8, 20 11 after suffering ice damage during breakup. Drainage Area 35.5 sq. mi. Gage Instrumentation LeveiTroll 500 vented transducer with Level Troll 500 non-vented transducer and compensating Barotroll. Original transducers lost during breakup May 20 II. Transducers are housed in l-1/4" wellpoint driven into streambed at original station location. Transducer cables are housed in 2" steel pipe leading to instrument shelter on right bank. Outside staff gage consists of standard enameled plates (graduated 0-3.34 feet and 3.34 to 6.67 feet) affixed to untreated 2x6'' supported in stream by steel pins driven into streambed. Gage Datum RM 3: Top of highest bedrock outcropping in channel approximately 60 feet below outside staff gage (OSS). Outcropping is located streamward approximately 1/3 of the bankfull width from the left bank. Elevation= 2.75 feet RM 4: Top head of 1/2 inch diameter lag bolt on upstream face of 18" Spruce tree located on right bank 1 0' shoreward and 7 ft downstream of the outside staff gage. Elevation 7.11 feet 2011-2013 Hydrology Report NETC Appendix II-I DAHP December 2013 Control RM 5: Top head of 1/2 inch diameter lag bolt on upstream face of 10" Birch tree located on right bank approximately 1 0' shoreward of the outside staff gage. Elevation= 7.20 feet GZF: 0.7 feet± The control is located approximately 70 ft downstream of the OSS gage and consists of cobbles and bed rock. Control should be stable at moderate to high flows. Remarks: Gage is located at site of discontinued USGS Station 15023640, Grant Lake Outlet near Aleknagik, Alaska. Original USGS datum not recovered. (USGS Reference marks RM 1 and RM2 not found). A good measuring section is located approximately 100 ft upstream from the OSS gage. Section should be good for most stages except low flows which may be measured near the control. Channel type = Rosgen C3-4. 2011-2013 Hydrology Report NETC Grant Lake Outlet GagingStation. Appendix II-2 DAHP December 2013 Grant Lake Outlet Station. RM 3. Grant Lake Outlet Station RM 4 and RM 5. RM5 to right (upstream) in photo. 201/-2013 Hydrology Report NETC Appendix II-3 DAHP December 2013 Grant River near mouth above Lake Kulik near Aleknagik, Alaska Gaging Station Description/Notes Location 59° 47' II "N, 158° 42' 25"W per Google Earth (WGS 84). Gage is located on the right bank ofGrantRiver approximately Y2 mile upstream of the stream's mouth at Lake Kulik. Elev. approx. 130 feet. Station was established on July 3, 2011. Drainage Area 44.7 sq. mi. Gage Instrumentation LevelTroll 500 vented transducer with Level Troll 500 non-vented transducer and compensating Barotroll. Transducers are housed in 1-1/4" wellpoint driven into streambed. Transducer cables are housed in 2" steel pipe leading to instrument shelter on right bank. Outside staff gage consists of standard enameled plates (graduated 3.34 - 6.67 feet and 6.67-9.99 feet) affixed to untreated 2x6'' supported in stream by steel pins driven into streambed. OSS is installed on downstream face of large split boulder where gage conduit is mounted. Gage Datum Control RM l:Top of nut on rock bolt in downstream face of boulder on right bank where gage conduit is mounted. RMl is 4.3 feet streamward ofthe right bank and 12 feet downstream from the instrument shelter. Elevation 7.15 feet RM 2: Top head of l/2 inch diameter lag bolt on shoreward face of 12" Willow tree located on left bank directly across from the gage. Tree is located 10' shoreward from the top ofthe stream's left bank. Elevation= 9.22 feet Gage Height@ Zero Flow (GZF): 3.76 feet± The control is located approximately 70 ft below OSS gage and consists of cobbles and bed rock. Control should be stable at moderate to high flows. 2011-2013 Hydrology Report NETC Appendix II-4 DAHP December 2013 Remarks A good section for measurements by wading is located 100 ft upstream from the OSS gage. Section should be good for measuring nearly all stages. Channel type = Rosgen C3-4. Grant River above Lake Kulik Gaging Station. 2011-2013 Hydrology Report NETC Appendix II-5 DAHP December 2013 2011-2013 Hydrology Report NETC Appendix II-6 DAHP December 2013 Lake Elva near Aleknagik, Alaska Gaging Station Description/Notes Location 59° 36' 17"N, 159° 7' 18"W per Google Earth (WGS 84 ). Gage is located on the left shoreline of Lake Elva below a stand of Alder brush approximately 400 feet upstream from the lake outlet. Elevation per USGS topographic map is 302 feet. Station was established on September I 0, 20 ll. Drainage Area 9.0 sq. mi. Gage Instrumentation LevelTroll 500 vented transducer with Level Troll 500 non-vented transducer and compensating Barotroll. Transducers are housed in 2" steel conduit protruding into pool below bedrock outcropping on right bank. Instrument shelter is located on top of outcropping. Outside staff gage consists of standard enameled plates (graduated 3.34- 6.67 feet and 6.67.34 to I 0.00 feet) affixed to untreated 2x6" supported by steel pins driven into lake bed. Gage Datum Control RM 1: Top of flat shelf on lakeshore boulder at gage. Shelf is located on water's side on upstream side of boulder. Elevation= 4.00 feet RM 2: Top head of downstream corner on same boulder as contains RM I. Elevation 3.75 feet The control is formed by the outlet of Lake Elva. The control should be stable at but is subject to ice effects at breakup and damming by avalanche. Remarks No signs of Discontinued USGS Gage found. 2011-2013 Hydrology Report NETC Appendix II-7 DAHP December 20/3 Aerial view of Lake Elva showing location of gaging station. 2011-2013 Hydrology Report NETC Appendix II-8 DAHP December 2013 Elva Creek near mouth at Lake Nerka near Aleknagik, Alaska Gaging Station Description/Notes Location 59° 34' 52"N, 159°3' 26"W per Google Earth (WGS 84). Gage is located on the right bank of Elva Creek appx. Y4 mile upstream ofthe stream's mouth at LakeNerka. Elev. approx. 400 feet. Station was established on September 9, 2011. Drainage Area 11.2 sq. mi. Gage Instrumentation LevelTroll 500 vented transducer with Level Troll 500 non-vented transducer and compensating Barotroll. Transducers are housed in 2" steel conduit protruding into pool below bedrock outcropping on right bank. Instrument shelter is located on top of outcropping. Outside staff gage consists of standard enameled plates (graduated 3.34- 6.67 feet and 6.67.34 to 10.00 feet) affixed to untreated 2x6" supported in stream by steel pins driven into streambed. Gage Datum Control RM 1: Top of large prominent boulder in stream channel at gage location. An "X" has been filed into the top of the boulder marking the location of RM 1 Elevation = 10.00 feet RM 2: Top head of 1/2 inch diameter lag bolt on upstream face of an 8" Spruce tree located on left bank opposite ofthe stream gage and 1 0 feet shoreward of the top of the stream bank. Elevation = 12.56 feet The control consists of cobbles and is located approximately 40 ft below the gage. At high flows, a vegetated middle bar may control gage height. Control should be stable at moderate to high flows. 2011-2013 Hydrology Report NETC Appendix 11-9 DAHP December 2013 Ae rial views of lower Elva Creek and Lake Nerka showing Elva Creek station location and boulder containing RMl. 2011-2013 Hydrology Report NETC Appendix II-10 DAHP December 2013 APPENDIX II Stage/Discharge Measurements Summary 2011-2013 Hydrology Report NETC Appendix II -II DAHP December 2013 $<-----.... -·-.by ......... OucloM -..c:S,DSP ~ll.2011 MCS.,OSl,!W" J'IH!i!l,l:CU MCS,tr!IT,It€1" ,.,;w8,20U .IK!i.,O!iT",Itl.l iuMS.Xill \ICS.tlSf.llfJ'J-llt.lOtl MC!>,DS"f,Rf_l 0 J"'fyol,lOit liotCS,CIST",II£JJcly4,.!1'1lt MCS,DST"' ~pt.t.l'OH ~~I.O.lDU ___ .....,_ MCS,MT,UJ' Jvtyi,2tll1 MCS.O'.ST".IIEJ lvfyl,.!Ot1 MCS.~T.IIOrNtv\,:toll lo4CS.~f' ~t~4.i011 GW',ltU s.pt~lO.N.lJ ..... u..-.. ~/MT"'/II'fl ~<•J.t\,lm1 ~5-0H,IIU"JulyS,]Q]l M<~'.ru.t.IW Ju!yS,XIU w;!S,OI.T~ ~~~~~~1,1:6H W.!I,Ol>f" S•pt.....O..W.lmt .... " .... _.....,_ MCS.~T".I!tl h•M\20!1 MCt OS':'. 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In all tests, ADCP measurements were made concurrent with conventional discharge measurements to allow comparison with standard equipment/techniques. The ADCP was found to provide excellent results but with some limitations. The ADCP is not suited for very low flows as a tethered boat. Winter measurements will still require conventional techniques, including measurements under ice cover. The StreamPro ADCP does has a routine, called "Section by Section", which permits it to measure discharge by making point readings at various stations along the stream section which does permit the unit to measure low flows or through a hole bored through ice cover making it function much like a conventional Price meter. This feature was not evaluated. While the section by section routine is undoubtedly valuable, the complex electronics of the ADCP still warrant taking conventional gear along, particularly in winter. Measurement No. 2 on Elva Creek was affected by turbulent flow and standing waves due to the high runoff. These water conditions caused the manufactures boat to roll excessively even to the point of capsize on one measurement attempt making discharge measurements extremely difficult. These same conditions also affected the concurrent conventional measurement that was made (Elva Creek Measurement No. 1). Modifications can be made to the StreamPro ADCP's tethered boat through the addition of retractable skegs mounted on the exterior of the unit's catamaran hull a small drogue may also be useful. ADCP measurements were much more expeditious than conventional measurements. On average, an ADCP measurement was made in approximately 1/3 the time of a conventional measurement. This is significant because measurements may be made at multiple stations during the same day thereby reducing field efforts or a measurement may be completed where it might not have been possible to complete with conventional equipment. An example of such a case is an early pickup brought forth by the pilot's knowledge of forthcoming weather. It is believed that the time to make a measurement via ADCP will likely decrease further as users become more familiar with the unit operation , further increasing its benefit. ADCP Trials are summarized below in Table III-I. Draft 20/1 Hydrology Report NETC Appendix III-1 DAHP April. 2012 Table 111-1. ADCP/Conventional Discharge Measurements Comparison Measurement Duration, Result, Result, Station cfs cfs Nos. minutes (Conv.) (ADCP) Grant Lake 3,4* 20*/40 310 291 Outlet Grant 109.4 Lake 6*, 7 28*/40 106 Outlet Grant River I*, 2, 3* 18*/48/17* 130 131.0 /133.5 Elva Creek 1, 2* 15*/46 186.0 203.1 Lake Elva 1,2*,3# 35/20*171# 86.8/97.1 93.4 Outlet *ADCP Measurement # precision measurement ( 48 verticals) ## Comparison between measurement no. 3 and ADCP measurement. Draft 2011 Hydrology Report NETC Appendix Ill-2 Conventional rating E (2%) E (2%) G(5%) F (8%) F (8%) Variance 19 cfs (+6%) 3.4 cfs (+3.2%) +1.7% # 17.1 (+9.2%) -3.7## (-3.8%) DAHP April, 2012