Geology topics

Research about Santa Clara River

Source-linked reports with geographic coverage including Santa Clara River.

4 recordsLinked to original sources

USGS2022

Local groundwater decline exacerbates response of dryland riparian woodlands to climatic drought

Dryland riparian woodlands are considered to be locally buffered from droughts by shallow and stable groundwater levels. However, climate change is causing more frequent and severe drought events, accompanied by warmer temperatures, collectively threatening the persistence of these groundwater dependent ecosystems through a combination of increasing evaporative demand and decreasing groundwater supply. We conducted a dendro-isotopic analysis of radial growth and seasonal (semi-annual) carbon isotope discrimination (Δ 13 C) to investigate the response of riparian cottonwood stands to the unprecedented California-wide drought from 2012 to 2019, along the largest remaining free-flowing river in Southern California. Our goals were to identify principal drivers and indicators of drought stress for dryland riparian woodlands, determine their thresholds of tolerance to hydroclimatic stressors, and ultimately assess their vulnerability to climate change. Riparian trees were highly responsive to drought conditions along the river, exhibiting suppressed growth and strong stomatal closure (inferred from reduced Δ 13 C) during peak drought years. However, patterns of radial growth and Δ 13 C were quite variable among sites that differed in climatic conditions and rate of groundwater decline. We show that the rate of groundwater decline, as opposed to climate factors, was the primary driver of site differences in drought stress, and trees showed greater sensitivity to temperature at sites subjected to faster groundwater decline. Across sites, higher correlation between radial growth and Δ 13 C for individual trees, and higher inter-correlation of Δ 13 C among trees were indicative of greater drought stress. Trees showed a threshold of tolerance to groundwater decline at 0.5 m year −1 beyond which drought stress became increasingly evident and severe. For sites that exceeded this threshold, peak physiological stress occurred when total groundwater recession exceeded ~3 m. These findings indicate that drought-induced groundwater decline associated with more extreme droughts is a primary threat to dryland riparian woodlands and increases their susceptibility to projected warmer temperatures.

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USGS2020

Final report: Southwestern Willow Flycatcher (Empidonax traillii extimus) and Western Yellow-billed Cuckoo (Coccyzus americanus occidentalis) surveys and habitat availability modeling on the Santa Clara River, California, 26 March 2020

Our project aimed to conduct population surveys for Southwestern Willow Flycatcher (Empidonax trailii extimus; SWFL) and Yellow-billed Cuckoo (Coccyzus americanus; YBCU) in 2018 and 2019, apply existing habitat models to illustrate and predict past, current, and future habitat suitabilities for these two species, and update and standardize classification and mapping of riparian vegetation to reflect recent conditions along the lower 50 miles of the Santa Clara River. Models developed by Hatten and Paradzick (2003), Hatten, et al. (2010), Hatten (2016), and Johnson et al. (2016) were applied to the SCR to provide California Department of Fish and Wildlife (CDFW) and the U.S. Fish and Wildlife Service (USFWS) with useful tools for management of resources for SWFL and YBCU.

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USGS2019

Recovery planning in a dynamic system: Integrating uncertainty into a decision support tool for an endangered songbird

Along the Santa Clara River in California, populations of the federally and state-listed Least Bell's Vireo ( Vireo bellii pusillus ) are recovering from near extirpation. Habitat protection and restoration, as well as controlling rates of brood parasitism, are thought to be the primary drivers of this recovery. Continuing successful management of this population faces multiple challenges due to the highly dynamic and unpredictable nature of the system, lack of clearly defined and measurable recovery criteria, parametric and stochastic uncertainty, and data limitations. Many of these management challenges are not unique to Least Bell's Vireo and require careful balancing of limited resources into the future. We developed a decision support tool as a user interface for exploring the underlying uncertainty in a population viability analysis under an array of different management scenarios. The tool was designed to assist with the planning and coordination between conservation partners in the region in three distinct aspects of the decision-making process: defining the problem and setting clear goals and objectives, exploring the consequences of potential alternative actions, and identifying criteria for ongoing evaluation and monitoring. The general framework for the design of this decision support tool is broadly applicable to many management and decision-making scenarios that share these common challenges.

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USGS2005

Comparison of heat and bromide as ground-water tracers near streams

Heat and bromide were compared as tracers for examining stream/ground water exchanges along the middle reaches of the Santa Clara River, California, during a 10-hour surface water sodium bromide injection test. Three cross sections that comprise six shallow (<1 m) piezometers were installed at the upper, middle, and lower sections of a 17 km long study reach, to monitor temperatures and bromide concentrations in the shallow ground water beneath the stream. A heat and ground water transport simulation model and a closely related solute and ground water transport simulation model were matched up for comparison of simulated and observed temperatures and bromide concentrations in the streambed. Vertical, one-dimensional simulations of sediment temperature were fitted to observed temperature results, to yield apparent streambed hydraulic conductivities in each cross section. The temperature-based hydraulic conductivities were assigned to a solute and ground water transport model to predict sediment bromide concentrations, during the sodium bromide injection test. Vertical, one-dimensional simulations of bromide concentrations in the sediments yielded a good match to the observed bromide concentrations, without adjustment of any model parameters except solute dispersivities. This indicates that, for the spatial and temporal scales examined on the Santa Clara River, the use of heat and bromide as tracers provide comparable information with respect to apparent hydraulic conductivities and fluxes for sediments near streams. In other settings, caution should be used due to differences in the nature of conservative (bromide) versus nonconservative (heat) tracers, particularly when preferential flowpaths are present.

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