Estimation of groundwater residence time with deeply-derived carbon mixture considered in California

Science of the Total Environment (Elsevier) | December 16th, 2022

Groundwater has experienced long-term overdraft due to drought and human activities in California, resulting in issues of land subsidence and groundwater anthropogenic co

Groundwater has experienced long-term overdraft due to drought and human activities in California, resulting in issues of land subsidence and groundwater anthropogenic contamination. As a useful indicator of groundwater renewal rate and its residence time, groundwater age has been conventionally investigated based on 14C content and 3H concentration. However, the influence of deeply-derived (endogenic) CO2 mixture is not fully and quantitatively considered, although endogenic carbon contributes a large part of the dissolved inorganic carbon in groundwater. Combined with 3H concentration, both conventional and modified 14C-dating methods with endogenic CO2 mixture considered are employed for groundwater age determination in California. On average, the conventional groundwater 14C apparent age is overestimated by ~4.9 kyr or ~26.2 %, causing groundwater recharge rate underestimation and aquifer recovery time overestimation by ~46.0 % and ~26.2 %, respectively. High 3H concentration indicates modern water mixture in more than one fifth of groundwater samples, including those with high modified 14C apparent age (> 12 kyr, i.e., fossil groundwater) in the Central Valley and southern California, which are generally considered not to be recharged by modern water. Modern water mixture in old groundwater can potentially bring anthropogenic contamination to these groundwater resources, which should be paid attentions by the government and the managers. The results have important implications in evaluation of groundwater replenishment and its susceptibility to modern contamination in California, and in groundwater resources estimation globally.

Estimation of residential outdoor water use in Los Angeles, California

Landscape and Urban Planing (Elsevier) | July 1st, 2014

The current study analyzes existing methods for estimating outdoor use and landscape irrigation in highly developed residential areas across Los Angeles. Outdoor use was

The current study analyzes existing methods for estimating outdoor use and landscape irrigation in highly developed residential areas across Los Angeles. Outdoor use was estimated using three methods: two methods described by the Pacific Institute and a third approach that utilizes remotely sensed vegetation and water billing data. Monthly individual water use records were provided by the Los Angeles Department of Water and Power (LADWP) for 2000–2010. This period includes voluntary and mandatory restrictions due to drought conditions across the state. Records were aggregated to the census tract level to protect customer privacy. The two Pacific Institute methods, which are based on water billing data, generally underestimate outdoor use due to assumptions that the lowest water consumption month represents indoor use, which is likely not the case in Los Angeles. The remote-sensing model developed between single-family water use and the Landsat normalized difference vegetation index (NDVI) surplus performed well in greener areas of the city and indicates that landscape irrigation use represents 54% of total single-family water use. The model also predicts an average decrease in landscaping irrigation of 6% and by 35% during voluntary and mandatory restrictions, respectively. Voluntary conservation and mandatory waste restrictions were less effective for higher income groups in the city, while more stringent pricing and non-pricing mandatory restrictions in FY2010 had similar effects across income groups. Study results contribute to a better understanding of the partitioning of Los Angeles residential water use and can be utilized to evaluate pricing structures and target water conservation efforts.

Estrogen Receptor In Vitro Assay Linkage Studies

San Francisco Estuary Institute (SFEI) | July 30th, 2018

Our Phase 1 study indicated that it would be possible to link in vitro ER assays to in vivo endpoints (Mehinto et al. 2018). These conclusions were based on several expe

Our Phase 1 study indicated that it would be possible to link in vitro ER assays to in vivo endpoints (Mehinto et al. 2018). These conclusions were based on several experiments that were performed at the University of Florida and SCCWRP. Our conclusion was that in order to see higher order effects in Menidia, the dose of estrogens in the in vivo assay needed to be above the EC50 point for the in vitro assays. However, the dose response curve for the in vivo endpoints was broad starting at 20 ng E2/L and progressing to 20, 200 and 500 ng/L. Our Phase 1 experiments did not include the resolution to reduce uncertainty in estimated quantitative in vitro to in vivo linkage factors. While the data allowed us to extrapolate those values, it was decided that the experiment should be repeated another time with more intervening estradiol concentrations, to get a better determination. A second goal of the study was to measure estrogen equivalencies at 6 locations in San Francisco Bay, testing both the water and sediments, to determine the usefulness of the approach. Results from this study will begin to enable managers to determine whether or not additional cleanup is necessary for treated effluents that are disposed into sensitive estuarine environments.

Estuarine Habitat Use by White Sturgeon (Acipenser transmontanus)

University of California, Davis (UC Davis) | December 1st, 2020

White Sturgeon (Acipenser transmontanus), a species of concern in the San Francisco Estuary, is in relatively low abundance because of a variety of factors. The purpose o

White Sturgeon (Acipenser transmontanus), a species of concern in the San Francisco Estuary, is in relatively low abundance because of a variety of factors. The purpose of our study was to identify the estuarine habitat used by White Sturgeon to aid in the conservation and management of the species locally and across its range. We seasonally sampled sub-adult and adult White Sturgeon in the central estuary using setlines across a habitat gradient representative of three primary structural elements: shallow wetland channel (mean sample depth = 2 m), shallow open-water shoal (mean sample depth = 2 m), and deep open-water channel (mean sample depth = 7 m). We found that the shallow open-water shoal and deep open-water channel habitats were consistently occupied by White Sturgeon in spring, summer, and fall across highly variable water quality conditions, whereas the shallow wetland channel habitat was essentially unoccupied. We conclude that sub-adult and adult White Sturgeon inhabit estuaries in at least spring, summer, and fall and that small, shallow wetland channels are relatively unoccupied.

Estuary News, April 1993

Publisher not available | April 15th, 1993

Estuary News, April 1994

San Francisco Estuary Partnership (SFEP) | April 15th, 1994

Estuary News, April 1995

San Francisco Estuary Partnership (SFEP) | April 15th, 1995

Estuary News, April 1996

San Francisco Estuary Partnership (SFEP) | April 15th, 1996

Estuary News, April 1997

San Francisco Estuary Partnership (SFEP) | April 15th, 1997

Estuary News, April 1998

San Francisco Estuary Partnership (SFEP) | April 15th, 1998