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At least 127 records · Page 7Linked to original sources
USGS2004

Estimation of a water budget for 1972-2000 for the Grasslands Area, central part of the Western San Joaquin Valley, California

Equitable implementation of regulations restricting discharges from agricultural drains into the San Joaquin River requires a greater understanding of the influence of extreme precipitation events on the ground-water flow system. As part of a larger investigation, this study estimated ground-water recharge and ground-water pumpage, two important components of the water budget in the Grasslands drainage area in the central part of the western San Joaquin Valley, California, for the water years 1972 through 2000. These estimates will be used as inputs to a numerical simulation model of the regional ground-water flow system in the continuing investigation. Crop-acreage and surface-water delivery data were compiled for 14 water districts and 6 other areas comprising approximately 97 percent of the 600-square-mile study area. Little ground-water pumpage data exists for the study area. A climate-based approach was employed to estimate annual water-table recharge flux and ground-water pumpage for 11 water-budget areas. Ground-water pumpage was estimated from the residual irrigation demand after crop consumption of surface water. Estimated recharge flux to the water table for the entire study area averaged 0.8 ft/yr, and estimated ground-water pumpage per unit area for the entire study area averaged 0.5 ft/yr. Increased discharges from agricultural drains in the late 1990s may have been due partly to 4 years of high recharge from precipitation over the 6-year period from 1993 to 1998. Knowledge of the ratio of annual crop water demand to annual potential evapotranspiration, expressed as an aggregate crop coefficient, Kd, will facilitate estimation of annual water-budget components in future studies. Annual aggregate crop coefficients, calculated each year for the entire study area, were nearly constant at 0.59 from 1983 to 2000, and reasonably constant at 0.53 prior to 1983. The overall trend suggests continuous reductions in recharge from irrigation over time. This reduction is most likely due to gradual improvements in irrigation management. The recharge and pumpage estimates are both sensitive to the consumption-distribution ratio, and the pumpage estimate is sensitive to the cropped acreage.

Scientific Investigations Report↗
USGS2024

Bird habitat value and management priorities of the California Winter Rice Habitat Incentive Program

Flooding rice ( Oryza sativa ) agricultural fields during winter to facilitate rice straw decomposition has mitigated the loss of some of the natural wetlands in California’s Central Valley. We conducted bird surveys in 253 rice checks (2,158 ha) within 177 rice fields in the Sacramento Valley during the fall and winter of 2021-2022 and 2022-2023 to evaluate factors influencing bird use of winter-flooded, post-harvest rice fields enrolled in the California Winter Rice Habitat Incentive Program. We counted 143,932 birds from 57 species, including dabbling ducks (86.4%), geese (8.0%), shorebirds (0.9%), wading birds (0.7%), and other birds (4.0%). Extrapolating from the lowest densities observed in rice fields during the 70-day mandatory flooding period, we estimated that properties enrolled in this public-private partnership provided habitat for at least 271,312 birds day-1 (16,248 ha; 2021-2022) and 147,315 birds day-1 (8,448 ha; 2022-2023), totaling >10 million bird-use-days each winter. Water depth had the greatest influence on bird abundance and diversity. Relatively shallow water depths (≤13 cm) had greater abundance of shorebirds, wading birds, and geese, and higher diversity, whereas intermediate depths (~23 cm) resulted in the greatest dabbling duck abundance. Duck, goose, and wading bird abundances were greatest and species richness and family diversity were highest 8 days after the onset of flooding in rice fields (typically late October), followed by a decline in bird use until 65-87 days post flooding, after which bird use increased slightly. Bird abundance and species diversity were lowest in rice fields with the greatest hunting intensity (≥3 days week-1). We identified several habitat variables that could be managed and prioritized by landowner incentive programs to increase bird use of winter-flooded rice, including water depth, variation in emergent vegetation height, mudflat habitat availability, rice check shape, hunting intensity, and post-harvest treatment of residual rice straw.

California↗
USGS2004

Water-use trends in the desert southwest: 1950-2000

The population of the Desert Southwest is among the fastest growing in the country. In this area, ground-water supplies have been developed, surface-water resources have been fully appropriated, and conservation and conjunctive water-use measures are being used to meet water-resource needs. Complex networks of water-distribution systems have been developed to deliver surface-water supplies, and interstate agreements, such as the Colorado River Compact of 1922, help manage the distribution of water among many States in the Western United States, including Arizona, California, Nevada, New Mexico, and Utah. The Colorado River, which lies on the borders of Arizona, California, and Nevada, plays an important role in supplying water to the Southwest. Water from the Colorado River is used to irrigate extensive farmland in the southern California deserts and is delivered to southern and central Arizona through the Central Arizona Project canal for domestic and agricultural uses. It is also the source of much of the water used for domestic purposes in southern Nevada. Estimated water-withdrawal and related data were compiled from various sources to identify trends in Arizona, California, Nevada, New Mexico, and Utah. More water is used for agriculture than domestic and industrial use in these five States. From 1950 to 2000, however, the percentage increase in withdrawal for domestic water use exceeded that for agricultural use. The estimated amount of water withdrawn for domestic, agricultural, and industrial purposes in Arizona, California, Nevada, New Mexico, and Utah increased 58 percent, from 39.6 to 62.8 million acre-feet, from 1950 to 2000. During this period withdrawals for domestic water use, which included self-supplied domestic and public supply (all deliveries to residential, commercial, and some industrial users), increased 410 percent from 2.0 million to 10.2 million acre-feet and the population in these five Southwestern States increased 250 percent. From 1965 to 2000, water withdrawals for agriculture, which were primarily for irrigation of crops and livestock uses, increased 14 percent in the five States, from 44.0 to 50.2 million acre-feet, while irrigated acreage increased 12 percent from 12.6 to 14.1 million acres. Water-use trends in the Southwest are dominated by water use in California where crop acreage is more than twice as large as the combined crop acreages in Arizona, Nevada, New Mexico, and Utah, and the population in 2000 was more than three times larger than the combined population of these States. Withdrawals for agriculture in California accounted for 62 percent of the water withdrawals for agriculture in the five States in 1950 and 68 percent in 2000. Water withdrawals for domestic-water use in California declined from 82 percent of the total domestic-water withdrawals in all five States in 1950 to 70 percent in 2000, indicating that the need for domestic withdrawals increased more in Arizona, Nevada, New Mexico, and Utah combined than in California. The population of California is larger than the combined population of Arizona, New Mexico, Nevada, and Utah, but the combined population of these smaller States grew faster than the population of California. From 1950 to 2000 the California population increased 220 percent, but the combined population of the four other States increased 390 percent. From 1960 to 2000, public supply per-capita use increased in Arizona, New Mexico, and California, and decreased in Nevada and Utah. Crop-application rates (water withdrawal for irrigation of crops divided by the irrigated crop acreage) from 1965 to 2000 ranged from 2.32 acre-feet per acre in Utah in 1975 to 6.21 acre-feet per acre in Arizona in 2000. More water is used per acre of irrigated land in Arizona than in the other four States. This could be due to several reasons, including differences in climate, conveyance losses, length of growing season, and type of crops grown. Trends in water withdrawals for industrial use are difficult to identify because of differences in data reporting from year to year. From 1950 to 2000, withdrawal for industrial use in the five States was generally less than 6 percent of the total withdrawal. Withdrawal for industrial use was less than 4 percent of the total withdrawal in Arizona, except in 1990; industrial withdrawal was less than 6 percent in California and less than 7 percent in Nevada, New Mexico, and Utah, except in 1980 when in Utah it was almost 12 percent of the total withdrawal. From 1950 to 2000, ground-water withdrawals increased 324 percent in Nevada, 147 percent in New Mexico, 208 percent in Utah, and 52 percent in California. Ground-water withdrawal decreased 15 percent in Arizona. For all five States, ground-water withdrawals increased 62 percent.

Scientific Investigations Report↗
USGS2002

Selenium biotransformations into proteinaceous forms by foodweb organisms of selenium-laden drainage waters in California

Selenium contamination represents one of the few clear cases where environmental pollution has led to devastation of wildlife populations, most notably in agricultural drainage evaporation and power plant coal-fly ash receiving ponds. Complex biogeochemistry, in particular extensive biotransformations and foodchain transfer, governs Se ecotoxicology and toxicology, for which the mechanism(s) are still elusive. However, total waterborne Se concentration has been widely used as a criterion for regulating and mitigating Se risk in aquatic ecosystems, which does not account for Se biogeochemistry and its site-dependence. There is a need for more reliable indicator(s) that encompass Se ecotoxicity and/or toxicity. Selenomethionine warrants special attention since it simulates Se toxicosis of wildlife in laboratory feeding studies. While low in free selenomethionine, microphytes isolated from Se-laden agricultural evaporation ponds were abundant in proteinaceous selenomethionine. This prompted a more extensive survey of Se speciation in foodchain organisms including microphytes, macroinvertebrates, fish, and bird embryos residing mainly in the agricultural drainage systems of the San Joaquin Valley, California. Total Se in biomass, water-soluble fractions, and protein-rich fractions were measured along with GC-MS analysis of proteinaceous selenomethionine. In all foodchain organisms, water-soluble Se constituted the major fraction of total biomass Se, while proteinaceous Se was a substantial, if not dominant, fraction of the water-soluble Se. In turn, proteinaceous selenomethionine comprised an important fraction of proteinaceous Se. In terms of total biomass Se, an average 1400-fold of Se biomagnification from water to microphytes was observed while subsequent transfer from microphytes to macroinvertebrates exhibited an average of only 1.9-fold. The latter transfer was more consistent and greater in extent for proteinaceous Se and proteinaceous selenomethionine, which is consistent with their importance in foodchain transfer. Proteinaceous Se in the omnivorous carp (Cyprinus carpio) liver also demonstrated a relation to ovarian lesions, while deformed stilt (Himantopus mexicanus) embryo was more abundant in proteinaceous selenomethionine than were normal embryos. Although limited in the number of organisms surveyed, these findings provide an impetus for further field and laboratory feeding studies to substantiate the hypothesis that proteinaceous selenomethionine underlies Se ecotoxicity, which may in turn prove to be a reliable indicator of Se risk in aquatic ecosystems. Copyright ?? 2002 Elsevier Science B.V.

Aquatic Toxicology↗
USGS2010

Effects of Groundwater Development on Uranium: Central Valley, California, USA

Uranium (U) concentrations in groundwater in several parts of the eastern San Joaquin Valley, California, have exceeded federal and state drinking water standards during the last 20 years. The San Joaquin Valley is located within the Central Valley of California and is one of the most productive agricultural areas in the world. Increased irrigation and pumping associated with agricultural and urban development during the last 100 years have changed the chemistry and magnitude of groundwater recharge, and increased the rate of downward groundwater movement. Strong correlations between U and bicarbonate suggest that U is leached from shallow sediments by high bicarbonate water, consistent with findings of previous work in Modesto, California. Summer irrigation of crops in agricultural areas and, to lesser extent, of landscape plants and grasses in urban areas, has increased Pco2 concentrations in the soil zone and caused higher temperature and salinity of groundwater recharge. Coupled with groundwater pumping, this process, as evidenced by increasing bicarbonate concentrations in groundwater over the last 100 years, has caused shallow, young groundwater with high U concentrations to migrate to deeper parts of the groundwater system that are tapped by public-supply wells. Continued downward migration of U-affected groundwater and expansion of urban centers into agricultural areas will likely be associated with increased U concentrations in public-supply wells. The results from this study illustrate the potential longterm effects of groundwater development and irrigation-supported agriculture on water quality in arid and semiarid regions around the world.

California↗
USGS1992

Accounting System for Water Use by Vegetation in the Lower Colorado River Valley

The Colorado River is the principal source of water in the valley of the Colorado River between Hoover Dam and the international boundary with Mexico (fig. 1). Agricultural, domestic, municipal, industrial, hydroelectric-power genera-tion, and recreation are the primary uses of river water in the valley. Most of the consumptive use of water from the river occurs downstream from Davis Dam, where water is diverted to irrigate crops along the river or is exported to interior regions of California and Arizona. Most of the agricultural areas are on the alluvium of the flood plain; in a few areas, land on the alluvial terraces has been cultivated. River water is consumed mainly by vegetation (crops and phreatophytes) on the flood plain. Crops were grown on 70.3 percent of the vegetated area classified by using 1984 digital image satellite data. Phreatophytes, natural vege-tation that obtain water from the alluvial aquifer, covered the remaining vegetated areas on the uncultivated flood plain. Most of the water used for irrigation is diverted or pumped from the river. In some areas, water is pumped from wells completed in the alluvial aquifer, which is hydraulically connected to the river.

Open-File Report↗
USGS2022

Underwater videographic observations of domesticated Delta smelt in field enclosures

The delta smelt ( Hypomesus transpacificus ) is a small, euryhaline fish species endemic to the Sacramento–San Joaquin Delta; it is protected under the U.S. and California Endangered Species Acts, and because of declines in population abundance, the delta smelt may be vulnerable to extinction. The California Department of Water Resources (DWR) is conducting studies to test the viability of using domesticated fish to supplement the wild population of delta smelt. These studies have focused on examining the health and survival of domesticated delta smelt placed inside enclosures (circular cages that are approximately 1.5 meters tall by 1 meter in diameter) into the wild. We completed two parts within this study using underwater cameras inside the enclosures to observe fish behavior and their responses to certain stimuli. In both parts of the study, delta smelt behaviors were broadly categorized into two basic categories: (1) normal and (2) alarm. Normal behavior was characterized as calm, non-polarized, and docile swimming behavior. Alarm behavior was characterized by sudden and rapid darting, polarized frantic swimming activity, and tighter schooling polarization of individuals. The first part of the study took place in a semi-controlled agricultural pond on the campus of the University of California, Davis. At this agricultural pond, we developed methods of observation and documented how fish behaved in response to enclosure disturbances associated with routine cleaning and service that is required during extended field deployments of the enclosures. We observed that delta smelt behavior changed from normal to alarm at the onset of an enclosure service and from alarm to normal within about 2 minutes after the service ended. The second part of the study was completed in cooperation with the DWR. In October 2019, DWR deployed three enclosures in the Sacramento River near Rio Vista, California. To monitor survival rate of delta smelt, DWR permitted us to deploy cameras in one enclosure to document the frequency and duration of alarm behaviors exhibited by delta smelt and the frequency, duration, and intensity of three types of disturbances: (1) noise generated from passing boats, (2) noise generated from the enclosure moving in response to wave energy, and (3) vertical movements of the enclosure generated from wave energy. Alarm behaviors averaged about 2 minutes in duration and occurred most frequently during the evening compared to midday or morning. Each disturbance variable exhibited substantial variability in duration and intensity and occurred least frequently during the morning and evening compared to midday. Alarm behaviors appeared to be most associated with high intensity enclosure noises and vertical movements; however, limited replicate samples prohibited developing a statistical relation. Alarm behaviors did not directly contribute to injury or mortality of individual delta smelt; however, indirect or sublethal effects of alarm behaviors were not examined.

California↗
USGS1989

Texture and depositional history of near-surface alluvial deposits in the central part of the western San Joaquin Valley, California

Saline conditions and associated high levels of selenium and other soluble trace elements in soil, shallow ground water, and agricultural drain water of the western San Joaquin Valley, California, have prompted a study of the texture of near-surface alluvial deposits in the central part of the western valley. Texture is characterized by the percentage of coarse-grained sediment present within a specified subsurface depth interval and is used as a basis for mapping the upper 50 feet of deposits. Resulting quantitative descriptions of the deposits are used to interpret the late Quaternary history of the area. Three hydrogeologic units--Coast Range alluvium, flood-basin deposits, and Sierran sand--can be recognized in the upper 50 feet of deposits in the central part of the western San Joaquin Valley. The upper 30 feet of Coast Range alluvium and the adjacent 5 to 35 feet of flood-basin deposits are predominantly fine grained. These fine-grained Coast Range deposits are underlain by coarse-grained channel deposits. The fine-grained flood basin deposits are underlain by coarse-grained Sierran sand. The extent and orientation of channel deposits below 20 feet in the Coast Range alluvium indicate that streams draining the Coast Range may have been tributary to the axial stream that deposited the Sierran sand and that streamflow may have been to the southeast. The fining-upward stratigraphic sequence in the upper 50 feet of deposits and the headward retreat of tributary stream channels from the valley trough with time support a recent hypothesis of climatic control of alluviation in the western San Joaquin Valley.

California↗
USGS2015

Land-use impacts on water resources and protected areas: applications of state-and-transition simulation modeling of future scenarios

Human land use will increasingly contribute to habitat loss and water shortages in California, given future population projections and associated land-use demand. Understanding how land-use change may impact future water use and where existing protected areas may be threatened by land-use conversion will be important if effective, sustainable management approaches are to be implemented. We used a state-and-transition simulation modeling (STSM) framework to simulate spatially-explicit (1 km 2 ) historical (1992-2010) and future (2011-2060) land-use change for 52 California counties within Mediterranean California ecoregions. Historical land use and land cover (LULC) change estimates were derived from the Farmland Mapping and Monitoring Program dataset and attributed with county-level agricultural water-use data from the California Department of Water Resources. Five future alternative land-use scenarios were developed and modeled using the historical land-use change estimates and land-use projections based on the Intergovernmental Panel on Climate Change's Special Report on Emission Scenarios A2 and B1 scenarios. Spatial land-use transition outputs across scenarios were combined to reveal scenario agreement and a land conversion threat index was developed to evaluate vulnerability of existing protected areas to proximal land conversion. By 2060, highest LULC conversion threats were projected to impact nearly 10,500 km 2 of land area within 10 km of a protected area boundary and over 18,000 km 2 of land area within essential habitat connectivity areas. Agricultural water use declined across all scenarios perpetuating historical drought-related land use from 2008-2010 and trends of annual cropland conversion into perennial woody crops. STSM is useful in analyzing land-use related impacts on water resource use as well as potential threats to existing protected land. Exploring a range of alternative, yet plausible, LULC change impacts will help to better inform resource management and mitigation strategies.

California↗
USGS2022

Comparing imidacloprid, clothianidin, and azoxystrobin runoff from lettuce fields using a soil drench or treated seeds in the Salinas Valley, California

Neonicotinoid insecticide use has increased over the last decade, including as agricultural seed treatments (application of chemical in a coating to the seed prior to planting). In California, multiple crops, including lettuce, can be grown using neonicotinoid treated seeds or receive a direct neonicotinoid soil application (drenching) at planting. Using research plots, this study compared pesticide runoff in four treatments: (1) imidacloprid seed treatment; (2) clothianidin seed treatment; (3) imidacloprid drench and an azoxystrobin seed treatment; and (4) a control with no pesticidal treatment. Neonicotinoid and azoxystrobin concentrations were measured in surface water runoff during six irrigations events in the 2020 growing seasons. Results showed runoff concentrations up to 1308 (±1200) ng L −1 for imidacloprid drench treatment, 431 (±100) ng L −1 for clothianidin seed treatment, 135 (±60) ng L −1 for imidacloprid seed treatment, 13 (±10) ng L −1 for azoxystrobin seed treatment (treatments averaged). The percent of applied mass in runoff over the entire sampling period varied by compound; the imidacloprid seed treatment and drench were similar (0.015 and 0.019%, respectively) to the clothianidin seed treatment (0.036%) while the azoxystrobin seed treatment was much higher (15%). Although the proportion of imidacloprid in runoff was similar for imidacloprid treatments, the mass applied during soil drench was > 4x the amount applied from the imidacloprid seed treatment. Surface soils were collected before planting and at the end of the trial. The neonicotinoids were detected in soil throughout the study and average maximum concentrations were 9–13 ng g −1 ; azoxystrobin was detected in only two soils at concentrations up to 0.57 ng g −1 . These results elucidate the comparative mass runoff resulting from planting treated seed and soil drench applications and highlight the value of additional work to characterize off-site transport from the many commodities that may be utilizing treated seeds.

California↗
USGS2020

Mitigating land subsidence in the Coachella Valley, California, USA: An emerging success story

Groundwater has been a major source of agricultural, municipal, and domestic water supply since the early 1920s in the Coachella Valley, California, USA. Land subsidence, resulting from aquifer-system compaction and groundwater-level declines, has been a concern of the Coachella Valley Water District (CVWD) since the mid-1990s. As a result, the CVWD has implemented several projects to address groundwater overdraft that fall under three categories – groundwater substitution, conservation, and managed aquifer-recharge (MAR). The implementation of three projects in particular – replacing groundwater extraction with surface water from the Colorado River and recycled water (Mid-Valley Pipeline project), reducing water usage by tiered-rate costs, and increasing groundwater recharge at the Thomas E. Levy Groundwater Replenishment Facility – are potentially linked to markedly improved groundwater levels and subsidence conditions, including in some of the historically most overdrafted areas in the southern Coachella Valley. Groundwater-level and subsidence monitoring have tracked the effect these projects have had on the aquifer system. Prior to about 2010, water levels persistently declined, and some had reached historically low levels by 2010. Since about 2010, however, groundwater levels have stabilized or partially recovered, and subsidence has stopped or slowed substantially almost everywhere it previously had been observed; uplift was observed in some areas. Furthermore, results of Interferometric Synthetic Aperture Radar analyses for 1995–2017 indicate that as much as about 0.6 m of subsidence occurred; nearly all of which occurred prior to 2010. Continued monitoring of water levels and subsidence is necessary to inform the CVWD about future mitigation measures. The water management strategies implemented by the CVWD can inform managers of other overdrafted and subsidence-prone basins as they seek solutions to reduce overdraft and subsidence.

California↗
USGS2008

Groundwater flow and solute movement to drain laterals, western San Joaquin Valley, California: 1. Geochemical assessment

A study was undertaken to quantitatively evaluate the hydrologic processes affecting the chemical and isotopic composition of drain lateral water in a drained agricultural field in the western San Joaquin Valley, California. The results elucidate the process of mixing of deep and shallow groundwater (below and within 6 m from land surface) entering the drain laterals. The deep groundwater was subject to evapoconcentration prior to drainage system installation and has been displaced downward (to depths greater than 6 m) in the groundwater system. The proportions of deep and shallow groundwater entering the drain laterals was calculated from the end-member oxygen 18 compositions determined in groundwater samples. The percentage of total drain lateral flow which is deep groundwater flow is about 30% for the shallow drain lateral (1.8 m below land surface) (drain lateral 1)) and 60% for the deep drain lateral (2.7 m below land surface (drain lateral 2)). During irrigation, the percentages of deep groundwater flow decrease to 0 and 30% for the shallow and deep drain laterals, respectively. Selenium concentrations in drain lateral waters decrease during irrigation but selenium loads increase. Total estimated annual loads were 1.1 and 5.4 kg of selenium for drain laterals 1 and 2, respectively. Substantial percentages of the annual load occurred during 8 days of irrigation, 23 and 9% for drain laterals 1 and 2, respectively.

California↗
USGS2025

Irrigated agriculture influences selenium levels in an endangered marsh bird

Selenium bioaccumulation in aquatic food webs poses risks to wildlife, particularly in wetlands receiving irrigation runoff. The Salton Sea, California’s largest lake, is primarily sustained by agricultural drainage. This drainage creates wetland habitat along the lakeshore that many bird species depend on, including the federally endangered Yuma Ridgway’s rail ( Rallus obsoletus yumanensis ). However, these marshes may pose an ecological trap – attracting rails despite high selenium exposure. We captured rails during the 2020–2023 breeding seasons and compared rail selenium levels within three types of marshes (fed with irrigation runoff, Colorado River water, or groundwater). We collected blood, breast feathers, and head feathers of rails in all three water sources for selenium comparisons. We tagged adult rails with GPS transmitters to locate nests and foraging locations where we collected eggshells, unhatched eggs, and prey. We assessed selenium exposure by collecting multiple prey species commonly eaten by rails in all three water sources. Selenium concentrations varied among sampling locations. Selenium concentrations in most sample types were predominately influenced by water source and marsh inflow velocity (sometimes in combination with marsh size). Distance to inflow, however, did not influence selenium concentrations in any sample type. Selenium concentrations were highest in agricultural-fed marshes compared to river-fed and spring-fed marshes. Increased marsh inflow velocities resulted in lower selenium concentrations. Given the risk of an ecological trap, our results suggest that supplementing wetlands with Colorado River water could mitigate selenium bioaccumulation in Yuma Ridgway’s rails.

California↗
USGS1978

Status of the peregrine falcon in the Rocky Mountains and the southwestern United States, Baja California, and Mexico (south of Texas)

About 31 pairs of peregrines still nest north of Mexico, from Idaho and Montana south through West Texas, New Mexico and Arizona. At least thirty-six additional pairs nest in Mexico. Although the nesting sites are occupied, the tissues of the peregrine?s prey species still contain high concentrations of pesticides. The eggs in some Rocky Mountain eyries have shells which are precariously thin and have high residue levels of DDE in their contents. Increasing economic development is encroaching on the peregrine habitat throughout its range in western North America. In Baja California. and Mexico south of Texas this involves increased agricultural activity including use of organochlorine pesticides, increased tourism and increased use of the Gulf of California both for commercial and sport fishing, with their potential disturbance of eyrie sites and reduction of the peregrine?s aquatic feeding prey base. As the fish in the Gulf decrease in number, some of the avian species on which peregrines prey will likewise decrease. This ultimately may effect the peregrine. These factors may have been involved in the demise of the peregrine on Baja California?s Pacific coast. Furthermore, throughout its range, residential, industrial, mining, geothermal, recreational and other types of development and land use practices sometimes destroy habitat essential to the survival of the peregrine. A recent request for the protection of an historical site in California as Critical Habitat under Section 7 of the Endangered Species Act was rejected because peregrines, although observed there, were not known to have produced eggs or young at the site for several decades. With inadequate protection of abandoned, but still suitable, historical eyrie sites, the peregrine may have an insufficient number of eyries to reoccupy in recovery attempts. The lack of present occupancy of a site, without biological evidence that the site is no longer suitable for reoccupancy, is insufficient cause to give up the site to the pressures of development. Since destruction of habitat is forever, preservation of this essential habitat is of utmost importance to the survival of the species. On the other hand, we must not allow the peregrine, or other of the endangered species, to be used as levers for the sole purpose of restricting economic development. When an impasse between the two does occur, our defense of the endangered species must be justified on sound biological evidence if the Endangered Species Act of 1973 is to survive. The formation of the recovery teams, the development of recovery plans, and the success of captive breeding and reintroduction projects are all on the plus side of the ledger for the peregrine. They suggest optimism for the future of the peregrine, providing use of DDT is restricted both north and south of our southern border, and a sufficient number of the still suitable inactive eyrie sites are preserved to effect recovery. We need to categorize all active and inactive sites on the basis of quality and/or suitability for reoccupancy and preserve those required for the recovery of the species. Categorizing inactive eyries as to suitability for reoccupancy will provide land management agencies information badly needed for critical value judgements affecting the future of the peregrine falcon in the West.

Book chapter↗
USGS2010

Agricultural wetlands as potential hotspots for mercury bioaccumulation: Experimental evidence using caged fish

Wetlands provide numerous ecosystem services, but also can be sources of methylmercury (MeHg) production and export. Rice agricultural wetlands in particular may be important sites for MeHg bioaccumulation due to their worldwide ubiquity, periodic flooding schedules, and high use by wildlife. We assessed MeHg bioaccumulation within agricultural and perennial wetlands common to California’s Central Valley during summer, when the majority of wetland habitats are shallowly flooded rice fields. We introduced caged western mosquitofish ( Gambusia affinis ) within white rice ( Oryza sativa ), wild rice ( Zizania palustris ), and permanent wetlands at water inlets, centers, and outlets. Total mercury (THg) concentrations and body burdens in caged mosquitofish increased rapidly, exceeding baseline values at introduction by 135% to 1197% and 29% to 1566% among sites, respectively, after only 60 days. Mercury bioaccumulation in caged mosquitofish was greater in rice fields than in permanent wetlands, with THg concentrations at wetland outlets increasing by 12.1, 5.8, and 2.9 times over initial concentrations in white rice, wild rice, and permanent wetlands, respectively. In fact, mosquitofish caged at white rice outlets accumulated 721 ng Hg/fish in just 60 days. Mercury in wild mosquitofish and Mississippi silversides ( Menidia audens ) concurrently sampled at wetland outlets also were greater in white rice and wild rice than permanent wetlands. Within wetlands, THg concentrations and body burdens of both caged and wild fish increased from water inlets to outlets in white rice fields, and tended to not vary among sites in permanent wetlands. Fish THg concentrations in agricultural wetlands were high, exceeding 0.2 μg/g ww in 82% of caged fish and 59% of wild fish. Our results indicate that shallowly flooded rice fields are potential hotspots for MeHg bioaccumulation and, due to their global prevalence, suggest that agricultural wetlands may be important contributors to MeHg contamination.

California↗
USGS2008

High-resolution foraminiferal, isotopic, and trace element records from holocene estuarine deposits of San Francisco Bay, California

A 3.5-m gravity core (DJ6-93SF-6) from San Francisco Bay reveals a complex paleoclimatic history of the region over the last 3870 cal YBP. A polynomial equation based on 11 AMS 14C ages provides an excellent age model for the core, and environmental proxies for water temperature and salinity are derived from various foraminiferal abundances, stable carbon and oxygen isotopes, and Mg/Ca ratios. Two foraminiferal associations were identified by Q-mode cluster analysis: a colder-water Elphidium excavatum association and the warmer-water Ammonia beccarii-Elphidium gunteri association. The E. excavatum association dominates the core for all but about 600 years out of the last four millennia. At 3870 cal YBP, water temperatures were warm (13.9??C) and freshwater inflow was reduced compared with today. From 3590 to 2860 cal YBP, temperatures dropped 0.5??C and the climate remained dry. This was followed by a period of pronounced lower ??13C values, indicating that conditions became considerably wetter from 2860 to 2170 cal YBP. During this interval, the temperature oscillated frequently, peaking at 13.9??C at 2710 cal YBP, then dropping shortly thereafter to 12.8??C at 2420 cal YBP. Freshwater inflow gradually decreased between 2170 and 1950 cal YBP with a minimal rise in temperature, then changed quickly to colder and wetter conditions at 1900 cal YBP. Drier conditions then prevailed until 1480 cal YBP with water temperatures fluctuating between 13.1??C and 13.8??C, followed by wetter climate from 1480 to 1320 cal YBP. A significant faunal shift from the E. excavatum association to the A. beccarii-E. gunteri association occurred from 1250 to 650 cal YBP, possibly due to regional warming, decreased oxygen availability, and/or a change in the phyto-plankton community. Associated with this change in faunal composition were warm and dry conditions, representative of the Medieval Warm Period (Medieval Climatic Anomaly). A climatic shift coincident with the onset of the Little Ice Age (LIA I and LIA II) is evident from 650 to 280 cal YBP, with the return of the E. excavatum association and an extreme drop in ??18O values, all indicating increased precipitation and fresh water inflow. This was followed by generally drier conditions to the present, except for a brief wet period around 100 cal YBP, and fairly consistent water temperatures in the middle 13??C, except for a drop to 12.8??C at 200 cal YBP. Two significant faunal changes occur near the top of the core. First, there is the reappearance of the A. beccarii-E. gunteri association, suggesting that, once again, regional warming has taken place, oxygen availability has declined, and/or environmental conditions changed such that diatoms have become a scarce food source. Second, there is the first appearance of the invasive Japanese foraminifera Trochammina hadai Uchio, a species that commonly lives in highly polluted areas and is an indicator of eutrophication in its native estuaries. At the same time, freshwater inflow decreased, which may be explained by global warming during the last 100 years, or more likely due to modern water diversion for agriculture in the central valley of California. ADDITIONAL INDEX WORDS: Climate, San Francisco Bay, Holocene, foraminifers, isotopes, trace metals, Medieval Warm Period, Little Ice Age.

Conference Paper↗
USGS2000

Pesticides in surface water measured at select sites in the Sacramento River basin, California, 1996-1998

Pesticides were measured in one urban stream, one agricultural stream, one site on the Sacramento River, and one large flood control channel over a period of 18 months during 1996-1998. All sites were located within the Sacramento River Basin of California. Measurements were made on 83 pesticides or pesticide transformation products by either gas chromatography/mass spectrometry or by high performance liquid chromatography with ultraviolet light spectrometry. Some pesticides were detected frequently at the agricultural stream and downstream in the Sacramento River and at the flood control channel of the Sacramento River. These were pesticides related to rice farming (molinate, carbofuran, thiobencarb, and bentazon); herbicides used both agriculturally or for roadside maintenance (diuron, simazine, and metolachlor); or insecticides used on orchards and row corps (diazinon and chlorpyrifos). No pesticide concen-trations above enforceable water quality criteria were measured at either the agricultural site or the Sacramento River sites. In contrast to the agricul-tural site, insecticides used for household, lawn, or garden maintenance were the most frequently detected pesticides at the urban site. Diazinon, an organophosphate insecticide, exceeded recom-mended criteria for the protection of aquatic life, and the diazinon levels were frequently above known toxic levels for certain zooplankton species at the urban site. Because of the low discharge of the urban stream, pesticide concentrations were greatly diluted upon mixing with Sacramento River water.

California↗
USGS2025

Rice cultivation supports growth and survival of a threatened semi-aquatic reptile

Integration of agroecosystems and other working landscapes with protected lands and waters is critical to the conservation of Earth's biodiversity. Rice agroecosystems support many species by providing aquatic habitat where natural wetlands have been altered or drained. In regions with long dry seasons, rice fields and associated irrigation canals provide essential habitat for wetland-dependent species. We quantified the spatial scale and magnitude of the effect of rice growing on the growth and survival of the giant gartersnake ( Thamnophis gigas ), a threatened species that persists primarily in areas of rice agriculture in the Central Valley of California, USA. We used structural causal models to identify drought condition as a key confounder to adjust for when estimating the total effect of rice growing on demographic rates. We analyzed capture-mark-recapture data from 19 populations of giant gartersnakes with an integrated growth–survival model and used distance-weighted covariates to account for the decline in influence of rice with increasing distance from our study sites. We found strong support for a positive effect of rice grown within 1.9 km of a canal on giant gartersnake growth. There was also support for a positive effect of rice on giant gartersnake survival, although the spatial scale extended out to 5 km or more. Our results demonstrate how active rice growing benefits giant gartersnakes inhabiting irrigation canals and demonstrate an approach for studying landscape effects on wildlife in agroecosystems.

California↗