USGS Water-Year Summary for Site 12175000

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	Available Parameters
	00065 Gage height(Obs.,Mean)
	99065 Gage height(Obs.,Mean) [meters]

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Water year 2024: 2023-10-01 to 2024-09-30

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USGS Water-Year Summary 2024

12175000 ROSS RESERVOIR NEAR NEWHALEM, WA

LOCATION - Lat 48°43'58", long 121°04'02" referenced to North American Datum of 1927, in SE 1/4 sec.35, T.38 N., R.13 E., Whatcom County, WA, Hydrologic Unit 17110005, Ross Lake National Recreation Area, at Ross Dam on Skagit River, 1.0 mi downstream from Ruby Creek, 9.1 mi northeast of Newhalem, and at mile 105.2.

DRAINAGE AREA - 999 mi². of which 400 mi² is in Canada.

REVISIONS HISTORY -

WSP 1932: Drainage area.

Prior to 10/2020, data were published as 'feet above NGVD29' but were also said to be 1.79 ft above NGVD29 from survey of unknown accuracy. Gage data are and have always been referenced to the as-built elevation of the dam and are now published as 'gage-height' for clarity. Gage datum is 6.18 feet above NAVD88 from Seattle City Lights survey of 10/2018.

SURFACE-WATER RECORDS

PERIOD OF RECORD - March 1940 to current year (monthend elevations and contents only prior to October 1946). Prior to October 1945, published as "Ruby Reservoir near Newhalem."

GAGE - Water stage recorder. Datum of gage is City of Seattle Ross Dam As-Built datum which is 6.18 ft. above NAVD88 (from Seattle City Lights survey of Sept. 2018). Prior to May 2020, gage datum was referenced to 1.79 ft. above NGVD of 1929, U.S. Coast and Geodetic Survey datum. Accuracy of the prior NGVD29 reference is questionable and only the NAVD88 conversion should be used. Prior to Sept. 24, 1940, nonrecording gage on west shore at site upstream from Ross Dam at same datum. June 29, 1943, to Apr. 29, 1948, nonrecording gage on right bank at site 500 ft. upstream from dam at present datum.

COOPERATION - Capacity table furnished by City of Seattle. This station is maintained by the United States under agreement with Canada.

REMARKS - Reservoir is formed by concrete-arch dam completed to elevation 1,615 ft in 1949, storage began Mar. 11, 1940. Starting about July 1, 1967, taintor gates were extended to elevation 1,602.50 ft. Usable storage, 1,052,300 acre-ft between elevations 1,475 ft, lower limit of operation, and 1,602.5 ft, top of taintor gates. An additional 95,000 acre-ft of storage may be obtained during major floods by surcharge of the reservoir to a maximum elevation of 1,610.5 ft. Dead storage below elevation 1,250 ft, 1,175 acre-ft. Water used by City of Seattle for power development. Figures given herein represent total contents. U.S. Geological Survey satellite telemeter at station.

EXTREMES FOR PERIOD OF RECORD - Maximum contents, 1,443,460 acre-ft, July 20, 1981, elevation, 1,603.23 ft; minimum contents observed since dam was completed in 1949, 51,760 acre-ft, Apr. 5, 1952, elevation, 1,348.50 ft. CAPACITY TABLE (Based on 25-foot contour intervals furnished by City of Seattle in 1943)

Elevation   Contents    Elevation   Contents    Elevation   Contents 
 (feet)    (acre-feet)   (feet)    (acre-feet)   (feet)    (acre-feet)
        
 1,490      454,480      1,525      678,950      1,575      1,130,200
 1,500      509,240      1,550      888,320      1,603      1,440,700