Geology topics

James Callegary

Publications and source records attributed to James Callegary.

5 recordsLinked to original sources

USGS2013

Challenge theme 2: assuring water availability and quality in the 21st century: Chapter 4 in United States-Mexican Borderlands: Facing tomorrow's challenges through USGS science

Along the United States–Mexican border, the health of communities, economies, and ecosystems is inextricably intertwined with the availability and quality of water, but effective water management in the Borderlands is complicated. Water users compete for resources, and their needs are increasing. Managers are faced with issues such as finding a balance between agriculture and rapidly growing cities or maintaining public supplies while ensuring sufficient resources for aquatic ecosystems. In addition to human factors, the dry climate of the Borderlands, as compared to more temperate regions, also increases the challenge of balancing water supplies between humans and ecosystems. Warmer, drier, and more variable conditions across the southwestern United States—the projected results of climate change (Seager and others, 2007)—would further stress water supplies.

United States-Mexico Borderlands↗

USGS2012

Socio-environmental health analysis in Nogales, Sonora, Mexico

In Nogales, Sonora, Mexico, some neighborhoods, or colonias, have intermittent delivery of water through pipes from the city of Nogales’s municipal water-delivery system while other areas lack piped water and rely on water delivered by truck or pipas. This research examined how lifestyles, water quality, and potential disease response, such as diarrhea, differs seasonally from a colonia with access to piped water as opposed to one using alternative water-delivery systems. Water samples were collected from taps or spigots at homes in two Nogales colonias. One colonia reflected high socio-environmental conditions where residents are supplied with municipal piped water (Colonia Lomas de Fatima); the second colonia reflected low socio-environmental conditions, lacking access to piped water and served by pipas (Colonia Luis Donaldo Colosio). A survey was developed and implemented to characterize perceptions of water quality, health impacts, and quality of life. Water samples were analyzed for microbial and inorganic water-quality parameters known to impact human health including, Escherichia coli (E. coli), total coliform bacteria, arsenic, and lead. A total of 21 households agreed to participate in the study (14 in Colosio and 7 in Fatima). In both colonias metal concentrations from water samples were all well below the United States Environmental Protection Agency’s (US EPA’s) maximum contaminant levels. E. coli concentrations exceeded the US EPA’s drinking-water standard in Colosio but not Fatima. Total coliform bacteria were present in over 50 % of households in both colonias. Microbial contamination was significantly higher in the summer than in the winter in both colonias. Resulting analysis suggests that residents in colonias without piped water are at a greater risk of gastrointestinal illness from consumption of compromised drinking water. Our survey corroborated reports of gastrointestinal illness in the summer months but not in the winter. Chloride was found to be significantly greater in Colosio (median 29.2 mg/L) although still below the US EPA’s maximum contaminant levels of 250 mg/L. Ongoing binational collaboration can promote mechanisms to improve water quality in cities located in the US–Mexico border.

Water Quality, Exposure, and Health↗

USGS2012

Effects of climate change and population growth on the transboundary Santa Cruz aquifer

The USA and Mexico have initiated comprehensive assessment of 4 of the 18 aquifers underlying their 3000 km border. Binational management of groundwater is not currently proposed. University and agency researchers plus USA and Mexican federal, state, and local agency staff have collaboratively identified key challenges facing the Santa Cruz River Valley Aquifer located between the states of Arizona and Sonora. The aquifer is subject to recharge variability, which is compounded by climate change, and is experiencing growing urban demand for groundwater. In this paper, we briefly review past, current, and projected pressures on Santa Cruz groundwater. We undertake first-order approximation of the relative magnitude of climate change and human demand drivers on the Santa Cruz water balance. Global circulation model output for emissions scenarios A1B, B1, and A2 present mixed trends, with annual precipitation projected to vary by ±20% over the 21st century. Results of our analysis indicate that urban water use will experience greater percentage change than climate-induced recharge (which remains the largest single component of the water balance). In the Mexican portion of the Santa Cruz, up to half of future total water demand will need to be met from non-aquifer sources. In the absence of water importation and with agricultural water use and rights increasingly appropriated for urban demand, wastewater is increasingly seen as a resource to meet urban demand. We consider decision making on both sides of the border and conclude by identifying short- and longer-term opportunities for further binational collaboration on transboundary aquifer assessment.

Santa Cruz Aquifer↗

USGS2010

The Border Environmental Health Initiative: Investigating the transboundary Santa Cruz watershed

In 2004 the U.S. Geological Survey (USGS) launched the Border Environmental Health Initiative (BEHI), a major project encompassing the entire U.S.-Mexico border region. In 2009, a study of the Santa Cruz River Watershed (SCW), located in the border region of Arizona and Sonora, Mexico, was initiated as part of the BEHI. In this borderland region of the desert Southwest, human health and the ecosystems on which humans rely depend critically on limited water resources. Surface water is scarce during much of the year, and groundwater is the primary source for industrial, agricultural, and domestic use. In order to identify risks to water resources in the SCW, and the potential consequences to riparian ecosystems and ultimately human health, the USGS is using an interdisciplinary and integrative approach that incorporates the expertise of geographers, hydrologists, biologists, and geologists to track organic and inorganic contaminants and their effects from sources to sinks in sediment, water, plants, and animals. Existing groundwater and surface-water models are being used and modified to assess contaminant and sediment transport.

Arizona, Sonora↗

USGS2010

Nogales flood detention study

Flooding in Ambos Nogales often exceeds the capacity of the channel and adjacent land areas, endangering many people. The Nogales Wash is being studied to prevent future flood disasters and detention features are being installed in tributaries of the wash. This paper describes the application of the KINEROS2 model and efforts to understand the capacity of these detention features under various flood and urbanization scenarios. Results depict a reduction in peak flow for the 10-year, 1-hour event based on current land use in tributaries with detention features. However, model results also demonstrate that larger storm events and increasing urbanization will put a strain on the features and limit their effectiveness.

Open-File Report↗