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New Mexico Water Science Center


U.S. GEOLOGICAL SURVEY
Scientific Investigations Report 2005-5118


Streamflow and Water-Quality Trends of the Rio
Chama and Rio Grande, Northern and Central New
Mexico, Water Years 1985 to 2002

By Jeff B. Langman and Emma O. Nolan

ABSTRACT

The City of Albuquerque plans to divert San Juan-Chama Project water from the Rio Grande for potable water use. This report examines streamflow and water-quality trends in the Rio Chama and the Rio Grande for water years 1985 to 2002 following the implementation of reservoir storage agreements in northern and central New Mexico. Streamflow/water-quality stations used for this study include the Rio Grande stations of Taos, Otowi, San Felipe, and Albuquerque and the Rio Chama station of Chamita.

Water years 1985 to 2002 were a period of larger than average precipitation and streamflow compared to the stations. historical averages. Annual precipitation and streamflow trended downward during the study period because of a drought during 1999 to 2002. Streamflow in the Rio Chama and Rio Grande was divided into three distinct seasonal periods that corresponded to natural and anthropogenic influences: fall/winter baseflow (November through February), snowmelt runoff (March through June), and the irrigation/monsoon (July through October) seasons.

A calcium bicarbonate water type was evident at all study area stations on the Rio Chama and Rio Grande. Specific conductance increased downstream, but alkalinity and pH did not substantially change in the downstream direction. Nearly all nitrogen and phosphorous concentrations were less than 1 milligram per liter for all stations. Median trace-element concentrations and maximum radionuclide concentrations did not exceed drinking-water standards. Anthropogenic compounds were infrequently detected in the Rio Chama and Rio Grande, and concentrations did not exceed drinking-water standards.

Water quality in the Rio Chama and Rio Grande varied spatially and temporally during water years 1985 to 2002. Specific conductance increased downstream in the Rio Grande during the fall/winter baseflow and snowmelt runoff seasons but was similar at the Taos, Otowi, and San Felipe stations during the irrigation/monsoon season. This similarity was a result of the release of stored water from Abiquiu Reservoir and Cochiti Lake, which masked the natural influences that increased specific conductance in the downstream direction during the other seasons. During all seasons, pH decreased and major ion concentrations remained stable at the Albuquerque station compared with the San Felipe station, but no single influence could be identified that caused these conditions. Manganese and uranium concentrations at the Otowi and San Felipe stations were largest during the fall/winter baseflow and smallest during the snowmelt runoff, indicating that ground-water inflows likely influenced these concentrations.

Water-quality temporal trends were evaluated for selected constituents during the study period and during the individual seasons. Downward trends in major ion concentrations were similar in magnitude at the Taos and Otowi stations, indicating that an upstream influence and (or) the downward trend in annual precipitation was the main reason(s) for these trends. The stations most affected by reservoirs, Chamita and San Felipe, were the only stations at which downward trends in major ions were apparent for flow-adjusted concentrations but not for seasonally correlated low-adjusted concentrations, which indicates fewer seasonal differences at these stations due to reservoir operations.

TABLE OF CONTENTS

Abstract
Introduction
         Purpose and scope
         Description of the study area
                   Physiography
                   Climate
                   Streamflow of the Rio Chama and Rio Grande
                   Influences on streamflow and water quality in the study area
                             Reservoirs
                             Tributaries
                             Ground-water inflows and outflows
                             Evapotranspiration
                             Irrigation diversions and inflow
                   Previous studies
         Acknowledgment
         Methods of analysis
                   Water-quality spatial trend analysis
                   Streamflow and water-quality seasonal trend analysis
                   Streamflow and water-quality temporal trend analysis
Streamflow trends of the Rio Chama and Rio Grande, water years 1985 to 200
         Seasonal trends in streamflow
         Temporal trends in climate and streamflow
Water-quality trends of the Rio Chama and Rio Grande, water years 1985 to 2002
         Water-quality spatial trends
                   Basic water chemistry and physical properties
                   Major ions
                   Nutrients, organic carbon, and bacteria
                   Trace elements
                   Radionuclides
                   Anthropogenic compounds
         Water-quality seasonal trends
                   Basic water chemistry and physical properties
                   Major ions
                   Nutrients, organic carbon, and bacteria
                   Trace elements
                   Radionuclides
         Water-quality temporal trends
Summary
References cited
Supplemental information: Summary statistics and listing of analyzed anthropogenic compounds


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