U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Map 3377

Any use of trade, product, or firm names in this publication is for descriptive 

purposes only and does not imply endorsement by the U.S. Government

This map was printed on an electronic plotter directly from digital files. 

Dimensional calibration may vary between electronic plotters and between 

X and Y directions on the same plotter, and paper may change size due to 

atmospheric conditions; therefore, scale and proportions may not be true on 

plots of this map.

Digital files available at https://doi.org/10.3133/sim3377 or 

http://pubs.usgs.gov/sim/3377/. Data release, boosted regression tree 

(BRT) model method, and model fit statistics are available at 

https://doi.org/10.5066/F7FX77K4.

Suggested citation: Rosecrans, C.Z., Nolan, B.T., Gronberg, J.M., 2017, 

Predicted pH at the domestic and public supply drinking water depths, 

Central Valley, California: U.S. Geological Survey Scientific Investigations 

Map 3377, 1 sheet, scale 1:2,400,000, https://doi.org/10.3133/sim3377. ISSN 2329-132X (online)

https://doi.org/10.3133/sim3377

Predicted pH in Depth Zones Used by Domestic and Public 

Drinking Water Supply Wells, Central Valley, California

By

Celia Z. Rosecrans, Bernard T. Nolan, and Jo Ann M. Gronberg

2017

42°

124°

122°

40°

38°

116°

120°

118°

34°

116°

36°

42°

118°

120°

122°

124°

40°

38°

36°

34°

120°

120°

36°

36°

38°

38°

40°

40°

122°

122°

120°

120°

36°

36°

38°

38°

40°

40°

122°

122°

Base modified from U.S. Geological Survey Principal Aquifers of N N

the 48 Conterminous United States, Hawaii, Puerto Rico, and the 

U.S. Virgin Islands (http://water.usgs.gov/GIS/metadata/usgswrd/

XML/aquifers_us.xml); Groundwater Availability of the Central 

Valley Aquifer, California (http://pubs.usgs.gov/pp/1766/), and 

other Federal digital data, various scales; Albers Equal-Area Conic 

projection, standard parallels are 29° 30" and 45° 30"; North

American Datum of 1983

Base modified from U.S. Geological Survey digital data, various

scales; Albers Equal-Area Conic projection, standard parallels

are 29° 30" and 45° 30"; North American Datum of 1983 50 0 25 50 MILES

SCALE 1:2,400,000

25

50 25 0 25 50 KILOMETERS

EXPLANATION EXPLANATION

Principal aquifer units 

Basin and Range basin fill

Basin and Range carbonate rock 

California Coastal Basin

Central Valley aquifer system

Other rocks

Pacific Northwest

 basaltic rock

Pacific Northwest

 basin fill

Study area boundary

Prediction model boundary

Boosted regression tree

 training wells (n=1,003)

PREDICTED pH—DOMESTIC-SUPPLY

DEPTH ZONE1

 (100 feet below land surface)

PREDICTED pH—PUBLIC-SUPPLY

DEPTH ZONE1 (325 feet below land surface)

>6.4 to 6.6

>6.6 to 6.8

>6.8 to 7.0

>7.0 to 7.2

>7.2 to 7.4

>7.4 to 7.6

>7.6 to 7.8

>7.8 to 8.0

Prediction model

 boundary

Predicted pH, in standard units 

CALIFORNIA PRINCIPAL AQUIFERS

0 50 MILES

SCALE 1:4,100,000

50

50 0 50 KILOMETERS

1

Domestic and public supply depth zones represent median well depths of the training boosted regression tree (BRT) dataset that were stratified into shallow and deep drinking water supply depths, respectively, based on previous work. 

See data release link for summary of details and citation.