11181040 SAN LORENZO CREEK AT SAN LORENZO, CA
LOCATION.-Lat 37°41'03", long 122°08'20", in San Lorenzo (Soto) Grant, Alameda County, Hydrologic Unit
18050004, on left bank, 400 ft downstream from Washington Avenue Bridge in San Lorenzo, and 1.6 mi upstream from
mouth.
DRAINAGE AREA.-44.6 mi2.
PERIOD OF RECORD.-October 1967 to September 1978, October 1987 to current year.
WATER TEMPERATURE: Water years 1989-93 (storm season only).
SEDIMENT DATA: Water years 1989-93 (storm season only).
GAGE.-Water-stage recorder and crest-stage gage. Datum of gage is 6.13 ft above sea level (levels by Alameda
County Flood Control and Water Conservation District).
REMARKS.-Records poor. Flow partly regulated since October 1962 by Cull Creek Reservoir, capacity, 310 acre-ft,
and since January 1965 by Don Castro Reservoir, capacity, 380 acre-ft, 7 mi upstream. A few very small diversions
upstream from station.
EXTREMES FOR PERIOD OF RECORD.-Maximum discharge, 10,300 ft3/s, Feb. 3, 1998, gage height, 14.27 ft
from rating curve extended above 1,200 ft3/s; minimum daily, 0.01 ft3/s, several days in
June and July 1977.
EXTREMES FOR CURRENT YEAR.-Peak discharges greater than base discharge of 1,500 ft3/s, or maximum:
Discharge Gage height Discharge Gage height
Date Time (ft3/s) (ft) Date Time (ft3/s) (ft)
Feb. 7 1300 3,130 7.55 Feb. 27 0300 1,620 6.19
DISCHARGE, CUBIC FEET PER SECOND, WATER YEAR OCTOBER 1998 TO SEPTEMBER 1999
DAILY MEAN VALUES
DAY OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP
1 e3.2 1.3 31 3.9 29 41 29 21 e11 2.1 e1.6 e1.9
2 e3.2 1.1 14 3.5 26 39 28 20 e11 2.4 e2.1 e1.7
3 e3.1 .96 43 3.5 25 54 28 21 e11 2.9 e2.9 e1.4
4 e3.0 1.0 16 3.4 24 38 28 20 e10 3.0 e3.0 e1.3
5 e3.0 .99 45 3.3 23 37 87 18 e10 2.9 e4.0 e1.3
6 e3.1 6.6 34 3.6 93 37 41 18 e10 3.0 e8.2 e1.3
7 e3.3 32 11 3.4 934 36 26 17 e10 3.0 e3.2 e1.4
8 e3.4 17 8.3 3.4 118 42 138 17 e10 e2.9 e2.1 e1.7
9 e3.5 8.3 7.2 3.2 647 107 40 16 e10 e2.7 e2.2 e2.4
10 3.3 4.5 6.0 3.0 89 43 37 e16 e9.8 e2.6 e2.4 e1.4
11 3.3 6.1 5.9 3.3 53 40 90 e15 e9.4 e2.5 e2.6 e1.2
12 3.4 1.9 5.9 3.2 42 38 39 e14 e9.2 e2.5 e2.5 e1.1
13 3.7 4.5 22 3.3 42 37 33 e14 e8.5 e3.0 e2.7 e1.1
14 4.9 1.6 17 3.4 37 63 31 e13 e7.4 e3.0 e2.4 e1.2
15 4.6 1.6 6.7 29 32 64 29 e12 e6.7 e3.3 e1.9 e1.1
16 4.3 1.4 5.6 45 129 47 29 e12 e6.9 e3.4 e2.1 e1.2
17 4.8 4.3 5.2 9.4 424 39 28 e14 e6.7 e3.1 e2.5 e1.1
18 3.6 2.4 5.1 128 94 35 27 e13 e6.9 e2.7 e2.5 e.95
19 3.2 1.6 4.7 189 60 43 27 e14 e6.6 e2.9 e2.4 e.91
20 3.0 1.4 9.2 179 177 40 27 e12 e6.4 e2.9 e2.3 e1.2
21 3.1 2.3 4.8 40 214 36 27 e12 e6.5 e2.7 e2.3 e1.5
22 3.0 19 4.4 28 73 34 26 e11 e6.5 e2.6 e2.1 8.3
23 2.9 e76 4.4 130 59 41 26 e10 e6.8 e2.6 e2.0 2.9
24 45 18 4.1 48 52 35 25 e11 e5.2 e2.7 e2.3 e2.0
25 7.1 4.8 4.5 38 78 72 24 e11 e4.0 2.1 e2.2 e1.6
26 2.1 4.7 4.2 82 48 43 23 e11 e3.6 1.9 e2.0 e1.4
27 1.6 14 4.2 44 44 34 23 e12 e3.2 2.1 e2.1 e1.4
28 1.2 27 4.1 36 42 31 23 e12 e3.4 e2.0 e1.7 e1.3
29 1.2 28 4.1 33 --- 30 22 e13 e3.2 e1.9 e2.2 e1.4
30 1.2 209 4.1 31 --- 29 22 e13 e2.9 e1.8 e2.3 e1.2
31 1.3 --- 4.2 81 --- 34 --- e12 --- e1.6 e1.9 ---
TOTAL 140.6 503.35 349.9 1217.8 3708 1339 1083 445 222.8 80.8 78.7 49.86
MEAN 4.54 16.8 11.3 39.3 132 43.2 36.1 14.4 7.43 2.61 2.54 1.66
MAX 45 209 45 189 934 107 138 21 11 3.4 8.2 8.3
MIN 1.2 .96 4.1 3.0 23 29 22 10 2.9 1.6 1.6 .91
AC-FT 279 998 694 2420 7350 2660 2150 883 442 160 156 99
e Estimated.
STATISTICS OF MONTHLY MEAN DATA FOR WATER YEARS 1968 - 1999, BY WATER YEAR (WY)
OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP
MEAN 5.24 9.76 24.7 74.9 68.4 44.7 23.2 9.23 4.21 1.89 1.53 1.77
MAX 30.2 38.1 106 259 390 154 108 31.9 17.0 5.99 3.25 4.58
(WY) 1992 1974 1971 1997 1998 1995 1974 1996 1993 1998 1969 1975
MIN .23 1.49 1.41 1.14 2.15 1.83 2.07 .85 .066 .64 .11 .35
(WY) 1978 1991 1990 1991 1977 1972 1976 1972 1977 1990 1977 1988
SUMMARY STATISTICS FOR 1998 CALENDAR YEAR FOR 1999 WATER YEAR WATER YEARS 1968 - 1999
ANNUAL TOTAL 23520.95 9218.81
ANNUAL MEAN 64.4 25.3 22.3
HIGHEST ANNUAL MEAN 65.6 1998
LOWEST ANNUAL MEAN 2.38 1977
HIGHEST DAILY MEAN 2340 Feb 3 934 Feb 7 2400 Jan 21
1970
LOWEST DAILY MEAN .96 Nov 3 .91 Sep 19 .01 Jun 12
1977
ANNUAL SEVEN-DAY MINIMUM 1.1 Oct 30 1.1 Sep 13 .01 Jun 10
1977
INSTANTANEOUS PEAK FLOW 3130 Feb 7 10300 Feb 3
1998
INSTANTANEOUS PEAK STAGE 7.55 Feb 7 14.27 Feb 3
1998
ANNUAL RUNOFF (AC-FT) 46650 18290 16120
10 PERCENT EXCEEDS 164 45 45
50 PERCENT EXCEEDS 9.7 6.7 2.7
90 PERCENT EXCEEDS 2.3 1.6 .60
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