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USGS Water-Year Summary 2024
09486500 SANTA CRUZ RIVER AT CORTARO, AZ
LOCATION - Lat 32°21'04", long 111°05'38" referenced to North American Datum of 1927, in NW 1/4 NW 1/4 NW 1/4 sec.35, T.12 S., R.12 E., Pima County, AZ, Hydrologic Unit 15050302, on left bank about 300 ft upstream from bridge and streamward of county park, 0.5 mi southwest of Cortaro, about 1 mi downstream from Ina Road treatment plant, 2.6 mi downstream from Canada del Oro, and 3.7 mi downstream from Rillito Creek.
DRAINAGE AREA - 3,503 mi². of which 397 mi² is in Mexico.
REVISIONS HISTORY - WSP 1283: Drainage area. Revisions: Discharge for the period July 6, 2022, to Oct. 13, 2022, was revised on April 25, 2022. discharge was estimated to be lower during the event on 07/24/22. A comparison with nearby gages support lower flow at the Cortaro gage during this event. The data footprint was also questionable as the orifice line may have been fouled during this time.
SURFACE-WATER RECORDS
PERIOD OF RECORD - Oct. 1939 to June 1947 (published as "at Rillito"), July 1950 to Sept. 1984, Mar. to June 1990, July to Sept. 1990 (fragmentary record), Oct. 1990 to current year.
GAGE - Water-stage recorder. Datum of gage is 2,100.00 ft, above sea level. Prior to June 30, 1947, at site 5.5 mi downstream at different datum. July 8, 1950, to Jan. 20, 1966, at site on left bank 500 ft downstream of bridge at datum 19.11 ft lower. Jan. 20, 1966, to Sept. 30, 1984, at site on left bank 500 ft downstream of bridge at datum 23.11 ft lower. Aug. 1 to Oct. 19, 1990, at site on right bank 0.33 mi downstream from bridge at datum 30.20 ft lower. Apr. 10 to May 17, 1991, at site on bridge, 200 ft toward right bank, at different datum. Prior to Jul. 30, 2008 at site on left bank 700 ft downstream of bridge at present datum. Jul. 30, 2008 to present at site on left bank about 300 ft upstream of bridge. Supplementary water-stage recorder on downstream site on left bridge pier at datum 19.11 ft lower Aug. 29, 1969, to Sept. 30, 1984. Temporary water-stage recorder on right bank Oct. 27, 1983, to Sept. 30, 1984, at datum 20.80 ft lower. Prior to May 8, 1997 at site 300 ft upstream at different datum.
REMARKS - Record is good for discharges under 100 cfs and fair above that. Estimated discharges are poor. Base flow is effluent from combined municipal sewage treatment plants at Ina and Roger Roads.
EXTREMES FOR PERIOD OF RECORD - Maximum discharge, 65,000 ft³/s, Oct. 2, 1983, gage height, 16.57 ft from floodmark, computed by flood-routing method from Santa Cruz River at Tucson and Rillito Creek at Tucson; minimum, no natural flow for most of each year. (See REMARKS)
