scholarly journals Tectonic subsidence, geoid analysis, and the Miocene-Pliocene unconformity in the Rio Grande rift, southwestern United States: Implications for mantle upwelling as a driving force for rift opening

Geosphere ◽  
2018 ◽  
Vol 14 (2) ◽  
pp. 684-709 ◽  
Author(s):  
Jolante van Wijk ◽  
Daniel Koning ◽  
Gary Axen ◽  
David Coblentz ◽  
Evan Gragg ◽  
...  
Keyword(s):  
United States ◽  
Driving Force ◽  
Rio Grande ◽  
Tectonic Subsidence ◽  
Rio Grande Rift ◽  
Southwestern United States ◽  
Mantle Upwelling

scholarly journals Combining Uranium, Boron, and Strontium Isotope Ratios (234U/238U, δ11B, 87Sr/86Sr) to Trace and Quantify Salinity Contributions to Rio Grande River in Southwestern United States

2021 ◽  
Vol 2 ◽  
Author(s):  
Sandra Garcia ◽  
Pascale Louvat ◽  
Jerome Gaillardet ◽  
Syprose Nyachoti ◽  
Lin Ma
Keyword(s):  
United States ◽  
New Mexico ◽  
River Flow ◽  
Shallow Groundwater ◽  
Rio Grande ◽  
Isotope Ratios ◽  
Critical Zone ◽  
Southwestern United States ◽  
Isotopic Compositions ◽  
Rio Grande River

In semi-arid to arid regions, both anthropogenic sources (urban and agriculture) and deeper Critical Zone (groundwater with long flow paths and water residence times) may play an important role in controlling chemical exports to rivers. Here, we combined two anthropogenic isotope tracers: uranium isotope ratios (234U/238U) and boron isotope ratios (δ11B), with the 87Sr/86Sr ratios to identify and quantify multiple solute (salinity) sources in the Rio Grande river in southern New Mexico and western Texas. The Rio Grande river is a major source of freshwater for irrigation and municipal uses in southwestern United States. There has been a large disagreement about the dominant salinity sources to the Rio Grande and particularly significant sources are of anthropogenic (agriculture practices and shallow groundwater flows, groundwater pumping, and urban developments) and/or geological (natural groundwater upwelling) origins. Between 2014 and 2016, we collected monthly river samples at 15 locations along a 200-km stretch of the Rio Grande river from Elephant Butte Reservoir, New Mexico to El Paso, Texas, as well as water samples from agricultural canals and drains, urban effluents and drains, and groundwater wells. Our study shows that due to the presence of localized and multiple salinity inputs, total dissolved solids (TDS) and isotope ratios of U, B, and Sr in the Rio Grande river show high spatial and temporal variability. Several agricultural, urban, and geological sources of salinity in the Rio Grande watershed have characteristic and distinguishable U, Sr, and B isotope signatures. However, due to the common issue of overlapping signatures as identified by previous tracer studies (such as δ18O, δD, δ34S), no single isotope tracer of U, Sr, or B isotopes was powerful enough to distinguish multiple salinity sources. Here, combining the multiple U, Sr, and B isotope and elemental signatures, we applied a multi-tracer mass balance approach to quantify the relative contributions of water mass from the identified various salinity end members along the 200-km stretch of the Rio Grande during different river flow seasons. Our results show that during irrigation (high river flow) seasons, the Rio Grande had uniform chemical and isotopic compositions, similar to the Elephant Butte reservoir where water is stored and well-mixed, reflecting the dominant contribution from shallow Critical Zone in headwater regions in temperate southern Colorado and northern New Mexico. In non-irrigation (low flow) seasons when the river water is stored at Elephant Butte reservoir, the Rio Grande river at many downstream locations showed heterogeneous chemical and isotopic compositions, reflecting variable inputs from upwelling of groundwater (deeper CZ), displacement of shallow groundwater, agricultural return flows, and urban effluents. Our study highlights the needs of using multi-tracer approach to investigate multiple solutes and salinity sources in rivers with complex geology and human impacts.

scholarly journals Phytophthora Species in Rivers and Streams of the Southwestern United States

2016 ◽  
Vol 82 (15) ◽  
pp. 4696-4704 ◽  
Author(s):  
Rio A. Stamler ◽  
Soumalia Sanogo ◽  
Natalie P. Goldberg ◽  
Jennifer J. Randall
Keyword(s):  
United States ◽  
Plant Pathogens ◽  
Rio Grande ◽  
Phytophthora Species ◽  
Southwestern United States ◽  
Content Type ◽  
Rivers And Streams ◽  
San Juan River ◽  
Rio Grande River ◽  
Prevalent Species

ABSTRACTPhytophthoraspecies were isolated from rivers and streams in the southwestern United States by leaf baiting and identified by sequence analysis of internal transcribed spacer (ITS) ribosomal DNA (rDNA). The major waterways examined included the Rio Grande River, Gila River, Colorado River, and San Juan River. The most prevalent species identified in rivers and streams werePhytophthora lacustrisandP. riparia, both members ofPhytophthoraITS clade 6.P. gonapodyides,P. cinnamomi, and an uncharacterizedPhytophthoraspecies in clade 9 were also recovered. In addition, six isolates recovered from the Rio Grande River were shown to be hybrids ofP. lacustris×P. riparia. Pathogenicity assays usingP. ripariaandP. lacustrisfailed to produce any disease symptoms on commonly grown crops in the southwestern United States. Inoculation ofCapsicum annuumwithP. ripariawas shown to inhibit disease symptom development when subsequently challenged withP. capsici, a pathogenicPhytophthoraspecies.IMPORTANCEManyPhytophthoraspecies are significant plant pathogens causing disease on a large variety of crops worldwide. Closer examinations of streams, rivers, and forest soils have also identified numerousPhytophthoraspecies that do not appear to be phytopathogens and likely act as early saprophytes in aquatic and saturated environments. To date, thePhytophthoraspecies composition in rivers and streams of the southwestern United States has not been evaluated. This article details a study to determine the identity and prevalence ofPhytophthoraspecies in rivers and streams located in New Mexico, Arizona, Colorado, Utah, and Texas. Isolated species were evaluated for pathogenicity on crop plants and for their potential to act as biological control agents.

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