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- Water-Year Summary reports summarize a year of hydrologic data in a printer-friendly format.
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USGS Water-Year Summary 2024
11045700 O'Neill Lake Spill Channel near Fallbrook, CA
LOCATION - Lat 33°19'44", long 117°19'35" referenced to North American Datum of 1927, in NW 1/4 NW 1/4 sec.08, T.10 S., R.4 W., San Diego County, CA, Hydrologic Unit 18070302, on Camp Joseph H. Pendleton Naval Reservation, on right bank, 100 ft upstream from spillway on O'Neill Lake, 1.3 mi upstream from confluence with Santa Margarita River, and 5.5 mi southwest of Fallbrook.
DRAINAGE AREA - 9.77 mi².
SURFACE-WATER RECORDS
PERIOD OF RECORD - October 1998 to February 2003, October 2003 to current year.
GAGE - Water-stage recorder and sharp-crested weir (wooden flashboards in four weir boxes). Datum of gage is 101.84 feet above NAVD of 1988.
REMARKS - Records for this station represent spill from O'Neill Lake. Minor seepage through weir flashboards may occur at times and is not indicated in records for this station. Water is sometimes diverted into O'Neill Lake from the Santa Margarita River via a diversion dam 0.55 mi above gage. Slight regulation by two small storage reservoirs upstream from gaging station on Fallbrook Creek near Fallbrook (station 11045300). See schematic diagram of Santa Margarita River Basin available from the California Water Science Center.
EXTREMES FOR PERIOD OF RECORD - Maximum discharge, estimation of 725 ft³/s, Jan. 22, 2017, gage height, 8.39ft, from rating curve developed on basis of sharp-crested weir computations; Maximum gage height, 9.32 ft, Dec. 22, 2010; no flow for all or most of each year.
