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STUDY UNIT DESIGN


The Central Arizona Basins study was designed to provide nationally comparable water-quality data and address local and national questions about water quality. The primary goal of the study was to understand the human and natural factors that affect the chemistry of ground and surface water and communities of aquatic organisms.

Surface-water chemistry and biological-sampling sites were divided between the two main hydrologic provinces in the study area: the Central Highlands and the Basin and Range Lowlands (see below). Ground-water samples were collected in three basins in the Basin and Range Lowlands. Human activities were least in the Sierra Vista subbasin, greatest in the West Salt River Valley, and intermediate in the Upper Santa Cruz Basin. Effects of agricultural activities on ground water were studied in the western part of the West Salt River Valley.

Ground-Water-Quality-Sampling site and Land Use. Map A. West Salt River. Map B. Sierra Vista Subbasin. Map C. Upper Santa Cruz Basin.
Stream-Sampling Site and Ecoregions, Location map.

 

SUMMARY OF DATA COLLECTION IN THE CENTRAL ARIZONA BASINS, 1995-98

Study
component

What data were collected and why

Types of sites sampled

Number of sites

Sampling frequency and period

Stream Chemistry

Basic fixed sites, general water quality

Streamflow, dissolved oxygen, pH, alkalinity, specific conductance, temperature, nutrients, major ions, organic carbon, and suspended sediment were measured to determine occurrence and distribution.

Streams selected to represent urban, mixed agricultural/urban, and forest/rangeland land uses were distributed throughout the study area. Basins ranged from 0 miles (at point sources) to 18,011 square miles.

9

Monthly plus high flows
Oct. 1995-Apr. 1998

Intensive fixed sites

Above constituents plus 87 pesticides and 85 volatile organic compounds.

Sites selected closer to urban and (or) agricultural areas so as to be more likely to reflect those land uses.

2

Monthly Jan. 1996-Dec. 1996, increased sampling frequency to approximately twice a month Dec. 1996-Feb. 1998

Fixed sites,
dissolved organic
carbon

Spectral characteristics of dissolved organic carbon from surface water were measured to determine sources.

Same sites as basic fixed sites and intensive fixed sites.

11

Monthly Jan. 1996- August 1997

Synoptic

Same as basic fixed sites, plus pesticides.

Three locations collocated with key sites for stream ecology synoptic.

3

Quarterly
Jan. 97-Oct. 97

Contaminants in bed sediment

Trace elements and (or) organic compounds to determine occurrence and distribution in streambed sediments.

Depositional zones of most basic and intensive stream-chemistry sites plus additional sites.

17

Once
May and June 1996

Contaminants in tissues of aquatic biota

Trace elements and (or) organic compounds to determine occurrence and distribution in tissues of fish, clams, and crayfish.

Same sites as sediment samples.

15

Once
May and June 1996

 

Stream Ecology

Basic sites

Communities of algae, invertebrates, and fish; and instream and riparian habitats surveyed to assess biological conditions of the study area.

Sites collocated with most basic and intensive stream-chemistry sites.

7


2

Once Oct. 1995-Jan. 1996

Annually 1995-1997

Synoptic

Communities of algae, invertebrates, and fish; and instream and riparian habitats surveyed to evaluate spatial variability.

Nine reaches along one segment of a stream with minimal anthropogenic influences.

9

Once
Oct.-Dec. 1996

Ground-Water Chemistry

Study Unit West Salt River Valley-
mixed land use

Nutrients, major ions, trace elements, volatile organic compounds, radon, dissolved organic carbon, and pesticides to assess water quality of the basin's aquifers.

Existing domestic, public-supply, irrigation, livestock, and industrial wells.

35

Once
1996-1997

 

Study Unit Upper Santa Cruz Basin- mixed land use

Nutrients, major ions, trace elements, volatile organic compounds, radon, dissolved organic carbon, and pesticides to assess water quality of the basin's aquifers.

Existing domestic, public-supply, irrigation, livestock, and industrial wells.

29

Once
1998

 

Study Unit Sierra Vista subbasin- mixed land use

Nutrients, major ions, trace elements, volatile organic compounds, radon, dissolved organic carbon, and pesticides to assess water quality of the basin's aquifers.

Existing domestic, public-supply, irrigation, and livestock wells.

19

Once
1996

 

Land use
West Salt River Valley- agricultural

Nutrients, major ions, trace elements, volatile organic compounds, radon, dissolved organic carbon, and pesticides to determine effects of agricultural land use on shallow ground-water quality.

Shallow monitoring wells.

9

Twice
Aug. 1997
Feb. 1998

 

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U.S. Geological Survey Circular 1213

Suggested citation:

Cordy, G.E., Gellenbeck, D.J., Gebler, J.B., Anning, D.W., Coes, A.L., Edmonds, R.J., Rees, J.A.H., and Sanger, H.W., 2000, Water Quality in the Central Arizona Basins, Arizona, 1995–98: U.S. Geological Survey Circular 1213, 38 p., on-line at https://pubs.water.usgs.gov/circ1213/

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