USGS Water-Year Summary 2021
14015000 MILL CREEK AT WALLA WALLA, WA
LOCATION - Lat 46°04'35", long 118°16'21" referenced to North American Datum of 1927, in NE 1/4 NW 1/4 sec.23, T.7 N., R.6 E., Walla Walla County, WA, Hydrologic Unit 17070102, on left bank 200 ft downstream from diversion dam, 1.5 mi east of Walla Walla, and at mile 10.5.
DRAINAGE AREA - 95.7 mi².
- WSP 1288: Drainage area. WSP 1348: 1943, 1945-46.
PERIOD OF RECORD - April 1941 to current year.
GAGE - Water-stage recorder and concrete control. Datum of gage is 1,165.49 ft above NGVD of 1929 (levels by U.S. Corps of Engineers). April 1941 to June 11, 1941, nonrecording gage, and June 11, 1941, to Jan. 22, 1957, water-stage recorder, at sites 0.8 mi downstream at different datum. U.S. Geological Survey telephone telemeter at station.
EXTREMES OUTSIDE PERIOD OF RECORD - Flood of Mar. 31 or Apr. 1, 1931, discharge not determined, was greatest since at least 1913. A discharge of about 11,000 ft³/s, based on a slope-area measurement, was determined for the 1931 peak at old City of Walla Walla diversion dam.
EXTREMES FOR PERIOD OF RECORD - Maximum discharge, 4700 ft³/s gage height 7.07 ft. February 7, 2020; no flow many days.