Publications

Land subsidence associated with ground-water-level declines has been recognized as a potential problem in Coachella Valley, California. Since the early 1920s, ground water has been a major source of agricultural, municipal, and domestic supply in the valley. Pumping of ground water resulted in water-level declines as large as 15 meters (50 feet) through the late 1940s. In 1949, the importation of

Obtaining values of net infiltration, groundwater travel time, and recharge is necessary at the Yucca Mountain site, Nevada, USA, in order to evaluate the expected performance of a potential repository as a containment system for high-level radioactive waste. However, the geologic complexities of this site, its low precipitation and net infiltration, with numerous mechanisms operating simultaneous

The relationship between sediment bed flux and bed shear stress during a pair of field experiments in a partially stratified estuary is examined in this paper. Time series of flow velocity, vertical density profiles, and suspended sediment concentration were measured continuously throughout the water column and intensely within 1 meter of the bed. These time series were analyzed to determine bed s

We examine soil organic matter (SOM) turnover and transport using C and N isotopes in soil profiles sampled circa 1949, 1978, and 1998 (a period spanning pulse thermonuclear 14C enrichment of the atmosphere) along a 3‐million‐year annual grassland soil chronosequence. Temporal differences in soil Δ14C profiles indicate that inputs of recently living organic matter (OM) occur primarily in the upper

Applications of transport time scales are pervasive in biological, hydrologic, and geochemical studies yet these times scales are not consistently defined and applied with rigor in the literature. We compare three transport time scales (flushing time, age, and residence time) commonly used to measure the retention of water or scalar quantities transported with water. We identify the underlying ass

We report measurements of seasonal variability in the C‐N stable isotope ratios of plants collected across the habitat mosaic of San Francisco Bay, its marshes, and its tributary river system. Analyses of 868 plant samples were binned into 10 groups (e.g., terrestrial riparian, freshwater phytoplankton, salt marsh) to determine whether C‐N isotopes can be used as biomarkers for tracing the origins

A portable system for bedform-mapping was evaluated in the delta of the lower Sacramento and San Joaquin Rivers, California, from 1998 to 2000. Bedform profiles were surveyed with a two-person crew using an array of four single-beam transducers on boats about 6 m in length. Methods for processing the bedform profiles into maps with geographic coordinates were developed for spreadsheet programs and

The associations of resident fish communities with environmental variables and stream condition were evaluated at representative sites within the Sacramento River Basin, California between 1996 and 1998 using multivariate ordination techniques and by calculating six fish community metrics. In addition, the results of the current study were compared with recent studies in the San Joaquin River drai

California's primary hydrologic system, the San Francisco estuary and its upstream watershed, is vulnerable to the regional hydrologic consequences of projected global climate change. Projected temperature anomalies from a global climate model are used to drive a combined model of watershed hydrology and estuarine dynamics. By 2090, a projected temperature increase of 2.1°C results in a loss of ab

Continuous, high-resolution δ18O records from cored sediments of Pyramid Lake, Nevada, indicate that oscillations in the hydrologic balance occurred, on average, about every 150 years (yr) during the past 7630 calendar years (cal yr). The records are not stationary; during the past 2740 yr, drought durations ranged from 20 to 100 yr and intervals between droughts ranged from 80 to 230 yr. Comparis

We have now entered an era of large-scale attempts to restore ecological functions and biological communities in impaired ecosystems. Our knowledge base of complex ecosystems and interrelated functions is limited, so the outcomes of specific restoration actions are highly uncertain. One approach for exploring that uncertainty and anticipating the range of possible restoration outcomes is comparati

One egg from each of 114 red-breasted merganser (Mergus serrator) nests in 1977 and 92 nests in 1978 was collected and later analyzed for organochlorines, polybrominated biphenyls (PBBs), polychlorinated styrenes (PCSs). and metals. One egg was also collected from each of the dabbling duck nests located: Twenty-nine of these eggs were analyzed for organochlorines and metals in 1977; 10 eggs were