Publications

The use of wetlands to support native fish research and conservation efforts in the Sacramento–San Joaquin Delta (Delta) of California is a growing priority. The purpose of our study was to examine the physiochemical and biological characteristics of select managed ponds in the Delta to determine if they would be suitable habitats for research involving the conservation of delta smelt...

Measurements of chlorophyll concentration reported by fluorometers (fChl) are used in environmental research and monitoring, as inputs to models, and in the interpretation of remote sensing data. Researchers and managers benefit from understanding how to interpret and ensure the accuracy of fChl data collected by in situ fluorometers. Although fChl values produced by different...

The longitudinal propagation of water-quality and ecological impairments in rivers during and after wildfires remain poorly understood. In Northern California, the 2022 McKinney Fire burned 243 km2 of the Klamath National Forest, with 83% of the burned area classified as moderate to high severity. During the active wildfire, a high-intensity monsoonal rain event triggered sediment-laden...

Since the 1980s, monarch butterfly (Danaus plexippus plexippus) populations across North America have declined by 80–95%. Although several studies have implicated pesticides as a contributing factor to their population declines, our understanding of monarch exposure levels in nature remains limited. In January 2024, a mass mortality event near an overwintering site in Pacific Grove...

Public supply water withdrawals represent 14% of all withdrawals in the conterminous United States (CONUS), supplying approximately 87% of the population with fresh water. Deliveries for public water supply are crucial for associating water use amounts with populations because they often differ from total withdrawals due to wholesales, transfers, losses, and other factors. Understanding...

Contamination of groundwater by oil-field fluids in proximity to oil and gas development has been an issue of concern to water users and regulators given long histories of development and legacy disposal practices. A robust set of geochemical tracers including petroleum hydrocarbon compounds, thermogenic gases, inorganic ion concentrations, stable isotopes, radioactive isotopes, and...

Insecticide and fungicide seed coatings have become prevalent in conventional agriculture in recent decades. From 2015 to 2021, the AltEn bioenergy plant (Mead, Nebraska, USA) generated ethanol from almost 100% unused/expired treated corn seeds. This use of these seeds for ethanol production resulted in the accumulation of large amounts of contaminated wastewater and solid residue, a...

Managing water resources in semiarid watersheds is challenging due to limited supply and uncertain future climate conditions. This paper examines the impact of future climate changes on an urban watershed in southern California using an integrated hydrologic model. GSFLOW modeling software is used to simulate the nonlinear relationships between climate trends and precipitation...

Decline in availability of fresh groundwater has expanded interest in brackish groundwater resources; however, the distribution of brackish groundwater is poorly understood. Water resources in sedimentary basins across the United States often overlie oil and gas development. Mapping of groundwater total dissolved solids (TDS) using data from oil well geophysical logs has become an...

Pesticides are used globally for a wide range of applications including agricultural, forestry, roadsides, freshwater systems, and personal use. While pesticides have ensured efficient crop production, they are frequently transported away from application sites and are found in almost all terrestrial and aquatic environments. Pesticides are frequently detected in watersheds and rivers...

The Clear Lake Hitch (Lavinia exilicauda chi) is a minnow endemic to Clear Lake, Lake County, California. This species is listed as a threatened species under the California Endangered Species Act and has been petitioned for listing under the United States Endangered Species Act. In 2017, the U.S. Geological Survey, in cooperation with the U.S. Fish and Wildlife Service, initiated a...