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USGS2003

Hydrological response to earthquakes in the Haibara well, central Japan - I. Groundwater level changes revealed using state space decomposition of atmospheric pressure, rainfall and tidal responses

For the groundwater level observed at the Haibara well, Shizuoka Prefecture, central Japan, time series analysis using state-space modelling is applied to extract hydrological anomalies related to earthquakes. This method can decompose observed groundwater level time series into five components: atmospheric pressure, tidal, and precipitation responses, observation noise, and residual water level. The decomposed responses to atmospheric pressure and precipitation are independently determined and are consistent with the expected response to surface loading. In the groundwater level at the Haibara well, 28 coseismic changes can be discerned during the period from 1981 April to 1997 December. There is a threshold in the relationship between earthquake magnitude and the well-hypocentre distance, above which earthquakes cause coseismic changes in the residual water level. All of the coseismic water level changes at the Haibara well are decreases, although 33 per cent of the estimated coseismic volumetric strain steps are contraction, which would be expected to cause water level increases. The coseismic changes in groundwater level are more closely proportional to the estimated ground motion than to coseismic volumetric strain steps, suggesting that ground motion due to earthquakes is the major cause of the coseismic water level drops and that the contribution from static strain is rather small. Possible pre- or inter-earthquake water level changes have occurred at the Haibara well and may have been caused by local aseismic crustal deformation.

Geophysical Journal International↗

USGS2003

Hydric soils in a southeastern Oregon vernal pool

Vernal pools on the High Lava Plain of the northern Great Basin become ponded in most years, but their soils exhibit weak redoximorphic features indicative of hydric conditions. We studied the hydrology, temperature, redox potentials, soil chemistry, and soil morphology of a vernal pool to determine if the soils are hydric, and to evaluate hydric soil field indicators. We collected data for 3 yr from piezometers, Pt electrodes, and thermocouples. Soil and water samples were analyzed for pH, organic C, and extractable Fe and Mn. Soils were ponded from January through April or May, but subsurface saturation was never detected. Soil temperatures 50 cm below the surface rose above 5°C by March. Clayey Bt horizons perched water and limited saturation to the upper 10 cm. Redox potentials at a 5-cm depth were often between 200 and 300 mV, indicating anaerobic conditions, but producing soluble Fe 2+ concentrations <1 mg L −1 Extractable soil Fe contents indicated Fe depletion from pool surface horizons and accumulation at or near the upper Bt1 horizon. Depletions and concentrations did not satisfy the criteria of any current hydric soil indicators. We recommend development of new indicators based on acceptance of fewer, less distinct redox concentrations for recognition of a depleted A horizon, and on presence of a thin zone containing redox concentrations located in the upper part of the near-surface perching horizon.

Soil Science Society of America Journal↗

USGS2006

Metallogeny of the Great Basin: Crustal evolution, fluid flow, and ore deposits

The Great Basin physiographic province in the Western United States contains a diverse assortment of world-class ore deposits. It currently (2006) is the world’s second leading producer of gold, contains large silver and base metal (Cu, Zn, Pb, Mo, W) deposits, a variety of other important metallic (Fe, Ni, Be, REE’s, Hg, PGE) and industrial mineral (diatomite, barite, perlite, kaolinite, gallium) resources, as well as petroleum and geothermal energy resources. Ore deposits are most numerous and largest in size in linear mineral belts with complex geology. U.S. Geological Survey (USGS) scientists are in the final year of a research project initiated in the fall of 2001 to increase understanding of relations between crustal evolution, fluid flow, and ore deposits in the Great Basin. Because of its substantial past and current mineral production, this region has been the focus of numerous investigations over the past century and is the site of ongoing research by industry, academia, and state agencies. A variety of geoinformatic tools was used to organize, reinterpret, and display, in space and time, the large amounts of geologic, geophysical, geochemical, and hydrologic information deemed pertinent to this problem. This information, in combination with concentrated research on (1) critical aspects of the geologic history, (2) an area in northern Nevada that encompasses the major mineral belts, and (3) important mining districts and deposits, is producing new insights about the interplay between key tectonic events, hydrothermal fluid flow, and ore genesis in mineral belts. The results suggest that the Archean to Holocene history of the Great Basin was punctuated by several tectonic events that caused fluids of different origins (sea water, basinal brine, meteoric water, metamorphic water, magmatic water) to move through the crust. Basement faults reactivated during these events localized deformation, sedimentation, magmatism, and hydrothermal fluid flow in overlying rocks to form mineral belts that contain ore deposits of different types and ages that are locally superimposed (demonstrating inheritance). Fluid flow in these systems also was influenced by the distribution of permeable lithologies and paleotopographic highs and lows. Hydrothermal fluids evolved from their initial chemistries towards compositions that reflect the ƒ O 2 and ƒ S 2 buffering capacity of, and the ligands and metals present in, the rocks (±older mineralization) through which they moved. In northern Nevada, where gold deposits are relatively common, carbonaceous, pyritic strata buffered fluids of diverse origins to H 2 S-rich compositions so they could transport gold repeatedly over Paleozoic-Cenozoic time (convergent evolution). Ore formed where metal-laden fluids encountered effective physicochemical traps. Maps of Neogene basin fill and erosion surfaces identify areas where preexisting ore deposits have been progressively exposed or concealed. Comparisons with analogous terrains and deposit types in other parts of the world provide global context. The initial findings and some of the databases, geologic maps, sections, reconstructions, hydrogeologic models, topical syntheses, regional overviews, short courses, field guides, and deposit comparisons produced by project staff and associated managers, contractors, and collaborators have been presented in numerous abstracts, symposia, USGS publications, and professional journals over the last 5 years (see the extensive bibliography). Notable among these was the 2005 Geological Society of Nevada symposium in Reno, Nevada, and the 2005 Geological Society of America annual meeting in Salt Lake City, Utah, where project results were presented to audiences from around the nation and world. The final results of the project will be submitted for publication in 2007 to appropriate USGS and professional journals. A special issue of GEOSPHERE, scheduled for publication in 2007, will be devoted to the results of this project and related work. This special issue will reach an international audience and be available worldwide on the internet. Much of the research for this project has concentrated on areas that will receive the focused attention of the mining industry in the future. As such, the data and interpretations generated by this project have direct use for land-use managers in Federal, State, and local agencies. Improved hydrogeologic models developed by this project will considerably enhance ongoing and future water resource investigations in the region. The increased understanding of when, where, and how hydrothermal systems produce significant economic deposits has direct uses for mineral exploration and for future USGS mineral resource assessments in the Great Basin and other parts of the world.

Great Basin↗

USGS2015

Soil greenhouse gas emissions and carbon budgeting in a short-hydroperiod floodplain wetland

Understanding the controls on floodplain carbon (C) cycling is important for assessing greenhouse gas emissions and the potential for C sequestration in river-floodplain ecosystems. We hypothesized that greater hydrologic connectivity would increase C inputs to floodplains that would not only stimulate soil C gas emissions but also sequester more C in soils. In an urban Piedmont river (151 km 2 watershed) with a floodplain that is dry most of the year, we quantified soil CO 2 , CH 4 , and N 2 O net emissions along gradients of floodplain hydrologic connectivity, identified controls on soil aerobic and anaerobic respiration, and developed a floodplain soil C budget. Sites were chosen along a longitudinal river gradient and across lateral floodplain geomorphic units (levee, backswamp, and toe slope). CO 2 emissions decreased downstream in backswamps and toe slopes and were high on the levees. CH 4 and N 2 O fluxes were near zero; however, CH 4 emissions were highest in the backswamp. Annual CO 2 emissions correlated negatively with soil water-filled pore space and positively with variables related to drier, coarser soil. Conversely, annual CH 4 emissions had the opposite pattern of CO 2 . Spatial variation in aerobic and anaerobic respiration was thus controlled by oxygen availability but was not related to C inputs from sedimentation or vegetation. The annual mean soil CO 2 emission rate was 1091 g C m −2  yr −1 , the net sedimentation rate was 111 g C m −2  yr −1 , and the vegetation production rate was 240 g C m −2  yr −1 , with a soil C balance (loss) of −338 g C m −2  yr −1 . This floodplain is losing C likely due to long-term drying from watershed urbanization.

Virginia↗

USGS2026

Response of juvenile Chinook Salmon to an experimental reservoir operation to facilitate downstream migration

Objectives High-head dams and storage reservoirs impact ecological processes, impeding recovery efforts of Pacific salmon Oncorhynchus spp. in the western United States. These projects can delay migration, increase risks of predation and disease, and induce mortality for juvenile Pacific salmon during downstream passage. To mitigate these negative effects, large-scale changes to dam operations have been proposed as interim measures or alternatives to engineered fish passage solutions. A novel deep drawdown operation of the Lookout Point Project (two dams and reservoirs) in Oregon serves as a case study for learning from a large-scale management experiment. Beginning in July 2024, Lookout Point Reservoir was slowly lowered to attain minimal levels from mid-November to mid-December with the intent of expediting downstream passage through the project for juvenile Chinook Salmon Oncorhynchus tshawytscha . We evaluated the impacts of the months-long operation on two life histories of juvenile Chinook Salmon with different rearing environments and growth rates. Methods Acoustic telemetry was used to monitor juvenile Chinook Salmon in the Lookout Point Project. Environmental data, including water temperature and hydrological conditions, were collected. We fitted a time-integrated migration survival model to these data to estimate the effects of management-influenced covariates and fish length on apparent survival and residence time in each reach of the Lookout Point Project. Results Larger fish had higher survival than smaller fish in each reach of the Lookout Point Project. Apparent survival through each dam of the Lookout Point Project was highest and forebay residence times lowest during the latter part of the drawdown (late November). However, early periods of the drawdown (September) were associated with a transition from a thermally stratified reservoir to a warm isothermal reservoir that negatively impacted reservoir survival. Conclusions The deep drawdown of the Lookout Point Project achieved the management intent to improve downstream passage for juvenile Chinook Salmon at the lowest reservoir elevations but also caused unintended changes in the reservoir rearing environment prior to full drawdown. Further research could resolve remaining uncertainties regarding the overall effectiveness of drawdown operations with respect to the population dynamics of different juvenile life history strategies. Understanding these factors would help optimize future management actions aimed at Pacific salmon recovery above the Lookout Point Project.

Oregon↗

USGS2009

Kootenai River velocities, depth, and white sturgeon spawning site selection – A mystery unraveled?

The Kootenai River white sturgeon Acipenser transmontanus population in Idaho, US and British Columbia (BC), Canada became recruitment limited shortly after Libby Dam became fully operational on the Kootenai River, Montana, USA in 1974. In the USA the species was listed under the Endangered Species Act in September of 1994. Kootenai River white sturgeon spawn within an 18-km reach in Idaho, river kilometer (rkm) 228.0–246.0. Each autumn and spring Kootenai River white sturgeon follow a ‘short two-step’ migration from the lower river and Kootenay Lake, BC, to staging reaches downstream of Bonners Ferry, Idaho. Initially, augmented spring flows for white sturgeon spawning were thought to be sufficient to recover the population. Spring discharge mitigation enhanced white sturgeon spawning but a series of research investigations determined that the white sturgeon were spawning over unsuitable incubation and rearing habitat (sand) and that survival of eggs and larvae was negligible. It was not known whether post-Libby Dam management had changed the habitat or if the white sturgeon were not returning to more suitable spawning substrates farther upstream. Fisheries and hydrology researchers made a team effort to determine if the spawning habitat had been changed by Libby Dam operations. Researchers modeled and compared velocities, sediment transport, and bathymetry with post-Libby Dam white sturgeon egg collection locations. Substrate coring studies confirmed cobbles and gravel substrates in most of the spawning locations but that they were buried under a meter or more of post-Libby Dam sediment. Analysis suggested that Kootenai River white sturgeon spawn in areas of highest available velocity and depths over a range of flows. Regardless of the discharge, the locations of accelerating velocities and maximum depth do not change and spawning locations remain consistent. Kootenai River white sturgeon are likely spawning in the same locations as pre-dam, but post-Libby Dam water management has reduced velocities and shear stress, thus sediment is now covering the cobbles and gravels. Although higher discharges will likely provide more suitable spawning and rearing conditions, this would be socially and politically unacceptable because it would bring the river elevation to or in excess of 537.66 m, which is flood stage. Thus, support should be given to habitat modifications incorporated into a management plan to restore suitable habitat and ensure better survival of eggs and larvae.

Journal of Applied Ichthyology↗

USGS1985

Management of ground water and evolving hydrogeologic studies in New Jersey : a heavily urbanized and industrialized state in the northeastern United States

New Jersey is the most densely populated and one of the most industrialized states in the United States. An abundance of freshwater and proximity to major northeastern metropolitan centers has facilitated this development. Pumpage of freshwater from all aquifers in the State in 1980 was 730 million gallons per day (2.76 million cubic meters per day). Management and efficient development of the ground-water resources of the State are the responsibility of the New Jersey Department of Environmental Protection. Laws have been enacted and updated by the State legislature to manage water allocation and to control the disposal of hazardous wastes. Present resource management is guided by the New Jersey Water-Supply Master Plan of 1981. Funding for management activities is partially derived from the sale of state-approved bonds. Effective planning and regional management require accurate and up-to-date hydrologic information and analyses. The U.S. Geological Survey, in cooperation with the New Jersey Geological Survey, is conducting three intensive ground-water studies involving the collection and interpretation of hydrologic data to meet the urgent water-management needs of New Jersey. These studies are part of a long-term cooperative program and are funded through the Water-Supply Bond Act of 1981. They began in 1983 and are scheduled to be completed in 1988. The project areas are situated in the New Jersey part of the Atlantic Coastal Plain in and near Atlantic City, Camden, and South River. They range in size from 400 to 1,200 mil (1,040 to 3,120 km2). The studies are designed to define the geology, hydrology, and geochemistry of the local ground-water systems. The results of these studies will enable the State to address more effectively major problems in these areas such as declining water levels, overpumping, saltwater intrusion, and ground-water contamination resulting from the improper disposal of hazardous wastes. Specific objectives of these studies by the U.S. Geological Survey are to (1) develop an accurate and up-to-date hydrogeologic data base, (2) design and implement a data-collection program and establish a computerized information management system, (3) refine the conceptualization of the ground-water flow system, and (4) define the geochemistry of the aquifer system by conducting a water-quality appraisal. The objectives are accomplished by standard hydrogeologic methods. Information concerning hydrogeologic framework, ground-water levels, water use, hydraulic characteristics, and water quality in the study areas is compiled from all available sources. Additional data needed are collected through well inventories, surface geophysical surveys, water-quality samplings, water-level measurements, and a well-drilling program. Interpretation of the flow system is based on the use of standard analytical techniques and digital flow modeling. Calibrated flow models will provide ground-water managers with a mechanism to develop and test regional water-supply strategies. Definition of the geochemistry of the aquifer system is accomplished through a variety of methods which depend on the problems and available data in the particular study area. The approach includes statistical analysis of water-quality data, reaction-path modeling, and determination of the movement of chemical constituents using analytical and numerical modeling techniques. A combined staff of 25 to 30 professionals and technicians from the New Jersey District office of the U.S. Geological Survey is committed to the three studies. The staff has specialists in geohydrology, numerical modeling, geochemistry, geophysics, and computer science. The findings of these studies will be published in data reports, interpretive reports, instructional manuals and journal articles.

New Jersey↗

USGS2016

Variability of runoff-based drought conditions in the conterminous United States

In this study, a monthly water-balance model is used to simulate monthly runoff for 2109 hydrologic units (HUs) in the conterminous United States (CONUS) for water-years 1901 through 2014. The monthly runoff time series for each HU were smoothed with a 3-month moving average, and then the 3-month moving-average runoff values were converted to percentiles. For each HU, a drought was considered to occur when the HU runoff percentile dropped to the 20th percentile or lower. A drought was considered to end when the HU runoff percentile exceeded the 20th percentile. After identifying drought events for each HU, the frequency and length of drought events were examined. Results indicated that (1) the longest mean drought lengths occur in the eastern CONUS and parts of the Rocky Mountain region and the northwestern CONUS, (2) the frequency of drought is highest in the southwestern and central CONUS, and lowest in the eastern CONUS, the Rocky Mountain region, and the northwestern CONUS, (3) droughts have occurred during all months of the year and there does not appear to be a seasonal pattern to drought occurrence, (4) the variability of precipitation appears to have been the principal climatic factor determining drought, and (5) for most of the CONUS, drought frequency appears to have decreased during the 1901 through 2014 period.

International Journal of Climatology↗

USGS2007

Cleats and their relation to geologic lineaments and coalbed methane potential in Pennsylvanian coals in Indiana

Cleats and fractures in Pennsylvanian coals in southwestern Indiana were described, statistically analyzed, and subsequently interpreted in terms of their origin, relation to geologic lineaments, and significance for coal permeability and coalbed gas generation and storage. These cleats can be interpreted as the result of superimposed endogenic and exogenic processes. Endogenic processes are associated with coalification (i.e., matrix dehydration and shrinkage), while exogenic processes are mainly associated with larger-scale phenomena, such as tectonic stress. At least two distinct generations of cleats were identified on the basis of field reconnaissance and microscopic study: a first generation of cleats that developed early on during coalification and a second generation that cuts through the previous one at an angle that mimics the orientation of the present-day stress field. The observed parallelism between early-formed cleats and mapped lineaments suggests a well-established tectonic control during early cleat formation. Authigenic minerals filling early cleats represent the vestiges of once open hydrologic regimes. The second generation of cleats is characterized by less prominent features (i.e., smaller apertures) with a much less pronounced occurrence of authigenic mineralization. Our findings suggest a multistage development of cleats that resulted from tectonic stress regimes that changed orientation during coalification and basin evolution. The coals studied are characterized by a macrocleat distribution similar to that of well-developed coalbed methane basins (e.g., Black Warrior Basin, Alabama). Scatter plots and regression analyses of meso- and microcleats reveal a power-law distribution between spacing and cleat aperture. The same distribution was observed for fractures at microscopic scale. Our observations suggest that microcleats enhance permeability by providing additional paths for migration of gas out of the coal matrix, in addition to providing access for methanogenic bacteria. The abundance, distribution, and orientation of cleats control coal fabric and are crucial features in all stages of coalbed gas operations (i.e., exploration and production). Understanding coal fabric is important for coal gas exploration as it may be related to groundwater migration and the occurrence of methanogenic bacteria, prerequisite to biogenic gas accumulations. Likewise, the distribution of cleats in coal also determines pathways for migration and accumulation of thermogenic gas generated during coalification. ?? 2007 Elsevier B.V. All rights reserved.

International Journal of Coal Geology↗

USGS2007

Prioritizing bottomland hardwood forest sites for protection and augmentation

Bottomland hardwood forest has been greatly diminished by conversion to agriculture. Less than 25% of the pre-Columbian bottomland hardwood forests remain in the southeastern United States. Because of the valuable ecological and hydrological functions performed by these forests, their conservation and restoration has been a high priority. Part of these restoration efforts has focused on developing tools that can be used for both assessments at the landscape level and policy implementation at the local level. The distribution of bottomland hardwood forests in the Cache and White River watersheds in eastern Arkansas were examined using existing GIS databases. Criteria were developed to select areas that should be conserved or augmented for wildlife habitat. Over 67% of the study area was classified as agriculture, with bottomland hardwood forest the next largest habitat class. The thickness of a forest fragment was defined as the radius of the largest circle that can be inscribed in a fragment. Thickness was used in three ways. First, individual forest fragments were identified and selected based on ecological function using criteria we established. Second, individual fragments that were too small to support interior species, but large enough that if moderately augmented they could recover that function, were identified and selected. These augmentable fragments were further prioritized by adjacency to habitat that might be suitable for reforestation, namely agriculture. Third, watersheds were prioritized for conservation and augmentation based on the size and distributions of forest fragment thickness and area within each watershed.

Arkansas↗

USGS2010

Fault-related clay authigenesis along the Moab Fault: Implications for calculations of fault rock composition and mechanical and hydrologic fault zone properties

The presence of clays in fault rocks influences both the mechanical and hydrologic properties of clay-bearing faults, and therefore it is critical to understand the origin of clays in fault rocks and their distributions is of great importance for defining fundamental properties of faults in the shallow crust. Field mapping shows that layers of clay gouge and shale smear are common along the Moab Fault, from exposures with throws ranging from 10 to ???1000 m. Elemental analyses of four locations along the Moab Fault show that fault rocks are enriched in clays at R191 and Bartlett Wash, but that this clay enrichment occurred at different times and was associated with different fluids. Fault rocks at Corral and Courthouse Canyons show little difference in elemental composition from adjacent protolith, suggesting that formation of fault rocks at those locations is governed by mechanical processes. Friction tests show that these authigenic clays result in fault zone weakening, and potentially influence the style of failure along the fault (seismogenic vs. aseismic) and potentially influence the amount of fluid loss associated with coseismic dilation. Scanning electron microscopy shows that authigenesis promotes that continuity of slip surfaces, thereby enhancing seal capacity. The occurrence of the authigenesis, and its influence on the sealing properties of faults, highlights the importance of determining the processes that control this phenomenon. ?? 2010 Elsevier Ltd.

Journal of Structural Geology↗

USGS2003

Hydrological response to earthquakes in the Haibara well, central Japan - II. Possible mechanism inferred from time-varying hydraulic properties

28 coseismic groundwater level decreases have been observed at the Haibara well, Shizuoka prefecture, central Japan, from 1981 to 1997. These groundwater level changes cannot be explained as the poroelastic response to coseismic static strain. We use the atmospheric pressure and tidal responses of the well, rock properties measured on core samples from the same formation and pumping test results to characterize the hydraulic and mechanical properties of the aquifer. The responses of the Haibara well to the M2 Earth tide constituent and to atmospheric pressure have varied over time. In particular, increasing amplitude and decreasing phase lags were observed after the 1993 pumping test, as well as after earthquakes that caused coseismic water level changes. The tidal response, together with the surface load efficiency derived from the atmospheric pressure response, is used to estimate the mechanical properties of the aquifer. The largest amplitude of the M2 constituent, 2.2 mm, is small enough to imply that pore fluid in this system is approximately twice as compressible as water, possibly due to the presence of a small amount of exsolved gas. Diffusion of a coseismic pressure drop near the well could account for the observed time histories of the water level changes. The time histories of the water level drops are well matched by the decay of a coseismic pressure drop at least 80 m away from the well. Removal of a small amount of gas from the formation in that location might in turn explain the coseismic pressure drops.

Geophysical Journal International↗

USGS2006

Predicting crappie recruitment in Ohio reservoirs with spawning stock size, larval density, and chlorophyll concentrations

Stock-recruit models typically use only spawning stock size as a predictor of recruitment to a fishery. In this paper, however, we used spawning stock size as well as larval density and key environmental variables to predict recruitment of white crappies Pomoxis annularis and black crappies P. nigromaculatus, a genus notorious for variable recruitment. We sampled adults and recruits from 11 Ohio reservoirs and larvae from 9 reservoirs during 1998-2001. We sampled chlorophyll as an index of reservoir productivity and obtained daily estimates of water elevation to determine the impact of hydrology on recruitment. Akaike's information criterion (AIC) revealed that Ricker and Beverton-Holt stock-recruit models that included chlorophyll best explained the variation in larval density and age-2 recruits. Specifically, spawning stock catch per effort (CPE) and chlorophyll explained 63-64% of the variation in larval density. In turn, larval density and chlorophyll explained 43-49% of the variation in age-2 recruit CPE. Finally, spawning stock CPE and chlorophyll were the best predictors of recruit CPE (i.e., 74-86%). Although larval density and recruitment increased with chlorophyll, neither was related to seasonal water elevation. Also, the AIC generally did not distinguish between Ricker and Beverton-Holt models. From these relationships, we concluded that crappie recruitment can be limited by spawning stock CPE and larval production when spawning stock sizes are low (i.e., CPE , 5 crappies/net-night). At higher levels of spawning stock sizes, spawning stock CPE and recruitment were less clearly related. To predict recruitment in Ohio reservoirs, managers should assess spawning stock CPE with trap nets and estimate chlorophyll concentrations. To increase crappie recruitment in reservoirs where recruitment is consistently poor, managers should use regulations to increase spawning stock size, which, in turn, should increase larval production and recruits to the fishery.

North American Journal of Fisheries Management↗

USGS2011

Wetland vegetation in Manzala lagoon, Nile Delta coast, Egypt: Rapid responses of pollen to altered nile hydrology and land use

The pollen record in a sediment core from Manzala lagoon on the Nile delta coastal margin of Egypt, deposited from ca. AD 1860 to 1990, indicates rapid coastal wetland vegetation responses to two primary periods of human activity. These are associated with artificially altered Nile hydrologic regimes in proximal areas and distal sectors located to ∼1200 km south of Manzala. Freshwater wetland plants that were dominant, such as Typha and Phragmites , decreased rapidly, whereas in the early 1900s, brackish water wetland species ( e.g. , Amaranthaceae) increased. This change occurred after closure of the Aswan Low Dam in 1902. The second major modification in the pollen record occurred in the early 1970s, after Aswan High Dam closure from 1965 to 1970, when Typha pollen abundance increased rapidly. Massive population growth occurred along the Nile during the 130 years represented by the core section. During this time, the total volume of lagoon water decreased because of conversion of wetland areas to agricultural land, and input of organic-rich sediment, sewage (municipal, agricultural, industrial), and fertilizer in Manzala lagoon increased markedly. Although the wetland plant community has continued to respond to increasingly intensified and varied human-induced pressures in proximal sectors, the two most marked changes in Manzala pollen best correlate with distal events ( i.e. , closure of the two dams at Aswan). The study also shows that the two major vegetation changes in Manzala lagoon each occurred less than 10 years after closure upriver of the Low and High dams that markedly altered the Nile regime from Upper Egypt to the coast.

Manzala Lagoon↗

USGS2009

Responses of stream nitrate and dissolved organic carbon loadings to hydrological forcing and climate change in an upland forest of the northeast USA

[1] In coming decades, higher annual temperatures, increased growing season length, and increased dormant season precipitation are expected across the northeastern United States in response to anthropogenic forcing of global climate. We synthesized long-term stream hydrochemical data from the Sleepers River Research Watershed in Vermont, United States, to explore the relationship of catchment wetness to stream nitrate and DOC loadings. We modeled changes in growing season length and precipitation patterns to simulate future climate scenarios and to assess how stream nutrient loadings respond to climate change. Model results for the 2070–2099 time period suggest that stream nutrient loadings during both the dormant and growing seasons will respond to climate change. During a warmer climate, growing season stream fluxes (runoff +20%, nitrate +57%, and DOC +58%) increase as more precipitation (+28%) and quick flow (+39%) occur during a longer growing season (+43 days). During the dormant season, stream water and nutrient loadings decrease. Net annual stream runoff (+8%) and DOC loading (+9%) increases are commensurate with the magnitude of the average increase of net annual precipitation (+7%). Net annual stream water and DOC loadings are primarily affected by increased dormant season precipitation. In contrast, decreased annual loading of stream nitrate (−2%) reflects a larger effect of growing season controls on stream nitrate and the effects of lengthened growing seasons in a warmer climate. Our findings suggest that leaching of nitrate and DOC from catchment soils will be affected by anthropogenic climate forcing, thereby affecting the timing and magnitude of annual stream loadings in the northeastern United States.

Vermont↗

USGS2009

The changing global carbon cycle: Linking plant-soil carbon dynamics to global consequences

Most current climate-carbon cycle models that include the terrestrial carbon (C) cycle are based on a model developed 40 years ago by Woodwell & Whittaker (1968) and omit advances in biogeochemical understanding since that time. Their model treats net C emissions from ecosystems as the balance between net primary production (NPP) and heterotrophic respiration (HR, i.e. primarily decomposition). Under conditions near steady state, geographic patterns of decomposition closely match those of NPP, and net C emissions are adequately described as a simple balance of NPP and HR (the Woodwell-Whittaker model). This close coupling between NPP and HR occurs largely because of tight coupling between C and N (nitrogen) cycles and because NPP constrains the food available to heterotrophs. Processes in addition to NPP and HR become important to understanding net C emissions from ecosystems under conditions of rapid changes in climate, hydrology, atmospheric CO 2 , land cover, species composition and/or N deposition. Inclusion of these processes in climate-C cycle models would improve their capacity to simulate recent and future climatic change. Processes that appear critical to soil C dynamics but warrant further research before incorporation into ecosystem models include below-ground C flux and its partitioning among roots, mycorrhizas and exudates; microbial community effects on C sequestration; and the effects of temperature and labile C on decomposition. The controls over and consequences of these processes are still unclear at the ecosystem scale. Carbon fluxes in addition to NPP and HR exert strong influences over the climate system under conditions of rapid change. These fluxes include methane release, wildfire, and lateral transfers of food and fibre among ecosystems. Water and energy exchanges are important complements to C cycle feedbacks to the climate system, particularly under non-steady-state conditions. An integrated understanding of multiple ecosystem-climate feedbacks provides a strong foundation for policies to mitigate climate change. Synthesis . Current climate systems models that include only NPP and HR are inadequate under conditions of rapid change. Many of the recent advances in biogeochemical understanding are sufficiently mature to substantially improve representation of ecosystem C dynamics in these models.

Journal of Ecology↗

USGS1992

Hydrological, geomorphological, and chemical effects of Hurricane Andrew on coastal marshes of Louisiana

Hydrological conditions are reported for the hurricane-induced storm surge at marsh sites in Terrebonne and Barataria Basins. There was a 6 hour or greater delay in the arrival of the storm surge at interior marsh sites compared to coastal locations. A water surge of about 1.5 m with a salinity of 10–15‰ was recorded at an intermediate salinity marsh site in Terrebonne Basin where significant geomorphological changes occurred with lateral movement and stacking of marsh vegetation and sediment, erosion, and the conversion of wetlands to open water. A residual salt wedge attributed to the storm surge was detected in sediments at this intermediate marsh site about 55 days after the hurricane. In the pore water, at 30 cm in depth, there were increases in alkalinity, ammonia, phosphate, and manganese, but not iron or sulfide, although there was a significant depletion of sulfur with respect to chloride. The increases in concentration of these species in the pore water suggests that there was an increase in organic matter decomposition. Although increases in sulfide phytotoxicity were not obvious, the residual salinity of pore water may influence wetland loss through longer-term impacts on macrophyte production. Storm-induced sediment deposition, which will help ameliorate wetland loss, was observed at a salt marsh site in Terrebonne Basin.

Louisiana↗

USGS1996

Mapping playa evaporite minerals and associated sediments in Death Valley, California, with multispectral thermal infrared images

Efflorescent salt crusts and associated sediments in Death Valley, California, were studied with remote-sensing data acquired by the NASA thermal infrared multispectral scanner (TIMS). Nine spectral classes that represent a variety of surface materials were distinguished, including several classes that reflect important aspects of the playa groundwater chemistry and hydrology. Evaporite crusts containing abundant thenardite (sodium sulfate) were mapped along the northern and eastern margins of the Cottonball Basin, areas where the inflow waters are rich in sodium. Gypsum (calcium sulfate) crusts were more common in the Badwater Basin, particularly near springs associated with calcic groundwaters along the western basin margin. Evaporite-rich crusts generally marked areas where groundwater is periodically near the surface and thus able to replenish the crusts though capillary evaporation. Detrital silicate minerals were prevalent in other parts of the salt pan where shallow groundwater does not affect the surface composition. The surface features in Death Valley change in response to climatic variations on several different timescales. For example, salt crusts on low-lying mudflats form and redissolve during seasonal-to-interannual cycles of wetting and desiccation. In contrast, recent flooding and erosion of rough-salt surfaces in Death Valley probably reflect increased regional precipitation spanning several decades. Remote-sensing observations of playas can provide a means for monitoring changes in evaporite facies and for better understanding the associated climatic processes. At present, such studies are limited by the availability of suitable airborne scanner data. However, with the launch of the Earth Observing System (EOS) AM-1 Platform in 1998, multispectral visible/near-infrared and thermal infrared remote-sensing data will become globally available.

Journal of Geophysical Research B: Solid Earth↗