TACOMA HYDROELECTRIC PROJECT PROJECT EFFECTS ON THE WATER QUANTITY AND QUALITY OF THE ANIMAS RIVER

TACOMA HYDROELECTRIC PROJECT PROJECT EFFECTS ON THE WATER QUANTITY AND QUALITY OF THE ANIMAS RIVER Prepared for: PUBLIC SERVICE CO. OF COLORADO Durango, Colorado Prepared by: DEVINE TARBELL & ASSOCIATES, INC. Portland, Maine NOVEMBER 27

TACOMA HYDROELECTRIC PROJECT PROJECT EFFECTS ON THE WATER QUANTITY AND QUALITY OF THE ANIMAS RIVER TABLE OF CONTENTS Section Title Page No. 1. PURPOSE AND BACKGROUND...1 2. SYNTHETIC UNIMPAIRED HYDROGRAPH OF CASCADE CREEK...3 3. PROJECT OPERATIONS...4 4. POTENTIAL REFERENCE WATERSHEDS...6 5. DEVELOPMENT OF HYDROLOGY USING SELECTED REFERENCE SITES...9 6. WATER QUALITY ASSESSMENT...14 7. SUMMARY OF RESULTS...16 8. REFERENCES...2 APPENDICES APPENDIX A - POR SYNTHESIZED HYDROLOGY FLOW EXCEEDANCE TABLES AND GRAPHS APPENDIX B - REPRESENTATIVE WET YEAR (1997) SYNTHESIZED HYDROLOGY FLOW EXCEEDANCE TABLES AND GRAPHS APPENDIX C - REPRESENTATIVE DRY YEAR (22) SYNTHESIZED HYDROLOGY FLOW EXCEEDANCE TABLES AND GRAPHS APPENDIX D - REPRESENTATIVE NORMAL YEAR (24) SYNTHESIZED HYDROLOGY FLOW EXCEEDANCE TABLES AND GRAPHS APPENDIX E - REPRESENTATIVE WET, DRY AND NORMAL HYDROGRAPHS APPENDIX F - COMPARISON OF FLOW DATA FOR CASCADE CREEK ABOVE CASCADE CREEK DIVERSION DAM AND CDWR S RECORDS FOR PSCO S CASCADE CREEK DIVERSIONS i

TACOMA HYDROELECTRIC PROJECT PROJECT EFFECTS ON THE WATER QUANTITY AND QUALITY OF THE ANIMAS RIVER LIST OF FIGURES Figure Title Page No. 1 EFFECTS OF PROJECT OPERATIONS ON TRACE METAL CONCENTRATIONS IN THE ANIMAS RIVER BELOW TACOMA POWERHOUSE (22)...15 2 CASCADE CREEK AT THE CASCADE CREEK DIVERSION DAM UNIMPAIRED AND IMPAIRED HYDROLOGY FOR REPRESENTATIVE NORMAL YEAR (24)...17 3 CASCADE CREEK ABOVE THE CONFLUENCE WITH THE ANIMAS RIVER UNIMPAIRED AND IMPAIRED HYDROLOGY FOR REPRESENTATIVE NORMAL YEAR (24)...17 4 ANIMAS RIVER ABOVE CASCADE CREEK UNIMPAIRED AND IMPAIRED HYDROLOGY FOR REPRESENTATIVE NORMAL YEAR (24)...18 5 ANIMAS RIVER BELOW CASCADE CREEK UNIMPAIRED AND IMPAIRED HYDROLOGY FOR REPRESENTATIVE NORMAL YEAR (24)...18 6 ANIMAS RIVER ABOVE TACOMA POWERHOUSE UNIMPAIRED AND IMPAIRED HYDROLOGY FOR REPRESENTATIVE NORMAL YEAR (24)...19 7 ANIMAS RIVER BELOW TACOMA POWERHOUSE UNIMPAIRED AND IMPAIRED HYDROLOGY FOR REPRESENTATIVE NORMAL YEAR (24)...19 ii

TACOMA HYDROELECTRIC PROJECT PROJECT EFFECTS ON THE WATER QUANTITY AND QUALITY OF THE ANIMAS RIVER LIST OF TABLES Table Title Page No. 1 USGS GAGES IN THE PROJECT VICINITY...7 2 COMPARISON OF CASCADE CREEK AT THE CASCADE CREEK DIVERSION DAM BASIN AND USGS GAGE VALLECITO CREEK NEAR BAYFIELD...1 3 COMPARISON OF CASCADE CREEK ABOVE THE CONFLUENCE WITH THE ANIMAS RIVER BASIN AND VALLECITO CREEK NEAR BAYFIELD GAGE...11 4 COMPARISON OF ANIMAS RIVER ABOVE CASCADE CREEK AND ANIMAS RIVER BELOW SILVERTON GAGE...12 5 COMPARISON OF ANIMAS RIVER ABOVE TACOMA POWERHOUSE AND ANIMAS RIVER BELOW SILVERTON GAGE...12 6 COMPARISON OF ANIMAS RIVER BELOW TACOMA POWERHOUSE AND ANIMAS RIVER BELOW SILVERTON GAGE...13 7 EFFECTS OF PROJECT OPERATIONS ON TRACE METAL CONCENTRATIONS IN THE ANIMAS RIVER BELOW TACOMA POWERHOUSE (22)...14 iii

Section 1 Purpose and Background This report describes the development of hydrologic data for certain watersheds associated with the Tacoma Hydroelectric Project. This study was performed in support of an analysis of the potential effects of the Tacoma Project on the water flows and water quality of the Animas River. The Tacoma Project is located approximately 2 miles north of Durango, Colorado, on a high intermountain plateau west of the Animas River in La Plata and San Juan counties. The Project is owned and operated by Public Service Company of Colorado (PSCo). This report includes discussion of methods used to evaluate and develop the unimpaired hydrology of the Animas River and the influence of the Project operations on that unimpaired hydrology as it might effect specific water quality parameters, specifically dilutional effects on organics, metals, and nutrient loadings. The hydrology of the Project area was developed using a straight-line or linear proration methodology. The proration method estimates unimpaired flows for a region of interest using unimpaired streamflow measurements from one or more reference basins. The equation below estimates unimpaired flows based on an area-weighted correlation to flows at a reference site: Q target A = A target reference Q reference where: Qtarget is the flow (cfs) for the basin of interest, Qreference is the flow (cfs) for the reference basin, Atarget is the drainage area (square miles) for the basin of interest, Areference is the drainage area (square miles) for the reference basin. Drainage areas were taken directly from U.S. Geological Survey (USGS) records where available, or by using Geographic Information Systems (GIS) based calculations. 1

Section 1 Purpose and Background Once the basin hydrologic data are established, the dilutional effects of Project operations on the Animas River related to metals, organics, or nutrient concentrations can be estimated as follows: Q A = Q N + Q P TM A = Q A x C 1 C 2 = TM A / Q N where Q A = Animas River average daily flow below Tacoma powerhouse Q N = Animas River average daily unimpaired flow below Tacoma powerhouse Q P = Net Tacoma plant flow (Q Out Q In ) TM A = Total parameter loading in the Animas below Tacoma powerhouse C 1 = Parameter concentration in Animas River below Tacoma powerhouse C 2 = Parameter concentration in Animas River under unimpaired flow conditions The Cascade Creek drainage above PSCo s diversion dam is an undeveloped watershed located virtually entirely within the boundaries of the San Juan National Forest. Relative to the Animas River drainage, very little mining or development activity has occurred in the Cascade Creek drainage. The waters of Cascade Creek above the diversion dam have excellent physical and chemical water quality characteristics. It is generally agreed that the water quality of Cascade Creek related to the parameters of organics, metals, and nutrient loading is significantly better than that of the Animas River. This being the case, then the following also holds true: when: Q A > Q N; C 1 < C 2 Q A < Q N ; C 1 > C 2 2

Section 2 Synthetic Unimpaired Hydrograph of Cascade Creek The proration methodology requires hydrologic similarity between the basin of interest and the reference drainage. Hydrologic similarity implies that the Project and reference sites possess comparable physical characteristics such as climate, land cover, elevation, aspect, and geology. If the features of the watershed of interest deviate from that of the reference site, the prorated unimpaired stream flows may deviate accordingly; therefore, when the character of the Project and reference sites differ significantly, application of the proration method provides less reliable results. For hydrologically similar unimpaired watersheds, it has been shown that drainage area correlates well with flow rate. Consequently, to estimate the unimpaired streamflow of a regulated drainage, the reference site should be unregulated and have a sufficiently long period of record. If, however, a completely natural reference site is not available, a site with limited regulation should be chosen to minimize the effects of cumulative errors. The high mountains of southwestern Colorado experience a relatively large amount of meteorological variation due largely to the effects of orographic lift and precipitation shadowing. Indeed, these processes can occur on very small spatial scales leading to equally significant variability in basin runoff response. While the mechanisms of lift and shadowing cannot easily be measured, the aforementioned watershed characteristics (e.g., climate, topography, land cover, elevation, aspect, and geology) influence these processes. To minimize this variability and provide accuracy to the streamflow estimates for the Project basin, a reference site in close proximity to Cascade Creek with reasonably comparable precipitation, elevation, aspect, slope, and percent water body was selected. 3

Section 3 Project Operations The Tacoma Project is located about 2 miles north of Durango, Colorado, on a high intermountain plateau west of the Animas River in La Plata and San Juan Counties. The Project was constructed in 195 and 196. Water supply for operation of the facilities originates in three drainage basins: Cascade Creek, Little Cascade Creek, and Elbert Creek. The Project consists of the Cascade Creek diversion facilities and four dams Cascade Creek Diversion Dam, Aspaas Dam, Stagecoach Dam, and Terminal Dam which impounds the main storage reservoir, Electra Lake. The Cascade Creek diversion facilities deliver the major water supply component for the Tacoma Project. These facilities consist of an approximately 1-foot-high concrete diversion dam on Cascade Creek with a normal water level at approximately 8,9 feet 1 ; 4,2 feet of 1-footdiameter, semi-circular, elevated wooden flume; a 1,4-foot-long, 6-inch-diameter steel inverted siphon crossing Cascade Creek; and a 14,5-foot-long, 64-inch-diameter steel pipeline. The Cascade Creek Diversion Dam is located 3.9 miles upstream of the confluence of Cascade Creek and Lime Creek at Purgatory Flats. After its confluence with Lime Creek, Cascade Creek flows approximately another 2.8 miles to where it enters the Animas River. Water from Cascade Creek is transported through the Cascade Creek diversion facilities and then released into Little Cascade Creek. A gaging station recording flows exiting the Cascade Creek diversion pipe is located at the outlet of the pipe before the flow enters Little Cascade Creek. The open channel of Little Cascade Creek carries the water to Aspaas Lake located just north of Electra Lake. Flows in Little Cascade Creek are then diverted at Aspaas Dam into Electra Lake, which is formed by Terminal Dam on the main channel of Elbert Creek. An 11,4-foot-long steel penstock extends from Electra Lake to the Tacoma powerhouse. The maximum static head between Electra Lake and the Tacoma powerhouse is 1,77 feet. 1 All elevations are provide in mean sea level (msl) datum. 4

Section 3 Project Operations Aspaas Lake impounds approximately 24 acre-feet of water at the normal maximum operating level of 8,377 feet. The corresponding reservoir surface area is approximately 4 acres. Columbine Lake is located within the Project Boundary along the flowline that delivers Project water diverted from Cascade Creek into Electra Lake. The small timber dam at the downstream end of Columbine Lake has been breached. There are no plans to rebuild the dam as it serves no Project purpose. The pond is roughly.5 miles long with a surface area of approximately 4 acres. The lake is generally less than 5 feet deep and has no usable storage. The normal water surface elevation of Columbine Lake is approximately 8,8 feet. Terminal Dam impounds Electra Lake, a reservoir with about 2,6 acre-feet of active storage at its normal maximum water surface elevation of 8,377 feet. The corresponding surface area is approximately 8 acres. During normal water years, Electra Lake is filled by runoff during the spring and early summer. Runoff from snowmelt typically occurs from late April through July, with peak flows occurring in late May to mid-june. During the spring runoff period, the plant is operated at a constant daily output, otherwise known as a base-load schedule. Over a number of weeks, generation is increased gradually to balance outflow with inflow into Electra Lake. Once plant capacity is reached, excess inflow is used to fill Electra Lake. Beginning in August, the plant is operated at a reduced capacity in order to maintain the level of Electra Lake to within several feet of its normal high water level (elevation 8,377 feet). In August and September, the output of the plant is reduced as snowmelt is exhausted and streamflows subside. In anticipation of next spring s runoff, the plant output is increased in late November or early December, operated on a peaking schedule, to gradually drawdown the reservoir to its winter settings with a normal minimum operating level of 8,357 feet. 5

Section 4 Potential Reference Watersheds The development of reference basins for the watersheds related to the Tacoma Project began with a compilation of the available USGS gages in the vicinity of the Project area (Table 1). This list of gages was reviewed for applicability based on the period of record, drainage area size, elevation, and average annual precipitation. The color-coding provided in Table 1 shows the first step in the process of searching for a reference basin based on initial screening selection criteria. The three screening methodologies employed are described below: Period of Record - Gages were excluded that had less than 1 consecutive years of hydrology, or a Period of Record (POR) which did not include recent years due to the potential for changes in watershed characteristics resulting from development and/or recent land use practices. Drainage Area - Gages with a drainage area greater than 5 square miles or approximately two times the drainage area of the Animas River above Cascade Creek were excluded from the list to avoid inaccuracies due to dissimilarities in watershed characteristics such as the tendency for larger basins to have lower slopes while typically encompassing a larger range of elevations. Basin Characteristics - Basin characteristics such as elevation, geographic orientation, average annual precipitation and water transfers were reviewed to identify gages with significantly different characteristics. Representative hydrology for Cascade Creek at the PSCo diversion dam was previously estimated in the Cascade Creek Hydrology report developed by Devine Tarbell & Associates, Inc. ([DTA] 26) wherein the reference gage selected was the USGS stream gage at Vallecito Creek near Bayfield 93529. 6

Section 4 Potential Reference Watersheds TABLE 1 USGS GAGES IN THE PROJECT VICINITY Gage Site USGS Gage ID Elevation, feet above msl Drainage area, mi 2 Period of Record Animas River above Tacoma 93595 7,52 348 1/1/1945-9/3/1956 Animas River at Durango 93615 6,52 692 1/1/1897 - Present Animas River at Howardsville 93575 9,617 55.9 1/1/1935-9/3/1982 Animas River at Silverton 9358 9,29 7.6 1/1/1991 - Present Animas River below Silverton 93592 9,2 146 1/1/1991 - Present Beaver Creek near Norwood 9173 8,1 4.6 1/1/1941-9/3/1981 Cimarron River near Cimarron 9126 8,642 66.6 1/1/1954 - Present Cebolla Creek near Lake City 91215 1,2 25.2 8/1/1946-9/3/1954 Cement Creek at Silverton 935855 9,38 2.1 1/1/1991 - Present Cow Creek near Ridgway 91471 7,62 45.4 1/1/1955-9/3/1973 Dolores River at Dolores 91665 6,94 54 1/1/1895-9/3/25 Dolores River below Rico 9165 8,422 15 1/1/1951 - Present Dolores River near Mcphee 91675 6,666 817 1/1/1938-9/3/1952 East Fork Dallas Creek near Ridgway 91465 7,98 16.8 1/1/1947-9/3/197 E. Fork San Juan R ab Sand Ck, nr Pagosa Spgs 93399 7,94 64.1 1/1/1956 3/3/23 East Mancos River near Mancos 9369 7,475 11.9 4/1/1937-9/3/1951 Fall Creek near Durango 93612 7,8 7.18 1/1/1959-9/3/1965 Fall Creek near Fall Creek 9172 7,929 33.4 8/1/1941-9/3/1959 Florida River below Lemon Reservoir 93629 7,92 68.8 1/1/1955-9/3/1963 Florida River near Durango 93635 7,65 17 1/1/1967-9/3/1982 Florida River near Durango 9363 7,32 97.4 1/1/191-9/3/196 Hermosa Creek near Hermosa 9361 6,76 171 1/1/192-9/3/198 Junction Creek near Durango 93614 7,46 26.3 1/1/1959-9/3/1965 La Plata River at Hesperus 93655 8,15 37 1/1/1917-9/3/25 Lake Fork below Mill Gulch near Lake City 91234 9,4 57.5 1/1/1981-9/3/1986 Lightner Creek near Durango 9362 6,534 66 1/1/1927-9/3/1949 Legend For Table 1: Short Period of Record / No Recent Hydrology Large Drainage Area Dissimilar Basin Characteristics 7

Section 4 Potential Reference Watersheds Gage Site USGS Gage ID Elevation, feet above msl Drainage area, mi 2 Period of Record Lime Creek near Silverton 93591 9,5 33.9 1/1/1956-9/3/1961 Los Pinos River near Bayfield 93535 7,583 27 1/1/1927-9/3/1986 Lost Canyon Creek at Dolores 9167 6,92 73.5 3/1/1941-9/3/1948 Lost Canyon Creek near Dolores 916695 7,3 71.3 4/1/1984 - Present Mancos River near Manco 937 7,235 71.5 1/1/1931-9/3/1938 Middle Fork Piedra River near Pagosa Springs 93472 8,21 32.2 1/1/1969-9/3/1975 Middle Fork Piedra River near Dyke 934725 7,845 34.1 1/1/1977-9/3/1983 Middle Mancos River near Mancos 93695 7,5 12.1 4/1/1938-9/3/1951 Mineral Creek above Silverton 93589 9,98 11 1/1/1968-9/3/1975 Mineral Creek near Silverton 9359 9,399 43.9 1/1/1936-9/3/1949 North Clear Creek below Continental Reservoir 82145 1,2 51.7 5/1/1929-9/3/1998 Piedra River near Pagosa Springs 93475 7,64 82.3 1/1/1936-9/3/1954 Piedra River near Piedra 93495 6,51 371 1/1/1939-9/3/1973 Red Mountain Creek above Ironton 91445 9,586 18.1 1/1/1947-12/31/1955 Rio Grande River near Creede 82135 9,3 163 6/1/199-9/3/1998 San Miguel River near Placerville 91725 7,3 31 1/1/191 - Present Turkey Creek near Pagosa Springs 9342 7,617 23 5/1/1937 9/3/1949 Uncompahgre River below Ouray 9146 7,67 75.2 1/1/1913-9/3/1929 Uncompahgre River near Ridgway 91462 6,878 149 1/1/1958 - Present Vallecito Creek near Bayfield 93529 7,96 72.5 1/1/1962 - Present Weminuche Creek near Pagosa Springs 9349 7,958 53.4 4/1/1937-9/3/1949 West Dolores River near Stoner 9166 7,55 162 3/1/1941-9/3/1944 West Fork San Juan R, near Pagosa Springs 9345 8,4 41.2 4/1/1937 9/3/1953 Williams Creek near Pagosa Springs 93485 7,81 43.7 1/1/1937-9/3/1949 Wilson Gulch near Durango 936255 6,58 6.5 6/7/1995-9/3/25 Legend For Table 1: Short Period of Record / No Recent Hydrology Large Drainage Area Dissimilar Basin Characteristics 8

Section 5 Development of Hydrology Using Selected Reference Sites An analysis of the potential sites listed in Table 1 according to basin characteristics lead to the following selections of reference basins for the watersheds associated with the Tacoma Project: Cascade Creek at the Cascade Creek Diversion Dam reference basin is Vallecito Creek near Bayfield 93529 Cascade Creek above the confluence with the Animas River reference basin is Vallecito Creek near Bayfield 93529 Animas River above Cascade Creek reference basin is Animas River below Silverton 93592 Animas River above Tacoma Powerhouse reference basin is Animas River below Silverton 93592 Animas River below Tacoma Powerhouse reference basin is Animas River below Silverton 93592 Using the Proration Method discussed in Sections 1 and 2, the unimpaired hydrology for the Project-related sites was estimated using the reference basins identified above. Each of the Project-related sites are discussed below. Cascade Creek at the Cascade Creek Diversion Dam - Impaired and unimpaired hydrology data was developed for Cascade Creek at the Cascade Creek Diversion Dam (37 39'37"N, 17 48'43"W). Based on a comparison of significant watershed characteristics, the USGS Gage 93529 Vallecito Creek near Bayfield was selected as the reference site for Cascade Creek at the Cascade Creek Diversion Dam. An unimpaired hydrology set for the Cascade Creek basin was developed by a straight drainage area proration of the Vallecito gage dataset. A comparison of selected basin parameters is presented in Table 2. 9

Section 5 Development of Hydrology Using Selected Reference Sites TABLE 2 COMPARISON OF CASCADE CREEK AT THE CASCADE CREEK DIVERSION DAM BASIN AND USGS GAGE VALLECITO CREEK NEAR BAYFIELD Cascade Creek at the Cascade Creek diversion dam Vallecito Creek Drainage Area (mi 2 ) 26.2 72.6 Gage Elevation (msl) 8,97 7,96 Maximum Elevation (msl) 13,72 14,38 Average Elevation (msl) 11,179 11,35 Average Basin Slope (%) 43.53 56. Percent of Basin Area covered by Water bodies.6%.62% Area-Weighted Average Annual Precipitation (in) 39.7 4.97 The regulated streamflows for Cascade Creek below the Cascade Creek diversion dam were calculated using the Annual Water Diversion Reports for Cascade Creek published by the Colorado Division of Water Resources (Office of the State Engineer). The Cascade Creek diversion dam is operated in a run-of-river mode utilizing available flows up to the maximum capacity of the diversion facilities. The maximum capacity of the diversion facilities is not precisely known, but is reported to be approximately 275 cfs (Tacoma Project, May 25 Pre- Application Document). Accordingly, the impaired streamflow at Cascade Creek diversion dam was defined as the unimpaired flows minus the flows diverted into the conveyance facilities. This approach does not account for leakage from the conveyance facilities or dam. Leakage at the diversion dam has been roughly estimated at about 1 cfs, but varies seasonally. Cascade Creek above the confluence with the Animas River - Natural and regulated hydrology data were also developed for Cascade Creek above its confluence with the Animas River (37 36'1"N, 17 46'16"W) using the USGS Gage 93529 Vallecito Creek near Bayfield. A comparison of significant watershed characteristics is presented in Table 3. 1

Section 5 Development of Hydrology Using Selected Reference Sites TABLE 3 COMPARISON OF CASCADE CREEK ABOVE THE CONFLUENCE WITH THE ANIMAS RIVER BASIN AND VALLECITO CREEK NEAR BAYFIELD GAGE Cascade Creek above confluence with Animas River Vallecito Creek Gage Drainage Area (mi 2 ) 85.4 72.6 Gage Elevation (msl) 7,693 7,96 Maximum Elevation (msl) 13,72 14,38 Average Elevation (msl) 1,721 11,35 Average Basin Slope (%) 38.9 56. Percent of Basin Area covered by Water bodies.51%.62% Area-Weighted Average Annual Precipitation (in) 36.4 4.97 The incremental drainage area between Cascade Creek above its confluence with the Animas River and Cascade Creek at the Cascade Creek diversion dam was estimated to be 59.7 mi 2. The incremental unimpaired hydrology for Cascade Creek above its confluence with the Animas River was developed by prorating the Vallecito USGS gage data to this incremental drainage area and then adding the unimpaired hydrology for the Cascade Creek at the Cascade Creek diversion dam unimpaired hydrology yielding a cumulative Cascade Creek unimpaired hydrology. It should be noted that neither travel time nor attenuation between locations were taken into account. The impaired hydrology for Cascade Creek above its confluence with the Animas River was developed by adding the Cascade Creek at its Cascade Creek diversion dam impaired hydrology to the incremental unimpaired hydrology of Cascade Creek above its confluence with the Animas River. Animas River above Cascade Creek - Based on the initial screening criteria and a comparison of significant watershed characteristics, USGS gage 93592, Animas River below Silverton, was selected as the reference site for the Animas River above Cascade Creek (37 36'1"N, 17 46'16"W). Watershed characteristics for the two basins are identified in Table 4. 11

Section 5 Development of Hydrology Using Selected Reference Sites TABLE 4 COMPARISON OF ANIMAS RIVER ABOVE CASCADE CREEK AND ANIMAS RIVER BELOW SILVERTON GAGE Animas River above Cascade Creek Site Animas River below Silverton Gage Drainage Area 254 146 Gage Elevation (msl) 7,684 9,199 Maximum Elevation (msl) 14,35 13,871 Average Elevation (msl) 11,427 11,441 Average Basin Slope (%) 54.1 51.1 Percent of Basin Area covered by Water bodies.47%.52% Area-Weighted Average Annual Precipitation (in) 35.4 35.2 Unimpaired hydrology for the Animas River above Cascade Creek was estimated by prorating the Animas River gage data to the drainage area of the Animas River above Cascade Creek. The Animas River above Cascade Creek is upstream of any Project influence. Consequently, the impaired and unimpaired hydrology are identical related to any Tacoma Project effects. Animas River above Tacoma Powerhouse - Based on similarities in watershed characteristics, USGS gage 93592, Animas River below Silverton, was also selected as the reference site for the Animas River above Tacoma Powerhouse (37 31'24 N, 17 46'58 W). A comparison of characteristics for the two basins is presented in Table 5. TABLE 5 COMPARISON OF ANIMAS RIVER ABOVE TACOMA POWERHOUSE AND ANIMAS RIVER BELOW SILVERTON GAGE Animas River above Tacoma Powerhouse Site Animas River below Silverton Gage Drainage Area (mi 2 ) 373 146 Gage Elevation (msl) 7,287 9,199 Maximum Elevation (msl) 14,35 13,871 Average Elevation (msl) 11,17 11,441 Average Basin Slope (%) 48.64 51.1 Percent of Basin Area covered by Water bodies.59%.52% Area-Weighted Average Annual Precipitation (in) 35.3 35.2 Unimpaired hydrology for the Animas River above the Tacoma powerhouse was created by prorating the Animas River below Silverton USGS gage streamflow record to the drainage area of the Animas River above the Tacoma powerhouse minus the Cascade Creek drainage area. The unimpaired hydrology of Cascade Creek at its confluence with the Animas River was then 12

Section 5 Development of Hydrology Using Selected Reference Sites added to this drainage area. Time of travel and attenuation between the locations were not taken into account. The impaired hydrology for the Animas River above Tacoma powerhouse drainage area was created by summing the unimpaired hydrology for the Animas River above Cascade Creek and the impaired hydrology for Cascade Creek. Again, time lag and attenuation between the locations were not taken into account. Animas River below Tacoma Powerhouse - Based on similarities in relevant watershed characteristics, USGS gage 93592, Animas River below Silverton, was also selected as the reference site for the Animas River below Tacoma powerhouse (37 31'24 N, 17 46'58 W). The overall similarities of the two basins are summarized in Table 6. TABLE 6 COMPARISON OF ANIMAS RIVER BELOW TACOMA POWERHOUSE AND ANIMAS RIVER BELOW SILVERTON GAGE Animas River below Tacoma Powerhouse Site Animas River below Silverton Gage Basin Drainage Area (mi 2 ) 373 146 Gage Elevation (msl) 7,287 9,199 Maximum Elevation (msl) 14,35 13,871 Average Elevation (msl) 11,17 11,441 Average Basin Slope (%) 48.64 51.1 Percent of Basin Area covered by Water bodies.59%.52% Area-Weighted Average Annual Precipitation (in) 35.3 35.2 Impaired or regulated hydrology for Animas River below Tacoma Powerhouse was developed by summing the impaired hydrology developed for the Animas River above Tacoma powerhouse and the historic water releases from the Tacoma powerhouse. The unimpaired hydrology for the Animas River below Tacoma powerhouse is identical to that of the Animas River above Tacoma powerhouse. 13

Section 6 Water Quality Assessment Water quality data in the form of the concentration of the trace metals cadmium, copper and zinc for the Animas River below Silverton during the months of February, May, June, July and September were obtained from the USGS report entitled Using Water-Quality Profiles to Characterize Seasonal Water Quality and Loading in the Upper Animas River Basin, Southwestern Colorado. A correlation was developed between river flow and the total metal loading in the Animas River. This correlation was used to determine the trace metal concentration for each month of the year which was subsequently used to estimate the effects on water quality in the Animas River due to the operations at Tacoma powerhouse. For purposes of this study, a total metal load was estimated by summing the concentration of the three trace metals. The concentration of trace metals at the gaging station on the Animas River below Silverton was assumed to be equal to the concentration at the Animas River above the confluence with the Cascade Creek site. A total metal concentration for the impaired and unimpaired hydrology data set for above and below the Tacoma powerhouse was created assuming the trace metal concentrations in Cascade Creek are significantly lower than those of the Animas River. Combining the unimpaired and impaired hydrology data with these metal loadings, the effects of Project operations on total metal concentrations in the Animas River below Tacoma powerhouse are summarized below in Table 7 and shown graphically in Figure 1 for a low-flow year (22). TABLE 7 EFFECTS OF PROJECT OPERATIONS ON TRACE METAL CONCENTRATIONS IN THE ANIMAS RIVER BELOW TACOMA POWERHOUSE (22) Month Trace Metal Concentration (mg/l) Unimpaired Impaired Percent Change January.52.39 25 February.53.35 34 March.5.38 24 April.31.32-3 May.26.27-4 June.32.34-6 July.43.44-2 August.44.45-2 September.35.37-6 October.34.35-3 November.39.4-3 December.49.38 22 14

Section 6 Water Quality Assessment FIGURE 1 EFFECTS OF PROJECT OPERATIONS ON TRACE METAL CONCENTRATIONS IN THE ANIMAS RIVER BELOW TACOMA POWERHOUSE (22).7.6 Total Metal Concentration,milligrams per liter.5.4.3.2.1. Jan 1 Jan 15 Jan 29 Feb 12 Feb 26 Mar 12 Mar 26 Apr 9 Apr 23 May 7 May 21 Jun 4 Jun 18 Jul 2 Jul 16 Jul 3 Aug 13 Aug 27 Sep 1 Sep 24 Oct 8 Oct 22 Nov 5 Nov 19 Dec 3 Dec 17 Dec 31 Date Analysis of water quality in the Animas River below the Tacoma powerhouse during a dry year shows that Project operations tend to have a minor adverse impact on water quality during months when the facility is operated in a base-load schedule (higher flow months), typically from mid-april through November, and a considerable positive impact when the facility is in a peaking schedule (low flow months), typically December through mid-april. 15

Section 7 Summary of Results Two reference gages were used in the development of hydrology data sets for Project watersheds: Vallecito Creek near Bayfield gage (USGS No. 93529) and Animas River below Silverton gage (USGS No. 93592). Other data sources included the historic operation records for the Cascade Creek diversion dam gage and the Tacoma powerhouse. The gages were selected based on basin characteristics and POR. Appendices A through D include tables and figures showing comparisons of the unimpaired and impaired hydrology sets for representative wet, dry, and normal years and the POR. Figures 2 through 7 show the synthetic hydrographs developed for each site of interest for the representative normal year (24). Appendix E includes the synthetic hydrographs developed for each site for the representative wet, dry, and normal years. Appendix F shows annual and monthly comparisons of the CDWR record of the Cascade Creek diverted flows and the estimated flows above the Cascade Creek diversion dam using the Vallecito Creek synthesized flow record for the period of November 1, 198 through October 31, 24. As discussed in Section 6, the analysis of water quality in the Animas River below the Tacoma powerhouse for a dry year shows that the Project typically has a minor negative impact on the water quality in the Animas River below the Tacoma Powerhouse during higher river flow periods and a considerable positive impact during lower flow periods. This is due to the relative importance of either net storage or net releases during these time periods given the water in Electra Lake which has significantly better water quality than the water in the Animas River. Given that other dilution-related parameters (e.g., organics, nutrient loading) would be affected in the same manner as that identified as metals, it can be concluded that Project effects related to organics and nutrient loading are very similar to the effect predicted for metals. 16

FIGURE 2 CASCADE CREEK AT THE CASCADE CREEK DIVERSION DAM UNIMPAIRED AND IMPAIRED HYDROLOGY FOR REPRESENTATIVE NORMAL YEAR (24) 6 5 4 3 2 1 January February March April May June July August September October NovemberDecember Unimpaired Impaired FIGURE 3 CASCADE CREEK ABOVE THE CONFLUENCE WITH THE ANIMAS RIVER UNIMPAIRED AND IMPAIRED HYDROLOGY FOR REPRESENTATIVE NORMAL YEAR (24) 1,8 1,6 1,4 1,2 1, 8 6 4 2 January February March April May June July August September October NovemberDecember Unimpaired Impaired 17

FIGURE 4 ANIMAS RIVER ABOVE CASCADE CREEK UNIMPAIRED AND IMPAIRED HYDROLOGY FOR REPRESENTATIVE NORMAL YEAR (24) 3,5 3, 2,5 2, 1,5 1, 5 January February March April May June July August September October NovemberDecember Unimpaired Impaired FIGURE 5 ANIMAS RIVER BELOW CASCADE CREEK UNIMPAIRED AND IMPAIRED HYDROLOGY FOR REPRESENTATIVE NORMAL YEAR (24) 4,5 4, 3,5 3, 2,5 2, 1,5 1, 5 January February March April May June July August September October NovemberDecember Unimpaired Impaired 18

FIGURE 6 ANIMAS RIVER ABOVE TACOMA POWERHOUSE UNIMPAIRED AND IMPAIRED HYDROLOGY FOR REPRESENTATIVE NORMAL YEAR (24) 5, 4,5 4, 3,5 3, 2,5 2, 1,5 1, 5 January February March April May June July August September October NovemberDecember Unimpaired Impaired FIGURE 7 ANIMAS RIVER BELOW TACOMA POWERHOUSE UNIMPAIRED AND IMPAIRED HYDROLOGY FOR REPRESENTATIVE NORMAL YEAR (24) 5, 4,5 4, 3,5 3, 2,5 2, 1,5 1, 5 January February March April May June July August September October NovemberDecember Unimpaired Impaired 19

Section 8 References Devine Tarbell & Associates, Inc.. 26. Tacoma Hydroelectric Project Cascade Creek Hydrology. August 26. Leib, Kenneth J.; Mast, M. Alisa; Wright, Winfield G. 23. Using Water-Quality Profiles to Characterize Seasonal Water Quality and Loading in the Upper Anima River Basin, Southwestern Colorado. Public Service Company of Colorado. 25. Pre-Application Document, Tacoma Hydroelectric Project (FERC Project No. 12589). May 25. U.S. Department of Agriculture; Natural Resources Conservation Service. Undated. Colorado Precipitation Data/Maps. [Online] URL: http://www.ncgc.nrcs.usda.gov/ products/datasets/climate/data/precipitation-state/co.html. (Accessed August 26.) U.S. Geological Survey. National Water Information System Surface -Water Data for Colorado. [Online] URL: http://waterdata.usgs.gov/co/nwis/dv/?referred_module=sw. (Accessed August 3, 26.) P:\Xcel\132.1\WP\6-OtherStds&Rpts\Project Effects\T-Proj Effcts on WQ-7114.doc AS/JB/elt 132.1.6/8. November 4, 27 2

APPENDICES

APPENDIX A POR SYNTHESIZED HYDROLOGY FLOW EXCEEDANCE TABLES AND GRAPHS

Synthesized Unimpaired and for the POR of the Animas River Above Cascade Creek Percent Annual January February March April May June July August September October November December 1.% 53 53 62 65 9 21 17 118 11 11 122 6 57 99.% 69 62 64 71 99 244 23 125 15 115 124 71 64 98.% 72 67 65 72 15 256 259 132 19 127 125 77 68 97.% 76 67 65 72 11 262 32 14 118 143 127 79 72 96.% 78 69 67 74 111 277 427 15 122 153 129 83 75 95.% 81 71 71 74 113 32 539 158 128 159 131 9 78 94.% 83 71 71 74 117 322 596 168 133 161 131 96 83 93.% 85 71 72 76 119 343 613 191 138 167 133 99 85 92.% 87 71 74 76 125 36 649 218 154 171 134 11 85 91.% 88 72 74 76 133 38 75 235 168 173 134 117 87 9.% 92 74 74 78 139 394 758 239 168 175 136 118 88 89.% 94 76 74 8 145 415 83 248 17 178 138 12 88 88.% 95 78 74 81 15 435 84 253 17 181 14 122 9 87.% 99 8 75 83 151 457 855 262 174 182 141 124 92 86.% 12 8 76 83 152 472 866 272 178 186 143 124 92 85.% 16 8 76 85 155 481 874 277 182 187 145 125 92 84.% 16 81 78 85 159 489 97 281 184 191 147 127 94 83.% 11 83 78 86 163 51 962 287 186 194 147 127 94 82.% 111 83 78 87 166 519 979 297 187 198 148 127 94 81.% 113 83 78 88 168 533 1,5 33 19 199 15 129 95 8.% 117 83 8 88 17 556 1,54 39 191 21 152 129 95 79.% 117 85 8 9 171 571 1,74 32 194 21 155 131 97 78.% 12 85 8 91 173 582 1,84 324 198 25 157 131 99 77.% 12 85 8 92 174 592 1,112 337 21 27 16 133 11 76.% 124 86 81 92 177 66 1,123 343 25 21 163 134 12 75.% 125 87 81 92 178 612 1,152 356 29 21 165 134 13 74.% 127 87 81 94 178 621 1,179 369 213 212 166 134 16 73.% 129 88 81 95 18 633 1,195 378 216 214 169 136 16 72.% 131 88 81 96 184 643 1,28 386 218 217 17 136 16 71.% 133 88 81 97 186 659 1,242 393 222 219 171 136 16 7.% 134 88 83 99 187 673 1,259 44 226 222 173 136 16 69.% 136 88 83 99 189 684 1,272 424 23 223 175 138 11 68.% 138 9 83 1 191 695 1,277 436 233 224 178 138 11 67.% 14 92 83 12 194 75 1,299 448 237 224 18 138 11 66.% 141 92 85 12 198 717 1,36 463 244 227 182 14 111 65.% 145 92 85 12 21 731 1,326 472 246 23 184 141 112 64.% 147 95 85 14 23 744 1,352 5 249 231 189 141 113 63.% 148 95 85 14 29 767 1,375 522 254 235 193 141 113 62.% 152 99 85 16 216 777 1,43 542 257 237 194 142 113 61.% 154 11 87 16 219 788 1,47 553 263 239 198 143 113 6.% 157 12 88 16 221 83 1,425 566 265 24 198 143 115 59.% 161 13 88 18 224 815 1,452 585 269 24 199 145 115 58.% 166 16 88 18 23 826 1,47 597 274 242 2 145 115 57.% 17 16 88 11 232 851 1,52 69 278 246 23 145 117 56.% 173 16 9 11 239 867 1,531 617 283 249 24 146 117 55.% 177 16 9 11 243 897 1,546 627 286 249 27 147 117 54.% 182 18 9 11 247 916 1,556 631 292 25 29 147 117 53.% 186 11 92 11 253 954 1,583 636 296 251 29 147 118 52.% 19 11 92 111 258 976 1,593 643 32 256 21 148 12 51.% 194 11 92 113 26 986 1,611 652 38 258 212 148 12 5.% 198 11 94 113 262 1,9 1,648 661 313 261 215 15 12 49.% 23 111 95 117 267 1,46 1,659 682 318 265 216 15 12 48.% 29 113 95 117 27 1,67 1,685 7 321 265 217 152 122 47.% 214 113 95 117 272 1,86 1,75 722 328 267 219 152 122 46.% 219 115 96 118 273 1,13 1,736 741 33 268 221 154 124 45.% 224 115 97 12 276 1,128 1,764 753 338 274 221 154 124 44.% 231 117 98 12 283 1,157 1,785 772 344 277 223 156 124 43.% 239 117 99 12 286 1,179 1,82 787 348 281 224 156 124 42.% 245 117 11 12 29 1,232 1,838 797 352 286 224 157 124 41.% 251 118 11 12 292 1,244 1,873 815 359 29 226 157 125 4.% 26 12 12 123 297 1,251 1,891 832 365 296 228 159 125 39.% 265 12 12 124 299 1,28 1,926 848 379 31 23 163 126 38.% 274 12 12 124 32 1,296 1,944 865 39 37 231 164 127 37.% 283 12 14 127 36 1,39 2,14 869 397 313 233 166 127 36.% 293 12 16 129 311 1,323 2,35 885 421 32 235 168 129 35.% 36 122 16 131 317 1,356 2,13 916 428 324 235 168 13 34.% 319 122 18 131 32 1,378 2,13 94 445 328 24 171 131 33.% 33 124 18 134 323 1,399 2,191 964 456 334 242 173 131 32.% 346 124 11 138 325 1,431 2,225 979 469 343 244 173 131 31.% 36 124 11 138 334 1,461 2,262 996 478 348 245 175 133 3.% 378 125 11 14 338 1,52 2,295 1,35 486 359 247 177 133 29.% 398 126 113 141 342 1,544 2,333 1,67 495 362 249 177 134 28.% 424 127 113 141 349 1,576 2,362 1,88 51 369 251 178 134 27.% 449 127 113 145 353 1,63 2,416 1,111 59 376 26 178 134 J:\Projects\Xcel Energy\132.1-Tacoma\6-OtherStdspts\Basin Hydrlgy\ Appendix A-1-1 OrigGraphics\Appendix A.xls

Synthesized Unimpaired and for the POR of the Animas River Above Cascade Creek Percent Annual January February March April May June July August September October November December 26.% 477 129 113 147 355 1,632 2,492 1,147 519 38 261 18 134 25.% 51 129 117 148 36 1,657 2,531 1,176 529 395 263 182 136 24.% 528 131 117 15 364 1,722 2,57 1,22 545 47 269 182 136 23.% 564 131 118 152 369 1,749 2,598 1,25 557 42 271 185 138 22.% 599 131 12 154 375 1,765 2,665 1,273 568 431 279 186 138 21.% 631 133 12 156 378 1,82 2,74 1,292 587 435 279 187 138 2.% 676 133 125 157 387 1,926 2,739 1,327 66 446 285 189 14 19.% 732 134 131 159 396 1,944 2,774 1,369 643 46 289 191 141 18.% 782 134 131 161 41 2,52 2,84 1,397 72 469 293 193 141 17.% 825 134 131 163 46 2,13 2,894 1,414 74 484 299 194 146 16.% 871 134 133 169 415 2,169 2,933 1,43 756 495 37 194 148 15.% 949 136 134 171 425 2,246 3,4 1,58 767 59 323 196 148 14.% 1,15 138 137 173 434 2,297 3,63 1,521 8 515 336 196 15 13.% 1,92 138 138 176 44 2,368 3,12 1,551 81 526 341 2 15 12.% 1,186 138 14 182 453 2,43 3,141 1,635 831 531 35 21 152 11.% 1,272 141 141 188 476 2,469 3,197 1,665 85 547 355 23 154 1.% 1,349 141 141 196 491 2,546 3,234 1,716 885 553 376 25 156 9.% 1,43 143 143 2 51 2,617 3,257 1,756 912 584 396 27 156 8.% 1,555 145 143 29 527 2,723 3,322 1,851 927 63 48 27 157 7.% 1,674 145 145 212 532 2,845 3,393 1,968 957 644 422 21 159 6.% 1,82 147 147 212 567 2,952 3,479 2,122 992 679 438 212 161 5.% 2,56 148 148 224 6 3,4 3,537 2,275 1,3 76 47 216 164 4.% 2,333 148 15 234 633 3,182 3,645 2,386 1,41 789 496 228 17 3.% 2,58 152 152 247 77 3,234 3,746 2,615 1,96 826 52 256 175 2.% 2,933 152 163 282 781 3,435 3,828 2,833 1,185 927 545 263 186 1.% 3,32 157 173 335 866 3,729 3,92 3,34 1,272 1,38 58 281 194.1% 3,974 18 183 469 943 4,6 4,5 4,69 1,361 1,749 631 312 228.1% 4,18 185 184 481 967 4,27 4,63 4,144 1,37 2,36 634 322 25 Appendix A-1-2 J:\Projects\Xcel Energy\132.1-Tacoma\6-OtherStdspts\Basin Hydrlgy\ OrigGraphics\Appendix A.xls

Animas River Above Cascade Creek Annual Flow for the POR 4,5 4, 3,5 3, 2,5 2, 1,5 1, 5 % 1% 2% 3% 4% 5% 6% 7% 8% 9% 1% Animas River Above Cascade Creek January Flow for the POR 2 18 16 14 12 1 8 6 4 2 % 1% 2% 3% 4% 5% 6% 7% 8% 9% 1% Appendix A-1 graphs - 1

Animas River Above Cascade Creek February Flow for the POR 2 18 16 14 12 1 8 6 4 2 % 1% 2% 3% 4% 5% 6% 7% 8% 9% 1% Animas River Above Cascade Creek March Flow for the POR 6 5 4 3 2 1 % 1% 2% 3% 4% 5% 6% 7% 8% 9% 1% Appendix A-1 graphs - 2

Animas River Above Cascade Creek April Flow for the POR 1,2 1, 8 6 4 2 % 1% 2% 3% 4% 5% 6% 7% 8% 9% 1% Animas River Above Cascade Creek May Flow for the POR 4,5 4, 3,5 3, 2,5 2, 1,5 1, 5 % 1% 2% 3% 4% 5% 6% 7% 8% 9% 1% Appendix A-1 graphs - 3

Animas River Above Cascade Creek June Flow for the POR 4,5 4, 3,5 3, 2,5 2, 1,5 1, 5 % 1% 2% 3% 4% 5% 6% 7% 8% 9% 1% Animas River Above Cascade Creek July Flow for the POR 4,5 4, 3,5 3, 2,5 2, 1,5 1, 5 % 1% 2% 3% 4% 5% 6% 7% 8% 9% 1% Appendix A-1 graphs - 4

Animas River Above Cascade Creek August Flow for the POR 1,6 1,4 1,2 1, 8 6 4 2 % 1% 2% 3% 4% 5% 6% 7% 8% 9% 1% Animas River Above Cascade Creek September Flow for the POR 2,5 2, 1,5 1, 5 % 1% 2% 3% 4% 5% 6% 7% 8% 9% 1% Appendix A-1 graphs - 5

Animas River Above Cascade Creek October Flow for the POR 7 6 5 4 3 2 1 % 1% 2% 3% 4% 5% 6% 7% 8% 9% 1% Animas River Above Cascade Creek November Flow for the POR 35 3 25 2 15 1 5 % 1% 2% 3% 4% 5% 6% 7% 8% 9% 1% Appendix A-1 graphs - 6

Animas River Above Cascade Creek December Flow for the POR 3 25 2 15 1 5 % 1% 2% 3% 4% 5% 6% 7% 8% 9% 1% Appendix A-1 graphs - 7

Synthesized for the POR of the Animas River Below Cascade Creek Percent Annual January February March April May June July August September October November December 1.% 74 74 79 82 131 324 199 143 12 131 148 76 79 99.% 88 82 82 86 144 378 237 15 127 14 152 91 86 98.% 91 88 83 89 151 4 32 159 135 158 154 98 92 97.% 94 89 84 9 16 416 375 171 146 18 155 11 93 96.% 97 91 85 91 17 424 498 18 151 19 156 17 97 95.% 11 91 85 93 175 45 639 188 159 198 16 115 11 94.% 14 93 87 95 179 469 697 26 171 28 163 123 12 93.% 17 94 89 96 187 56 737 228 18 212 166 134 16 92.% 19 94 89 97 192 526 791 256 193 215 167 144 18 91.% 112 95 89 97 197 544 842 275 196 22 168 147 19 9.% 115 95 89 99 23 565 94 291 199 224 169 15 112 89.% 119 96 89 11 28 597 952 33 23 231 17 155 112 88.% 121 97 9 12 211 623 1,7 312 21 232 174 156 113 87.% 124 97 9 13 214 645 1,34 322 215 237 178 157 114 86.% 128 98 91 15 216 665 1,5 332 219 241 18 158 115 85.% 131 99 92 17 217 679 1,13 344 225 247 183 16 116 84.% 133 1 93 18 22 69 1,144 355 226 25 186 161 117 83.% 136 11 94 19 225 698 1,189 364 235 254 187 162 119 82.% 139 12 94 19 228 741 1,218 37 242 258 189 164 119 81.% 142 13 95 112 236 758 1,266 378 246 263 192 165 119 8.% 144 13 95 114 239 785 1,312 381 251 265 196 165 12 79.% 147 14 95 115 24 8 1,366 39 256 267 2 166 121 78.% 15 15 97 115 242 817 1,392 396 259 271 23 167 123 77.% 152 15 98 117 245 833 1,46 49 264 274 25 168 124 76.% 154 16 1 118 249 846 1,457 422 268 276 27 169 126 75.% 156 18 11 12 252 856 1,469 437 272 283 211 169 127 74.% 158 18 11 122 253 879 1,481 447 28 284 214 169 128 73.% 162 19 12 123 255 892 1,499 458 283 286 217 17 128 72.% 166 19 13 125 257 98 1,53 479 285 288 22 17 129 71.% 168 19 14 127 26 924 1,529 492 289 289 221 171 13 7.% 171 11 15 128 27 932 1,571 58 293 294 224 171 131 69.% 173 112 15 13 272 948 1,61 532 3 296 225 172 133 68.% 176 113 16 131 275 958 1,652 555 34 298 23 172 133 67.% 178 114 16 132 283 975 1,671 571 35 31 235 173 135 66.% 181 115 17 134 288 997 1,687 584 311 36 239 174 136 65.% 185 116 18 135 293 1,17 1,76 619 318 38 242 175 137 64.% 188 118 18 137 299 1,27 1,726 639 322 39 244 176 138 63.% 191 119 18 138 38 1,45 1,752 664 334 314 246 176 139 62.% 196 12 19 139 314 1,13 1,767 685 336 317 249 177 14 61.% 21 121 11 14 316 1,143 1,84 69 343 319 251 178 141 6.% 25 121 11 14 321 1,163 1,833 722 349 322 256 179 142 59.% 211 123 111 141 326 1,181 1,895 733 358 323 258 18 142 58.% 216 125 111 141 334 1,29 1,919 75 362 326 261 18 142 57.% 222 126 112 143 337 1,233 1,943 757 365 328 263 181 143 56.% 229 128 112 143 344 1,247 1,955 767 372 334 266 183 144 55.% 237 129 113 145 354 1,263 1,987 781 384 339 267 183 145 54.% 244 13 114 147 357 1,289 2,2 79 393 343 271 184 145 53.% 249 131 115 148 365 1,331 2,6 798 4 346 272 186 145 52.% 255 132 116 15 367 1,372 2,77 81 46 35 275 186 146 51.% 261 133 117 151 373 1,398 2,11 82 412 356 276 188 147 5.% 269 133 118 152 376 1,448 2,12 843 419 359 279 189 148 49.% 275 134 119 153 382 1,478 2,133 862 426 362 285 191 149 48.% 283 135 12 154 39 1,54 2,146 892 434 369 286 192 15 47.% 289 135 121 156 393 1,563 2,168 913 441 374 288 193 15 46.% 298 136 121 159 396 1,63 2,22 935 451 378 292 195 151 45.% 35 136 122 16 41 1,632 2,235 952 458 381 296 197 151 44.% 314 138 122 161 45 1,652 2,244 986 464 388 298 2 152 43.% 321 139 124 165 413 1,68 2,292 999 471 391 31 22 152 42.% 332 139 124 167 418 1,691 2,343 1,26 478 396 33 23 153 41.% 342 141 125 169 42 1,733 2,358 1,5 49 43 35 25 154 4.% 355 141 125 17 427 1,762 2,44 1,61 55 46 37 28 154 39.% 366 143 126 173 434 1,799 2,467 1,91 525 413 39 29 155 38.% 378 144 127 174 438 1,827 2,516 1,17 534 416 313 214 155 37.% 391 145 128 176 442 1,836 2,572 1,158 555 42 316 22 156 36.% 43 146 129 179 45 1,846 2,637 1,184 581 429 317 222 157 35.% 418 147 13 181 459 1,865 2,713 1,22 594 438 32 225 157 34.% 435 147 13 183 467 1,96 2,738 1,254 65 444 324 228 158 33.% 452 148 13 184 473 1,972 2,832 1,27 61 451 329 233 158 32.% 471 15 131 187 475 2,36 2,89 1,297 629 459 333 239 162 31.% 495 151 132 189 479 2,63 2,924 1,337 638 465 336 242 163 3.% 523 151 132 192 486 2,99 2,966 1,372 645 472 338 244 165 29.% 549 153 135 195 499 2,137 3,39 1,417 663 487 343 247 168 28.% 578 153 136 198 59 2,172 3,98 1,46 685 494 347 247 171 27.% 612 153 137 199 515 2,225 3,134 1,476 691 517 351 25 174 J:\Projects\Xcel Energy\132.1-Tacoma\6-OtherStdspts\Basin Hydrlgy\ Appendix A-2-1 OrigGraphics\Appendix A.xls

Synthesized for the POR of the Animas River Below Cascade Creek Percent Annual January February March April May June July August September October November December 26.% 644 153 138 21 518 2,235 3,187 1,52 79 525 36 252 176 25.% 682 154 139 22 526 2,298 3,232 1,547 723 531 365 252 178 24.% 715 156 14 23 529 2,359 3,285 1,578 734 537 369 253 178 23.% 753 156 142 25 543 2,386 3,327 1,66 768 55 372 255 179 22.% 796 156 143 21 55 2,459 3,364 1,631 788 558 379 257 18 21.% 847 157 148 212 554 2,556 3,415 1,692 833 582 382 258 18 2.% 97 158 152 215 556 2,661 3,481 1,714 863 6 391 261 182 19.% 974 159 154 22 567 2,792 3,55 1,736 96 613 397 263 183 18.% 1,35 161 156 224 574 2,882 3,62 1,764 951 633 41 266 185 17.% 1,124 162 157 226 578 2,92 3,698 1,814 98 646 412 268 186 16.% 1,217 164 161 231 586 2,959 3,798 1,882 1,12 657 425 271 186 15.% 1,277 166 163 237 621 3,36 3,833 1,899 1,12 67 435 272 189 14.% 1,392 168 17 246 64 3,116 3,928 1,914 1,135 683 449 275 19 13.% 1,484 17 172 251 65 3,226 3,999 2,1 1,186 694 461 278 193 12.% 1,595 17 174 261 678 3,334 4,73 2,3 1,223 719 468 28 195 11.% 1,69 172 176 274 76 3,424 4,115 2,9 1,252 73 475 285 197 1.% 1,794 173 177 281 721 3,446 4,151 2,156 1,265 745 55 287 198 9.% 1,918 176 177 298 749 3,511 4,183 2,257 1,277 797 524 291 22 8.% 2,61 177 178 34 762 3,623 4,233 2,44 1,325 842 567 295 24 7.% 2,196 179 179 312 822 3,75 4,34 2,56 1,343 871 592 34 27 6.% 2,386 18 183 32 848 3,879 4,52 2,648 1,397 935 65 313 212 5.% 2,725 184 185 327 881 3,965 4,674 2,798 1,462 986 625 321 217 4.% 3,36 189 187 353 928 4,18 4,795 2,985 1,556 1,56 648 326 22 3.% 3,378 191 191 381 1,52 4,261 4,895 3,213 1,66 1,137 679 333 23 2.% 3,82 192 212 428 1,125 4,66 4,941 3,619 1,677 1,397 72 339 241 1.% 4,249 194 224 518 1,223 5,194 5,13 4,41 1,789 1,787 76 361 243.1% 5,263 199 236 673 1,345 5,65 5,253 5,99 2,86 3,156 93 44 258.1% 5,647 21 238 69 1,363 5,669 5,278 5,193 2,129 3,654 98 416 266 Appendix A-2-2 J:\Projects\Xcel Energy\132.1-Tacoma\6-OtherStdspts\Basin Hydrlgy\ OrigGraphics\Appendix A.xls

Synthesized for the POR of the Animas River Below Cascade Creek Percent Annual January February March April May June July August September October November December 1.% 69 69 75 8 126 31 19 136 118 128 144 74 73 99.% 84 76 78 83 138 354 227 144 124 137 146 89 81 98.% 87 83 8 85 144 373 288 153 13 155 149 95 87 97.% 9 85 8 87 153 386 36 163 141 176 152 99 9 96.% 93 86 81 88 162 394 478 172 147 186 154 15 93 95.% 96 87 82 89 17 418 612 18 157 196 156 113 95 94.% 1 89 83 9 174 432 669 2 169 2 158 121 97 93.% 12 89 84 92 18 463 74 217 174 25 16 127 11 92.% 15 9 84 92 183 487 753 245 186 29 161 137 12 91.% 18 9 85 93 188 54 84 262 188 212 161 141 14 9.% 111 91 85 94 192 532 861 276 191 218 163 145 16 89.% 114 92 86 95 199 547 92 288 194 22 166 147 18 88.% 116 92 86 96 22 566 958 297 21 224 167 15 19 87.% 12 93 86 99 25 61 979 38 25 227 169 151 19 86.% 123 94 87 11 27 613 991 316 21 231 171 152 11 85.% 125 95 88 13 29 62 1,46 325 215 235 174 153 111 84.% 128 96 89 13 21 632 1,91 338 221 239 176 154 111 83.% 131 97 9 15 214 648 1,119 347 228 243 178 155 112 82.% 134 97 9 16 22 679 1,154 351 233 251 182 156 114 81.% 136 99 91 18 227 76 1,196 356 237 253 186 157 114 8.% 138 99 91 11 229 725 1,248 365 24 254 19 157 115 79.% 141 1 92 111 23 746 1,283 371 244 254 191 159 116 78.% 144 11 94 111 232 766 1,298 38 249 259 193 16 118 77.% 146 11 95 112 233 774 1,337 389 251 261 195 16 12 76.% 148 12 96 113 235 785 1,347 43 256 264 199 161 122 75.% 15 12 97 114 238 792 1,353 416 259 266 22 161 122 74.% 153 13 98 117 24 812 1,375 429 263 268 23 162 123 73.% 156 14 98 118 242 829 1,398 438 266 271 26 162 124 72.% 159 14 99 119 245 849 1,423 46 268 274 29 163 125 71.% 161 15 99 121 249 856 1,443 47 273 277 21 163 126 7.% 164 16 1 123 253 863 1,466 487 278 278 213 164 127 69.% 166 17 11 125 261 878 1,512 51 28 281 215 164 128 68.% 17 18 11 126 263 888 1,54 528 284 284 219 165 129 67.% 172 19 12 127 267 912 1,565 545 291 287 224 166 13 66.% 173 11 13 129 272 916 1,577 558 295 289 228 166 13 65.% 177 11 13 13 278 919 1,59 578 297 292 232 167 133 64.% 18 113 14 131 286 931 1,617 63 34 295 234 168 134 63.% 184 114 14 133 289 965 1,639 63 311 297 234 169 134 62.% 188 115 15 134 295 1,4 1,651 644 315 3 238 17 135 61.% 191 116 15 135 299 1,44 1,684 658 319 31 242 17 135 6.% 196 116 15 135 32 1,6 1,717 678 328 35 244 17 136 59.% 23 118 16 136 37 1,86 1,773 7 332 36 246 171 136 58.% 27 119 17 136 312 1,1 1,81 712 339 39 248 172 137 57.% 212 121 17 137 317 1,112 1,89 718 342 313 25 172 137 56.% 219 122 18 138 323 1,129 1,831 727 354 317 252 173 138 55.% 227 123 19 139 329 1,161 1,847 744 359 32 254 174 138 54.% 232 124 11 143 337 1,177 1,884 75 368 322 255 176 138 53.% 236 125 111 144 342 1,227 1,91 761 375 326 257 177 139 52.% 243 126 112 145 349 1,241 1,935 765 379 329 258 178 139 51.% 249 127 113 146 35 1,261 1,95 779 389 332 261 18 141 5.% 254 128 114 147 354 1,314 1,967 81 395 336 264 181 141 49.% 261 128 114 148 359 1,353 1,984 825 399 341 267 182 142 48.% 267 129 115 149 362 1,372 2, 866 47 347 269 184 143 47.% 275 13 116 151 366 1,427 2,26 871 412 35 273 185 143 46.% 282 13 116 154 37 1,467 2,59 883 418 354 277 186 144 45.% 29 131 118 155 377 1,57 2,8 912 423 358 28 187 146 44.% 297 132 118 156 383 1,528 2,115 927 433 361 282 191 146 43.% 34 133 119 159 385 1,536 2,128 946 439 367 285 193 146 42.% 313 134 12 161 386 1,544 2,195 975 449 372 287 194 147 41.% 322 135 121 163 393 1,59 2,29 99 453 378 289 196 147 4.% 332 135 121 165 396 1,619 2,238 1,5 47 384 291 198 148 39.% 345 137 121 167 4 1,65 2,296 1,32 487 387 294 199 148 38.% 356 138 123 169 41 1,661 2,357 1,56 57 39 297 24 149 37.% 367 139 123 17 411 1,68 2,423 1,85 52 396 299 28 15 36.% 379 14 124 173 423 1,73 2,466 1,113 551 45 33 29 151 35.% 391 141 124 175 428 1,722 2,532 1,185 559 416 34 213 151 34.% 411 143 124 176 432 1,745 2,563 1,22 565 421 38 217 152 33.% 426 144 125 178 438 1,82 2,655 1,217 58 426 312 221 152 32.% 443 145 125 18 444 1,862 2,711 1,231 584 435 316 225 154 31.% 463 146 127 182 449 1,911 2,745 1,278 599 442 318 227 157 3.% 49 146 127 185 456 1,944 2,82 1,36 615 447 32 23 158 29.% 515 147 128 187 462 1,97 2,845 1,347 63 456 325 232 16 28.% 545 147 13 189 469 2,2 2,917 1,383 641 469 329 234 161 27.% 576 148 131 191 475 2,5 2,971 1,399 65 484 332 235 163 J:\Projects\Xcel Energy\132.1-Tacoma\6-OtherStdspts\Basin Hydrlgy\ Appendix A-2-3 OrigGraphics\Appendix A.xls