Steve Ackley (Former Employee)

Our objective is to determine the relative propensity of sediment material formed under two different in situ coagulation treatments (iron sulfate, polyaluminum chloride) to release MeHg into surface waters under environmentally relevant conditions that may affect flocculant stability and MeHg production rates.

The USGS partners with local, state, and other federal agencies through cooperative agreements for a variety of reasons. The USGS and partners jointly plan the scientific work conducted under cooperative agreements resulting in science that has broad relevance to address current water issues. Partners choose to work with the USGS because of the agency's broad technical expertise, its long-standing...

The USGS has been a leader in the development of hydrologic and geochemical simulation models since the 1960's. USGS models are widely used to predict responses of hydrologic systems to changing stresses, such as increases in precipitation or ground-water pumping rates, as well as to predict the fate and movement of solutes and contaminants in water.

The Basin Characterization Model (BCM) is a simple grid-based model that calculates the water balance for any time step or spatial scale by using climate inputs, precipitation, minimum and maximum air temperature. The BCM can translate fine-scale maps of climate trends and projections into the hydrologic consequences, to permit evaluation of the impacts to water availability at regional, watershed...

The objective specific to work conducted by the CAWSC is to produce a continuous time-series of suspended-sediment flux at an existing site in Alviso Slough.

Over time, the flow of water into the San Antonio Reservoir has caused the build-up of sediment, decreasing storage capacity. Since water storage is a crucial issue in California, up-to-date information on the reservoir is needed. To accomplish this, the San Francisco Public Utilities Commission approached the USGS California Water Science Center to conduct a bathymetric (depth) survey and other...

This field work on the Sacramento River will be performed at two scales: a coarse-scale sampling from Keswick Dam to the I-5 Bridge near the city of Sacramento using Hobo stage recorders at approximately 10 – 20 km spacing; and fine-scale surveys in two reaches, one from approximately 30 km upstream and downstream of Colusa and another 30 km reach downstream of Knight’s Landing using Hobo stage...

This study will provide an analysis tool for forecasting seasonal and longer term streamflow variations, and for evaluating climate and land cover variations in the Kings River Basin. This study will directly or indirectly address several water-resource issues identified in the USGS Science Strategy document (USGS, 2007): drinking water availability, the suitability of aquatic habitat for biota...

The objective of this study is to provide downscaled ensemble projections of climate and hydrology for the next century for the state of California with specific application to the San Francisco Bay Area.

The proposed study is designed to better establish relationships between patterns of delta smelt abundance and properties of suspended particles as measured by optical and acoustical techniques.

Phytoplankton are an important part of aquatic food webs and ecosystems. These single-celled plants grow faster in the stronger light of spring or summer, resulting in population explosions called phytoplankton blooms. These blooms in turn feed zooplankton (free-floating aquatic microorganisms), providing food for many aquatic species, including fish, shrimp, crabs, and other invertebrates.

Tidal marshes provide animal habitats and prevent erosion. Expanding towns and cities have claimed major parts of San Francisco Bay’s marshland. Sediment deposits are essential to rebuilding tidal marshes and keeping existing marshes intact. In the southern part of the Bay, the largest tidal wetland restoration project on the west coast is underway. Sediment flux measurements are key in deciding...