Water-Resources Investigations Report 02-4188
U.S. Geological Survey Water-Resources Investigations Report 02-4188, 117 pages (Published 2002)
By Scott K. Anderholms
Prepared in Cooperation with the New Mexico Environment Department
This report is available online in pdf format: USGS WRIR 02-4188 (3 MB)
As part of the National Water-Quality Assessment Program, surface-water and ground-water samples were collected in 1994 and 1995 for analysis of common constituents, nutrients, dissolved organic carbon, trace elements, radioactivity, volatile organic compounds, and pesticides to characterize surfacewater quality and shallow ground-water quality and to determine factors affecting water quality in the Rincon Valley, south-central New MexicoSamples of surface water were collected from three sites on the RioGrande and from sites on three agricultural drains in the Rincon Valley in January 1994 and 1995, April 1994, and October 1994Ground-water samples were collected in late April and early May 1994 from 30 shallow wells that were installed during the investigation.
Dissolved-solids concentrations in surface water ranged from 434 to 1,510 milligrams per liter (mg/L). Dissolved-solids concentrations were smallest in water from the Rio Grande below Caballo Dam and largest in the drainsNitrite plus nitrate concentrations ranged from less than 0.05 to 3.3 mg/L as nitrogen, and ammonia concentrations ranged from less than 0.015 to 0.33 mg/L as nitrogen in surface-water samples.
Trace-element concentrations in surface water were significantly smaller than the acute-fisheries standardsOne or more pesticides were detected in 34 of 37 surface-water samplesDCPA (dacthal) and metolachlor were the most commonly detected pesticidesNo standards have been established for the pesticides analyzed for in this study.
Dissolved-solids concentrations in shallow ground water ranged from 481 to 3,630 mg/LAll but 2 of 30 samples exceeded the secondary maximum contaminant level for dissolved solids of 500 mg/L. Water from about 73 percent of the wells sampled exceeded the secondary maximum contaminant level of 250 mg/L for sulfate, and water from about 7 percent of the wells sampled exceeded the secondary maximum contaminant level of 250 mg/L for chloride. Nitrite plus nitrate concentrations ranged from less than 0.05 to 33 mg/L as nitrogen in shallow ground water.Water from about 17 percent of the well samples exceeded the maximum contaminant level of 10 mg/L as nitrogen for nitrite plus nitrate.
Trace-element concentrations in shallow ground water generally were small (1 to 10 micrograms per liter)The proposed maximum contaminant level of 20 micrograms per liter for uranium was exceeded in about 13 percent of the samplesThe secondary maximum contaminant level of 300 micrograms per liter for iron was exceeded in about 17 percent of the samples and of 50 micrograms per liter for manganese was exceeded in about 83 percent of the samples. Samples from about 23 percent of the wells exceeded the maximum contaminant level of 15 picocuries per liter for gross alpha activity.
One or more pesticides were detected in water from 12 of 30 wells sampledThe pesticides or pesticide metabolites diazinon, metolachlor, napropamide, p,p’-DDE, and prometon were detected in one or more samplesMetolachlor and prometon were the most commonly detected pesticidesHealth advisories for the pesticides detected in shallowground water (no maximum contaminant levels have been established for the pesticides detected) are 10 to 300 times larger than the concentrations detected.
Infiltration, evaporation, and transpiration of irrigation water are important factors affecting the concentrations of common constituents in shallow ground water in the Rincon ValleyDissolution and precipitation of minerals and mixing of shallow ground water and inflow of ground water from adjacent areas also affect the composition of shallow ground water and water in the drains.
Relatively large nitrite plus nitrate concentrations in several shallow ground-water samples indicate leaching of fertilizers in some areas of the Rincon ValleyMolybdenum and uranium concentrations in part of the Rincon Valley are affected by inflow of ground water to the valley from adjacent areasA large amount of the gross alpha activity in shallow ground water is from uranium isotopesGross beta activity increases with dissolved potassium, indicating that part of the dissolved gross beta activity is from potassium-40.
The detection of a larger number of different pesticides in surface water than in ground water indicates that pesticides are entering surface water as runoff from fields or that the number of ground-water samples collected and the time of year that the samples were collected did not adequately represent the composition of ground water in the Rincon Valley that discharges to the drains.
On the basis of pesticide concentrations detected in shallow ground water in the Rincon Valley, large amounts of the pesticides analyzed for are not leaching from land surface into ground waterThere is some indication that several pesticides are leaching downward into shallow ground water (metolachlor and prometon especially); however, the concentrations detected in shallow ground water are significantly smaller than any standards or health advisories issued by the U.SEnvironmental Protection Agency.
Forward
Abstract
Introduction
Purpose and scope
Previous work
Acknowledgments
Description of study area
Climate
Surface-water/irrigation system
Ground-water hydrology
Ground-water/surface-water relations
Land use/land cover
Study design
Methods
Well site selection
Well installation
Water sampling
Bed-material sampling
U.S. Geological Survey National Water Quality Laboratory methods
Quality assurance/quality control of data
Surface-water quality
Field properties and common constituents
Nutrients and dissolved organic carbon
Trace elements
Pesticides
Shallow ground-water quality
Field properties and common constituents
Nutrients and dissolved organic carbon
Trace elements
Radioactivity and radon-222
Volatile organic compounds
Pesticides
Pesticides, pesticide metabolites, gross polychlorinated biphenols, and gross polychlorinated naphthalenes in bed material
Factors affecting water quality in the Rincon Valley
Common constituents
Nutrients
Trace elements
Radioactivity and radon-222
Volatile organic compounds
Pesticides
Summary and conclusions
References
This report is available online in pdf format: USGS WRIR 02-4188 (4 MB)
To view the PDF document, you need the Adobe Acrobat® Reader installed on your computer(A free copy of the Acrobat® Reader may be downloaded from Adobe Systems Incorporated.)
Scott K. Anderholm, 2002, Water-quality assessment of the Rio Grande Valley, Colorado, New Mexico, and Texas--Surface-water quality, shallow ground-water quality, and factors affecting water quality in the Rincon Valley, south-central New Mexico, 1994-95: U.SGeological Survey Water-Resources Investigations Report 02–4188
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