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Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

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At least 307 records · Page 17Linked to original sources
USGS2008

Not all water becomes wine: Sulfur inputs as an opportune tracer of hydrochemical losses from vineyards

California's widespread and economically important vineyards offer substantial opportunities to understand the interface between hydrology and biogeochemistry in agricultural soils. The common use of native sulfur (S) as a fumigant or soil additive provides a novel way to isotopically differentiate among sulfate (SO 4 2− ) pools, allowing the estimation of water and SO 4 2− budgets. The objectives of this study were (1) to characterize the near‐surface hydrological flow paths in a vineyard during irrigation and storm events and (2) to determine how those flow paths affect the fate and transport of SO 4 2− across seasons. Integrating hydrological theory with measurements of SO 4 2− concentration and sulfate‐S isotopic ratios (expressed as [SO 4 2− ] and δ 34 S, respectively) in inputs, soil water, and leachate provided a means of determining flow paths. Low [SO 4 2− ] and δ 34 S in leachate during 4‐h irrigation events reflect minimal engagement of the soil matrix, indicating that preferential flow was the dominant path for water in the near surface. In contrast, high [SO 4 2− ] and δ 34 S values during 8‐h irrigation and storm events reflect near‐complete engagement of the soil matrix, indicating that lateral flow was the dominant pathway. Because hydrologic response and SO 4 2− mobility are tightly coupled in these soils, the magnitude of water fluxes through the near surface controls S cycling both on and off site. These results indicate that preferential flow is an important loss pathway to consider in managing both water resources and water quality (reactive elements) in vineyard land use systems.

Water Resources Research↗
USGS2023

Shallow deformation on the Kirby Hills fault, Sacramento–San Joaquin Delta, California (USA), revealed from high-resolution seismic reflection data and coring in a fluvial system

The Sacramento–San Joaquin Delta (Delta) in California (USA) is an important part of the state’s freshwater system and is also a major source of agricultural and natural resources. However, the Delta is traversed by a series of faults that make up the easternmost part of the San Andreas fault system at this latitude and pose seismic hazard to this region. In this study, we use new high-resolution chirp subbottom data to map and characterize the shallow expression of the Kirby Hills fault, where it has been mapped to cross the Sacramento River at the western extent of the Delta. The fault is buried here, but we document a broad zone of deformation associated with the eastern strand of the fault that changes in character, along strike, across ~600 m of the river channel. Radiocarbon dates from sediment cores collected in the Sacramento River provide some minimum constraints on the age of deformation. We do not observe evidence of the western strand as previously mapped. We also discuss difficulties of conducting a paleoseismologic study in a fluvial environment.

California↗
USGS2026

Arizona Water Science Center activities at Lees Ferry, Arizona

Introduction In 1921, the U.S. Geological Survey (USGS) established a streamgage on the Colorado River at Lees Ferry, Arizona, to monitor the river’s flow and level as it enters Grand Canyon. The following year, the seven States encompassing the Colorado River Basin (Arizona, California, Colorado, Nevada, New Mexico, Utah, and Wyoming) negotiated the 1922 Colorado River Compact to regulate distribution of the river’s waters between them. The compact divided the basin into two regions—the Upper Basin and the Lower Basin—and established the dividing point between them about one mile downstream from Lees Ferry, just below the confluence of the Colorado and Paria Rivers. The Colorado River at Lees Ferry streamgage (USGS station 09380000) is one of the most important streamgages in the United States because it is used to measure how much water passes from the Upper Basin to the Lower Basin through Glen Canyon Dam. The dam, constructed between 1956 and 1966, generates hydropower and stores water in Lake Powell reservoir, which is used to provide Upper and Lower Basin states with the water allotted to them by the compact. Lower Basin states depend on releases from the dam to receive their allotments. The Lees Ferry streamgage, located less than 16 miles downstream from Glen Canyon Dam, produces publicly available, real-time water data that allows the Colorado River’s streamflow below the dam to be monitored. Most years, the Colorado River runs dry before reaching its historical terminus at the Gulf of California in Mexico, so measuring and monitoring the river at Lees Ferry is critical for the Lower Basin ecosystems, agricultural resources, and municipal industries that rely on the river’s every drop. Additionally, Grand Canyon river guides and recreationalists depend on water level data from the Lees Ferry streamgage to determine when to run rapids and camp on sandbars. Streamflow and water-quality data collected at Lees Ferry are also important for monitoring the health of the Colorado River’s aquatic life because some species, including fish and macroinvertebrates, require certain water conditions to survive, reproduce, and spawn. The Arizona Water Science Center is responsible for maintaining and collecting water data from the Lees Ferry streamgage. The Arizona Water Science Center is a branch of the USGS dedicated to providing high quality, impartial water data to resource managers and the public for their use in understanding and managing critical water resources in Arizona and the Southwest.

Arizona↗
USGS2007

Effects of agriculture and urbanization on quality of shallow ground water in the arid to semiarid western United States, 1993-2004

Within the Western United States, agricultural and rural lands are being developed into commercial and residential areas. With changes in land use and increasing population, greater demands are placed on water resources for agricultural, industrial, and domestic supplies. Many areas in the Western United States rely exclusively on ground water as their source of drinking water. Areas that use surface-water resources often need to supplement this supply with ground water. Generally, shallow ground water is susceptible to fluctuating water quality within relatively short time scales and therefore can be used as an indicator of land-use stresses that may, in time, affect deep aquifer systems. This regional study examines data on shallow ground-water quality collected from 1993 to 2004 from 273 agricultural and 181 urban wells from 7 U.S. Geological Survey National Water-Quality Assessment study units in Arizona, California, Nevada, New Mexico, south-central Colorado, and Utah. This report determines important influences that land-use practices may have on the quality of recently recharged ground water, which may ultimately affect deep water supplies within the region.

Scientific Investigations Report↗
USGS2021

Western pond turtles in the Mojave Desert? A review of their past, present, and possible future

= The western pond turtle ( WPT ) was formerly considered a single species ( Actinemys or Emys marmorata ) that ranged from southern British Columbia, Canada to Baja California, México. More recently it was divided into a northern and a southern species. WPTs are found primarily in streams that drain into the Pacific Ocean, although scattered populations exist in endorheic drainages of the Great Basin and Mojave deserts. Populations in the Mojave Desert were long thought to be restricted to the Mojave River, but recently another population was documented in Piute Ponds, a terminal wetland complex associated with Amargosa Creek on Edwards Air Force Base. WPT fossils in the Mojave Desert are known from the Miocene to the Pleistocene. Recently, Pleistocene fossils have been found as far into the desert as Salt Springs, just south of Death Valley. The oldest fossil records suggest that WPTs were present in wetlands and drainages of the geological feature known as the Mojave block prior to the uplift of the Sierra Nevada Range about 8 Ma and prior to the ~ 3 Ma uplift of the Transverse Ranges. Archaeological records document use of turtles by Native Americans for food and cultural purposes 1,000 or more years ago at the Cronese Lakes on the lower Mojave River and Oro Grande on the upper river. The first modern publication documenting their presence in the Mojave River was 1861. Museum specimens were collected as early as 1937. These fossil and early literature records support the indigenous status of WPTs to the Mojave River. However, mtDNA -based genetic evidence shows that Mojave River turtles share an identical haplotype with turtles on the California coast. Limited nuclear data show some minor differences. Overdraft of water from the Mojave River for municipal and agricultural uses, urban development, and saltcedar expansion are threats to the continued survival of WPTs in the Mojave River.

California, Nevada↗
USGS2023

Trade-offs in adapting to changes in climate, land use, and water availability in California

Changes in land use and land cover, water systems, and climate are inextricably linked, and their combined stresses have had severe impacts in many regions worldwide. Integrated adaptation planning can support adaptive capacity by helping institutions manage land and water resources at regional to local scales. Linkages between these stressors mean that planners are often faced with potential trade-offs, and how to couple social and environmental sustainability remains a key question. We explore these questions in California’s Central Coast, a region that is already experiencing serious water shortages, housing shortages, rapid expansion of perennial agriculture, and severe droughts that are projected to become worse with climate change. Linked models of land use change (the Land Use and Carbon + Water Simulator [LUCAS-W]), water resources (LUCAS-W), and climate (the Basin Characterization Model [BCM]) produced forecasts of exposure to regional changes at 270-m resolution. We worked with regional stakeholders to develop a matrix of nine vulnerability measures that assessed key sensitivities to these changes. Each vulnerability measure combined one of the three exposure projections with spatial datasets representing one of three sensitivity communities (agricultural, domestic, or ecological). We assessed how five scenarios of land-use and water management strategies under consideration by regional planners could provide institutional, top-down adaptive capacity, and whether there were trade-offs in sustainable development goals for these communities. We found that specific land and water management strategies could greatly reduce regional vulnerability, particularly programs to cap water extractions to sustainable levels. The most dramatic trade-off was between the strategy of water demand caps that increased risk of habitat loss and ecosystem preservation that increased water vulnerability. However, trade-offs were usually limited and spatially localized, suggesting local tailoring of the strategies we assessed could reduce them. Trade-offs were more frequent across exposure classes (land use vs. water vs. climate changes) rather than sensitivity classes (agricultural vs. domestic vs. ecological communities), suggesting win-win opportunities for natural resource management. Our vulnerability maps can inform prioritization efforts for local adaptation planning.

California↗
USGS2012

Coast Range Ecoregion: Chapter 1 in Status and trends of land change in the Western United States--1973 to 2000

The Coast Range Ecoregion, which covers approximately 57,338 km 2 (22,138 mi 2 ), is a thin, linear ecoregion along the Pacific Coast, stretching roughly 1,300 km from the Olympic Peninsula, in northwest Washington, to an area south of San Francisco, California (fig. 1) (Omernik, 1987; U.S. Environmental Protection Agency, 1997). It is bounded on the east by the Puget Lowland, the Willamette Valley, the Klamath Mountains, and the Southern and Central California Chaparral and Oak Woodlands Ecoregions. Almost the entire Coast Range Ecoregion lies within 100 km of the coast. Topography is highly variable, with coastal mountain ranges and valleys ranging from sea level to over 1,000 m in elevation (fig. 2). A maritime climate, along with high topographic relief, results in substantial, but regionally variable, amounts of rainfall, ranging from 130 cm to more than 350 cm per year. The favorable climate of the Coast Range Ecoregion has supported forests of Sitka spruce ( Picea sitchensis ) along its northern coast and coast redwoods ( Sequoia sempervirens ) along its southern coast, as well as Douglas-fir ( Pseudotsuga menziesii ), western red cedar ( Thuja plicata ), and western hemlock ( Tsuga heterophylla ) inland (Omernik, 1987). Today, however, much of the forest is heavily managed for logging (fig. 3), although the ecoregion still supports some of the largest remaining areas of old-growth forest in the Pacific Northwest. Agriculture is a minor component of the landscape, present locally in flat lands and valleys near the coast. Urban development is minimal; Eureka, California, is the only urban center in the ecoregion, with a population of over 26,000 (U.S. Census Bureau, 2000).

California;Oregon;Washington↗
USGS2001

Pesticides and amphibian declines in California, USA

Several species of anuran amphibians have undergone drastic population declines in the western United States over the last 10 to 15 years. In California, the most severe declines are in the Sierra Mountains east of the Central Valley and downwind of the intensely agricultural San Joaquin Valley. In contrast, coastal and more northern populations across from the less agrarian Sacramento Valley are stable or declining less precipitously. In this article, we provide evidence that pesticides are instrumental in declines of these species. Using Hyla regilla as a sentinel species, we found that cholinesterase (ChE) activity in tadpoles was depressed in mountainous areas east of the Central Valley compared with sites along the coast or north of the Valley. Cholinesterase was also lower in areas where ranid population status was poor or moderate compared with areas with good ranid status. Up to 50% of the sampled population in areas with reduced ChE had detectable organophosphorus residues, with concentrations as high as 190 ppb wet weight. In addition, up to 86% of some populations had measurable endosulfan concentrations and 40% had detectable 4,4′-dichlorodiphenyldichloroethylene, 4,4′-DDT, and 2,4′-DDT residues.

California↗
USGS2011

Carbon gas fluxes in re-established wetlands on organic soils differ relative to plant community and hydrology

We measured CO 2 and CH 4 fluxes for 6 years following permanent flooding of an agriculturally managed organic soil at two water depths (~25 and ~55 cm standing water) in the Sacramento–San Joaquin Delta, California, as part of research studying C dynamics in re-established wetlands. Flooding rapidly reduced gaseous C losses, and radiocarbon data showed that this, in part, was due to reduced oxidation of "old" C preserved in the organic soils. Both CO 2 and CH 4 emissions from the water surface increased during the first few growing seasons, concomitant with emergent marsh establishment, and thereafter appeared to stabilize according to plant communities. Areas of emergent marsh vegetation in the shallower wetland had greater net CO 2 influx (-485 mg Cm -1 h -1 ), and lower CH 4 emissions (11.5 mg Cm -2 h -1 ), than in the deeper wetland (-381 and 14.1 mg Cm -2 h -1 , respectively). Areas with submerged and floating vegetation in the deeper wetland had CH 4 emissions similar to emergent vegetation (11.9 and 12.6 mg Cm -2 h -1 , respectively), despite lower net CO 2 influx (-102 gC m -2 h -1 ). Measurements of plant moderated net CO 2 influx and CH 4 efflux indicated greatest potential reduction of greenhouse gases in the more shallowly flooded wetland.

California↗
USGS2006

Alteration of soil microbial communities and water quality in restored wetlands

Land usage is a strong determinant of soil microbial community composition and activity, which in turn determine organic matter decomposition rates and decomposition products in soils. Microbial communities in permanently flooded wetlands, such as those created by wetland restoration on Sacramento-San Joaquin Delta islands in California, function under restricted aeration conditions that result in increasing anaerobiosis with depth. It was hypothesized that the change from agricultural management to permanently flooded wetland would alter microbial community composition, increase the amount and reactivity of dissolved organic carbon (DOC) compounds in Delta waters; and have a predominant impact on microbial communities as compared with the effects of other environmental factors including soil type and agricultural management. Based on phospholipid fatty acid (PLFA) analysis, active microbial communities of the restored wetlands were changed significantly from those of the agricultural fields, and wetland microbial communities varied widely with soil depth. The relative abundance of monounsaturated fatty acids decreased with increasing soil depth in both wetland and agricultural profiles, whereas branched fatty acids were relatively more abundant at all soil depths in wetlands as compared to agricultural fields. Decomposition conditions were linked to DOC quantity and quality using fatty acid functional groups to conclude that restricted aeration conditions found in the wetlands were strongly related to production of reactive carbon compounds. But current vegetation may have had an equally important role in determining DOC quality in restored wetlands. In a larger scale analysis, that included data from wetland and agricultural sites on Delta islands and data from two previous studies from the Sacramento Valley, an aeration gradient was defined as the predominant determinant of active microbial communities across soil types and land usage. ?? 2005 Elsevier Ltd. All rights reserved.

Soil Biology and Biochemistry↗
USGS2014

Report of the committee on chemistry of natural waters, 1938–39

The membership of this Committee is as follows: C. S. Howard (Chairman), United States Geological Survey, Washington, D.C. I. A. Denison, National Bureau of Standards, Washington, D.C. W. P. Kelley, 119 Hilgard Hall, University of California, Berkeley, California A. C. Lane, 22 Arlington Street, Cambridge, Massachusetts C. S. Scofield, Bureau of Plant Industry, United States Department of Agriculture, Washington, D.C. D. G. Thompson, United States Geological Survey, Washington, D.C. T. G. Thompson, University of Washington, Seattle, Washington Studies on the corrosion of metals and soils have been continued at the National Bureau of Standards and a report of the recent findings was published under the title “Correlation of the electrolytic corrosion test with the active corrosiveness of soils,” by I. A. Denison and R. B. Darnielle [J. Res., Nation. Bur. Stan., No. 21, pp. 819‐830, December, 1938], Another paper on this subject by Kirk H. Logan was published under the title “Engineering significance of National Bureau of Standards soil corrosion data” [J. Res. Nation. Bur. Stan., pp. 109–125, January. 1939].

Eos, Transactions, American Geophysical Union↗
USGS2010

Integrated simulation of consumptive use and land subsidence in the Central Valley, California, for the past and for a future subject to urbanization and climate change

Competition for water resources is growing throughout California, particularly in the Central Valley where about 20% of all groundwater used in the United States is consumed for agriculture and urban water supply. Continued agricultural use coupled with urban growth and potential climate change would result in continued depletion of groundwater storage and associated land subsidence throughout the Central Valley. For 1962-2003, an estimated 1,230 hectare meters (hm3) of water was withdrawn from fine-grained beds, resulting in more than three meters (m) of additional land subsidence locally. Linked physically-based, supply-constrained and emanddriven hydrologic models were used to simulate future hydrologic conditions under the A2 climate projection scenario that assumes continued "business as usual" greenhouse gas emissions. Results indicate an increased subsidence in the second half of the twenty-first century. Potential simulated land subsidence extends into urban areas and the eastern side of the valley where future surface-water deliveries may be depleted.

California↗
USGS2026

Status and understanding of groundwater quality in the San Joaquin Valley Kern County subbasin domestic-supply aquifer study unit, 2022—California GAMA Priority Basin Project

The quality of water accessed by domestic wells (here referred to as domestic groundwater resources) in the San Joaquin Valley Kern County subbasin (basin number 5-022.14) was assessed as part of the California Groundwater Ambient Monitoring and Assessment (GAMA) Program Priority Basin Project (GAMA-PBP), in cooperation with the California State Water Resources Control Board. Kern County is at the southern end of the San Joaquin Valley in California, and about 30,000 residents are estimated to use privately owned domestic wells for drinking water. Domestic wells typically draw from shallower parts of the aquifer system than public-supply wells and can be more vulnerable to effects from surface activities. Kern County is host to a highly productive agricultural industry, with Bakersfield as the main urban center. The Kern River runs through Bakersfield from the southern Sierra Nevada and intersects the Kern Water Bank, one of the largest groundwater banking operations in California, at the Kern River Intertie. The section of the Kern River running through the Kern Water Bank is dry most years. Kern County also encompasses some of the most productive oil and gas basins in California, with extensive underground and surface disposal of oil-field wastewater. This study was based on data collected from 33 sites sampled by the U.S. Geological Survey for the GAMA-PBP in 2022. To provide context for the water quality assessment, measured concentrations were compared to regulatory and non-regulatory health-based and aesthetic benchmarks. A grid-based method was used to estimate the proportions of the groundwater resources used for domestic-supply wells that have water-quality constituents below (low relative concentration), approaching (moderate relative concentration), or above (high relative concentration) benchmark concentrations. At least one measured constituent with a regulatory benchmark was categorized as having a high relative concentration in 72 percent of the aquifer area used for domestic groundwater resources. Inorganic constituents were detected at high concentrations in 45 percent of the domestic groundwater resources, and the constituents detected above regulatory benchmarks were arsenic, nitrate, and uranium. At least one organic constituent was detected at high concentrations in 41 percent of the domestic groundwater resources, and the constituents exceeding regulatory benchmarks were the fumigants 1,2,3-trichloropropane (1,2,3-TCP), 1,2-dibromo-3-chloropropane (dibromochloropropane [DBCP]), 1,2-dibromoethane (EDB), and the per-and polyfluoroalkyl substance (PFAS) perfluorooctanesulfonate. The disinfection by-product chloroform, the fumigant 1,2-dichloropropane, the herbicides atrazine and hexazinone, and the herbicide degradates 2-chloro-6-ethylamino-4-amino-s-triazine, 2-chloro-4,6-diamino-s-triazine, 4-hydroxychlorothalonil, and metolachlor sulfonic acid were detected in more than 10 percent of domestic groundwater resources, but concentrations did not exceed regulatory benchmarks. Land use, groundwater age (fraction of modern water and mean age), and geochemical environment (oxic or anoxic conditions, pH, alkalinity) were associated with the distribution of high relative concentrations of inorganic and organic constituents. Young, oxygenated water is recharged along the Kern River and adjacent recharge ponds, or as irrigation water in the agricultural areas. High concentrations of nitrate and volatile organic compounds occurred in the oxic water in urban and agricultural areas. The fumigants 1,2,3-TCP, DBCP, and EDB were reported throughout the agricultural areas, whereas chloroform, tetrachloroethene, and PFAS were associated with urban land use. High uranium concentrations were associated with young, modern groundwater in agricultural areas with low pH and high bicarbonate. Total dissolved solids increased with distance from the Kern River, as the contributions of fresh, oxic water decreased. High concentrations of arsenic were present in older anoxic or alkaline groundwater away from areas of recharge. Overall, groundwater age, redox conditions, and the source of recharge as a result of different land uses contribute to large aquifer-scale portions of domestic groundwater resources that exceed health-based benchmarks for nitrate, uranium, and fumigant concentrations.

California↗
USGS2015

Feasibility and potential effects of the proposed Amargosa Creek Recharge Project, Palmdale, California

Historically, the city of Palmdale and vicinity have relied on groundwater as the primary source of water, owing, in large part, to the scarcity of surface water in the region. Despite recent importing of surface water, groundwater withdrawal for municipal, industrial, and agricultural use has resulted in groundwater-level declines near the city of Palmdale in excess of 200 feet since the early 1900s. To meet the growing water demand in the area, the city of Palmdale has proposed the Amargosa Creek Recharge Project (ACRP), which has a footprint of about 150 acres along the Amargosa Creek 2 miles west of Palmdale, California. The objective of this study was to evaluate the long-term feasibility of recharging the Antelope Valley aquifer system by using infiltration of imported surface water from the California State Water Project in percolation basins at the ACRP. Three monitoring sites were constructed, and geophysical surveys (gravity, seismic, and resistivity) were completed to define the thickness of valley-fill deposits, depth to water, and location of faults that could influence groundwater flow. Data collected at the monitoring sites, and results from the geophysical surveys, were used to identify three northwest-southeast trending faults in the vicinity of the proposed recharge facility; these faults are probably related to the nearby San Andreas fault zone. Water levels collected from wells at the monitoring sites showed water-level altitude differences as much as 230 feet between the upgradient and downgradient sides of the faults, indicating that these faults are barriers to groundwater flow. Lithologic and geophysical logs indicated the presence of a coarse gravel and sand unit extending from land surface to about 150 feet below land surface that did not appear to be disrupted by faulting. Water samples collected from the monitoring wells were analyzed for major ions, nutrients, trace elements, dissolved organic carbon, volatile organic compounds, stable isotopes of oxygen (oxygen-18) and hydrogen (hydrogen-2, or deuterium), and the radioactive isotopes of hydrogen (hydrogen-3, or tritium) and carbon (carbon-14, or 14 C) to determine the water quality of the aquifer system and to help determine the source and age of the groundwater. Results of the water-quality analysis indicated that the source of natural recharge is Amargosa Creek near the ACRP, but that the creek does not provide modern-day recharge downstream of the ACRP. Potential effects of artificial recharge at the ACRP were evaluated by using a local-scale model of groundwater flow. On the basis of geologic samples collected during drilling, the hydraulic conductivity of the sand and gravel unit in the upper 150 feet was assumed to range from 10 to 100 feet per day. To address the goal of minimizing the potential for liquefaction during an earthquake from water-table rise associated with groundwater recharge at the ACRP, simulated water levels were constrained to remain at least 50 feet below land surface, except beneath the proposed artificial-recharge facility. The hydraulic conductivities of faults were estimated on the basis of water-level data and an estimate of natural recharge along Amargosa Creek. With assumed horizontal hydraulic conductivities of 10 and 100 feet per day in the upper 150 feet, the simulated maximum artificial recharge rates to the regional flow system at the ACRP were 3,400 and 9,400 acre-feet per year, respectively. These maximum recharge rates were limited primarily by the horizontal hydraulic conductivity in the upper 150 feet and by the liquefaction constraint. Future monitoring of water-level and soil-water content changes during the proposed project would allow improved estimation of aquifer hydraulic properties, the effect of the faults on groundwater movement, and the overall recharge capacity of the ACRP.

California↗
USGS2007

Selenium concentrations in irrigation drain inflows to the Salton Sea, California, October 2006 and January 2007

This report presents raw data on selenium concentrations in samples of water, sediment, detritus, and selected food-chain matrices collected from selected agricultural drains in the southern portion of the Salton Sea during October 2006 and January 2007. Total selenium and selenium species were determined in water samples, whereas total selenium was determined in sediment, detritus, algae, plankton, midge larvae (Family Chironomidae), and two fish species (western mosquitofish, Gambusia affinis , and sailfin molly, Poecilia latipinna ).

Open-File Report↗
USGS2023

Crop water productivity from cloud-Based landsat helps assess California’s water savings

Demand for food and water are increasing while the extent of arable land and accessible fresh water are decreasing. This poses global challenges as economies continue to develop and the population grows. With agriculture as the leading consumer of water, better understanding how water is used to produce food may help support the increase of Crop Water Productivity (CWP; kg/m 3 ), the ratio of crop output per unit of water input (or crop per drop). Previous large-scale CWP studies have been useful for broad water use modeling at coarser resolutions. However, obtaining more precise CWP, especially for specific crop types in a particular area and growing season as outlined here are important for informing farm-scale water management decision making. Therefore, this study focused on California’s Central Valley utilizing high-spatial resolution satellite imagery of 30 m (0.09 hectares per pixel) to generate more precise CWP for commonly grown and water-intensive irrigated crops. First, two products were modeled and mapped. 1. Landsat based Actual Evapotranspiration (ET a ; mm/d) to determine Crop Water Use (CWU; m 3 /m 2 ), and 2. Crop Productivity (CP; kg/m 2 ) to estimate crop yield per growing season. Then, CWP was calculated by dividing CP by CWU and mapped. The amount of water that can be saved by increasing CWP of each crop was further calculated. For example, in the 434 million m 2 study area, a 10% increase in CWP across the 9 crops analyzed had a potential water savings of 31.5 million m 3 of water. An increase in CWP is widely considered the best approach for saving maximum quantities of water. This paper proposed, developed, and implemented a workflow of combined methods utilizing cloud computing based remote sensing data. The environmental implications of this work in assessing water savings for food and water security in the 21st century are expected to be significant.

California↗
USGS2003

Preliminary assessment of DOC and THM precursor loads from a freshwater restored wetland, an agricultural field, and a tidal wetland in the Sacramento-San Joaquin River Delta

Water exported from the Sacramento-San Joaquin River Delta supplies drinking water to more than 22 million people in California. At certain times of the year, Delta waters contain relatively high concentrations of dissolved organic carbon (DOC) and bromide. During these times, chlorination of Delta water for drinking water disinfection will form disinfection byproducts, such as trihalomethanes (THMs), that can exceed the U.S. Environmental Protection Agency's maximum contaminant level for THMs of 80 mg/L. Important sources of DOC and THM precursors (types of DOC that form THMs when chlorinated) to the Delta include rivers, drainage water from peat islands, water from wetlands and areas with extensive riparian vegetation, and in-channel growth of algae and macrophytes. Due to proposed ecosystem restoration and creation of wetlands in the Delta, there is an urgent need for information on the relative loads of DOC and THM precursors produced from three different land uses: restored wetlands constructed for subsidence mitigation, tidal wetlands, and agricultural operations. We have been conducting research in the Delta to provide this information. A restored wetland and agricultural field located on Twitchell Island, and a tidal wetland on Browns Island have been monitored for flow, DOC, and THM precursors. Initial results indicate that the loads of DOC and THM precursors are similar for the restored wetland (surface water only) and the agricultural field. These land uses produce DOC loads of about 14 and 11 g C/m2/yr, respectively, and THM precursor loads of about 1.7 and 1.0 g THM/m2/yr, respectively. Estimates of DOC and THM precursor loads for the tidal wetland site on Browns Island and seepage associated with the restored wetland are being developed.

Conference Paper↗
USGS2023

Natural climate solutions provide robust carbon mitigation capacity under future climate change scenarios

Natural climate solutions (NCS) are recognized as an important tool for governments to reduce greenhouse gas emissions and remove atmospheric carbon dioxide. Using California as a globally relevant reference, we evaluate the magnitude of biological climate mitigation potential from NCS starting in 2020 under four climate change scenarios. By mid-century NCS implementation leads to a large increase in net carbon stored, flipping the state from a net source to a net sink in two scenarios. Forest and conservation land management strategies make up 85% of all NCS emissions reductions by 2050, with agricultural strategies accounting for the remaining 15%. The most severe climate change impacts on ecosystem carbon materialize in the latter half of the century with three scenarios resulting in California ecosystems becoming a net source of carbon emissions under a baseline trajectory. However, NCS provide a strong attenuating effect, reducing land carbon emissions 41-54% by 2100 with total costs of deployment of 752–777 million USD annually through 2050. Rapid implementation of a portfolio of NCS interventions provides long-term investment in protecting ecosystem carbon in the face of climate change driven disturbances. This open-source, spatially-explicit framework can help evaluate risks to NCS carbon storage stability, implementation costs, and overall mitigation potential for NCS at jurisdictional scales.

California↗