Bucks Creek Hydroelectric Project, FERC Project No. 619 Proposed Study Plan WR-S3 STUDY DESCRIPTION WR-S3 DEVELOP UNIMPAIRED AND REGULATED HYDROLOGY FOR PROJECTAFFECTED STREAM REACHES AND EVALUATE WITH INDICATORS OF HYDROLOGIC ALTERATION MODEL Revised May 2014 STUDY GOAL AND OBJECTIVE The Bucks Creek Project (Project) Pre-Application Document (PAD), November 15, 2013, identified issues associated with water resources for which the existing, relevant, and reasonably available information is insufficient to address the issues. These issues are: WR-1 Potential Project effects on water temperature in Project reservoirs and Project-affected stream reaches WR-2 Consistency of Project reservoirs and Project-affected stream reaches with Water Quality Standards FA-4 species. Effects of Project operations on common amphibian and aquatic reptile FA-5 Effects of the Project on instream habitat in Project-affected streams. RWL-1 Effects of the Project on riparian habitat in tributaries. RWL-2 Effects of the Project on wetland habitat along reservoir margins. RTE-1 Effects of Project operations on special-status amphibian and aquatic reptile species The goal of this study is to develop the essential additional information to supplement the existing information, which is necessary to address the identified issues. The specific information to be developed is the unimpaired and regulated flow regimes for affected reaches of the Bucks, Grizzly and Milk Ranch creeks and to evaluate against Licensees’ existing Indicators of Hydrologic Alteration (IHA). EXISTING INFORMATION Section 5.2 of the PAD contains extensive information on Project-related hydrology, including (1) data on the current hydrologic conditions of the Project features and related waterways, (2) historical records of precipitation, and (3) morphometric characteristics of Project reservoirs. Appendix E of the PAD contains monthly and annual flow duration curves for stream gages on the Milk Ranch, Bucks, and Grizzly creek watersheds, and Appendix G contains generation and outflow records for the two powerhouses at the Project. The Licensees also maintain extensive streamflow gaging data and reservoir elevation data in its archives. 1 Bucks Creek Hydroelectric Project, FERC Project No. 619 ©2014, Pacific Gas and Electric Company and the City of Santa Clara WR-S3 Bucks Creek Hydroelectric Project, FERC Project No. 619 Proposed Study Plan Stream gaging information and precipitation records are available from the U.S. Geological Survey (USGS), California Department of Water Resources (DWR), and Licensees. However, because the Project facilities have been in place since about 1929, information or evaluation of the hydrology in the entire Project-affected stream reaches prior to construction of the Project does not exist. An unimpaired and regulated hydrology was prepared for the Bucks and Grizzly Creek portion of the Project in an Indicators of Hydrologic Alteration (IHA) study (PG&E 2003). The synthesized record of mean daily streamflows covers a 32-year period from 1970 through 2001. Because of the lack of any accurate streamflow or storage information on Milk Ranch Creek, streamflows were not synthesized for any points in that basin (PG&E 2003). NEXUS BETWEEN THE PROJECT AND RESOURCE TO BE STUDIED AND HOW THE RESULTS WILL BE USED Project construction, operation, and maintenance activities directly and indirectly affect the Project stream hydrology. The results of this study will be used in conjunction with the results of other, resource-specific studies to evaluate potential Project effects and develop management measures that may be employed to address those effects. The study will address the relevant hydrological management goals stated within applicable resource management plans (PNF 1988). STUDY AREA AND STUDY SITES The Study Area includes (1) Milk Ranch Creek from the inflow to Three Lakes to the North Fork Feather River (NFFR), (2) Bucks Creek from the inflow to Bucks Lake to Lower Bucks Lake, (3) Bucks Creek from the inflow to Lower Bucks Lake to the NFFR, and (4) Grizzly Creek from the inflow to Grizzly Forebay to the NFFR. Hydrologic records will be compiled so that unimpaired flow can be determined for Three Lakes, Bucks Lake, and Grizzly Forebay. The Licensees propose using the already developed unimpaired flow estimates for Bucks Lake and Grizzly Forebay (PG&E 2003). Both regulated and unimpaired flow will be determined at four points in the Project area used in the IHA analysis (see below). As part of developing the database, hydrologic records from various streams in the Milk Ranch, Bucks, and Grizzly creek watersheds, as well as active feeder streams, will also be reviewed. The anticipated study nodes are as follows: Milk Ranch Creek (downstream of Three Lakes, USGS Gage 11403300), Milk Ranch Creek Conduit outlet (USGS Gage 11403450), Bucks Creek (downstream of Bucks Lake, USGS Gage 11403530), Bucks Creek (downstream of Lower Bucks Lake, USGS Gage 11403520), Bucks Creek (near Bucks Lake, USGS Gage 11403500), Bucks Creek Powerhouse outflow (USGS Gage 11403700), Bucks Creek Tunnel outlet (USGS Gage 11404100), 2 Bucks Creek Hydroelectric Project, FERC Project No. 619 ©2014, Pacific Gas and Electric Company and the City of Santa Clara Bucks Creek Hydroelectric Project, FERC Project No. 619 Proposed Study Plan Grizzly Creek (inflow to Grizzly Forebay, USGS Gage 11404250), Grizzly Creek (downstream of Grizzly Forebay, USGS Gage 11404300), and Grizzly Powerhouse outflow (USGS Gage 11404240). WR-S3 Specifically excluded from the Study Area are areas where access is unsafe (very steep terrain or high water flows) or private property for which Licensees have not received specific approval from the landowner to enter the property to perform the study. The Licensees will make a good faith effort to obtain access to private property to conduct the study. METHODS To develop the regulated and unregulated hydrological database for the Project, two different methods will be used: summation and proration. The primary method for synthesizing streamflow data will use mass balance equations for all points where gaging station records and/or observer’s reports are available. All available USGS and Licensee data will be used to compute the unimpaired daily average flows for the study period. For periods of missing data, the daily flow data may be estimated from previous or following records, by comparison with other station records from the same or nearby basins and/or by using a rainfall-runoff simulation model, if necessary. The representative basin(s) will be selected based on similarities in configuration (e.g., size, climate, topography, elevation, geology). The daily flows may also be estimated by using flow data at nearby unregulated streams and adjusting its magnitude by multiplying data by a factor based on the ratio of their respective drainage areas. Summation and proration are described below. Summation Summation uses mass balance equations for all points where gaging station records and/or observer’s reports were available. For reservoirs, this incorporates the determination of inflows using the hydrologic water budget equation: S = I – O where the change in storage (S) equals inflow (I) minus outflow (O). The summation method also assimilates stream flow gage data from contributing drainage areas and accounts for losses from diversion flows. Proration The proration method estimates daily, unimpaired flows for a given watershed of interest based upon unimpaired flow data in a similar (reference) watershed. The unimpaired flow data in the reference watershed is then prorated to the watershed of interest by applying a drainage area ratio factor (i.e., drainage area ratio equals drainage area of watershed of interest divided by drainage area of reference watershed). If the unimpaired flow data for the reference watershed are accurate, then the proration method is very effective when applied to watersheds with similar physical characteristics (e.g., climate, topography, elevation, geology). Accretion to the channel is assumed to be positive and will be estimated based on contributing area. 3 Bucks Creek Hydroelectric Project, FERC Project No. 619 ©2014, Pacific Gas and Electric Company and the City of Santa Clara Bucks Creek Hydroelectric Project, FERC Project No. 619 Proposed Study Plan WR-S3 As recommended by Richter et al. (1998, 1997, 1996), IHA statistics are normally calculated at riverine locations where measured hydrology data (mean daily flows) are available for about 20 to 30 years from both the pre-Project and Project period. The Licensees’ approach will differ from this normal approach in one major way. Because 30 years of pre-Project flow data are not available for all Project-affected stream reaches, Licensees will utilize the 32-year (1970-2001) synthesized unimpaired flow developed for the existing IHA analysis (PG&E 2003). Milk Ranch Creek unimpaired and regulated flow will be developed for the same time period using the above techniques. The length of hydrologic record developed will ultimately be determined by the completeness of the data sets available for analysis and simulation. Currently, Licensees intend to use at least a 30-year period of record, which would include a reasonable range of wet, dry, critically dry and normal water year conditions. Water year type classifications may be developed that would be applicable to the Milk Ranch, Bucks, and Grizzly creek watersheds, depending on review of the hydrologic data and in consultation with the Relicensing Participants. If water year types are necessary, inflow data for the period of record would be ranked and broken into four or five categories (e.g., critically dry, dry, normal, and wet) based on exceedance percentages. ANALYSIS The Licensees propose to use the IHA analysis developed in 2003 for this project (PG&E 2003). This analysis allowed for assessment of changes in the hydrologic condition on the associated environmental concerns at four sites within the Project area: Bucks Creek at the Lower Bucks Lake Diversion Dam (Upper Bucks); Bucks Creek at the North Fork Feather River (Lower Bucks); Grizzly Creek at the Grizzly Forebay Dam (Upper Grizzly); and Grizzly Creek at the North Fork Feather River (Lower Grizzly). There are 32 statistical metrics that focus on descriptors of the streamflow regime that are considered to be important to the biological and physical integrity of the river. The 32 metrics derived in the IHA analysis can be clustered into five specific groups, which can then be used to assess potential environmental impact. The ecosystem influence for each of the 32 metrics is well described in the methods. The five groups for the IHA metrics, which are identified in the IHA protocol as described by Richter et al. (1996, 1997, and 1998), are listed below: Magnitude of monthly water conditions, Magnitude and duration of annual extreme water conditions, Timing of annual extreme water conditions, Frequency and duration of high and low pulses, and Rate and frequency of change in water conditions. The statistical parameters derived using this method will allow for evaluation of the Projectaffected reaches. The IHA program analyzes the noted metrics using the Range of Variability Approach (RVA). This analysis determines the statistical variation of each of the 32 metrics in the pre-development condition. The model then computes the expected frequency values by 4 Bucks Creek Hydroelectric Project, FERC Project No. 619 ©2014, Pacific Gas and Electric Company and the City of Santa Clara Bucks Creek Hydroelectric Project, FERC Project No. 619 Proposed Study Plan WR-S3 percentile categories for both the pre- and post-development. The IHA factor ((observed frequency-expected frequency)/expected frequency) is then computed. The analysis assumes that the two values should be approximately equal. Annual and monthly flow duration curves of regulated and unimpaired flows will also be constructed for the Milk Ranch, Bucks, and Grizzly creek watersheds. Flood frequency statistics will be reviewed and summarized. Sources for flood information could include probable maximum flood studies and/or studies by federal agencies such as the U.S. Army Corps of Engineers and USGS. CONSISTENCY WITH GENERALLY ACCEPTED SCIENTIFIC PRACTICE The methods used for development of the regulated and unimpaired hydrology database are widely used for this purpose and accepted in the scientific and engineering communities. For the IHA evaluation the Licensees’ existing study (PG&E 2003) utilized approaches still in common practice today. The most recent IHA program (version 7; 2005) has added more metrics and groupings, but retains the ones evaluated in the PG&E study and both follow Richter et al. (1996, 1997, and 1998). PRODUCTS Study products will include a presentation to resource agency personnel and other interested parties. Study results will be provided to the Relicensing Participants as soon as possible after the data are collected, tabulated, summarized and checked for quality (i.e., Quality Assurance/Quality Control); this is anticipated to be in the second quarter of 2016. The Licensees intend to have study results, to the degree complete, available in sufficient time to allow collaborative development of possible protection, mitigation, and enhancement (PM&E) measures for inclusion in its Preliminary Licensing Proposal due on August 3, 2016. A summary of the information and findings will be included in Exhibit E of the Application for New License. Data gathered as part of the study will be also included as an appendix to the License Application. RELATIONSHIP TO OTHER STUDIES Information developed in this study will also be useful in understanding how Project operations affect various Project-related resources, including Study Plan GS-S1, Erosion and Sedimentation; Study Plan FA-S3, Benthic Macroinvertebrates; Study Plan RTE-S1, Specialstatus Amphibian and Aquatic Reptiles; and Study Plan RWL-S1, Riparian and Wetland Survey. Data developed from this study would also be used in Study Plan WR-S4, Develop Project Operation Model. The results of this study would allow for precise scoping of these studies. SCHEDULE Since the development of the regulated and unimpaired hydrological database is important for timely considerations by other studies and is based on existing information, Licensees will commence this study as soon as possible after its review and discussion among resource agencies and other interested parties. It is anticipated that the hydrological database will be developed by fall 2014. 5 Bucks Creek Hydroelectric Project, FERC Project No. 619 ©2014, Pacific Gas and Electric Company and the City of Santa Clara WR-S3 Bucks Creek Hydroelectric Project, FERC Project No. 619 Proposed Study Plan LEVEL OF EFFORT AND COST The preliminary estimated cost for the study, broken down by major tasks, is as follows: Office Work ......................................................$ 47,000 Geomorphic Interpretation ................................$ 40,000 Analysis.............................................................$ 13,000 Products.............................................................$ 25,000 Total (2014 dollars) .........................................$ 125,000 REFERENCES PNF (Plumas National Forest). 1988. Plumas National Forest land and resource management plan. Department of Agriculture, Quincy, California. August 26, 1988. Available at: http://www.fs.usda.gov/land/plumas/landmanagement. Richter, B.D., J.V. Baumgartner, D.P. Braun, and J. Powell, and D.P. Braun. 1996. A method for assessing hydrologic alteration within ecosystems. Conservation Biology 10:11631174. Richter, B.D., J.V. Baumgartner, D.P. Braun, and J. Powell. 1998. A spatial assessment of hydrologic alterations within a river network. Regulated Rivers: Research & Management 14:329-340. Richter, B.D., J.V. Baumgartner, D.P. Braun, and R. Wiginton, and D.P. Braun. 1997. How much water does a river need? Freshwater Biology 37:231-349. TNC (The Nature Conservancy), Totten Software Design, and Smythe Scientific Software. 2006. Indicators of hydrologic alteration version 7 users manual. The Nature Conservancy. July 2006. 6 Bucks Creek Hydroelectric Project, FERC Project No. 619 ©2014, Pacific Gas and Electric Company and the City of Santa Clara