Geology topics

C.A. Van Zante

Publications and source records attributed to C.A. Van Zante.

4 recordsLinked to original sources

USGS2025

Tracking the sources of metals to the San Juan River, Four Corners Region, USA: An introduction to the thematic issue

Surface water quantity and quality is important for arid and semi-arid regions where many people, including underserved and Indigenous communities, rely on a scarce resource for drinking water, irrigation, livestock and ceremonial uses. The southwestern United States, and specifically the Four Corners Region (Colorado, Arizona, New Mexico and Utah), is an example of this situation. Elevated concentrations of metals including aluminium, arsenic and lead were identified in previous studies and this study in the San Juan River from below the Navajo Dam, through the Navajo Nation to Mexican Hat, Utah. An interdisciplinary team applied approaches and principles of geology, geochemistry, geomorphology, hydrology and statistics to gain a better understanding of the tributaries supplying the source(s) of metals to the San Juan River. This introductory paper provides an overview of the ‘Metal geochemical fingerprinting to identify sub-watershed source contributions to surface water at a regional arid watershed scale, Four Corners Region, USA’ thematic collection . An overview of sampling sites, techniques and potential sources of metals is provided. Approaches used in this study could be applied to investigations in similar systems globally.

Four Corners region↗

USGS2025

Evaluating sediment transport and metal sorption in the San Juan River watershed

The physical and chemical characteristics of sediment influence the transport of metals in rivers. The San Juan River and its tributaries are located in the Four Corners Region in the southwestern United States and the watershed contains a wide variety of potential metal sources. Comparisons of past and present sediment data provide insight into the effects of seasonality and storm events on the transport of sediment within a watershed. Comparisons suggest finer (<0.63 µm) sediment particles increase at a greater rate during intense storm events than coarser sediment particles. These fine, clay-sized sediments have a greater potential for metal sorption. Statistical analyses compared upper and lower portions of the San Juan River. Results show that total elemental concentration decreases in sediments (1785.15 μ g l −1 ) and that concentrations increase in the aqueous phase (2063.08 μ g l −1 ) downstream in the San Juan River. Analyses using geochemical and scanning electron microscopy with energy dispersive spectroscopy suggest that sediment clay particles are the most likely constituent to transport metals in the San Juan River. Metal transport is further aided by metal oxide coatings that develop on the surfaces of larger particles. Increases in aggregation of fine-grained particles in the downstream portions of the San Juan River are also likely to bind elements within sediments, which can act as both a source and sink for metals in the lower watershed. CEC , geochemistry , PSD

Arizona, Colorado, New Mexico, Utah↗

USGS2025

Applying geological unit distribution and chemical weathering indices to evaluate potential lithological sources of Al, As and Pb to the San Juan River, Four Corners region, USA

In arid to semi-arid landscapes, sporadic monsoonal events, varying widely in scale and distribution, can generate overland flow resulting in streamflow in ephemeral channels. These channels may contain metal-laden sediments that are a by-product of the weathering and erosion of local geological units. To evaluate the potential for local geology to contribute aluminium (Al), arsenic (As) and lead (Pb) to the San Juan River, northwestern New Mexico, USA, the distributions of geological units were delineated for 12 hydrological basins within the greater San Juan River watershed. Concentrations of Al, As and Pb in the predominant geological units were compiled from data in the National Geochemical Database. Chemical indices of weathering (CIW) were calculated for geological units with greater than 5% coverage in the entire San Juan River watershed. Based on CIWs of the major geological units, the Mesaverde Group (CIW = 95.2), Chinle and Dolores Formations ( combined ) (CIW = 93.3), and Mancos Shale ( combined ) (CIW = 82.6) are the most likely units to weather, erode and contribute sediments with elevated concentrations of Al, As and Pb to the San Juan River. The results of this study show the importance of understanding geological sources of sediments because they could be substantial contributors of constituents of concern to water, especially in arid environments where surface water may be the only source of water in the region.

Arizona, Colorado, New Mexico, Utah↗

USGS2024

A comparison of water-quality and stormwater inflow and outflow during habitat restoration at the McEwen storm drainage pond, South Valley, Albuquerque, New Mexico, 2020–22

In 2020, the U.S. Geological Survey began targeted monitoring, in partnership with Bernalillo County, at three locations within the McEwen storm drainage pond to evaluate and compare the water quality of stormwater as it enters and exits the study area, which is channelized and routes urban stormwater runoff through a wetland area. Stage in McEwen pond and precipitation at a nearby precipitation gage were evaluated to observe relations between rainfall and stage, as well as how long the stage remained elevated at the site. Peak stage ranged from 0.73 to 2.4 feet, with the time to reach peak stage at McEwen pond ranging from 45 minutes to 10 hours and 45 minutes. The stage remained elevated for a median of 3 days. Monitored water-quality parameters included physical parameters, bacteria, sediment, and nutrients. Bacteria was the only parameter that frequently exceeded the New Mexico Water Quality standard. Significant differences (p less than 0.05) among sites were few, consisting of those for total nitrogen and dissolved ammonia concentrations, which decreased toward the middle of the pond and were lower in the outflow from the pond compared to concentrations at the east and west sites. The middle of McEwen pond showed an increase in the percentage of fine-grained sediment, which suggests that larger particles settled into the pond and were further filtered as water traveled through the swales. Concentrations of suspended sediment and dissolved nutrients were significantly lower in 2022 compared to previous years. Although the site is still undergoing restoration and plants are becoming established, observations over the last several years indicate that site restoration has resulted in changes to the study area through processes such as nutrient uptake and the filtering of larger sediment particles.

New Mexico↗