A5030915812- Hydrology and Watershed Management Studies
- Groundwater flow and contamination studies
- Soil and Unsaturated Flow
- Species Distribution and Climate Change
- Plant Water Relations and Carbon Dynamics
- Groundwater and Isotope Geochemistry
- Fire effects on ecosystems
- Ecology and Vegetation Dynamics Studies
- Cryospheric studies and observations
- Landslides and related hazards
- Rangeland and Wildlife Management
- Soil Geostatistics and Mapping
- Flood Risk Assessment and Management
- Climate variability and models
- Water Quality and Resources Studies
- Tree-ring climate responses
- Hydraulic Fracturing and Reservoir Analysis
- Fish Ecology and Management Studies
- Climate change and permafrost
- Plant and animal studies
- Geology and Paleoclimatology Research
- Soil erosion and sediment transport
- Forest ecology and management
- Wildlife Ecology and Conservation
- Reservoir Engineering and Simulation Methods
Public Knowledge
2023
United States Geological Survey
2013-2022
California Water Science Center
2012-2022
California Science Center
2012-2021
Oregon State University
1987-2013
Johnson Space Center
2011
Weatherford College
2008
Lawrence Berkeley National Laboratory
1995
University of California, Berkeley
1995
Denver Federal Center
1995
Abstract Global synthesis of the findings from ∼140 recharge study areas in semiarid and arid regions provides important information on rates, controls, processes, which are critical for sustainable water development. Water resource evaluation, dryland salinity assessment (Australia), radioactive waste disposal (US) among primary goals many these studies. The chloride mass balance (CMB) technique is widely used to estimate recharge. Average rates estimated over large (40–374 000 km 2 ) range...
Existing studies on the impacts of climate change groundwater recharge are either global or basin/location-specific. The lack specificity to inform decision making, while local do little clarify potential changes over large regions (major river basins, states, groups states), a scale often important in development water policy. An analysis impact across western United States (west 100° longitude) is presented synthesizing existing and applying current knowledge processes amounts. Eight...
Recent studies suggest that species distribution models (SDMs) based on fine-scale climate data may provide markedly different estimates of climate-change impacts than coarse-scale models. However, these disagree in their conclusions how scale influences projected distributions. In rugged terrain, grids not capture topographically controlled variation at the constitutes microhabitat or refugia for some species. Although finer are therefore considered to better reflect climatic conditions...
Significance Declines in the number of large trees temperate and tropical forests have attracted attention, given their disproportionate importance to forest structure, function, carbon storage. Yet, factors responsible for these declines are unclear. By comparing historic (1930s) contemporary (2000s) surveys California forests, we document that across 120,000 km 2 , declined by up 50%, corresponding a 19% decline average basal area associated biomass, despite increases small tree density....
Resource managers need spatially explicit models of hydrologic response to changes in key climatic drivers across variable landscape conditions. We demonstrate the utility a Basin Characterization Model for California (CA-BCM) integrate high-resolution data on physical watershed characteristics with historical or projected climate predict watershed-specific responses. The CA-BCM applies monthly regional water-balance model simulate responses at spatial resolution 270-m grid. has been...
Abstract Pervasive warming can lead to chronic stress on forest trees, which may contribute mortality resulting from fire‐caused injuries. Longitudinal analyses of plots across the western US show that high pre‐fire climatic water deficit was related increased post‐fire tree probabilities. This relationship between climate and fire present after accounting for defences injuries, appeared influence effects crown stem Climate interactions did not vary substantially geographical regions, major...
Values of average annual precipitation (AAP) are desired for hydrologic studies within a watershed containing Yucca Mountain, Nevada, potential site high-level nuclear-waste repository. Reliable values AAP not yet available most areas this because sparsity measurements and the need to obtain over sufficient length time. To estimate entire watershed, historical data station elevations were obtained from network 62 stations in southern Nevada southeastern California. Multivariate geostatistics...
Abstract Rapid climate change jeopardizes tree populations by shifting current zones. To avoid extinction, must tolerate, adapt, or migrate. Here we investigate geographic patterns of genetic variation in valley oak, Quercus lobata Née, to assess how underlying structure might influence this species’ ability survive change. First, understand lineages shape spatial patterns, examine historical colonization. Second, the correlation between multivariate nuclear and climatic variation. Third,...
Evaluating the environmental impacts of climate change on water resources and biological components landscape is an integral part hydrologic ecological investigations, resultant land resource management in twenty-first century. Impacts both simulated parameters processes are relevant at scales that reflect heterogeneity complexity landscapes. At present, simulations available from global models [GCMs] require downscaling for or applications. Using statistically downscaled future projections...
The costly interactions between humans and wildfires throughout California demonstrate the need to understand relationships them, especially in face of a changing climate expanding human communities. Although number statistical process-based wildfire models exist for California, there is enormous uncertainty about location future fires, with previously published estimates increases ranging from nine fifty-three percent by end century. Our goal assess role anthropogenic influences on state's...
Whitebark pine ( Pinus albicaulis Engelm.) in subalpine zones of eastern California experienced significant mortality from 2007 to 2010. Dying stands were dense (mean basal area 47.5 m 2 /ha), young 176 years), and even-age; mean stand was 70%. Stands at low elevations 2993 m), on northerly aspects, warmer, drier climates relative the regional species distribution. White blister rust not observed; mountain beetle infestations extensive. Ring widths negatively correlated with climatic water...
Values of average annual precipitation (AAP) may be important for hydrologic characterization a potential high-level nuclear-waste repository site at Yucca Mountain, Nevada. Reliable measurements AAP are sparse in the vicinity and estimates were needed an isohyetal mapping over 2600-square-mile watershed containing Mountain. Estimates obtained with multivariate geostatistical model developed using elevation data from network 42 stations southern Nevada southeastern California. An additional...
This paper describes how heat dissipation sensors, used to measure soil water matric potential, were analyzed develop a normalized calibration equation and temperature correction method. Inference of potential depends on correlation between the variable thermal conductance sensor's porous ceramic potential. Although this varies among we demonstrate normalizing procedure that produces single relationship. Using sensors from three sources different methods, resulted in mean absolute error 23%...
Potential climate change effects on aspects of conjunctive management water resources can be evaluated by linking models with fully integrated groundwater–surface models. The objective this study is to develop a modeling system that links global regional hydrologic models, using the California Central Valley as case study. new method supply and demand framework used simulate analyze potential use. Supply‐constrained demand‐driven linkages in are represented linked precipitation‐runoff...
In addition to biodiversity conservation, California rangelands generate multiple ecosystem services including livestock production, drinking and irrigation water, carbon sequestration. rangeland ecosystems have experienced substantial conversion residential land use more intensive agriculture. To understand the potential impacts services, we developed six spatially explicit (250 m) climate/land change scenarios for Central Valley of surrounding foothills consistent with three...
Recent increases in tree mortality rates across the western USA are correlated with increasing temperatures, but mechanisms remain unresolved. Specifically, could predominantly be a consequence of temperature-induced either (1) drought stress, or (2) effectiveness tree-killing insects and pathogens. Using long-term data from California's Sierra Nevada mountain range, we found that water-limited (low-elevation) forests was unambiguously best modeled by climatic water deficit, consistent first...
Concern over rapid global changes and the potential for interactions among multiple threats are prompting scientists to combine modelling approaches understand impacts on biodiversity. A relatively recent development is combination of species distribution models, land-use change predictions, dynamic population models predict relative combined climate change, altered disturbance regimes species' extinction risk. Each component introduces its own source uncertainty through different parameters...
We present a unique water-balance approach for modeling snowpack under historic, current and future climates throughout the Sierra Nevada Ecoregion. Our methodology uses finer scale (270 m) than previous regional studies incorporates cold-air pooling, an atmospheric process that sustains cooler temperatures in topographic depressions thereby mitigating snowmelt. results are intended to support management conservation of snow-dependent species, which requires characterization suitable habitat...
Abstract Seedling establishment is a critical step that may ultimately govern tree species’ distribution shifts under environmental change. Annual variation in the location of seed rain and microclimates results transient “windows opportunity” for seedling across landscape. These windows vary at fine spatiotemporal scales are not considered most assessments climate change impacts on species range dynamics habitat displacement. We integrate field trials conducted southern Sierra Nevada...
Existing methods for dynamic calibration of tipping-bucket rain gauges (TBRs) can be time consuming and labor intensive. A new automated system has been developed to calibrate TBRs with minimal effort. The consists a programmable pump, datalogger, digital balance, computer. Calibration is performed in two steps: 1) pump 2) gauge calibration. Pump ensures precise control water flow rates delivered the funnel; conversion bucket tip times actual rainfall rates. one 10 selected typically...