1

2

3

4

Figure 3-1. Isohyetal Map of San Lorenzo Valley

Pacific Ocean

0 1 2 miles

BenLomond

BoulderCreek

QuailHollow

Olympia

Felton

SantaCruz

Pasa-tiempo

ScottsValley

*Contours generalized for estimating 1937-96 average watershed precipitation; adopted from larger map by Geomatrix, 1999.

San Lorenzo River watershed

SLVWD diversion watershed

NM JohnsonSLVWD Water Supply Master Plan

40 Isohyetal (in/yr)*Precipitation station used in mapping.Selected precip. stations:

1. Lockheed2. SLVWD Office3. Ben Lomond 44. Santa Cruz

A. Pescadero CkB. San Lorenzo R. Waterman SwitchC. Boulder CkD. Zayante CkE. Bean CkF. San Vicente CkG. San Lorenzo R. at Big Trees

AB

D

C

G

F

Selected USGS Stream Gaging Stations

E

Figure 3-2Satellite Images of Typical Pacific Storms

Imagery source: www.goes.noaa.gov/

Tropical moisture entrained in jet stream.

SLVWD Water Supply Master Plan NM Johnson

a. Cold Cyclonic Storm b. Warm Advective Storm

Southwest Northeast

<30" 50" 60+" 50" <45" 50+" 30" 25" 15"

Santa Clara Valley

Santa Cruz Mountains

Average Annual Precipitation (in/yr)

Ben Lomond Mtn.San Lorenzo Valley

Coast San

Lore

nzo

Riv

er

SouthSan

FranciscoBay

Bonny Doon SummitCastle Rock

Mt. Bielawski

SLVWD Watersheds

Boulder CkBen LomondFelton

DavenportSanta Cruz

ScottsValley

Los Gatos

Figure 3-4Schematic Coast-to-South Bay Profile Illustrating Orographic Influence on Rainfall Distribution

(adopted from Geomatrix, 1999; see Fig. 3-3 for approximate line of profile)

San Jose

Santa Clara Valley

Figure 3-3Radar Image Showing Influence of Ben Lomond Mountain on Rainfall Distributon

ppt-xsec4.xls Fig 6/7/2007 4:18 AM NM Johnson

Figure 3-5Monthly Average Rainfall and Streamflow, Selected Stations

a. Comparison of Three Rainfall Stations

0%

5%

10%

15%

20%

25%

Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep

Perc

ent o

f Ave

rage

Ann

ual R

ainf

all

Ben Lomond 4, WY's 1973-2007

Santa Cruz, WY's 1931-2006

Lockheed, WY's 1959-2006

b. Rainfall versus Streamflow

0%

5%

10%

15%

20%

25%

Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep

Perc

ent o

f Ave

rage

Ann

ual R

ainf

all a

nd S

trea

mflo

w

Average of 3 Rainfall Stations (Table 3-4)

Average of 6 Gaged Streams (Table 3-9)

Ppt-SC-LH4.xls Fig-MthAvg 6/7/2007 4:00 AM NM Johnson

BL4-Daily-Hist2.xls Fig 6/7/2007 4:19 AM NM Johnson

Figure 3-6Frequency of Cumulative Daily to Monthly Rainfall at Ben Lomond, 1973-2006

50% 20%30%40%60%70%80%90%100%

0.01

0.1

1

10

100

0% 10% 20% 30% 40% 50% 60% 70% 80%Percent of Time Rainfall is Greater Than

Cum

ulat

ive

Rai

nfal

l (in

ches

)Percent of Time Rainfall is Less Than

1-DAY 14-DAY7-DAY3-DAY2-DAY 30-DAY21-DAY

Max. Rainfall* (inches) Date(s) 1-day 11.5 1/4/82 2-day 16.1 1/4-5/82 3-day 16.1 1/3-5/82 7-day 20.4 2/12-18/8614-day 22.8 12/18-31/0521-day 27.2 1/30-2/19/8630-day 32.7 1/26-2/24/98

*Based on daily readings

Source: http://hurricane.ncdc.noaa.gov/dly/DLY

Santa Cruz

0%

50%

100%

150%

200%

1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010Water Years

Ann

ual R

ainf

all (

% f

avg)

Lockheed Facility

0%

50%

100%

150%

200%

1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010Water Years

Ann

ual R

ainf

all (

% f

avg)

Ben Lomond 4

0%

50%

100%

150%

200%

1970 1980 1990 2000 2010

Water YearsA

nnua

l Rai

nfal

l (%

f av

g)Figure 3-7

Water-Year Rainfall at Santa Cruz, Lockheed, and Ben Lomond Staions

Years with ≤75% average rainfall Years with 76-90% average rainfall

Apparent Santa Cruz upward trend partially explained by likely change(s) in station location pre-1950, as indicated by double mass curve analysis (Geomatrix, 1999). Since 1950, Santa Cruz upward trend continues while Lockheed trend becomes flat. Significance of Ben Lomond upward trend uncertain due to short record length.

Source: see Tables 3-1 through 3-4.

Ppt-SC-LH6.xls Fig-WYs 5/18/2009 6:16 AM NM Johnson

Moving-Average Minimums* Moving-Average Maximums*Yrs Santa Cruz Lockheed Santa Cruz Lockheed1 35% 1924 37% 1924 213% 1941 226% 18902 52% 1976-77 48% 1976-77 182% 1940-41 189% 1982-833 62% 1869-71 53% 1929-31 171% 1940-42 159% 1982-84 *Color-coded by

common overlapping periods.

4 66% 1928-31 59% 1928-31 162% 1940-43 145% 1995-985 67% 1987-91 62% 1927-31 149% 1940-44 140% 1982-866 71% 1987-92 63% 1926-31 145% 1938-43 139% 1995-007 73% 1869-75 65% 1924-30 141% 1937-43 130% 1995-018 74% 1924-31 62% 1924-31 138% 1936-43 127% 1995-029 74% 1869-77 65% 1923-31 133% 1937-45 123% 1978-8610 77% 1868-77 66% 1922-31 131% 1936-45 123% 1965-7412 78% 1869-80 69% 1921-31 126% 1995-06 122% 1995-0614 79% 1918-31 67% 1920-31 123% 1993-06 118% 1993-0616 80% 1916-31 69% 1919-21 122% 1937-52 116% 1969-8420 80% 1869-88 72% 1916-35 117% 1937-56 116% 1967-86

25%

50%

75%

100%

125%

150%

175%

200%

225%

0 5 10 15 20Length of Moving Average Period (yrs)

Mov

ing-

Ave

rage

Rai

nfal

l (pe

rcen

t of a

vera

ge)

Santa Cruz

Lockheed

Ben Lomond 4

Minimumfor Period

Maximum for Period

Figure 3-8Minimum and Maximum Moving-

Average Rainfall

Ppt-SC-LH4.xls FigMvAvg 6/7/2007 4:01 AM NM Johnson

Ppt-SC-LH6.xls FigCumDepAvg 5/18/2009 6:17 AM NM Johnson

Figure 3-9Water-Year Rainfall Cumulative Departure from Average

-700%

-600%

-500%

-400%

-300%

-200%

-100%

0%

100%

200%

1860

1870

1880

1890

1900

1910

1920

1930

1940

1950

1960

1970

1980

1990

2000

2010

Water Years

Cum

ulat

ive

Dep

artu

re fr

om A

vera

ge (%

of a

vera

ge)

Lockheed (entire record)Santa Cruz (since 1889)

Santa Cruz (entire record)

Drought = downward segmentsAverage period = flat segmentsWet period = upward segments

1917-37 Drought

Pre-1890 Drought

1987-94 Drought1975-77

Drought

Source: http://wwwcimis.water.ca.gov/cimis/info.jsp

Figure 3-10CIMIS Reference Evapotranspiration for Central Coast Region

8

3 8

Monthly CIMIS Reference Evapotranspiration for Santa Cruz County Zones

0

1

2

3

4

5

6

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Ref

eren

ce E

vapo

tran

spir

atio

n (E

To,

inch

es)

Zone 1 -- Coastal Fog BeltZone 2 --Coastal Mixed FogZone 3 -- Coastal Valleys

CIMIS Map2.xls CentralCoast 6/7/2007 4:20 AM

1 Pilarcitos Ck at Half Moon Bay 2 Purisima Ck near Half Moon Bay 3 San Gregorio Ck at San Gregorio4 Pescadero Ck near Pescadero5 Butano Ck near Pescadero6a Scott Ck above Little Ck6b Scott Ck near Davenport7 San Vicente Ck near Davenport8 Laguna Ck near Davenport9 Majors Ck near Santa Cruz10 San Lorenzo R at Waterman Switch11 Boulder Ck at Boulder Creek12 Bear Ck at Boulder Creek13 Newell Ck at Ben Lomond14 Zayante Ck at Zayante15 Bean Ck near Scotts Valley16 San Lorenzo River at Big Trees

17 Carbonera Ck at Scotts Valley18 Branciforte Ck at Santa Cruz19 West Br. Soquel Ck near Soquel20 Soquel Ck near Soquel21 Soquel Ck at Soquel22 Aptos Ck near Aptos23 Aptos Ck at Aptos24 Corralitos Ck near Corralitos25 Corralitos Ck at Freedom26 San Francisquito Ck at Stanford University 27 Saratoga Ck at Saratoga28 Los Gatos Ck at Los Gatos 29 Guadalupe Ck at Guadalupe 30 Uvas Ck above Uvas Res near Morgan Hill31 Bodfish Ck near Gilroy32 Pescadero Ck near Chittenden (See Table 3-8 for summary of gaged records)

Figure 3-11USGS Gaged Watersheds in

the Santa Cruz Mountains Region(adopted from Geomatrix, 1999)

SantaCruz

Davenport

PaloAlto

MorganHill

LosGatos

SLVWDDiversions

Pacific Ocean

ppt-q-4.xls Fig 6/7/2007 4:12 AM NM Johnson

Figure 3-12Correlation Between Estimated Mean Annual Rainfall and Unit

Streamflow for USGS Gaged Streams in the Santa Cruz Mountains Region

Soquelnear Sq

Soquel at Sq SaratogaScott

SLRBT

Scott above Little San Vicente

Boulder

Laguna

ZayanteNewell

BearSLR at Waterman Switch

MajorsWB Soquel

Branciforte

Corralitos at Cor

Bean

Carbonera

Uvas

Butano

Apots near AptosGuadalupe

Purisima

Aptos at Aptos

Corralitos at Fdm

San Gregorio

San Francisquito

Pilarcitos

Bodfish

Pescadero

Pescadero

Los Gatos

Ben Lomond Mtn

Ben Lomond

Santa Cruz

Quail HollowZaynte Soils

0

5

10

15

20

25

30

25 30 35 40 45 50 55 60Watershed Average Rainfall (in/yr)

Wat

ersh

ed A

vera

ge U

nit S

trea

mflo

w (i

n/yr

)

Adjusted to 1937-1996 average (Table 3-8)

SLVWD diversion watershed estimate*

Soil-Water Budget Estimates (Table 3-6)

*Adopted from Geomatrix, 1999. See Figure 3-11 for map of gaged watersheds.

Figure 3-13Water-Year Streamflow of San Lorenzo River and Pescadero Creek

Source: see Table 3-10.

San Lorenzo River at Big Trees*

0%

50%

100%

150%

200%

250%

300%

1930 1940 1950 1960 1970 1980 1990 2000 2010

Water Years

Ann

ual S

trea

mflo

w (%

f av

g)

*Adjusted (Table 3-9)

Pescadero Creek

0%

50%

100%

150%

200%

250%

300%

350%

400%

1950 1960 1970 1980 1990 2000 2010

Water Years

Ann

ual S

trea

mflo

w (%

f av

g)

Years with ≤50% average streamflowYears with 50-90% average streamflow

Sec3 USGS-Gaged-Records2.xls Fig-WY 5/18/2009 6:34 AM NM Johnson

Pescadero Creek near Pescadero

0

10

20

30

40

50

Boulder Creek at Boulder Creek

0

5

10

15

20

25

San Lorenzo River at Waterman Switch

0

5

10

15

Zayante Creek at Zayante

0

5

10

15

San Lorenzo River at Big Trees

0

50

100

150

Oct

-74

Oct

-75

Oct

-76

Oct

-77

Oct

-78

Oct

-79

Oct

-80

Oct

-81

Oct

-82

Oct

-83

Oct

-84

Oct

-85

Oct

-86

Oct

-87

Oct

-88

Oct

-89

Oct

-90

Oct

-91

Oct

-92

Oct

-93

Oct

-94

Mea

n D

aily

Str

eam

flow

(cfs

)

Bean Creek near Scotts Valley

0

5

10

15

Oct

-88

Oct

-89

Oct

-90

Oct

-91

Oct

-92

Oct

-93

Oct

-94

Plots show 1975-77 and 1987-94 droughts. Note effect of October 1989 Loma Prieta earthquake.

Source: http://nwis.waterdata.usgs.gov/ca/nwis/sw

Figure 3-14Mean Daily Streamflow, Selected Streams, WY's 1975-1995

Drought-HGs.xls Sheet1 6/7/2007 4:23 AM NM Johnson

USGS-Gaged-Records2.xls Fig-WY-Ppt-Q 6/7/2007 4:16 AM NM Johnson

Figure 3-15Correlation Between Annual Rainfall and Unit Streamflow

Selected Periods of Gaged Record

'74

'75

'76'77

'78

'79

'80

'81

'82

'83

'84

'85

'86

'87

'88

'89'90 '91

'92

'93

'94

'95

'96

'97

'98

'99

'00

'01'02

'03

'04

'05

'06

0%

50%

100%

150%

200%

250%

300%

25% 50% 75% 100% 125% 150% 175% 200%Water-Year Rainfall (% of average)

Wat

er-Y

ear

Stre

amflo

w (%

of a

vera

ge)

San Lorenzo River flow* vs Ben Lomondrainfall (WY's 1974-2006; dated)

San Lorenzo River flow* vs Lockheed rainfall(WY's 1937-2006)

Boulder Creek flow vs Ben Lomond rainfall(WY's 1977-1992)

San Lorenzo River vs Lockheed wet- & dry-period averages (WY's 1937-2006)

Gaged watershed averages (as % of averagefor all watersheds; Table 3-8, Fig. 3-12)

Soil-water budget estimates (as % of averagefor all cases; Table 3-6)

*At Big Trees gage; approx. adjustment for major diversions. See Tables 3-8 & -10 for sources.

Drain-age

Area

Water-shed Rain-fall

Unit Streamflow*

ETTotal

* BaseflowStorm Run-off(% of

Total)Stream (mi2) (in/yr) (in/yr)

Pescadero Ck 45.9 39.9 13.0 4.8 37% 8.2 27.0San Vicente Ck 5.9 50.9 20.5 10.0 49% 10.5 30.4

SLR at Waterman Switch 6.2 44.6 14.7 6.1 41% 8.6 29.9Boulder Ck 11.4 52.8 21.8 8.4 38% 13.4 30.9Zayante Ck 11.1 43.8 14.9 5.2 35% 9.7 29.0

Bean Ck 9.0 43.7 18.1 6.8 38% 11.2 25.7SLR at Big Trees 106.6 46.0 17.3 7.1 41% 10.2 28.7

*Normalized to 1937-2006; thus, values of total streamflow differ slightly from Table 3-8.

Hydrographs are of average mean daily flow for indicated periods of record.Source: http://nwis.waterdata.usgs.gov/ca/nwis/sw

Pescadero Creek,WY's 1952-2006

0

25

50

75

100

125

150

175

1-Oct 1-Nov 1-Dec 1-Jan 1-Feb 1-Mar 1-Apr 1-May 1-Jun 1-Jul 1-Aug 1-Sep

Mea

n D

aily

Flo

w (c

fs)

StormflowBaseflow

San Lorenzo Riverat Waterman Switch,

WY's 1969-1992

0

5

10

15

20

25

30

1-Oct 1-Nov 1-Dec 1-Jan 1-Feb 1-Mar 1-Apr 1-May 1-Jun 1-Jul 1-Aug 1-Sep

Mea

n D

aily

Flo

w (c

fs)

StormflowBaseflow

Boulder Creek,WY's 1977-1992

0

10

20

30

40

50

60

70

80

1-Oct 1-Nov 1-Dec 1-Jan 1-Feb 1-Mar 1-Apr 1-May 1-Jun 1-Jul 1-Aug 1-Sep

Mea

n D

aily

Flo

w (c

fs)

StormflowBaseflow

Zayante Creek,WY's 1958-1992

0

5

10

15

20

25

30

35

40

45

1-Oct 1-Nov 1-Dec 1-Jan 1-Feb 1-Mar 1-Apr 1-May 1-Jun 1-Jul 1-Aug 1-Sep

Mea

n D

aily

Flo

w (c

fs)

StormflowBaseflow

Bean Creek,WY's 1990-2006

0

5

10

15

20

25

30

35

40

1-Oct 1-Nov 1-Dec 1-Jan 1-Feb 1-Mar 1-Apr 1-May 1-Jun 1-Jul 1-Aug 1-Sep

Mea

n D

aily

Flo

w (c

fs)

StormflowBaseflow

San Lorenzo Riverat Big Trees,

WY's 1937-2006

0

50

100

150

200

250

300

350

400

1-Oct 1-Nov 1-Dec 1-Jan 1-Feb 1-Mar 1-Apr 1-May 1-Jun 1-Jul 1-Aug 1-Sep

Mea

n D

aily

Flo

w (c

fs)

StormflowBaseflow

Figure 3-16Estimated Avearge Stormflow-Baseflow Hydrograph Separation, Selected Gaged Streams

San Vicente Creek,WY's 1970-1985

0

5

10

15

20

25

30

35

40

1-Oct 1-Nov 1-Dec 1-Jan 1-Feb 1-Mar 1-Apr 1-May 1-Jun 1-Jul 1-Aug 1-Sep

Mea

n D

aily

Flo

w (c

fs)

StormflowBaseflow

Qb-summary2.xls Sheet1 6/7/2007 4:24 AM NM Johnson

Source: www.wrcc.dri.edu/summary/climsmnca.html Figure 3-17Annual Mean Temperature, Selected Stations, 1945-2005

Santa Cruz y = -0.0168x + 69.006

y = 0.0369x + 55.841

y = 0.0907x + 42.677

40

45

50

55

60

65

70

75

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Ann

ual A

vera

ge T

empe

ratu

re (o

F)

Ben Lomond 4y = 0.0175x + 73.479

y = 0.0071x + 58.552

y = -0.0033x + 43.623

40

45

50

55

60

65

70

75

80

1970 1975 1980 1985 1990 1995 2000 2005

Ann

ual A

vera

ge T

empe

ratu

re (o

F)

San Gregorio 2SE

y = 0.014x + 44.117

y = 0.0075x + 54.278

y = 0.0008x + 64.447

40

45

50

55

60

65

70

1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Ann

ual A

vera

ge T

empe

ratu

re (o

F)

Los Gatos

y = 0.0366x + 44.972

y = 0.0126x + 58.77

y = -0.0112x + 72.561

40

45

50

55

60

65

70

75

80

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Ann

ual A

vera

ge T

empe

ratu

re (o

F)

Temp-SC.xls Sheet7 6/7/2007 4:25 AM NM Johnson

y = 0.001x + 0.2557

y = 0.0013x + 0.2337

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0.55

1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010Water Years

Coe

ffic

ient

of V

aria

bilit

y

Santa CruzLockheed

Figure 3-18Coefficient of Variation for Moving 10-Year Periods of Annual Precipitaion,

Study Area and Statewide, 1880's to Present

From: CDWR, July 2006

Source: see Table 3-4

Ppt-SC-LH4.xls Fig-CoefVar 6/7/2007 4:04 AM NM Johnson