WATER QUALITY OF CALERO RESERVOIR, SANTA CLARA COUNTY, CALIFORNIA, 1981-83 By Daphne G. Clifton and Isabel S. Gloege U.S. GEOLOGICAL SURVEY Water-Resources Investigations Report 86-4105 Prepared in cooperation with the SANTA CLARA VALLEY WATER DISTRICT CN I o m Sacramento, California 1987 DEPARTMENT OF THE INTERIOR DONALD PAUL MODEL, Secretary U.S. GEOLOGICAL SURVEY Dallas L. Peck, Director For additional information Copies of this report write to: can be purchased from: District Chief Books and Open-File U.S. Geological Survey Reports Section Federal Building, Room W-2234 U.S. Geological Survey 2800 Cottage Way Box 25425, Federal Center Sacramento, CA 95825 Denver, CO 80225 CONTENTS Page Page Abstract 1 Physical and chemical Introduction 2 characteristics Continued Purpose and scope 2 Specific conductance 22 Description of the study area 2 Major ions 23 Reservoirs 2 Trace constituents 25 Geology and soils 4 Mercury in bottom sediments 26 Climate 4 Nitrogen and phosphorus 26 Field and laboratory methods 4 Biological characteristics 29 Calero Reservoir 4 Phytoplankton composition and Almaden-Calero Canal 6 chlorophyll-a concentrations 29 Quality-assurance program 6 Primary productivity 30 Sampling design 7 Trophic-state index 31 Physical and chemical Bacteria 31 characteristics 7 Comparisons of water-quality Reservoir volume 7 conditions with water-quality Water temperature and thermal criteria 33 stratification 10 Future studies 33 Water transparency and light Summary 35 transmission 14 References cited 36 Dissolved oxygen 20 Glossary of selected terms 38 pH 22 ILLUSTRATIONS Page Figure 1-2. Maps showing: 1. Location of the study area 3 2. Calero Reservoir and Almaden-Calero canal sampling stations 5 3-4. Graphs showing: 3. Monthly maximum and monthly mean reservoir volume for Calero Reservoir, 1936-83 8 4. Monthly maximum and monthly mean reservoir volume for Calero Reservoir, 1981-83 9 5. Diagram showing thermal stratification pattern in temperate lakes and reservoirs 11 6-7. Profiles showing: 6. Seasonal water temperature, dissolved oxygen, pH, specific conductance, and water transparency for Calero Reservoir, center station, for 1982 12 7. Light extinction in Calero Reservoir, center station, 1981-83 16 8. Graphs showing seasonal mean concentrations of dissolved and total nitrogen species, total phosphorus and orthophosphorus, dissolved silica, chlorophyll-a and -b, and phytoplankton concentrations for Calero Reservoir, 1981-83 17 9. Trilinear diagrams showing major-ion composition, in percent, of water in Calero Reservoir and Almaden-Calero canal for 1981-83 24 Contents III TABLES Page Table 1. Secchi disk, chlorophyll-a, and total phosphorus concentrations; and trophic-state indices for Calero Reservoir, 1981-83 15 2. Taxonomy of dominant phytoplankton in Calero Reservoir 18 3. Dominant phytoplankton and phytoplankton counts in Calero Reservoir, center station 19 4. Light- and dark-bottle estimates of primary productivity in Calero Reservoir, center station, 1981-83 21 5. Trace-element concentrations for Calero Reservoir, center station, 1981-83 27 6. Bacterial concentrations and turbidity in Almaden-Calero canal and Calero Reservoir, 1981-83 32 7. Measured properties and constituents not in compliance with water- quality criteria for Calero Reservoir and the Almaden-Calero canal, 1981-83 34 CONVERSION FACTORS For readers who prefer to use International System (SI) units rather than inch-pound units, the conversion factors for the terms used in this report are listed below. In this report, water-quality units are SI; all other units are inch-pound. Multiply By To obtain acre 0.4047 hectares acre-ft (acre-foot) 1,233 cubic meter foot 0.3048 meter ft 3 /s (cubic foot per second) 0.02832 cubic meter per second inch 25.4 millimeter in/yr (inch per year) 25.4 millimeter per year mile 1.609 kilometer mi 2 (square mile) 2.590 square kilometer degree Fahrenheit (°F) 'C = 5/9 (°F-32) degree Celsius (°C) IV Contents Additional abbreviations cell/mL cell per milliliter col/100 mL colony per 100 milliliters C0 2 carbon dioxide m meter m3 /d cubic meter per day Urn micrometer Ug/L microgram per liter meq/L milliequivalent per liter mg/L milligram per liter (mg 0 2 /ni3 )/d milligram oxygen per cubic meter per day uS/cm at 25°C microsiemen per centimeter at 25 degrees Celsius NTU nephelometric turbidity unit N nitrogen P phosphorus TSI trophic state index 0 2 oxygen WATER YEAR A water year is a 12-month period, October 1 through September 30, designated by the calendar year in which it ends. In this report, years are water years unless otherwise noted. TRADE NAMES The use of brand or trade names in this report is for identification purposes and does not imply endorsement by the U.S. Geological Survey. Contents V WATER QUALITY OF CALERO RESERVOIR, X SANTA CLARA COUNTY, CALIFORNIA, 1981-83 By Daphne G. Clifton 1 and Isabel S. Gloege 2 ABSTRACT Calcium and magnesium were the dominant cations and bicarbonate the dominant an- Data were collected from December 1980 ion in Calero Reservoir. Concentrations to September 1983 to describe water- of total recoverable mercury in the bot­ quality conditions of Calero Reservoir tom sediments in Calero Reservoir ranged and the Almaden-Calero canal, Santa Clara from 0.06 to 0.85 milligram per kilogram, County, California. Results show that but concentrations in the water column water in Calero Reservoir and the canal were generally less than 1 microgram per generally met water-quality criteria, as liter. Mean total nitrogen concentration identified by the California Regional in Calero Reservoir was 1.00 milligram Water Quality Control Board, San Fran­ per liter, much of it in dissolved form cisco Bay Region, for municipal and (mean concentration was 0.85 milligram domestic supply, water contact and per liter). Mean total organic nitrogen noncontact recreation, warmwater fish concentration in Calero Reservoir was habitat, wildlife habitat, and fish 0.65 milligram per liter, and mean total spawning. Water-temperature profiles nitrate concentration was 0.21 milligram show that Calero Reservoir can be classi­ per liter. Mean total phosphorus and fied as a warm monomictic reservoir. dissolved orthophosphorus concentrations Water-transparency profiles showed rapid were 0.05 and 0.019 milligram per liter, attenuation of light with depth in the respectively. water column. The depth of the euphotic zone ranged from 1.5 to 5.0 meters. In The blue-green alga Anacystis generated winter and spring, light-extinction large blooms in Calero Reservoir in fall, values generally were high throughout the and the diatom Cyclotella caused major water column; in summer and fall, values spring blooms. Net primary productivity generally were high near the reservoir in the euphotic zone ranged from -2,000 bottom. Dissolved-oxygen concentrations to 10,000 milligrams of oxygen per square were less than 5.0 milligrams per liter meter per day, and the median value in in about 22 percent of the measurements the euphotic zone was 930. Carlson's primarily summer and fall samples in trophic-state index, calculated using hypolimnetic water representing one- to water transparency, total phosphorus, and two-thirds of reservoir volume. Median chlorophyll-a values, indicated that the pH values were 7.9 in the reservoir reservoir was eutrophic. and 8.4 in the canal. Mean specific- conductance values were 299 microsiemens Fecal-coliform bacteria concentrations per centimeter at 25 degrees Celsius in were less than 20 colonies per 100 milli- the reservoir and 326 in the canal. liters in the reservoir and less than 200 ^.S. Geological Survey. 2 Santa Clara Valley Water District. Abstract I colonies per 100 milliliters in the Data collected at three reservoir sta­ canal. Fecal-streptococcal bacteria con­ tions and one canal station include centrations were generally less than 45 vertical profiles of water temperature, colonies per 100 milliliters in the specific conductance, pH, dissolved reservoir and up to 260 colonies per 100 oxygen, light transmission, and transpar­ milliliters in the canal. ency. Other data include major chemical ions, nutrients, selected trace elements, bacteria, phytoplankton, and primary INTRODUCTION productivity. An analysis of total recoverable mercury in the sediment and Built in 1935 as part of a multiple- dissolved mercury in the water column is reservoir construction project in Santa also presented, because mercury has been Clara Valley, Calero Reservoir (fig. 1) detected in high concentrations in tis­ is used for water conservation, flood sues of fish collected from the reservoir control, and recreation. The drainage (Britton and others, 1974). area is small in relation to reservoir storage capacity, so that supplemental water from the Almaden Reservoir is also DESCRIPTION OF THE STUDY AREA stored in Calero Reservoir. The Santa Clara Valley Water District plans to Reservoirs augment water supplies with water from the San Luis Reservoir via a canal now under construction. This canal water Calero Reservoir (fig. 1) is in the will be temporarily stored in Calero western foothills of northern Santa Clara Reservoir prior to conveyance to city County about 10 miles south of San Jose, reservoirs. Because little was known California. Surrounding vegetation con­ about current water quality in Calero sists of oak and pine trees and annual Reservoir or the potential effects of grasses used for pasture. There are few introducing San Luis Reservoir water, the residential dwellings and no commercial U.S. Geological Survey and the Santa activities around Calero Reservoir. The Clara Valley Water District (SCVWD) began main dam, which rises 90 feet above a cooperative sampling program to define Arroyo Calero (Calero Creek) to a crest current water quality of the Calero altitude of 490 feet, provides a maximum Reservoir prior to the introduction of capacity of 10,160 acre-ft at the spill­ San Luis Reservoir water. way crest at altitude 483.9 feet. At this altitude, the reservoir has an area of 358 acres, a length of 2.2 miles, and PURPOSE AND SCOPE a 9-mile shoreline.