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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 199 records · Page 11Linked to original sources
USGS2014

Africa-wide monitoring of small surface water bodies using multisource satellite data: A monitoring system for FEWS NET

Continental Africa has the highest volume of water stored in wetlands, large lakes, reservoirs, and rivers, yet it suffers from problems such as water availability and access. With climate change intensifying the hydrologic cycle and altering the distribution and frequency of rainfall, the problem of water availability and access will increase further. Famine Early Warning Systems Network (FEWS NET) funded by the United States Agency for International Development (USAID) has initiated a large-scale project to monitor small to medium surface water points in Africa. Under this project, multisource satellite data and hydrologic modeling techniques are integrated to monitor several hundreds of small to medium surface water points in Africa. This approach has been already tested to operationally monitor 41 water points in East Africa. The validation of modeled scaled depths with field-installed gauge data demonstrated the ability of the model to capture both the spatial patterns and seasonal variations. Modeled scaled estimates captured up to 60 % of the observed gauge variability with a mean root-mean-square error (RMSE) of 22 %. The data on relative water level, precipitation, and evapotranspiration (ETo) for water points in East and West Africa were modeled since 1998 and current information is being made available in near-real time. This chapter presents the approach, results from the East African study, and the first phase of expansion activities in the West Africa region. The water point monitoring network will be further expanded to cover much of sub-Saharan Africa. The goal of this study is to provide timely information on the water availability that would support already established FEWS NET activities in Africa. This chapter also presents the potential improvements in modeling approach to be implemented during future expansion in Africa.

Book chapter↗
USGS2016

Patterns and controls on nitrogen cycling of biological soil crusts

Biocrusts play a significant role in the nitrogen [N ] cycle within arid and semi-arid ecosystems, as they contribute major N inputs via biological fixation and dust capture, harbor internal N transformation processes, and direct N losses via N dissolved, gaseous and erosional loss processes (Fig. 1). Because soil N availability in arid and semi-arid ecosystems is generally low and may limit net primary production (NPP), especially during periods when adequate water is available, understanding the mechanisms and controls of N input and loss pathways in biocrusts is critically important to our broader understanding of N cycling in dryland environments. In particular, N cycling by biocrusts likely regulates short-term soil N availability to support vascular plant growth, as well as long-term N accumulation and maintenance of soil fertility. In this chapter, we review the influence of biocrust nutrient input, internal cycling, and loss pathways across a range of biomes. We examine linkages between N fixation capabilities of biocrust organisms and spatio-temporal patterns of soil N availability that may influence the longer-term productivity of dryland ecosystems. Lastly, biocrust influence on N loss pathways such as N gas loss, leakage of N compounds from biocrusts, and transfer in wind and water erosion are important to understand the maintenance of dryland soil fertility over longer time scales. Although great strides have been made in understanding the influence of biocrusts on ecosystem N cycling, there are important knowledge gaps in our understanding of the influence of biocrusts on ecosystem N cycling that should be the focus of future studies. Because work on the interaction of N cycling and biocrusts was reviewed in Belnap and Lange (2003), this chapter will focus primarily on research findings that have emerged over the last 15 years (2000-2015).

Book chapter↗
USGS2020

Global islands

A new map of global islands at a high spatial resolution (30 m) has been produced from a semi-automated interpretation of 2014 satellite imagery. The data are available in the public domain. The islands were classified by size into continental mainlands (5), big islands > 1 km 2 (21,818), and small islands ≤ 1 km 2 (318,868). The new high-resolution islands data are intended to support coastal ecosystem mapping efforts and assessments of threatened island biodiversity, among other applications. This chapter summarizes the global island mapping approach and results.

Book chapter↗
USGS2021

Weathering of slags

Weathering is a natural process causing the transformation of minerals, rocks, and related materials like glass under near-surface conditions. Although metallurgical slags are human-made materials, they also undergo natural weathering processes. As base metal slags weather, the released solutions may contain contaminants that could pose an environmental risk. On the other hand, weathering of ferrous slags is important because of the common reuse of the slags. This chapter summarizes factors that affect rates of slag weathering as well as defining and characterizing the two stages of weathering (incipient and advanced) as they are observed in a wide variety of individual phases and slags. We conclude that slags weather at different scales and rates depending on their chemistry and phase composition as well as the external conditions. Furthermore, weathering of slags is a process that is not perfectly reflected by natural processes because these materials are complex (in terms of texture, composition, and disequilibrium with surficial conditions) and not always analogous to rocks. Therefore, some information in this chapter on weathering is applicable to all slag types, some is relevant to only specific slag types, and some aspects require additional study.

Book chapter↗
USGS1997

Distribution and mobility of molybdenum in the terrestrial environment

Molybdenum (Mo) is an essential element for many plants and animals (Newton and Otsuka, 1980). Because of its chemical properties, Mo readily provides sites for reactions and catalysis in biochemical systems (Haight and Boston, 1973). It is therefore important to understand the processes that control the distribution, speciation, and behavior of Mo in the surficial environment. These processes will affect the bioavalability of Mo and ultimately its passage into the food chain. In this chapter we discuss the distribution of Mo in the terrestrial environment and examine the factors that control its mobility.

Book chapter↗
USGS2012

Shrews, rats, and a polecat in "the pardoner’s tale"

While historically existing animals and literary animal characters inform allegorical and metaphorical characterization in The Canterbury Tales, figurative usage does not erase recognition of the material animal. "The Pardoner's Tale," for one, challenges the terms of conventional animal metaphors by refocusing attention on common animals as common animals and common human creatures as something worse than vermin. Most attention has been paid to the larger animals-goat, hare, and horse-that constitute the physical portrait of Chaucer's Pardoner in the "General Prologue" and in the prologue to his tale.! Like these animals, rats and a polecat, together with rhetorical shrews, appear in this tale as well as in other literature, including bestiaries and natural histories. Equally to the purpose, these animals could be physically observed as constituents of both urban and rural landscapes in fourteenth-century England.2 In the Middle Ages, animals were part of the environment as well as part of the culture: they lived inside as well as outside the city gates, priory walls, and even domestic spaces; a rat in the street or the garden might not be any less welcome or uncommon than encountering someone's horses and goats nibbling vegetation or blocking a passage. Not being out of the ordinary, though, such animals could (and can) be overlooked or dismissed as com­mon, too familiar to register. This chapter reveals why readers and listeners should pay close attention to the things they think they know and what they hear about what they think they know.

Book chapter↗
USGS1992

Breeding population inventories and measures of recruitment

In this chapter we review the techniques used to measure two important parameters of waterfowl populations, size of breeding population and recruitment. If waterfowl are to be managed toward goals defined in terms of population sizes such as those in the recently signed North American Waterfowl Management Plan (U.S. Fish and Wildlife Service [USFWS] and Canadian Wildlife Service [CWS] 1986), there must be some measure of population size for the various species. Waterfowl managers usually measure population size during the breeding season, although for some species and in some areas winter inventories may be used. Population size is a function of natality and mortality. Other chapters in this volume deal in detail with the biology of those processes. This chapter discusses procedural aspects of measurement and reviews some of the operational systems that have been used to estimate population size and recruitment, especially in North America.

Book chapter↗
USGS2000

Environmental contaminants

Throughout the world, individuals and populations of herons are affected by environmental contaminants, leading to direct mortality, decreased reproductive success, or degradation of feeding habitat. Contaminants suspected or known to affect herons include organochlorine compounds, organophosphorus insecticides, trace elements, and petroleum (Parnell et al. 1988).General reviews on the effects of pesticides on birds (Risebrough 1986, 1991) and colonial water birds (Nisbet 1980) are presented elsewhere. The objective of this chapter is to review toxic effects of contaminants on herons. Unless otherwise noted, contaminant concentrations are presented as parts per million (ppm) on a wet weight (ww) basis.

Book chapter↗
USGS2008

Solute transport along stream and river networks

This chapter contains sections titled: Introduction Review of current knowledge Linking transport processes with the fluvial geomorphic template Forward-looking perspective Acknowledgements References

Book chapter↗
USGS2017

Volcano crisis communication: Challenges and solutions in the 21st century

This volume, Observing the volcano world: volcanic crisis communication, focuses at the point where the ‘rubber hits the road’, where the world of volcano-related sciences and all its uncertainties meet with the complex and ever-changing dynamics of our society, wherever and whenever this may be. Core to the issues addressed in this book is the idea of how volcanic crisis communication operates in practice and in theory. This chapter provides an overview of the evolution of thinking around the importance of volcanic crisis communication over the last century, bringing together studies on relevant case studies. Frequently, the mechanisms by which volcanic crisis communication occurs are via a number of key tools employed including: risk assessment, probabilistic analysis, early-warning systems, all of which assist in the decision-making procedures; that are compounded by ever-changing societal demands and needs. This chapter outlines some of the key challenges faced in managing responses to volcanic eruptions since the start of the 20th century, to explore what has been effective, what lessons have been learnt from key events, and what solutions we can discover. Adopting a holistic approach, this chapter aims to provide a contextual background for the following chapters in the volume that explore many of the elements discussed here in further detail. Finally, we consider the future, as many chapters in this book bring together a wealth of new knowledge that will enable further insights for investigation, experimentation, and development of future volcanic crisis communication.

Book chapter↗
USGS2020

Financial risk innovation: Development of earthquake parametric triggers for contingent credit instruments

The Inter-American Development Bank (IDB) has developed financial risk management strategies for natural disasters focusing primarily on the emergency phase of the catastrophes where financial support is more cost-efficient and certainly most needed. The main IDB financial instrument to provide liquidity in the aftermath of catastrophic events is the Contingent Credit Facility (CCF). The CCF is a parametric financial insurance product that makes payments upon the occurrence of events of specific characteristics previously defined with the country. Specifically, in the case of earthquake coverage, the USGS and IDB have been collaborating together in order to improve the trigger design of the loans. CCF is now based on parametric triggers that correlate the magnitude, intensity, and population exposure of the event with the payments. This chapter presents the IDB journey to develop this state-of-the-art parametric index for CCF earthquakes pay offs.

Book chapter↗
USGS2013

Valley plugs, land use, and phytogeomorphic response: Chapter 14

Anthropogenic alteration of fluvial systems can disrupt functional processes that provide valuable ecosystem services. Channelization alters fluvial parameters and the connectivity of river channels to their floodplains which is critical for productivity, nutrient cycling, flood control, and biodiversity. The effects of channelization can be exacerbated by local geology and land-use activities, resulting in dramatic geomorphic readjustments including the formation of valley plugs. Considerable variation in the response of abiotic processes, including surface hydrology, subsurface hydrology, and sedimentation dynamics, to channelization and the formation of valley plugs. Altered abiotic processes associated with these geomorphic features and readjustments influence biotic processes including species composition, abundance, and successional processes. Considerable interest exists for restoring altered fluvial systems and their floodplains because of their social and ecological importance. Understanding abiotic and biotic responses of channelization and valley-plug formation within the context of the watershed is essential to successful restoration. This chapter focuses on the primary causes of valley-plug formation, resulting fluvial-geomorphic responses, vegetation responses, and restoration and research needs for these systems.

Book chapter↗
USGS2015

Why are freshwater fish so threatened?

The huge diversity of freshwater fishes is concentrated into an area of habitat that covers only about 1% of the Earth's surface, and much of this limited area has already been extensively impacted and intensively managed to meet human needs (Dudgeon et al ., 2006). As outlined in Chapter 1, the number and proportions of threatened species tend to rise wherever fish diversity coincides with dense human populations, intensive resource use and development pressure. Of particular concern is the substantial proportion of the global diversity of freshwater fishes concentrated within the Mekong and Amazon Basins and west-central Africa (Berra, 2001; Abell et al ., 2008; Dudgeon, 2011; Chapter 1) with extensive exploitation of water resources planned to accelerate in future years (Dudgeon, 2011; Chapter 1). If current trends continue, and the social, political and economic models that have been used to develop industrialised regions of the world over the past two centuries prevail, then the future of a significant proportion of global diversity of freshwater fish species is clearly uncertain. Understanding why so many freshwater fish species are threatened requires some understanding of their biology, diversity, distribution, biogeography and ecology, but also some appreciation of the social, economic and political forces that are causing humans to destroy the natural ecosystems upon which we all ultimately depend. To begin to understand the diversity of freshwater fishes, we first need to consider the processes that generated and continue to sustain the diversity of species we see today. Based on an understanding of how freshwater fish diversity is generated and sustained, we consider how vulnerable or resilient various freshwater fishes are to the range of anthropogenic impacts that impinge on freshwater ecosystems. Finally, we discuss how social, political and economic drivers influence human impacts on natural systems, and the changes needed to current models of development that can lead to a sustainable future for humans and the diverse range of freshwater fish species with which we share our planet. The aim of this chapter is to provide an overview of the key issues and threats driving the declines in freshwater fish diversity identified in Chapter 1; subsequent chapters provide more detail on the key issues and address our options for developing a sustainable future for freshwater fishes.

Book chapter↗
USGS2012

Ecological consequences of manipulative parasites

This chapter considers the context in which manipulative parasites could have noticeable ecological effects. By this, we mean that a manipulation of a host that benefits a parasite can also indirectly affect other non-hosts in the system, sometimes in dramatic fashion. Such ecosystem-level changes could occur for manipulative parasites that have a strong effect on their host, a high rate of infection, and infect hosts that play important roles in the ecosystem. With a series of examples from the literature, the chapter describes how manipulative parasites can sometimes have strong indirect ecological effects. Still, little is known about how often these effects occur in nature.

Book chapter↗
USGS2011

Simulating effects of microtopography on wetland specific yield and hydroperiod

Specific yield and hydroperiod have proven to be useful parameters in hydrologic analysis of wetlands. Specific yield is a critical parameter to quantitatively relate hydrologic fluxes (e.g., rainfall, evapotranspiration, and runoff) and water level changes. Hydroperiod measures the temporal variability and frequency of land-surface inundation. Conventionally, hydrologic analyses used these concepts without considering the effects of land surface microtopography and assumed a smoothly-varying land surface. However, these microtopographic effects could result in small-scale variations in land surface inundation and water depth above or below the land surface, which in turn affect ecologic and hydrologic processes of wetlands. The objective of this chapter is to develop a physically-based approach for estimating specific yield and hydroperiod that enables the consideration of microtopographic features of wetlands, and to illustrate the approach at sites in the Florida Everglades. The results indicate that the physically-based approach can better capture the variations of specific yield with water level, in particular when the water level falls between the minimum and maximum land surface elevations. The suggested approach for hydroperiod computation predicted that the wetlands might be completely dry or completely wet much less frequently than suggested by the conventional approach neglecting microtopography. One reasonable generalization may be that the hydroperiod approaches presented in this chapter can be a more accurate prediction tool for water resources management to meet the specific hydroperiod threshold as required by a species of plant or animal of interest.

Book chapter↗
USGS2024

Partitioning of chemicals in aquatic organisms

Human populations have utilized heavy metals and persistent organic pollutants for their physiochemical properties in industrial, agricultural, and consumer goods for decades. Limited knowledge on their persistence and toxicological effects has resulted in organisms being exposed to some of the most problematic compounds ever generated by humans. Although overlap in exposure paradigms exists for historical and emerging contaminants, the different physiochemical properties, sources into the environment, and bioactivity of contaminants of emerging concern (CECs) have highlighted the importance of characterizing their risk to aquatic wildlife under chronic low-dose exposure scenarios. This chapter defines the fundamental terminology associated with characterizing the exposure paradigm in ecological risk assessment. The different sources and fate, routes of exposure, and biotransformation of common contaminants are covered using model chemicals to emphasize important factors that affect their partitioning among different environmental matrices. Finally, this chapter concludes with a discussion about bioaccumulation models and an example of how two similar CECs demonstrate different clearance rates and bioaccumulation potentials in fish.

Book chapter↗
USGS2014

Dust and human health

It is generally accepted that exposure to fine particulate matter may increase risk for human morbidity and mortality. Until recently, population health related studies examining the effects of particulate matter on human health generally examined anthropogenic (industry and combustion by-products) sources with few studies considering contributions from natural sources. This chapter provides an overview of naturally occurring inorganic mineral dust research and associated human health ailments and some of the challenges in elucidating the etiological mechanisms responsible.

Book chapter↗