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At least 199 records · Page 11Linked to original sources
USGS2012

Recent advances in simulation-optimization groundwater management modeling

In recent years, the aquifer simulation model has been combined with techniques of optimization to address important groundwater management problems. The combined simulation and optimization model accounts for the complex behavior of the groundwater system and identifies the best management strategy under consideration of the management objectives and constraints. Simulation-optimization groundwater management models have been developed for a variety of applications, such as restoration of contaminated groundwater, control of aquifer hydraulics, allocation of ground and surface water resources, and evaluation of groundwater policies [see reviews by Gorelick , 1983, 1990; Yeh , 1992; Ahlfeld and Heidari , 1994; Bredehoeft et al , 1994]. Gorelick [1983] divides groundwater management models into three categories: groundwater hydraulic management, groundwater quality management, and groundwater policy evaluation and allocation. This review focuses in detail on the recent advances made in groundwater hydraulic and groundwater quality management modeling, which encompasses most of the aquifer management work done in the past four years. For a review of recent research in groundwater policy evaluation and allocation, see Bredehoeft et al . [1994].

Reviews of Geophysics↗
USGS2021

Time to refine mercury mass balance models for fish

Mercury mass balance models (MMBMs) for fish are powerful tools for understanding factors affecting growth and food consumption by free-ranging fish in rivers, lakes, and oceans. Moreover, MMBMs can be used to predict the consequences of global mercury reductions, overfishing, and climate change on mercury (Hg) concentration in commercially and recreationally valuable species of fish. Such predictions are useful in decision-making by resource managers and public health policy makers, because mercury is a neurotoxin and the primary route of exposure of mercury to humans is via consumption of fish. Recent evidence has emerged to indicate that the current-day version of MMBMs overestimates the rate at which fish eliminate mercury from their bodies. Consequently, MMBMs overestimate food consumption by fish and underestimate Hg concentration in fish. In this perspective, we explore underlying reasons for this overestimation of Hg-elimination rate, as well as consequences and implications of this overestimation. We highlight emerging studies that distinguish species and sex as contributing factors, in addition to body weight and water temperature, that can play an important role in how quickly Hg is eliminated from fish. Future research directions for refining MMBMs are discussed.

Facets↗
USGS2005

Tamarisk tensions

In the August 2005 feature article, “Tiff over Tamarisk: Can a Nuisance Be Nice, Too?” the author raises several issues about which there is currently scientific debate, and presents some of the differing perspectives. A phenomenon surrounding discussions of tamarisk in the West is revealed and reinforced in the article—the polarized nature of the debate. Over the years, this polarization has fueled acrimonious exchanges between scientists and led to confusion regarding the effects of tamarisk, thus hindering the ability of resource managers to formulate clear policies for managing this species. Unfortunately, the author has perpetuated the polarized nature of the tamarisk debate by labeling two camps—“revisionists” and “traditionalists.”

BioScience↗
USGS1999

Consumption of rainbow smelt by walleye and salmonine fishes in eastern Lake Erie

At present, rainbow smelt appear to represent a key component of the eastern Lake Erie fish community as they are the dominant prey for virtually every open water predator, and are harvested directly by an important Ontario commercial fishery. In response to concern over the status of rainbow smelt in eastern Lake Erie, our objective was to quantify some primary top down forces of rainbow smelt mortality that include walleyes (Stizostedion vitreum), five stocked salmonine fishes, and the commercial fishery. This objective was to satisfy a need to understand whether consumption by the major fish predators was significant relative to the measured commercial harvest of rainbow smelt. Achieving this knowledge may provide fisheries managers with an improved basis for managing the rainbow smelt resource through adjustments to stocking policies and/or commercial fishing quotas.

Book chapter↗
USGS2011

Informal trail monitoring protocols: Denali National Park and Preserve

The National Park Service (NPS) accommodates nearly 300 million visitors per year, visitation that presents managers with substantial challenges at some 394 park units across some 83.6 million acres of protected lands. An increasing number of visitors inevitably contribute negative effects to fragile natural and cultural resources. Such visitation - related resource impacts can degrade natural conditions and processes and the quality of recreation experiences. According to the NPS Management Policies: ―The fundamental purpose of the national park system , established by the Organic Act and reaffirmed by the General Authorities Act, as amended, begins with a mandate to conserve park resources and values...The fundamental purpose of all parks also includes providing for the enjoyment of park resources and values by the people of the United States.‖ (NPS 2006 b , Section 1.4.3). However, what might appear to be dual mandates, visitation and resource protection, are clarified to reveal the primacy of resource protection. The Management Policies acknowledge that so me resource degradation is an inevitable consequence of visitation, but directs managers to ―ensure that any adverse impacts are the minimum necessary, unavoidable, cannot be further mitigated, and do not constitute impairment or derogation of park resources and values‖ (NPS 2006 b ).

Alaska↗
USGS2011

Geochemical database of feed coal and coal combustion products (CCPs) from five power plants in the United States

The principal mission of the U.S. Geological Survey (USGS) Energy Resources Program (ERP) is to (1) understand the processes critical to the formation, accumulation, occurrence, and alteration of geologically based energy resources; (2) conduct scientifically robust assessments of those resources; and (3) study the impacts of energy resource occurrence and (or) their production and use on both the environment and human health. The ERP promotes and supports research resulting in original, geology-based, non-biased energy information products for policy and decision makers, land and resource managers, other Federal and State agencies, the domestic energy industry, foreign governments, non-governmental groups, and academia. Investigations include research on the geology of oil, gas, and coal, and the impacts associated with energy resource occurrence, production, quality, and utilization. The ERP's focus on coal is to support investigations into current issues pertaining to coal production, beneficiation and (or) conversion, and the environmental impact of the coal combustion process and coal combustion products (CCPs). To accomplish these studies, the USGS combines its activities with other organizations to address domestic and international issues that relate to the development and use of energy resources.

Data Series↗
USGS2007

Fly Ash: From Cradle to Grave

The Energy Resources Program of the U.S. Geological Survey promotes and supports coal research to improve the understanding of the coal endowment of the United States. This results in geologically based, non-biased energy information products for policy and decision makers, land and resource managers, other federal and state agencies, the domestic energy industry, foreign governments, nongovernmental groups, academia, and other scientists. A more integrated approach to our coal quality work involves what we call a 'cradle to grave' approach. These types of studies focus not on just one aspect of the coal but rather on how or where different quality parameters form and (or) occur and what happens to them through the mining, production, transport, utilization and waste disposal process. An extensive suite of coal quality analyses, mineralogical, petrology, and leaching investigations are determined on samples taken from the different phases of the coal utilization process. This report consists of a tutorial that was given on June 10, 2007 at the 32nd International Technical Conference on Coal Utilization & Fuel Systems, The Power of Coal, Clearwater Coal Conference in Clearwater, Florida, USA. This tutorial covers how these studies are conducted and the importance of providing improved, comprehensive, science-based data sets for policy and decision makers.

Open-File Report↗
USGS2021

An assessment of the economic potential of lignite and leonardite resources in the Williston Basin, North Dakota

The Bureau of Land Management (BLM) requested assistance from the U.S. Geological Survey (USGS) to conduct an assessment study to identify areas that may have economic potential for the future extraction of lignite and leonardite resources in the Williston Basin in North Dakota. The study will be used by the BLM to assist with the preparation of a revised resource management plan for the Williston Basin, in accordance with BLM planning policies. The assessment of the economic potential of lignite resources required the establishment of criteria defining an economic lignite deposit. In consultation with the BLM, criteria were established to delineate drill holes that contained economic lignite beds. The criteria established are a minimum lignite bed thickness, a minimum cumulative lignite thickness, a maximum cumulative stripping ratio, and a maximum overburden. Likewise, an assessment of the economic potential of leonardite deposits required the establishment of criteria delineating drill holes that contained economic leonardite deposits. The criteria established are a minimum leonardite bed thickness, a minimum cumulative leonardite thickness, and a maximum overburden. The drill hole data utilized in this study were obtained from the National Coal Resources Data System database and from several coal companies. Data from more than 20,000 drill holes, both proprietary and nonproprietary, were used to compile areas of economic potential for lignite or leonardite. Areas delineated as having lignite or leonardite resources with economic potential, based on the established criteria, were present in 24 counties in the western portion of North Dakota. Areas of economic potential were delineated using a visual best-fit method without croplines. Areas defined as having economic potential for certain lignite beds or leonardite deposits may extend beyond known croplines in this study. Stratigraphically, the lignite and leonardite deposits in the Williston Basin in North Dakota are mostly found in the Paleocene Fort Union Formation. Thick (greater than 20 feet) and laterally extensive (greater than 5 square miles) lignite beds are present in the Fort Union Formation throughout the Sentinel Butte and Tongue River Members. Lignite beds are also present in the Ludlow Member of the Fort Union Formation, although they are not as numerous or thick as they are in the overlying Sentinel Butte and Tongue River Members. As a result of lateral facies changes and migrating fluvial channel complexes in the Fort Union Formation, lignite beds of varying thickness occupy different stratigraphic horizons vertically throughout the Williston Basin. The calculation of volumes for lignite and leonardite resources was not part of the scope of this study requested by the BLM, but a future study by the USGS may involve a comprehensive assessment of lignite resources and reserves in the Williston Basin. This future study could combine geologic data compiled in this study with geologic data from a previously unpublished 2019 assessment study by the USGS in the Williston Basin in eastern Montana. This future USGS study could also include the calculation of volumes for lignite resources and reserves, based on economic models derived using analogs from active mining operations in the Williston Basin and available spot market or contract coal prices.

North Dakota↗
USGS2002

Surface-water quality-assurance plan for the Wisconsin district of the U. S. Geological Survey, Water Resources Division

This surface-water quality-assurance plan documents the standards, policies, and procedures used by the Wisconsin District of the U.S. Geological Survey, Water Resources Division, for activities related to the collection, processing, storage, analysis, management, and publication of surface-water data. The roles and responsibilities of District personnel in following these policies and procedures including those related to safety and training are presented.

Wisconsin↗
USGS2001

Alaska: A twenty-first-century petroleum province

Alaska, the least explored of all United States regions, is estimated to contain approximately 40% of total U.S. undiscovered, technically recoverable oil and natural-gas resources, based on the most recent U.S. Department of the Interior (U.S. Geological Survey and Minerals Management Service) estimates. Northern Alaska, including the North Slope and adjacent Beaufort and Chukchi continental shelves, holds the lion's share of the total Alaskan endowment of more than 30 billion barrels (4.8 billion m 3 ) of oil and natural-gas liquids plus nearly 200 trillion cubic feet (5.7 trillion m 3 ) of natural gas. This geologically complex region includes prospective strata within passive-margin, rift, and foreland-basin sequences. Multiple source-rock zones have charged several regionally extensive petroleum systems. Extensional and compressional structures provide ample structural objectives. In addition, recent emphasis on stratigraphic traps has demonstrated significant resource potential in shelf and turbidite systems in Jurassic to Tertiary strata. Despite robust potential, northern Alaska remains a risky exploration frontier - a nexus of geologic complexity, harsh economic conditions, and volatile policy issues. Its role as a major petroleum province in this century will depend on continued technological innovations, not only in exploration and drilling operations, but also in development of huge, currently unmarketable natural-gas resources. Ultimately, policy decisions will determine whether exploration of arctic Alaska will proceed.

Alaska↗
USGS2006

The World Coal Quality Inventory: South America

Executive Summary-Introduction: The concepts of a global environment and economy are strongly and irrevocably linked to global energy issues. Worldwide coal production and international coal trade are projected to increase during the next several decades in an international energy mix that is still strongly dependent on fossil fuels. Therefore, worldwide coal use will play an increasingly visible role in global environmental, economic, and energy forums. Policy makers require information on coal, including coal quality data, to make informed decisions regarding domestic coal resource allocation, import needs and export opportunities, foreign policy objectives, technology transfer policies, foreign investment prospects, environmental and health assessments, and byproduct use and disposal issues. The development of a worldwide, reliable, coal quality database would help ensure the most economically and environmentally efficient global use of coal. The U.S. Geological Survey (USGS), in cooperation with many agencies and scientists from the world's coal producing countries, originally undertook a project to obtain representative samples of coal from most of the world's producing coal provinces during a limited period of time (roughly 1998-2005), which is called the World Coal Quality Inventory (WoCQI). The multitude of producing coal mines, coal occurrences, or limited accessibility to sites in some countries can preclude collecting more than a single sample from a mine. In some areas, a single sample may represent an entire coal mining region or basin. Despite these limitations in sampling and uneven distribution of sample collection, the analytical results can still provide a general overview of world coal quality. The USGS intends to present the WoCQI data in reports and, when possible, in Geographic Information System (GIS) products that cover important coal bearing and producing regions.

Open-File Report↗
USGS1980

Competition and performance in OCS oil and gas lease sales and lease development, 1954-1969

The oil and gas resources of the Outer Continental Shelf represent one of America's largest publicly-owned assets. Through 1978, OCS oil and gas leases had yielded \$40.5 billion in gross production value and produced over \$28.3 billion in direct revenue to the federal government. Policies and procedures for managing the oil and gas resources of the OCS were established by Congress in the Outer Continental Shelf Lands Act of 1953. The Department of Interior was given the central responsibility for carrying out this management role in the 1953 Act; this responsibility has been re-established in the 1978 Amendments to the OCS Lands Act. As stated in the 1978 legislation, the goals of OCS management are to: ...preserve, protect and develop oil and natural gas resources in a manner which is consistent with the need (A) to make such resources available to meet the Nation's energy needs as rapidly as possible... (C) to insure the public a fair and equitable return on the resources of the Outer Continental Shelf, and (D) to preserve and maintain free enterprise competition. As part of its continuing effort to monitor the effectiveness of federal policies relating to OCS oil and gas resources, the Conservation Division of U.S. Geological Survey, Department of Interior, has sponsored the research which is the basis for the present report. The objectives of the research have been to determine the extent to which the historical policies of OCS management have resulted in achievement of the goals set forth by Congress in the section quoted above.

Open-File Report↗
USGS2010

Design of Cycle 3 of the National Water-Quality Assessment Program, 2013-2022: Part 1: Framework of Water-Quality Issues and Potential Approaches

In 1991, the U.S. Congress established the U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) Program to develop long-term, nationally consistent information on the quality of the Nation's streams and groundwater. Congress recognized the critical need for this information to support scientifically sound management, regulatory, and policy decisions concerning the increasingly stressed water resources of the Nation. The long-term goals of NAWQA are to: (1) assess the status of water-quality conditions in the United States, (2) evaluate long-term trends in water-quality conditions, and (3) link status and trends with an understanding of the natural and human factors that affect water quality. These goals are national in scale, include both surface water and groundwater, and include consideration of water quality in relation to both human uses and aquatic ecosystems. Since 1991, NAWQA assessments and findings have fostered and supported major improvements in the availability and use of unbiased scientific information for decisionmaking, resource management, and planning at all levels of government. These improvements have enabled agencies and stakeholders to cost-effectively address a wide range of water-quality issues related to natural and human influences on the quality of water and potential effects on aquatic ecosystems and human health (http://water.usgs.gov/nawqa/xrel.pdf). NAWQA, like all USGS programs, provides policy relevant information that serves as a scientific basis for decisionmaking related to resource management, protection, and restoration. The information is freely available to all levels of government, nongovernmental organizations, industry, academia, and the public, and is readily accessible on the NAWQA Web site and other diverse formats to serve the needs of the water-resource community at different technical levels. Water-quality conditions in streams and groundwater are described in more than 1,700 publications (available online at http://water.usgs.gov/nawqa/bib/), and are documented by more than 14 million data records representing about 7,600 stream sites, 8,100 wells, and 2,000 water-quality and ecological constituents that are available from the NAWQA data warehouse (http://infotrek.er.usgs.gov/traverse/f?p=NAWQA:HOME:0). The Program promotes collaboration and liaison with government officials, resource managers, industry representatives, and other stakeholders to increase the utility and relevance of NAWQA science to decisionmakers. As part of this effort, NAWQA supports integration of data from other organizations into NAWQA assessments, where appropriate and cost-effective, so that more comprehensive findings are available across geographic and temporal scales.

Open-File Report↗
USGS2017

Scientific monitoring plan in support of the selected alternative of the Glen Canyon Dam Long-Term Experimental and Management Plan

Introduction The purpose of this document is to describe a strategy by which monitoring and research data in the natural and social sciences will be collected, analyzed, and provided to the U.S. Department of the Interior (DOI), its bureaus, and to the Glen Canyon Dam Adaptive Management Program (GCDAMP) in support of implementation of the Glen Canyon Dam Long-Term Experimental and Management Plan (LTEMP) (U.S. Department of the Interior, 2016a). The selected alternative identified in the LTEMP Record of Decision (ROD) (U.S. Department of the Interior, 2016b) describes various data collection, analysis, modeling, and interpretation efforts to be conducted by the U.S. Geological Survey’s (USGS) Grand Canyon Monitoring and Research Center (GCMRC), partner agencies, and cooperators that will inform decisions about operations of Glen Canyon Dam and management of downstream resources between 2017 and 2037, the performance period of the LTEMP. General data collection, analysis, modeling, and interpretation activities are described in this science plan, whereas specific monitoring and research activities and detailed study plans are to be described in the GCDAMP’s triennial work plans (TWPs) to be developed by the Bureau of Reclamation and GCMRC with input from partner agencies and cooperators during the LTEMP period, which are to be reviewed and recommended by the GCDAMP and approved by the Secretary of the Interior. The GCDAMP consists of several components, the primary committee being the Adaptive Management Work Group (AMWG). This Federal advisory committee is composed of 25 agencies and stakeholder groups and is chaired by the Secretary of the Interior’s designee. The AMWG makes recommendations to the Secretary of the Interior concerning operations of Glen Canyon Dam and other experimental management actions that are intended to fulfill some obligations of the Grand Canyon Protection Act of 1992. The Technical Work Group (TWG) is a subcommittee of the AMWG and provides technical advice to the AMWG. It is composed of technical and science representatives from the same agencies and stakeholder groups who serve on the AMWG. GCMRC is the primary science provider to the GCDAMP and also coordinates many aspects of the science performed by cooperators and partner agencies. The Science Advisors Program provides independent science reviews and advice at the request of the GCDAMP. The plan proposed here necessarily depends on (1) the protocol for decision-making and the requirements for scientific data reporting described in the LTEMP ROD, (2) the priorities of the GCDAMP as directed by the LTEMP ROD (see Department of the Interior, 2016b, section 6.1), (3) the priorities for monitoring and research in the conservation measures section of the Biological Opinion for the LTEMP (U.S. Department of the Interior, 2016b, LTEMP ROD attachment E), (4) the priorities for resource management and information needs established by Federal and State resource-management agencies within the GCDAMP, (5) scientific understanding about the linkage between the status of those resources and operations of Glen Canyon Dam, and (6) the need to resolve existing scientific uncertainties about the linkage between dam operations and the condition of resources. We note that resource-management prioritization is fundamentally a policy decision charged specifically to DOI for the Colorado River in Glen and Grand Canyons, as outlined most recently in the LTEMP ROD, and is not the responsibility of the GCMRC. However, it is the responsibility of the GCMRC to describe the nature of scientific understanding, the nature of scientific uncertainty, and the risk of making resourcemanagement decisions in the face of existing scientific uncertainty. The goals of science activities in the next 20 years are to inform operational decisions regarding Glen Canyon Dam operations described in the LTEMP ROD, resolve remaining scientific uncertainties, and to monitor resource trends that are affected entirely, or in part, by dam operations.

Open-File Report↗
USGS2018

Science for a risky world—A U.S. Geological Survey plan for risk research and applications

Executive Summary Natural hazards—including earthquakes, tsunamis, volcanic eruptions, landslides, hurricanes, droughts, floods, wildfires, geomagnetic storms, and pandemics—can wreak havoc on human communities, the economy, and natural resources for years following an initial event. Hazards can claim lives and cause billions of dollars in damage to homes and infrastructure as well as lost or compromised economic activity and threats to national security. They also can have adverse environmental, social, economic, and health effects that extend well beyond the immediate area, sometimes with global implications. Changes in population growth, climate, and urbanization may exacerbate hazard impacts. Because of the potential severity of a single hazard event, reducing risk—the potential loss of societally important assets caused by these hazards—is a high priority for everyone, including policy makers, community members, emergency managers, resource managers, utility operators, business owners, and planners. These stakeholders demand usable, user-centric information to support decisions for planning a resilient future and for responding to and recovering from unanticipated events in more adaptable and cost-effective ways. Meeting this demand requires maximizing the use of environmental observations; hazards science; and research on communications, social stressors, and human behavior to deliver risk information in forms that are accessible by decision makers and the public alike. To achieve this, scientists and stakeholders must collaborate to match community needs with actionable insights, research, products, and tools, using advances in technology to improve information discovery and delivery.

Circular↗
USGS1976

An environmental assessment of impacts of coal development on the water resources of the Yampa River basin, Colorado and Wyoming; Phase I work plan

Coal resources of the western United States are being developed at ever-increasing rates, causing concerns of the effects of mining and associated activities on the environment. The Yampa River basin in northwestern Colorado and south-central Wyoming is undergoing economic development of its coal, oil and gas, and uranium resources. The Yampa River basin assessment is a 21-year program of the U.S. Geological Survey. It is designed primarily to assess the availability and quality of the basin's water resources. The basin assessment also will evaluate potential environmental and selected socioeconomic impacts of energy-resource development plans proposed by mining and power companies. This report serves as a project work plan for the basin assessment's first-phase work activities. Economic development in the Yampa River basin will result in higher levels of residuals (noneconomic byproducts) being discharged into the environment. Residuals-management encompasses the technological and economic interrelationships that should be considered in order to comply with Federal and State environmental-control regulations regarding air quality, water quality, and disposal of solid wastes. The basin assessment, the first phase that is described by this report, is designed to provide Federal, State, and local decision-makers with the basic environmental information needed to formulate and to evaluate policies for the development of energy resources. The techniques applied and conclusions reached in the Yampa River basin assessment should aid similar studies of other energy-rich basins in the western United States.

Colorado, Wyoming↗
USGS1976

An environmental assessment of impacts of coal development on the water resources of the Yampa River basin, Colorado and Wyoming; Phase II work plan

Coal resources of the western United States are being developed at everincreasing rates, causing concerns of the effects of mining and associated activities on the environment. The Yampa River basin in northwestern Colorado and south-central Wyoming is undergoing economic development of its coal, oil and gas, and uranium resources. By 1990, the annual coal mining in the basin is expected to increase to 20 million tons (18 million tonnes), or more than 4 times the 1975 level. As a result, the regional population is expected to at least double over the same period. Power-generation plants fueled by coal are being expanded or constructed in the basin and will have a combined generating capacity of nearly 1,200 megawatts by 1980. The Yampa River Basin Assessment is a 2-year program of the U.S. Geological Survey. It is designed primarily to assess the availability and quality of the basin's water resources. The basin assessment also will evaluate potential environmental and selected socioeconomic impacts of energy-resource development plans proposed by mining and power companies. This report serves as a project work plan for the basin assessment. It describes the program objectives, and the various approaches of analysis and evaluation. Environmental studies are outlined for analyzing both the direct effects of various proposals regarding coal mining, transportation, and conversion, and the secondary effects resulting from increased population and urban growth. Economic development in the Yampa River basin will generate higher levels of residuals which are discharged into the environment. Residuals-management encompasses the technological and economic interrelationships that should be considered to comply with Federal and State environmental-control regulations regarding air quality, water quality, and disposal of solid wastes. The basin assessment described by this report is designed to provide Federal, State, and local decision-makers with the basic environmental information needed to formulate and to evaluate policies for the development of energy resources. The techniques applied and conclusions reached in the Yampa River Basin Assessment should aid similar studies in other energy-rich basins in the western United States.

Colorado, Wyoming↗
USGS2003

Assessment of selected inorganic constituents in streams in the Central Arizona Basins study area, Arizona and northern Mexico, through 1998

Stream properties and water-chemistry constituent concentrations from data collected by the National Water-Quality Assessment and other U.S. Geological Survey water-quality programs were analyzed to (1) assess water quality, (2) determine natural and human factors affecting water quality, and (3) compute stream loads for the surface-water resources in the Central Arizona Basins study area. Stream temperature, pH, dissolved-oxygen concentration and percent saturation, and dissolved-solids, suspended-sediment, and nutrient concentration data collected at 41 stream-water quality monitoring stations through water year 1998 were used in this assessment. Water-quality standards applicable to the stream properties and water-chemistry constituent concentration data for the stations investigated in this study generally were met, although there were some exceedences. In a few samples from the White River, the Black River, and the Salt River below Stewart Mountain Dam, the pH in reaches designated as a domestic drinking water source was higher than the State of Arizona standard. More than half of the samples from the Salt River below Stewart Mountain Dam and almost all of the samples from the stations on the Central Arizona Project Canal—two of the three most important surface-water sources used for drinking water in the Central Arizona Basins study area—exceeded the U.S. Environmental Protection Agency drinking water Secondary Maximum Contaminant Level for dissolved solids. Two reach-specific standards for nutrients established by the State of Arizona were exceeded many times: (1) the annual mean concentration of total phosphorus was exceeded during several years at stations on the main stems of the Salt and Verde Rivers, and (2) the annual mean concentration of total nitrogen was exceeded during several years at the Salt River near Roosevelt and at the Salt River below Stewart Mountain Dam. Stream properties and water-chemistry constituent concentrations were related to streamflow, season, water management, stream permanence, and land and water use. Dissolved-oxygen percent saturation, pH, and nutrient concentrations were dependent on stream regulation, stream permanence, and upstream disposal of wastewater. Seasonality and correlation with streamflow were dependant on stream regulation, stream permanence, and upstream disposal of wastewater. Temporal trends in streamflow, stream properties, and water-chemistry constituent concentrations were common in streams in the Central Arizona Basins study area. Temporal trends in the streamflow of unregulated perennial reaches in the Central Highlands tended to be higher from 1900 through the 1930s, lower from the 1940s through the 1970s, and high again after the 1970s. This is similar to the pattern observed for the mean annual precipitation for the Southwestern United States and indicates long-term trends in flow of streams draining the Central Highlands were driven by long-term trends in climate. Streamflow increased over the period of record at stations on effluent-dependent reaches as a result of the increase in the urban population and associated wastewater returns to the Salt and Gila Rivers in the Phoenix metropolitan area and the Santa Cruz River in the Tucson metropolitan area. Concentrations of dissolved solids decreased in the Salt River below Stewart Mountain Dam and in the Verde River below Bartlett Dam. This decrease represents an improvement in the water quality and resulted from a concurrent increase in the amount of runoff entering the reservoirs. Stream loads of water-chemistry constituents were compared at different locations along the streams with one another, and stream loads were compared to upstream inputs of the constituent from natural and anthropogenic sources to determine the relative importance of different sources and to determine the fate of the water-chemistry constituent. Of the dissolved solids transported into the Basin and Range Lowlands each year from the Central Arizona Project Canal and from streams draining the Central Highlands, about 1.2 billion kilograms accumulated in the soil, unsaturated zone, and aquifers in agricultural and urban areas as a result of irrigating crops and urban vegetation. Stream loads of phosphorus decreased from the 91st Avenue Wastewater-Treatment Plant downstream to the Gila River at Gillespie Dam, probably as a result of adsorption of phosphorus to the streambed sediments. In this same reach, stream loads of nitrogen increased, most likely because of inputs from fertilizers. The annual mass of nitrogen and phosphorus input to developed basins from quantifiable sources was much larger than the mass input to basins that had little or no municipal or agricul-tural development. These computed inputs exclude the mass of nitrogen and phosphorus from sources such as geologic formations and soils that could not be quantified. The quantifiable annual inputs of nitrogen and phosphorus for the upper Salt River Basin and the upper Verde River Basin were similar to those for the West Clear Creek Basin. This similarity suggests that the small amount of municipal and agricultural development in the upper Salt River and the upper Verde River Basins did not greatly change the basin input flux. For basins with minimal urban and agricultural development, the largest quantifiable source of nitrogen was precipitation, and the largest source of phosphorus was human bodily waste treated by sewer and septic systems. This was in contrast to developed basins, for which fertilizer was the largest quantifiable source of both nutrients. For most basins examined, quantifiable inputs of nitrogen and phosphorus from nonpoint sources were greater than inputs from point sources. This relation emphasizes the importance of land- and water-management policies that protect surface-water resources from nonpoint sources of nutrients as well as from point sources. The amount of nitrogen and phosphorus transpor-ted out of basins was a small fraction of the total for the quantifiable inputs. This result indicated that most of the nutrients input to basins were not transported out of the basins in surface water, but rather were transported to the subsurface (the soil, unsaturated zone, or aquifer), released to the atmosphere (such as volatilized ammonia), or incorporated into the biomass.

Central Arizona Basins study area↗