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.
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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 |
Table of Contents || Previous
Section || Next Section || Glossary
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, 199598: U.S. Geological Survey Circular 1213, 38 p., on-line at https://pubs.water.usgs.gov/circ1213/
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