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USGS2024

Concepts and evolution of urban hydrology.

Urbanization and climate change are exacerbating the flood risk and ecosystem degradation in urban catchments, with traditional stormwater management systems often overwhelmed. In this Review, we discuss changes in urban hydrology and approaches to stormwater management. Roughly 90% of rainfall on impervious surfaces and drainage infrastructure becomes run-off, enhancing rainfall export away from cities and leading to local water scarcity and downstream flooding and pollution. Projected increases in urban populations (68% in cities by 2050) and rainfall intensity (~12% in the 10-year and 50-year recurrence interval intensity, under 1.5 °C warming) will exacerbate these issues. Transforming stormwater systems is thus urgently needed, to mitigate flood risk and also to address community desires for environmental protection and enhanced water security. Opportunities include rain gardens and other nature-based stormwater control measures (which restore natural flows and offer other ecosystem services), smart sensor monitoring networks and real-time management (which sustain natural flow regimes, mitigate flood risk and protect ecosystem services) and stormwater harvesting (to avoid local water scarcity). Community acceptance of stormwater harvesting is as high as 96% and stormwater is a substantial resource, with volumes often exceeding demand in some parts of the world. Delivering additional transformations globally requires research into strategies to incentivize engagement and investment, and policies to guide governance of decentralized networks.

Nature Reviews Earth & Environment↗
USGS2021

Optimization of salt marsh management at the Eastern Shore of Virginia and Fisherman Island National Wildlife Refuges, Virginia, through use of structured decision making

Structured decision making is a systematic, transparent process for improving the quality of complex decisions by identifying measurable management objectives and feasible management actions; predicting the potential consequences of management actions relative to the stated objectives; and selecting a course of action that maximizes the total benefit achieved and balances tradeoffs among objectives. The U.S. Geological Survey, in cooperation with the U.S. Fish and Wildlife Service, applied an existing, regional framework for structured decision making to develop a prototype tool for optimizing tidal marsh management decisions at the Eastern Shore of Virginia and Fisherman Island National Wildlife Refuges in Virginia. Refuge biologists, refuge managers, and research scientists identified multiple potential management actions to improve the ecological integrity of six marsh management units within the refuges, totaling about 575 hectares, and estimated the outcomes of each action in terms of performance metrics associated with each management objective. Value functions previously developed at the regional level were used to transform metric scores to a common utility scale, and utilities were summed to produce a single score representing the total management benefit that could be accrued from each potential management action. Constrained optimization was used to identify the set of management actions, one per marsh management unit, that could maximize total management benefits at different cost constraints at the refuge scale. Results indicated that, for the objectives and actions considered here, total management benefits may increase consistently up to approximately $ 143,000, but that further expenditures may yield diminishing return on investment. Potential management actions in optimal portfolios at total costs less than $ 143,000 included digging runnels by hand to improve drainage from the marsh surface, breaching a road to restore natural hydrology, trapping predators to enhance nest success of tidal marsh birds, and reducing the abundance of Odocoileus virginianus (white-tailed deer) to minimize their effects on marsh vegetation. The potential management benefits were derived from expected increases in number of tidal marsh obligate breeding birds, species richness of nekton, and density of spiders (as an indicator of trophic health); and an expected decrease in duration of surface flooding. The prototype presented here does not resolve management decisions; rather, it provides a framework for decision making at the Eastern Shore of Virginia and Fisherman Island National Wildlife Refuges that can be updated as new data and information become available. Insights from this process may also be useful to inform future habitat management planning at the refuges.

Virginia↗
USGS2009

Effects of hydrologic infrastructure on flow regimes of California's Central Valley rivers: Implications for fish populations

Alteration of natural flow regimes is generally acknowledged to have negative effects on native biota; however, methods for defining ecologically appropriate flow regimes in managed river systems are only beginning to be developed. Understanding how past and present water management has affected rivers is an important part of developing such tools. In this paper, we evaluate how existing hydrologic infrastructure and management affect streamflow characteristics of rivers in the Central Valley, California and discuss those characteristics in the context of habitat requirements of native and alien fishes. We evaluated the effects of water management by comparing observed discharges with estimated discharges assuming no water management ("full natural runoff"). Rivers in the Sacramento River drainage were characterized by reduced winter–spring discharges and augmented discharges in other months. Rivers in the San Joaquin River drainage were characterized by reduced discharges in all months but particularly in winter and spring. Two largely unaltered streams had hydrographs similar to those based on full natural runoff of the regulated rivers. The reduced discharges in the San Joaquin River drainage streams are favourable for spawning of many alien species, which is consistent with observed patterns of fish distribution and abundance in the Central Valley. However, other factors, such as water temperature, are also important to the relative success of native and alien resident fishes. As water management changes in response to climate change and societal demands, interdisciplinary programs of research and monitoring will be essential for anticipating effects on fishes and to avoid unanticipated ecological outcomes.

California↗
USGS2009

Does sulphate enrichment promote the expansion of Typha domingensis (cattail) in the Florida Everglades?

1. The expansion of Typha domingensis into areas once dominated by Cladium jamaicense in the Florida Everglades has been attributed to altered hydrology and phosphorus enrichment, although increased concentrations of sulphate and phosphorus often coincide. The potential importance of hydrogen sulphide produced from sulphate in the expansion of Typha has received little attention. The present study aimed to quantify the comparative growth and photosynthetic responses of Cladium and Typha to sulphate/sulphide. 2. Laboratory experiments showed that Cladium is less tolerant of sulphide than Typha. Cladium was adversely affected at sulphide concentrations of approximately 0.22 mm, while Typha continued to grow well and appeared healthy up to 0.69 mm sulphide. 3. Experiments in field mesocosms provided strong support for species-specific differences in physiology and growth. Regardless of interstitial sulphide concentrations attained, Typha grew faster and had a higher photosynthetic capacity than Cladium. However, sulphide concentrations in the mesocosms reached only 0.18 mm which, based on the hydroponic study, was insufficient to affect the growth or photosynthetic responses of either species. Nevertheless, the upper range of sulphide (0.25-0.375 mm) in Everglades' soil is high enough, based on our results, to impact Cladium but not Typha. 4. This research supports the hypothesis that sulphide accumulation could affect plant species differentially and modify species composition. Consequently, the role of sulphate loading should be considered, in conjunction with hydroperiod, phosphorus availability and disturbances, in developing future management plans for the Everglades. ?? 2009 Blackwell Publishing Ltd.

Freshwater Biology↗
USGS2008

Relative importance of natural disturbances and habitat degradation on snail kite population dynamics

Natural disturbances and habitat degradation are major factors influencing the dynamics and persistence of many wildlife populations, yet few large-scale studies have explored the relative influence of these factors on the dynamics and persistence of animal populations. We used longterm demographic data and matrix population models to examine the potential effects of habitat degradation and natural disturbances on the dynamics of the endangered snail kite Rostrhamus sociabilis in Florida, USA. We found that estimates of stochastic population growth rate were low (0.90). Population growth rate (??) during the first half or our study period (1992 to 1998) was substantially greater than during the second half (1999 to 2005). These 2 periods were characterized by contrasting hydrological conditions. Although ?? was most sensitive to changes in adult survival, the analysis of life table response experiments revealed that a reduction in fertility of kites accounted for >80% of the observed decline in population growth rate. We examined the possibility that the reduction in ?? was caused by (1) habitat degradation due to management, (2) an increase in frequency of moderate drying events in recent years, and (3) both habitat degradation and an increase in frequency of moderate drying events. Our results suggest that both factors could potentially contribute to a large decrease in population growth rate. Our study highlights the importance of simultaneously considering short- and long-term effects of disturbances when modeling population dynamics. Indeed, focusing exclusively on one type of effect may be misleading to both our understanding of the ecological dynamics of the system and to management. The relevance of our results to management is heightened because the snail kite has been selected as a key performance measure of one of the most ambitious ecosystem restoration projects ever undertaken. ?? Inter-Research 2008.

Endangered Species Research↗
USGS2011

Spatial interpolation schemes of daily precipitation for hydrologic modeling

Distributed hydrologic models typically require spatial estimates of precipitation interpolated from sparsely located observational points to the specific grid points. We compare and contrast the performance of regression-based statistical methods for the spatial estimation of precipitation in two hydrologically different basins and confirmed that widely used regression-based estimation schemes fail to describe the realistic spatial variability of daily precipitation field. The methods assessed are: (1) inverse distance weighted average; (2) multiple linear regression (MLR); (3) climatological MLR; and (4) locally weighted polynomial regression (LWP). In order to improve the performance of the interpolations, the authors propose a two-step regression technique for effective daily precipitation estimation. In this simple two-step estimation process, precipitation occurrence is first generated via a logistic regression model before estimate the amount of precipitation separately on wet days. This process generated the precipitation occurrence, amount, and spatial correlation effectively. A distributed hydrologic model (PRMS) was used for the impact analysis in daily time step simulation. Multiple simulations suggested noticeable differences between the input alternatives generated by three different interpolation schemes. Differences are shown in overall simulation error against the observations, degree of explained variability, and seasonal volumes. Simulated streamflows also showed different characteristics in mean, maximum, minimum, and peak flows. Given the same parameter optimization technique, LWP input showed least streamflow error in Alapaha basin and CMLR input showed least error (still very close to LWP) in Animas basin. All of the two-step interpolation inputs resulted in lower streamflow error compared to the directly interpolated inputs.

Colorado, Georgia↗
USGS2002

Preliminary hydrogeologic assessment and study plan for a regional ground-water resource investigation of the Blue Ridge and Piedmont provinces of North Carolina

Prolonged drought, allocation of surface-water flow, and increased demands on ground-water supplies resulting from population growth are focuses for the need to evaluate ground-water resources in the Blue Ridge and Piedmont Provinces of North Carolina. Urbanization and certain aspects of agricultural production also have caused increased concerns about protecting the quality of ground water in this region. More than 75 percent of the State's population resides in the Blue Ridge and Piedmont Provinces in an area that covers 30,544 square miles and 65 counties. Between 1940 and 2000, the population in the Piedmont and Blue Ridge Provinces increased from 2.66 to 6.11 million; most of this increase occurred in the Piedmont. Of the total population, an estimated 1.97 million people, or 32.3 percent (based on the 1990 census), relied on ground water for a variety of uses, including commercial, industrial, and most importantly, potable supplies. Ground water in the Blue Ridge and Piedmont traditionally has not been considered as a source for large supplies, primarily because of readily available and seemingly limitless surface-water supplies, and the perception that ground water in the Blue Ridge and Piedmont Provinces occurs in a complex, generally heterogeneous geologic environment. Some reluctance to use ground water for large supplies derives from the reputation of aquifers in these provinces for producing low yields to wells, and the few high-yield wells that are drilled seem to be scattered in areas distant from where they are needed. Because the aquifers in these provinces are shallow, they also are susceptible to contamination by activities on the land surface. In response to these issues, the North Carolina Legislature supported the creation of a Resource Evaluation Program to ensure the long-term availability, sustainability, and quality of ground water in the State. As part of the Resource Evaluation Program, the North Carolina Division of Water Quality, Groundwater Section, in cooperation with the U.S. Geological Survey, initiated a multiyear study of ground water in the Blue Ridge and Piedmont Provinces. The study began in 1999. Most of the study area is underlain by a complex, two-part, regolith-fractured crystalline rock aquifer system. Thickness of the regolith throughout the study area is highly variable and ranges from 0 to more than 150 feet. The regolith consists of an unconsolidated or semiconsolidated mixture of clay and fragmental material ranging in grain size from silt to boulders. Because porosities range from 35 to 55 percent, the regolith provides the bulk of the water storage within the Blue Ridge and Piedmont ground-water system. At the base of the regolith is the transition zone where saprolite grades into unweathered bedrock. The transition zone has been identified as a potential conduit for rapid ground-water flow. If this is the case, the transition zone also may serve as a conduit for rapid movement of contaminants to nearby wells or to streams with channels that cut into 1 U.S. Geological Survey, Raleigh, North Carolina. 2 North Carolina Department of Environment and Natural Resources, Division of Water Quality, Groundwater Section. or through the transition zone. How rapidly a contaminant moves through the system largely may be a function of the characteristics of the transition zone. The transition zone is one of several topics identified during the literature review and data synthesis, for which there is a deficiency in data and understanding of the processes involved in the movement of ground water to surface water. Because the Blue Ridge and Piedmont study area is so large, and the hydrogeology diverse, it is not feasible to study all of the area in detail. A more feasible approach is to select areas that are most representative of the land use, geology, and hydrology to obtain an understanding of the hydrologic processes in the selected areas, and transfer the knowledge from these local "type areas" to similar regional hydrogeologic areas. For the purpose of this study, the term "type area" applies to a 10- to 100-square mile area within a hydrogeologic terrane where information is sufficient to develop and test a concept of ground-water flow by using analytical or numerical methods that can be validated by field measurements. Ideally, these type areas are selected to be representative of the flow system that is present wherever a particular hydrogeologic terrane is present. This report consists of two basic parts. The first part describes the results of a comprehensive review and synthesis of information and literature that provides the basic background for the study. This includes current (2002) knowledge regarding general geology and the hydrogeologic framework of the fractured-rock aquifer system that underlies the Blue Ridge and Piedmont Provinces. In spite of the quantity of information identified during the literature review and the amount of past work that has been documented, there are still research needs to be met. The second part of the report describes State ground-water issues and problems, available data, and data deficiencies. It also describes the design and implementation of efforts to characterize ground-water quality and to quantify factors that influence the movement and availability of ground water in the hydrogeologic terranes characterized by (1) massive or foliated crystalline rocks overlain by thick regolith and (2) massive or foliated crystalline rocks overlain by thin regolith. As of September 2001, seven sites had been identified as potential study sites to be used to characterize the hydrogeology and water quality of ype areas considered representative of the larger terranes. Detailed geologic mapping, core drilling, well installation, and surface and borehole geophysical surveys are in progress at four of the sites.

North Carolina↗
USGS2026

Developing a low-cost drone-based method for deploying and retrieving autonomous recording units in inaccessible areas

Autonomous Recording Units (ARUs) are increasingly used in research to support passive acoustic monitoring, but deployment in remote or inaccessible locations remains logistically challenging. Traditional manual placement is labor-intensive, time-consuming, potentially hazardous, and often limited to habitat edges, creating sampling biases and restricting spatial coverage. To address placement limitations in wetland systems, we developed and field-tested a low-cost, lightweight floating platform paired with a drone-based deployment and retrieval system. The drone-deployable ARU platform, constructed from inexpensive, off-the-shelf materials (~US $21 per unit), weighed ~560 g and was mounted with an ARU (AudioMoth) at ~1.2 m above water. The platform was designed for stability, portability, and compliance with Federal Aviation Administration Part 107 regulations. Field trials were conducted across 50 operations in various types of historical rice-field impoundments along the South Carolina coast, which provide critical habitat for secretive marsh birds such as rails (e.g ., Rallus, Laterallus , and Porzana ) and bitterns (e.g ., Botaurus and Ixobrychus ). All 50 deployments and retrievals were successful, demonstrating the robustness of the method under diverse hydrologic and vegetative conditions. Deployment times were significantly shorter than retrieval times (median 6 vs. 9 min), with retrieval requiring greater precision for hook engagement. Operation times scaled predictably with distance: deployment increased by 0.93 min/100 m (R 2 = 0.94) and retrieval by 1.17 min/100 m (R 2 = 0.95). No platform damage or displacement was observed, as emergent vegetation was likely providing natural anchoring. Our approach offers an affordable and effective solution for expanding ARU coverage in large, inaccessible wetlands, reducing sampling bias and enhancing biodiversity monitoring. With continued advances in drone payload capacity, battery endurance, and beyond-visual-line-of-sight flight regulations, our workflow could be adapted for deploying multi-sensor platforms (e.g., ARUs, eDNA samplers, water and air quality sensors, plant sample collectors, insect traps, and trail cameras) to support integrated biodiversity monitoring in challenging landscapes worldwide.

South Carollina↗
USGS2011

Vulnerability of riparian ecosystems to elevated CO 2 and climate change in arid and semiarid western North America

Riparian ecosystems, already greatly altered by water management, land development, and biological invasion, are being further altered by increasing atmospheric CO 2 concentrations ([CO 2 ]) and climate change, particularly in arid and semiarid (dryland) regions. In this literature review, we (1) summarize expected changes in [CO 2 ], climate, hydrology, and water management in dryland western North America, (2) consider likely effects of those changes on riparian ecosystems, and (3) identify critical knowledge gaps. Temperatures in the region are rising and droughts are becoming more frequent and intense. Warmer temperatures in turn are altering river hydrology: advancing the timing of spring snow melt floods, altering flood magnitudes, and reducing summer and base flows. Direct effects of increased [CO 2 ] and climate change on riparian ecosystems may be similar to effects in uplands, including increased heat and water stress, altered phenology and species geographic distributions, and disrupted trophic and symbiotic interactions. Indirect effects due to climate-driven changes in streamflow, however, may exacerbate the direct effects of warming and increase the relative importance of moisture and fluvial disturbance as drivers of riparian ecosystem response to global change. Together, climate change and climate-driven changes in streamflow are likely to reduce abundance of dominant, native, early-successional tree species, favor herbaceous species and both drought-tolerant and late-successional woody species (including many introduced species), reduce habitat quality for many riparian animals, and slow litter decomposition and nutrient cycling. Climate-driven changes in human water demand and associated water management may intensify these effects. On some regulated rivers, however, reservoir releases could be managed to protect riparian ecosystem. Immediate research priorities include determining riparian species' environmental requirements and monitoring riparian ecosystems to allow rapid detection and response to undesirable ecological change.

Global Change Biology↗
USGS2020

Reducing water scarcity by improving water productivity in the United States

Nearly one-sixth of U.S. river basins are unable to consistently meet societal water demands while also providing sufficient water for the environment. Water scarcity is expected to intensify and spread as populations increase, new water demands emerge, and climate changes. Improving water productivity by meeting realistic benchmarks for all water users could allow U.S. communities to expand economic activity and improve environmental flows. Here we utilize a spatially detailed database of water productivity to set realistic benchmarks for over 400 industries and products. We assess unrealized water savings achievable by each industry in each river basin within the conterminous U.S. by bringing all water users up to industry- and region-specific water productivity benchmarks. Some of the most water stressed areas throughout the U.S. West and South have the greatest potential for water savings, with around half of these water savings obtained by improving water productivity in the production of corn, cotton, and alfalfa. By incorporating benchmark-meeting water savings within a national hydrological model (WaSSI), we demonstrate that depletion of river flows across Western U.S. regions can be reduced on average by 6.2–23.2%, without reducing economic production. Lastly, we employ an environmentally extended input-output model to identify the U.S. industries and locations that can make the biggest impact by working with their suppliers to reduce water use 'upstream' in their supply chain. The agriculture and manufacturing sectors have the largest indirect water footprint due to their reliance on water-intensive inputs but these sectors also show the greatest capacity to reduce water consumption throughout their supply chains.

Conterminous United States↗
USGS2003

Temperature-pressure conditions in coalbed methane reservoirs of the Black Warrior basin: Implications for carbon sequestration and enhanced coalbed methane recovery

Sorption of gas onto coal is sensitive to pressure and temperature, and carbon dioxide can be a potentially volatile supercritical fluid in coalbed methane reservoirs. More than 5000 wells have been drilled in the coalbed methane fields of the Black Warrior basin in west-central Alabama, and the hydrologic and geothermic information from geophysical well logs provides a robust database that can be used to assess the potential for carbon sequestration in coal-bearing strata.Reservoir temperature within the coalbed methane target zone generally ranges from 80 to 125 ??F (27-52 ??C), and geothermal gradient ranges from 6.0 to 19.9 ??F/1000 ft (10.9-36.2 ??C/km). Geothermal gradient data have a strong central tendency about a mean of 9.0 ??F/1000 ft (16.4 ??C/km). Hydrostatic pressure gradients in the coalbed methane fields range from normal (0.43 psi/ft) to extremely underpressured (<0.05 psi/ft). Pressure-depth plots establish a bimodal regime in which 70% of the wells have pressure gradients greater than 0.30 psi/ft, and 20% have pressure gradients lower than 0.10 psi/ft. Pockets of underpressure are developed around deep longwall coal mines and in areas distal to the main hydrologic recharge zone, which is developed in structurally upturned strata along the southeastern margin of the basin.Geothermal gradients within the coalbed methane fields are high enough that reservoirs never cross the gas-liquid condensation line for carbon dioxide. However, reservoirs have potential for supercritical fluid conditions beyond a depth of 2480 ft (756 m) under normally pressured conditions. All target coal beds are subcritically pressured in the northeastern half of the coalbed methane exploration fairway, whereas those same beds were in the supercritical phase window prior to gas production in the southwestern half of the fairway. Although mature reservoirs are dewatered and thus are in the carbon dioxide gas window, supercritical conditions may develop as reservoirs equilibrate toward a normal hydrostatic pressure gradient after abandonment. Coal can hold large quantities of carbon dioxide under supercritical conditions, and supercritical isotherms indicate non-Langmiur conditions under which some carbon dioxide may remain mobile in coal or may react with formation fluids or minerals. Hence, carbon sequestration and enhanced coalbed methane recovery show great promise in subcritical reservoirs, and additional research is required to assess the behavior of carbon dioxide in coal under supercritical conditions where additional sequestration capacity may exist. ?? 2003 Elsevier Science B.V. All rights reserved.

International Journal of Coal Geology↗
USGS2020

Optimization of tidal marsh management at the Cape May and Supawna Meadows National Wildlife Refuges, New Jersey, through use of structured decision making

Structured decision making is a systematic, transparent process for improving the quality of complex decisions by identifying measurable management objectives and feasible management actions; predicting the potential consequences of management actions relative to the stated objectives; and selecting a course of action that maximizes the total benefit achieved and balances tradeoffs among objectives. The U.S. Geological Survey, in cooperation with the U.S. Fish and Wildlife Service, applied an existing, regional framework for structured decision making to develop a prototype tool for optimizing tidal marsh management decisions at the Cape May and Supawna Meadows National Wildlife Refuges in New Jersey. Refuge biologists, refuge managers, and research scientists identified multiple potential management actions to improve the ecological integrity of 13 marsh management units within the refuges and estimated the outcomes of each action in terms of performance metrics associated with each management objective. Value functions previously developed at the regional level were used to transform metric scores to a common utility scale, and utilities were summed to produce a single score representing the total management benefit that would be accrued from each potential management action. Constrained optimization was used to identify the set of management actions, one per marsh management unit, that would maximize total management benefits at different cost constraints at the refuge scale. Results indicated that, for the objectives and actions considered here, total management benefits may increase consistently up to approximately $ 785,000, but that further expenditures may yield diminishing return on investment. Management actions in optimal portfolios at total costs less than $ 785,000 included applying sediment to the marsh surface (thin layer deposition) in seven marsh management units, controlling the invasive reed Phragmites australis in four marsh management units, remediating hydrologic alterations in two marsh management units, and planting native vegetation in one marsh management unit. The management benefits were derived from expected improvements in the capacity for marsh elevation to keep pace with sea-level rise, increases in numbers of spiders (as an indicator of trophic health) and tidal marsh obligate birds, and increased cover of native vegetation. The prototype presented here provides a framework for decision making at the Cape May and Supawna Meadows National Wildlife Refuges that can be updated as new data and information become available. Insights from this process may also be useful to inform future habitat management planning at the refuges.

New Jersey↗
USGS1990

36C1 measurements and the hydrology of an acid injection site

In an area in western Tennessee (United States), an industrial firm is injecting acidic (pH = 0.1) iron chloride into permeable zones of carbonate rocks at depths ranging from 1000 to 2200 m below land surface. Overlying the injection zone at a depth of approximately 500 m below land surface is a regional fresh-water aquifer, the Knox aquifer. A study is currently underway to investigate whether the injection wells are hydraulically isolated from the fresh-water aquifer. Drilling of a test well that will reach a total depth of 2700 m has been initiated. The 36Cl content of 15 samples from the Knox aquifer, from monitor wells in the vicinity of the injection site, and from the test well have been analyzed. ?? 1990.

Nuclear Instruments and Methods in Physics Researc↗
USGS2003

Changes in the chemistry of lakes and precipitation in high-elevation national parks in the western United States, 1985–1999

High-elevation lakes in the western United States are sensitive to atmospheric deposition of sulfur and nitrogen due to fast hydrologic flushing rates, short growing seasons, an abundance of exposed bedrock, and a lack of well-developed soils. This sensitivity is reflected in the dilute chemistry of the lakes, which was documented in the U.S. Environmental Protection Agency's Western Lake Survey of 1985. Sixty-nine lakes in seven national parks sampled during the 1985 survey were resampled during fall 1999 to investigate possible decadal-scale changes in lake chemistry. In most lakes, SO 4 concentrations were slightly lower in 1999 than in 1985, consistent with a regional decrease in precipitation SO 4 concentrations and in SO 2 emissions in the western United States. Nitrate concentrations also tended to be slightly lower in 1999 than in 1985, in contrast with generally stable or increasing inorganic N deposition in the west. Differences in alkalinity were variable among parks but were relatively consistent within each park. Possible effects of annual and seasonal-scale variations in precipitation amount on lake chemistry were evaluated based on climate data available for the parks and an analysis of climatic effects at two research watersheds with long-term records. Results suggest that rain prior to sampling in 1985 may have caused elevated NO 3 in some lakes due to direct runoff of precipitation and flushing of NO 3 from alpine soils, which may explain some of the decrease in NO 3 concentrations observed in survey lakes.

Water Resources Research↗
USGS2007

Assessing the likely value of gravity and drawdown measurements to constrain estimates of hydraulic conductivity and specific yield during unconfined aquifer testing

Pumping of an unconfined aquifer can cause local desaturation detectable with high‐resolution gravimetry. A previous study showed that signal‐to‐noise ratios could be predicted for gravity measurements based on a hydrologic model. We show that although changes should be detectable with gravimeters, estimations of hydraulic conductivity and specific yield based on gravity data alone are likely to be unacceptably inaccurate and imprecise. In contrast, a transect of low‐quality drawdown data alone resulted in accurate estimates of hydraulic conductivity and inaccurate and imprecise estimates of specific yield. Combined use of drawdown and gravity data, or use of high‐quality drawdown data alone, resulted in unbiased and precise estimates of both parameters. This study is an example of the value of a staged assessment regarding the likely significance of a new measurement method or monitoring scenario before collecting field data.

Water Resources Research↗
USGS2008

A quantitative analysis of the Lassen hydrothermal system, north central California

Our conceptual model of the Lassen system is termed a liquid-dominated hydrothermal system with a parasitic vapor-dominated zone. The essential feature of this model is that steam and steam-heated discharge at relatively high altitudes in Lassen Volcanic National Park (LVNP) and liquid discharge with high chloride concentrations at relatively low altitudes outside LVNP are both fed by an upflow of high-enthalpy two-phase fluid within the Park. Liquid flows laterally away from the upflow area toward the areas of high-chloride discharge, and steam rises through a vapor-dominated zone to feed the steam and steam-heated features. Numerical simulations show that several conditions are necessary for the development of this type of system, including (1) large-scale topographic relief; (2) an initial period of convective heating within an upflow zone followed by (3) a change in hydrologic or geologic conditions that initiates drainage of liquid from portions of the upflow zone; and (4) low-permeability barriers that inhibit the movement of cold water into the vapor zone. Simulations of thermal fluid withdrawal south of LVNP, carried out in order to determine the effects of such withdrawal on portions of the hydrothermal system within the Park, generally showed decreases in pressure and liquid saturation beneath the vapor zone which resulted in temporary increases and subsequent decreases in the rate of upflow of steam. A generalized production-injection scenario that could mitigate the effects of development on both the high-chloride and steam-fed features was identified.

California↗
USGS1999

Isotopic composition of water in a deep unsaturated zone beside a radioactive-waste disposal area near Beatty, Nevada

The isotopic composition of water in deep unsaturated zones is of interest because it provides information relevant to hydrologic processes and contaminant migration. Profiles of oxygen-18 ( 18 O), deuterium (D), and tritium ( 3 H) from a 110-meter deep unsaturated zone, together with data on the isotopic composition of ground water and modern-day precipitation, are interpreted in the context of water-content, water-potential, and pore-gas profiles. At depths greater than about three meters, water vapor and liquid water are in approximate equilibrium with respect to D and 18 O. The vapor-phase concentrations of D and 18 O have remained stable through repeated samplings. Vapor-phase 3 H concentrations have generally increased with time, requiring synchronous sampling of liquid and vapor to assess equilibrium. Below 30 meters, concentrations of D and 18 O in pore water become approximately equal to the composition of ground water, which is isotopically lighter than modern precipitation and has a carbon-14 ( 14 C) concentration of about 26 percent modern carbon. These data indicate that net gradients driving fluxes of water, gas, and heat are directed upwards for undisturbed conditions at the Amargosa Desert Research Site (ADRS). Superimposed on the upward-directed flow field, tritium is migrating away from waste in response to gradients in tritium concentrations.

Nevada↗
USGS1996

The importance of floodplain forests in the conservation and management of neotropical migratory birds in the Midwest

Bottomland forests of the Central Forest Region of the Upper Midwest are found primarily on the floodplains of large rivers and include at least six types of forest communities. Birds breeding in bottomland forests are affected by extensive variation in latitude, climate, hydrology, forest succession, and change caused by anthropogenic disturbances. The floodplain forest bird community differs in species composition and in relative abundance from adjacent upland habitats. High abundances of some species are found in the floodplain and some species, such as the prothonotary warbler, brown creeper, yellow-billed cuckoo, yellow-bellied sapsucker, and great crested flycatcher, show a clear preference for floodplain forests. Studies of nesting success indicate that, for some species, nest success may be higher in the floodplain than in the uplands. Floodplain birds face threats due to large-scale loss of floodplain forest habitat. Conservation efforts should focus on restoring degraded floodplains by maintaining high tree species diversity and wide corridors. To accomplish this, the underlying hydrodynamics which support a diverse floodplain forest habitat may need to be restored. Large, contiguous tracts of floodplain and upland forests should be maintained where they exist and restored in other locations. This will provide some high quality habitat for area-sensitive neotropical migratory birds (NTMBs) in agricultural landscapes where small, scattered forest fragments are the rule. Future research efforts should examine the importance of floodplain forests in maintaining populations of neotropical migrants, especially birds experiencing population declines in adjacent uplands.

Book chapter↗