USGS Water-Year Summary for Site 14240446

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	62614 Elevation, lake/res, NGVD29(Obs.)

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Water year 2023: 2022-10-01 to 2023-09-30

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USGS Water-Year Summary 2023

14240446 CASTLE LAKE NEAR MOUNT ST. HELENS, WA

LOCATION - Lat 46°15'23", long 122°16'28" referenced to North American Datum of 1983, in SE 1/4 SW 1/4 sec.14, T.9 N., R.4 E., Cowlitz County, WA, Hydrologic Unit 17080005, Mount St. Helens National Volcanic Monument, on right bank near outflow of Castle Lake, 5.0 mi north by northwest of the northwest edifice of Mount St. Helens (at Toutle Glacier).

DRAINAGE AREA - 3.10 mi².

REVISIONS HISTORY - WDR WA-04-1: 2003. Drainage area revised in 2017.

SURFACE-WATER RECORDS

PERIOD OF RECORD - October 1993 to current year (records of contents for water year 1994 published in WDR-WA-94-1 are unreliable and should not be used).

GAGE - Water-stage recorder. Datum of gage is 2,498.95 ft above National Geodetic Vertical Datum of 1929 (U.S. Army Corps of Engineers benchmarks); gage readings have been reduced to elevations above National Geodetic Vertical Datum of 1929. To convert to North American Vertical Datum of 1988, add 1.84 ft (USGS Level 1 GNSS survey as per USGS T&M 11-D1).

REMARKS - As a result of the collapse of the north face of Mount St. Helens on May 18, 1980, a debris avalanche blocked the flow of South Fork Castle Creek forming Castle Lake. Castle Lake would have overtopped the blockage in late 1981 or early 1982. Overtopping most probably would have resulted in a quick release of lake waters as a result of rapid erosion of the blockage. Serious flooding probably would have resulted from the breakout of Castle Lake. As a result, the level of Castle Lake was stabilized with the construction of a spillway in 1981. Refer to report by Schuster, R.L., ed., 1986, Landslide Dams: Processes, Risk and Mitigation: Geotechnical Special Publication no. 3, American Society of Civil Engineers, 164 p., for history of Castle Lake as it was formed and impacted by the eruption and actions taken to reduce the resulting flood threat. U.S. Geological Survey satellite telemeter at station.

EXTREMES FOR PERIOD OF RECORD -

Full record: maximum elevation, 2,582.76 ft, Feb. 8, 1996; minimum elevation, 2,577.36 ft, Sept. 7, 2018.

WY2018 extremes: maximum elevation, 2580.85 ft, Nov. 23, 2017; minimum elevation, 2577.36 ft, Sept. 7, 2018

WY2019 extremes: maximum elevation, 2579.59 ft, April 11, 2019; minimum elevation, 2577.57 ft, Oct. 1, 2018

WY2020 extremes: maximum elevation, 2580.45 ft, Feb. 8, 2020; minimum elevation, 2577.44 ft, Sept. 8, 2020

WY2021 extremes: maximum elevation, 2580.36 ft, Jan. 13, 2021; minimum elevation, 2577.42 ft, Sept. 17, 2021