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Research about Mexico, United States

Source-linked reports with geographic coverage including Mexico, United States.

At least 235 records · Page 13Linked to original sources
USGS1998

Monitoring the water quality of the Nation's large rivers: Rio Grande NASQAN Program

The U.S. Geological Survey (USGS) has monitored the water quality in the Rio Grande Basin as part of the redesigned National Stream Quality Accounting Network (NASQAN) since 1995 (Hooper and others, 1997). The NASQAN program was designed to characterize the concentrations and transport of sediment and selected chemical constituents found in the Nation's large rivers-including the Mississippi, Colorado, and Columbia in addition to the Rio Grande. In these four basins, the USGS currently (1998) operates a network of 40 NASQAN sites, with an emphasis on quantifying the mass flux for each constituent (the amount of material moving past the site, expressed in tons per day). By applying a consistent flux-based approach in the Rio Grande Basin, the NASQAN program is generating the information needed to identify regional sources for a variety of constituents, including agricultural chemicals and trace elements, in the basin. The effect of the large reservoirs on the Rio Grande can be observed as constituent fluxes are routed downstream. The analysis of constituent fluxes on a basin-wide scale will provide the means to assess the influence of human activity on water-quality conditions in the Rio Grande.

Colorado, New Mexico, Texas↗
USGS1998

Vigilando la Calidad del Agua de los Grandes Rios de la Nacion: El Programa NASQAN del Rio Grande (Rio Bravo del Norte)

La Oficina del Estudio Geologico de los Estados Unidos (U.S. Geological Survey, 0 USGS) ha monitoreado la calidad del agua de la cuenca del Rio Grande (Rio Bravo del Norte) desde 1995 como parte de la rediseiiada Red Nacional para Contabilizar la Calidad del Agua de los Rios (National Stream Quality Accounting Network, o NASOAN) (Hooper and others, 1997). EI programa NASOAN fue diseiiado para caracterizar las concentraciones y el transporte de sedimento y constituyentes quimicos seleccionados, encontrados en los grandes rios de los Estados Unidos - incluyendo el Misisipi, el Colorado y el Columbia, ademas del Rio Grande. En estas cuatro cuencas, el USGS opera actualmente (1998) una red de 40 puntos de muestreo pertenecientes a NASOAN, con un enfasis en cuantificar el flujo en masa (la cantidad de material que pasa por la estacion, expresado en toneladas por dial para cada constituyente. Aplicacando un enfoque consistente, basado en la cuantificacion de flujos en la cuenca del Rio Grande, el programa NASOAN esta generando la informacion necesaria para identificar fuentes regionales de diversos contaminantes, incluyendo sustancias qui micas agricolas y trazas elementos en la cuenca. EI efecto de las grandes reservas en el Rio Grande se puede observar segun los flujos de constituyentes discurren a 10 largo del rio. EI analisis de los flujos de constituyentes a escala de la cuenca proveera los medios para evaluar la influencia de la actividad humana sobre las condiciones de calidad del agua del Rio Grande.

Colorado, New Mexico, Texas↗
USGS1998

Water-quality assessment of the Central Arizona Basins, Arizona and northern Mexico – Environmental setting and overview of water quality

The Central Arizona Basins study area in central and southern Arizona and northern Mexico is one of 60 study units that are part of the U.S. Geological Survey's National Water-Quality Assessment program. The purpose of this report is to describe the physical, chemical, and environmental characteristics that may affect water quality in the Central Arizona Basins study area and present an overview of water quality. Covering 34,700 square miles, the study area is characterized by generally north to northwestward-trending mountain ranges separated by broad, gently sloping alluvial valleys. Most of the perennial rivers and streams are in the northern part of the study area. Rivers and streams in the south are predominantly intermittent or ephemeral and flow in response to precipitation such as summer thunderstorms. Effluent-dependent streams do provide perennial flow in some reaches. The major aquifers in the study area are in the basin-fill deposits that may be as much as 12,000 feet thick. The 1990 population in the study area was about 3.45 million, and about 61 percent of the total was in Maricopa County (Phoenix and surrounding cities). Extensive population growth over the past decade has resulted in a twofold increase in urban land areas and increased municipal water use; however, agriculture remains the major water use. Seventy-three percent of all water with drawn in the study area during 1990 was used for agricultural purposes. The largest rivers in the study area-the Gila, Salt, and Verde-are perennial near their headwaters but become intermittent downstream because of impoundments and artificial diversions. As a result, the Central Arizona Basins study area is unique compared to less arid basins because the mean surface-water outflow is only 528 cubic feet per second from a total drainage area of 49,650 square miles. Peak flows in the northern part of the study area are the result of snowmelt runoff; whereas, summer thunderstorms account for the peak flows in the southern part. Ground water is the primary water supply in most of Arizona and the only source of drinking water used by communities in the southern half of the study area. Years of overpumping have caused water tables in basin fill to drop below once-perennial streams leaving streambeds dry, water too deep to pump economically, pumping of poorer quality water with depth, and earth fissures resulting from subsidence after dewatering of sediments. Natural processes-such as leaching of trace elements and major ions from geologic formations-and human activities-such as mining, agriculture, and urban development-have major effects on the quality of surface-water and ground-water resources in the Central Arizona Basins study area. Surface-water quality standards in Arizona are based on the designated use of the water such as full or partial body contact, fish consumption, aquatic and wildlife uses, and agriculture. Maintaining the biological integrity (health) of surface waters in Arizona is an important part of ensuring that these waters are suitable for designated uses. Important water-quality issues for surface water that are somewhat unique to Arizona include: (1) streamflows and riparian environments sustained by effluent from municipal wastewater-treatment plants that contains high concentrations of nutrients, potentially toxic trace elements and organic compounds, and fecal bacteria; (2) industrial, mining, agricultural, and municipal sources of contamination from Mexico; and (3) unpredictable high flows from major summer thunder storms causing stream-channel changes; high suspended-sediment concentrations and loads; sewage overflows; and breaching, erosion, and washout of landfills and mining operations. The quality of water in aquifers that are protected for drinking- water use is subject to standards that are in most cases equal to or more stringent than the primary drinking-water regulations of the U.S. Environmental Protection Agency. The general che

Arizona↗
USGS1997

Biology of the Rio Grande border region : A bibliography

This bibliography includes 1,913 references to the literature of the Rio Grande (Rio Bravo del Norte). The specific geographic area covered extends 100 km on either side of the river from Elephant Butte Dam in New Mexico to the Gulf of Mexico. The bibliography focuses on the biological literature, divided into major subject areas, and also includes supporting literature from the physical and environmental sciences.

Rio Grande (Rio Bravo del Norte)↗
USGS1997

Transboundary pollution: Persistent organochlorine pesticides in migrant birds of the Southwestern United States and Mexico

The hypothesis that migratory birds accumulate persistent organochlorine pesticides (POPs) during the winter in Latin America has been prevalent for many years, particularly since 1,1,1-trichloro-2,2–bis(p-chlorophenyl)ethane (DDT) was banned in the United States in 1972. It has been suggested that peregrine falcons ( Falco peregrinus ), black-crowned night herons ( Nycticorax nycticorax ), white-faced ibises ( Plegadis chihi ), various migratory waterfowl and shorebirds, and other avian species accumulate higher concentrations of POPs while on migration or on their wintering grounds in Latin America. Nonetheless, the data obtained thus far are limited, and there is no clear pattern to suggest that such accumulation occurs on a widespread basis. In this review wildlife contaminant studies conducted along the U.S.-Mexico border and throughout Mexico are discussed. The results for the most part seem to indicate that no major accumulation of 2,2-bis(p-chlorophenyl)-1,1-dichloroethylene) (DDE), the most persistent organochlorine compound, has occurred or been reported for most parts of Mexico. The majority of the DDE values in birds from Mexico were similar to those reported in birds from the southwestern United States during the same years. More work needs to be done, particularly in those cotton-producing areas of Mexico where DDT was applied heavily in the past (e.g., Chiapas and Michoacan). Because DDT is still used for malaria control and may still be used in agriculture in Chiapas, this state is probably the one where most migrant species would still be at a significant risk of increased accumulation of DDE and DDT.

Environmental Toxicology and Chemistry↗
USGS1997

Water-quality trends in the Rio Grande/Rio Bravo Basin using sediment cores from reservoirs

Water-quality trends reflect the relation between water quality and human activities, chronicling changes in concentrations of environmental contaminants, introduction of new contaminants, and successful efforts in environmental pollution remediation. Historical data available for analyzing trends often have severe limitations, from questionable accuracy to unknown sampling and analytic methodologies. Where data are unavailable or have such limitations, water-quality trends sometimes can be reconstructed using sediment cores from lakes and reservoirs. The purpose of this fact sheet is to summarize the findings of a study to assess historical changes in surface-water quality in the Rio Grande Basin (known as the Río Bravo Basin in Mexico) by analyzing changes in sediment chemistry in cores from three reservoirs: Elephant Butte Reservoir, Amistad International Reservoir, and Falcon International Reservoir (fig. 1). Sediments that erode from the land surface are transported by tributaries into the Rio Grande/Río Bravo. Metals and some persistent pesticides and industrial organic compounds sorb to these sediments, which eventually accumulate at the bottom of the reservoirs or are transported to the Gulf of Mexico. Although use of reservoir cores has limitations—for example, the cores do not record trends in non-persistent compounds—in many cases the data provide a partial historical record of water quality. In 1991, the U.S. Geological Survey (USGS) began full implementation of the National Water-Quality Assessment (NAWQA) Program (Leahy and others, 1990). Also in 1991, the State of Texas established the Clean Rivers Program (CRP) administered by the Texas Natural Resource Conservation Commission (TNRCC). The coring study reported here was a collaborative effort between the NAWQA Program and the CRP Rio Grande Border Environmental Assessment Team, with additional funding support from the El Paso County Water Improvement District No. 1.

Colorado, New Mexico, Texas↗
USGS1995

Simulation of ground-water flow in alluvial basins in south-central Arizona and parts of adjacent states

Numerical modeling was used to examine the character of aquifer systems in alluvial basins in south-central Arizona. The report documents the modeling approach, design and calibration procedures, and results of simulations made by using specific and general models. Transferability of geohydrologic information among basins was tested and generally proved successful. Extensive sensitivity testing was done on all models. Sensitivity to specific properties is related to geologic environment and the magnitude of predevelopment flow quantities.

Arizona, California, Nevada, New Mexico↗
USGS1994

Herbivory on shoalgrass by wintering redheads in Texas

An estimated 80% of redheads ( Aythya americana ) winter on the Laguna Madre of south Texas and Mexico and feed almost exclusively on shoalgrass ( Halodule wrightii ) rhizomes. Shoalgrass abundance has decreased by 60% over the past 30 years, and because the effects of shoalgrass loss on wintering redheads are unknown, we initiated a study to define habitat selection criteria and document the effect of wintering redheads on shoalgrass in the lower Laguna Madre, Texas. Redheads consumed an average of 75% of shoalgrass rhizome biomass at collection sites each winter. When rhizome biomass was grazed to a mean biomass of ltoreq 0.18 g dry mass/core (approximately 10 g dry mass/ml), shoalgrass did not recover to its previous level the following growing season. Thirty-three percent of the sites (10) were grazed below 0.18 g dry mass/core during both years of the study, while 64% (19) were grazed below 0.18 g during 1 or the other of the 2 winters. Ramet number was positively correlated ( P < 0.001, r 2 = 0.54) with rhizome biomass; however, this relationship was influenced by grazing intensity. Heavy grazing reduced the amount of rhizome attached to each ramet compared with ungrazed ramets. Grazing had no effect on root biomass ( P = 0.388), rhizome moisture content ( P = 0.553), or soil magnesium, phosphorous, and potassium ( P = 0.102, 0.499, 0.162, respectively). Redhead presence increased ( P = 0.042) soil nitrogen levels. Foraging areas selected by redheads within the lower Laguna Madre had lower ( P = 0.026) salinities (24 ppt) than areas not selected (35 ppt). Redheads did not select foraging areas in relation to crude protein levels in rhizomes. Shoalgrass habitat in the Laguna Madre should be protected from further losses and enhanced where possible.

Texas↗
USGS1994

Simulation of ground-water flow and the movement of saline water in the Hueco Bolson aquifer, El Paso, Texas, and adjacent areas

The Hueco bolson aquifer is being pumped at increasing rates to supply water for El Paso, Texas, and Ciudad Juarez, Mexico. Water-use projections for 1984-2000 indicate that the upward trend in pumping rates probably will continue, which will put an increasing burden on the limited freshwater resources of the aquifer. Near El Paso, saline water in the Rio Grande alluvium overlies freshwater in bolson deposits. Withdrawal of ground water has created a large cone of depression in the water table that is centered approximately under the El Paso-Ciudad Juarez urban area. The maximum depth of this cone in January 1984 was about 140 feet below the pre-development (before 1903) water table. The principal concern of the water-management agencies involved with the water supply for El Paso and Ciudad Juarez, and of the U.S. Department of Defense at Fort Bliss to the north of these cities is that the saline water underlying and surrounding the freshwater in the bolson deposits will begin to move into the intensively pumped freshwater zone. Intrusion of large volumes of saline water would contaminate the freshwater and make it unusable for municipal and industrial supply. Changes in ground-water quality, indicated by an increase in dissolved-solids concentrations in well water, have occurred near the El Paso airport and near the Rio Grande. This study focused primarily on simulation of historical and present (1984) ground-water flow and salinity of water in the Hueco bolson aquifer, to help understand and project the movement of saline water in the aquifer to January 2000. The objective of this study was to understand the movement of water resulting from historical and projected pumping, using numerical simulation of the transport of saline water. Results of the numerical simulations indicate that historical withdrawals of ground water have caused only slight movement of saline water, except near the Rio Grande. The saline water probably has moved laterally from the river alluvium into the bolson deposits and towards the wells located north and south of the river. Some downward movement of saline water has occurred; this movement was caused by withdrawals from wells screened only in the freshwater zone beneath the river alluvium. Simulation results further indicate that upconing of saline water into well screens probably is not, and will not become, a substantial problem. This conclusion is based on the assumption that the aquifer is anisotropic, specifically that horizontal intrinsic permeability is much greater than the vertical permeability. Results of the projected withdrawal simulations from 1984-2000 indicate that the general historical trend of saline-water movement probably will continue. The saline water in the Rio Grande alluvium is the major source of saline-water intrusion into the freshwater zone throughout the historical period and into the future on the basis of simulation results. Some saline water probably will continue to move downward from the Rio Grande alluvium to the freshwater below. Injection of treated sewage effluent into some wells will create a small zone of freshwater containing slightly increased amounts of dissolved solids in the northern area of the Texas part of the Hueco bolson aquifer. Many factors, such as well interference, pumping schedules, and other factors not specifically represented in the regional simulation, can substantially affect dissolved-solids concentrations at individual wells.

Chihuahua, Texas↗
USGS1994

History and present status of the northern elephant seal population

The northern elephant seal, Mirounga angustirostris , was presumed extinct by 1892 owing primarily to commercial harvesting for their blubber oil that began in the early 1800s. A small, residual breeding colony survived, however, and with legal protection from further hunting, it grew rapidly through the early 1900s. Immigrants steadily colonized other island and mainland sites in Baja California and California so that by 1991 seals were breeding on fifteen islands and at three mainland beaches. Sixty-four percent of 28,164 northern elephant seal pups born in 1991 were produced on two southern California Channel Islands, San Miguel and San Nicolas. The entire elephant seal population was estimated to number around 127,000 in 1991 and was apparently still increasing by more than 6% annually. The remarkable demographic vitality and sustained population increase of northern elephant seals has evidently been unaffected by the species' low genetic variability and contrasts with recent declines of some populations of the more genetically polymorphic southern elephant seal, M. leonina .

Baja California, California↗
USGS1993

Nonfuel mineral resources in the United States-Mexico border region: A progress report on information available from the Center for Inter-American Mineral Resource Investigations (CIMRI)

The exploitation of minerals has played a significant role in population growth and development of the U.S.Mexico border region. Recent proposed changes in regulations related to mining in the United States and changes in mining and investment regulations in Mexico have led to increased mineral exploration and development in Mexico, especially in the border region. As a preliminary step in the study of the mineral industry of this area, the Center for Inter-American Mineral Resource Investigations (CIMRI) of the U.S. Geological Survey has compiled mine and occurrence data for nonfuel minerals in the border region. Analysis of this information indicates that a wide variety of metallic and industrial mineral commodities are present which can be used in agriculture, infrastructure, environmental improvement, and other industries. Therefore, mining will continue to play a significant role in the economy of this region.

Circular↗
USGS1991

Implications for organic maturation studies of evidence of a geologically rapid increase and stabilization of vitrinite reflectance at peak temperature: Cerro Prieto geothermal system, Mexico

A short-term rapid heating and cooling of the rock in well M-94 below 1300 m was caused by a pulse of hot water passing through the edge of the Cerro Prieto, Mexico, geothermal system. Below 1300 m, the peak paleotemperatures were about 225-250 degrees C, but equilibrium well log temperatures indicate a decrease to 150-210 degrees C at present. This hot water pulse sharply increased vitrinite reflectance to levels comparable to those measured in the central part of the system, even though studies of apatite fission-track annealing indicate that the duration of heating was only 10{0}-10{1} yr in M-94, in contrast to 10{3}-10{4} yr in the central part of the system. These data indicate that sedimentary organic matter chemically reacts quickly to temperature increases of about 125 degrees C above ambient, even when the higher temperature existed for only 10{0}-10{1} yr. The quick change of the vitrinite reflectance geothermometer indicates that thermal maturation reactions can stabilize, after a geologically short period of heating, to a level consistent with peak temperature under moderate to high-temperature diagenesis in open, fluid-rich, geothermal systems. Cerro Prieto is one of the most intensively studied and well-known geothermal systems in the world. Thus, data from Cerro Prieto are a benchmark to compare with the predictions of published thermal maturation models such as those formulated by J. Karweil, N. V. Lopatin, and A. K. Burnham and J. J. Sweeney. These thermal maturation models inaccurately predict duration of heating at Cerro Prieto. The kinetic equations used in these models explicitly allow thermal maturation to continue indefinitely at peak temperature, which does not seem to be the case at Cerro Prieto.

Cerro Prieto fault↗
USGS1987

Spectral analysis of topography and gravity in the Basin and Range Province

A two-dimensional spectral analysis has been carried out for the topography and the Bouguer gravity anomaly of the Basin and Range Province in western North America. The aim was to investigate the possible presence of dominant wavelengths in the deformation pattern at the surface and at the depth of compensation. The results suggest that a 200-km wavelength in the deep compensating mass distribution has been inherited from an early tectonic phase of extension at an azimuth N65??E. The corresponding surface topography exhibits prominent overtones at wavelength of 100, 75, and possibly 45 km. It is argued that these characterize the non-linear rheology of the upper crust. The short wavelengths in the topography reflect the present phase of deformation, mixed with the results of the older deformations. These results point to a need to extend the physical models of lithospheric stretching beyond the presently available one-phase scenario. However, they show that the boudinage instability concept is consistent with the data.

Arizona, California, Nevada, New Mexico, Utah↗