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USGS2022

Fifty years of Landsat science and impacts

Since 1972, the Landsat program has been continually monitoring the Earth, to now provide 50 years of digital, multispectral, medium spatial resolution observations. Over this time, Landsat data were crucial for many scientific and technical advances. Prior to the Landsat program, detailed, synoptic depictions of the Earth's surface were rare, and the ability to acquire and work with large datasets was limited. The early years of the Landsat program delivered a series of technological breakthroughs, pioneering new methods, and demonstrating the ability and capacity of digital satellite imagery, creating a template for other global Earth observation missions and programs. Innovations driven by the Landsat program have paved the way for subsequent science, application, and policy support activities. The economic and scientific value of the knowledge gained through the Landsat program has been long recognized, and despite periods of funding uncertainty, has resulted in the program's 50 years of continuity, as well as substantive and ongoing improvements to payload and mission performance. Free and open access to Landsat data, enacted in 2008, was unprecedented for medium spatial resolution Earth observation data and substantially increased usage and led to a proliferation of science and application opportunities. Here, we highlight key developments over the past 50 years of the Landsat program that have influenced and changed our scientific understanding of the Earth system. Major scientific and programmatic impacts have been realized in the areas of agricultural crop mapping and water use, climate change drivers and impacts, ecosystems and land cover monitoring, and mapping the changing human footprint. The introduction of Landsat collection processing, coupled with the free and open data policy, facilitated a transition in Landsat data usage away from single images and towards time series analyses over large areas and has fostered the widespread use of science-grade data. The launch of Landsat-9 on September 27, 2021, and the advanced planning of its successor mission, Landsat-Next, underscore the sustained institutional support for the program. Such support and commitment to continuity is recognition of both the historic impact the program, and the future potential to build upon Landsat's remarkable 50-year legacy.

Remote Sensing of Environment↗

USGS2022

Holocene paleohydrology from alpine lake sediment, Emerald Lake, Wasatch Plateau of central Utah, USA

Holocene sediments at Emerald Lake in central Utah (3090 m asl) document the paleohydroclimatic history of the western Upper Colorado River headwater region. Multi-proxy analyses of sediment composition, mineralogy, and stable isotopes of carbonate (δ 18 O and δ 13 C) show changes in effective moisture for the past ca. 10,000 years at millennial to decadal timescales. Emerald Lake originated as a shallow, closed-basin cirque pond during the Early Holocene. By ca. 7000 cal yr BP, higher lake levels and carbonate δ 18 O values indicate rising effective moisture and higher proportions of summer precipitation continued at least until ca. 5500 cal yr BP when a landslide entered the lake margin. Between ca. 4500 and 2400 cal yr BP dry conditions at Emerald Lake envelop the timing of the ‘Late Holocene Dry Period’ identified at lower elevations. For the past ca. 2500 years, Emerald Lake δ 18 O values were relatively low, indicating wetter conditions and higher snow input (compared to rain), except for dry periods at ca. 2000 cal yr BP and during the Medieval Climate Anomaly at ca. 1000 and ca. 500 cal yr BP. Results provide a long-term perspective on precipitation extremes that influence regional water supplies from a snow-dominated catchment typical of the predominant source region for the Upper Colorado River.

Utah↗

USGS2012

Developing a national stream morphology data exchange: needs, challenges, and opportunities

Stream morphology data, primarily consisting of channel and foodplain geometry and bed material size measurements, historically have had a wide range of applications and uses including culvert/ bridge design, rainfall- runoff modeling, food inundation mapping (e.g., U.S. Federal Emergency Management Agency food insurance studies), climate change studies, channel stability/sediment source investigations, navigation studies, habitat assessments, and landscape change research. The need for stream morphology data in the United States, and thus the quantity of data collected, has grown substantially over the past 2 decades because of the expanded interests of resource management agencies in watershed management and restoration. The quantity of stream morphology data collected has also increased because of state-of-the-art technologies capable of rapidly collecting high-resolution data over large areas with heretofore unprecedented precision. Despite increasing needs for and the expanding quantity of stream morphology data, neither common reporting standards nor a central data archive exist for storing and serving these often large and spatially complex data sets. We are proposing an open- access data exchange for archiving and disseminating stream morphology data.

Eos, Transactions, American Geophysical Union↗

USGS2017

Estimating incision healing rate for surgically implanted acoustic transmitters from recaptured fish

Background Intracoelomic implantation of electronic tags has become a common method in fishery research, but rarely are fish examined by scientists after release to understand the extent that surgical incisions have healed. Walleye ( Sander vitreus ) are a valuable, highly exploited fishery resource in the Laurentian Great Lakes. Here, fishery capture of walleye with internal acoustic transmitters combined with a high reward program provided multiple opportunities to examine photographs and quantify the status of surgical incisions. Walleye ( n = 926) from reef and river spawning populations in Lake Erie and Lake Huron were implanted with acoustic transmitters during spring spawning events from 2011 to 2016. Incisions were closed with polydioxanone monofilament using two to three interrupted sutures. Out of 276 recaptured fish, 60 incision sites were clearly visible in photographs, and these were scored by two independent readers for incision closure, inflammation, and the presence of sutures. Results While incision sites were completely closed by 61 days post-release (95% CI 44–94), sutures remained for up to 866 days. Sutures were expelled serially during a protracted period, and the probability of observing at least one suture in a recaptured fish declined below 50% after 673 days (95% CI 442–1016). Inflammation at the incision increased during the first 71 days and then declined monotonically, remaining detectable at low levels. Conclusion Our results emphasized that sutures remained in free-ranging fish past the time when they were beneficial for incision healing. Most dissolvable sutures have been designed for use in endotherms where the body temperature and internal milieu differ dramatically from the conditions experienced by fishes in temperate climates. Identification of new suture materials for fish that facilitate healing while absorbing or dissolving in a reasonable period (e.g., a few weeks to three months) in colder temperatures (e.g., <12 °C) would be beneficial to mitigate potential adverse impacts from inflammation at the incision.

Animal Biotelemetry↗

USGS2022

Detection of Splendidofilaria sp. (Onchocercidae:Splendidofilariinae) Microfilaria within Alaskan ground-dwelling birds in the grouse subfamily tetraoninae using taqman probe-based real-time PCR

Grouse and ptarmigan (Galliformes) harbor fairly diverse helminth faunas that can impact the host's health, including filarial nematodes in the genus Splendidofilaria . As host and parasite distributions are predicted to shift in response to recent climate change, novel parasites may be introduced into a region and impose additional stressors on bird populations. Limited information is available on the prevalence of filariasis in Alaska galliforms. To date, no molecular surveys have been completed. Past studies relied on examining blood smears or total body necropsies, which are time-consuming and may not detect filarial parasites with low prevalence in hosts. Therefore, we developed a TaqMan probe-based real-time PCR assay targeting the cytochrome c oxidase 1 gene ( COI ) of Splendidofilaria to decrease processing times and increase sensitivity as well as provide baseline data on the diversity of filariid infections in galliform species in Alaska. We screened a combined total of 708 galliform samples (678 unique individual birds) from different tissues (blood, muscle, and lung) for the presence of filarial DNA across the state of Alaska. Real-time PCR screening revealed an overall prevalence of filarial infection of 9.5% across species: Bonasa umbellus (0%, n = 23), Dendragapus fuliginosus (0%, n = 8), Falcipennis canadensis (26.8%, n = 198), Lagopus lagopus (2.6%, n = 274), Lagopus leucura (0%, n = 23), Lagopus muta (3%, n = 166), and Tympanuchus phasianellus (12.5%, n = 16). We observed microfilarial infections throughout most of Alaska except in Arctic regions and the Aleutian Islands where viable vectors may not be present.

Journal of Parasitology↗

USGS1995

Bibliography, indices, and data sources of water-related studies, upper Colorado River basin, Colorado and Utah, 1872-1995

As part of the U.S. Geological Survey's National Water-Quality Assessment Program, current water-quality conditions in the Upper Colorado River Basin in Colorado and Utah are being assessed. This report is an initial effort to identify and compile information on water-related studies previously conducted in the basin and consists of a bibliography, coauthor and subject indices, and sources of available water-related data. Computerized literature searches of scientific data bases were carried out to identify past water-related studies in the basin, and government agencies and private organizations were contacted regarding their knowledge or possession of water-related publications and data. Categories of information in the bibliography include: aquatic biology, climate, energy development, geology, land use, limnology, runoff, salinity, surface- and ground-water hydrology, water chemistry, water quality and quantity, and water use and management. The approximately 1,400 indexed references date from 1872 through February 1995 and include books, journal articles, maps, and reports. In many instances, an abstract has been provided for a given reference. Sources of water-related data in the basin are included in a table.

Colorado, Utah↗

USGS1964

Availability of ground water in parts of the Acoma and Laguna Indian Reservations, New Mexico

The need for additional water has increased in recent years on the Acoma and Laguna Indian Reservations in west-central New Mexico because the population and per capita use of water have increased; the tribes also desire water for light industry, for more modern schools, and to increase their irrigation program. Many wells have been drilled in the area, but most have been disappointing because of small yields and poor chemical quality of the water. The topography in the Acoma and Laguna Indian Reservations is controlled primarily by the regional and local dip of alternating beds of sandstone and shale and by the igneous complex of Mount Taylor. The entrenched alluvial valley along the Rio San Jose, which traverses the area, ranges in width from about 0.4 mile to about 2 miles. The climate is characterized by scant rainfall, which occurs mainly in summer, low relative humidity, and large daily fluctuations of temperature. Most of the surface water enters the area through the Rio San Jose. The average annual streamflow past the gaging station Rio San Jose near Grants, N. Mex. is about 4,000 acre-feet. Tributaries to the Rio San Jose within the area probably contribute about 1,000 acre-feet per year. At the present time, most of the surface water is used for irrigation. Ground water is obtained from consolidated sedimentary rocks that range in age from Triassic to Cretaceous, and from unconsolidated alluvium of Quaternary age. The principal aquifers are the Dakota Sandstone, the Tres Hermanos Sandstone Member of the Mancos Shale, and the alluvium. The Dakota Sandstone yields 5 to 50 gpm (gallons per minute) of water to domestic and stock wells. The Tres Hermanos sandstone Member generally yields 5 to 20 gpm of water to domestic and stock wells. Locally, beds of sandstone in the Chinle and Morrison Formations, the Entrada Sandstone, and the Bluff Sandstone also yield small supplies of water to domestic and stock wells. The alluvium yields from 2 gpm to as much as 150 gpm of water to domestic and stock wells. Thirteen test wells were drilled in a search for usable supplies of ground water for pueblo and irrigation supply and to determine the geologic and hydrologic characteristics of the water-bearing material. The performance of six of the test wells suggests that the sites are favorable for pueblo or irrigation supply wells. The yield of the other seven wells was too small or the quality of the water was too poor for development of pueblo or irrigation supply to be feasible. However, the water from one of the seven wells was good in chemical quality, and the yield was large enough to supply a few homes with water. The tests suggest that the water in the alluvium of the Rio San Jose valley is closely related to the streamflow and that it might be possible to withdraw from the alluvium in summer and replenish it in winter. The surface flow in summer might be decreased by extensive pumpage of ground water, but on the other hand, more of the winter flow could be retained in the area by storage in the ground-water reservoir. Wells could be drilled along the axis of the valley, and the water could be pumped into systems for distribution to irrigated farms. The chemical quality of ground water in the area varies widely from one stratigraphic unit to another and laterally within each unit and commonly the water contains undesirably large amounts of sulfate. However, potable water has been obtained locally from all the aquifers. The water of best quality seemingly is in the Tres Hermanos Sandstone Member of the Mancos Shale and in the alluvium north of the Rio San Jose. The largest quantity of water that is suitable for irrigation is in the valley fill along the Rio San Jose. Intensive pumping of ground water from aquifers containing water of good quality may draw water of inferior chemical quality into the wells.

Water Supply Paper↗

USGS2001

Is it time to give up?

The world's coral reefs show rapid decline as a result of environmental change. Coral reef communities and organisms are stressed, potentially mortally, by (1) rising temperature, (2) rising atmospheric/surface ocean CO2 levels, (3) rising human populations, and (4) local aspects of climate change other than temperature. Further increase in all of these stressors is certain; the future rates and magnitudes of items 1-3 can be estimated with confidence to be substantially greater than changes in the recent past.

Conference Paper↗

USGS1959

Ground-water levels and related hydrologic data from selected observation wells in Nassau County, Long Island, New York

Nassau County has experienced a rapid growth in population and industry in the past 20 years that has resulted in increased development of its ground-water resources. The county is located in west-central Long Island and its boundaries enclose a land area of 274 square miles. The climate is relatively mild and precipitation averages 43 inches a year. The precipitation is the ultimate source of natural replenishment to the ground-water reservoir. Ground water is found in the pore spaces of unconsolidated sands, gravels, and clays which overlay a basement of crystalline bedrock.

New York↗

USGS2023

Sediment sources and connectivity linked to hydrologic pathways and geomorphic processes: A conceptual model to specify sediment sources and pathways through space and time

Sediment connectivity is a framework for transfer and storage of sediment among different geomorphic compartments across upland and channel network of the catchment sediment cascade. Sediment connectivity and dysconnectivity (i.e., source delivery and storage processes) are linked to the water cycle and hydrologic systems with the associated multiscale interactions with climate, soil, topography, ecology, and landuse/landcover under natural variability and human intervention. We review the sediment connectivity concept and frameworks developed in the last few decades to examine and quantify water and sediment transfer in catchment systems. Past conceptual models of connectivity have attempted to integrate multiple processes into sediment domain, including geomorphic, hydrologic, and ecological processes (i.e., “holistic approach to connectivity”). In particular, multiple studies highlight the importance of sediment and water interaction in defining landscape connectivity. There are also efforts to quantify the topographic controls on sediment connectivity, in the advent of increasingly high-resolution digital terrain models. More recent modeling efforts have integrated structural and functional connectivity through coupling topographic information with hydrologic simulation models. Though this recent modeling development is encouraging, a comprehensive sediment connectivity framework that integrates geomorphic and hydrologic processes across spatiotemporal scales is yet to be conceived. Such an effort will require understanding the governing hydrologic and geomorphic processes that control sediment source, storage, and transport. A conceptual model is proposed to describe dominant hydrologic-sediment connectivity regimes through spatial-temporal feedbacks between hydrologic processes (rainfall, flow routing, and water residence time) and geomorphic drivers (upland soil erosion and deposition, and geomorphic channel erosion and deposition response). Recent advancements in landscape monitoring techniques using geochemical tracers, remote-sensing, increasing availability of hydrologic monitoring data, and the integration of various analytic methods (e.g., isotopic hydrograph separation, stormflow concentration-discharge, hysteretic behavior analysis) have the potential to broaden the spatial and temporal scales of geomorphic observations and understanding of landscape sediment connectivity. Using the conceptual model as a “thinking” space, we examine sediment and hydrologic interactions in real world examples of watershed studies using multiple lines of evidence and modeling techniques.

Conference Paper↗

USGS2012

Nile Delta vegetation response to Holocene climate variability

A 7000 yr palynologic record from Burullus Lagoon, Nile Delta, Egypt, is assessed to investigate changes in terrestrial vegetation in response to Nile flow. Previous studies in this region have shown that sea-level rise in the early to mid-Holocene, and markedly increased human land use during the past several centuries, altered vegetation in and around the lagoon. The pollen record from this study documents changes in delta vegetation that likely reflect variations in Nile flow. We suggest that Cyperaceae pollen is a sensitive marker of precipitation over the Nile headwaters and the resultant Nile flow. Decreases in Cyperaceae pollen, interpreted as a marker for diminished Nile flow, as well as the increase in relative abundance of microscopic charcoal, occurred at ca. 6000–5500, ca. 5000, ca. 4200, and ca. 3000 cal. yr B.P. (calibrated years before present). These correspond to extreme regional and global aridity events associated with a more southerly mean position of the Intertropical Convergence Zone. These changes, also recorded by other proxy studies, indicate that several marked regional drought events affected the Nile Delta region and impacted ancient Egyptian and Middle Eastern civilizations.

Nile Delta↗

USGS1998

Cenozoic global sea level, sequences, and the New Jersey transect: Results from coastal plain and continental slope drilling

The New Jersey Sea Level Transect was designed to evaluate the relationships among global sea level (eustatic) change, unconformity-bounded sequences, and variations in subsidence, sediment supply, and climate on a passive continental margin. By sampling and dating Cenozoic strata from coastal plain and continental slope locations, we show that sequence boundaries correlate (within ±0.5 myr) regionally (onshore-offshore) and interregionally (New Jersey-Alabama-Bahamas), implicating a global cause. Sequence boundaries correlate with δ 18 O increases for at least the past 42 myr, consistent with an ice volume (glacioeustatic) control, although a causal relationship is not required because of uncertainties in ages and correlations. Evidence for a causal connection is provided by preliminary Miocene data from slope Site 904 that directly link δ 18 O increases with sequence boundaries. We conclude that variation in the size of ice sheets has been a primary control on the formation of sequence boundaries since ∼42 Ma. We speculate that prior to this, the growth and decay of small ice sheets caused small-amplitude sea level changes (<20 m) in this supposedly ice-free world because Eocene sequence boundaries also appear to correlate with minor δ 18 O increases. Subsidence estimates (backstripping) indicate amplitudes of short-term (million-year scale) lowerings that are consistent with estimates derived from δ 18 O studies (25–50 m in the Oligocene-middle Miocene and 10–20 m in the Eocene) and a long-term lowering of 150–200 m over the past 65 myr, consistent with estimates derived from volume changes on mid-ocean ridges. Although our results are consistent with the general number and timing of Paleocene to middle Miocene sequences published by workers at Exxon Production Research Company, our estimates of sea level amplitudes are substantially lower than theirs. Lithofacies patterns within sequences follow repetitive, predictable patterns: (1) coastal plain sequences consist of basal transgressive sands overlain by regressive highstand silts and quartz sands; and (2) although slope lithofacies variations are subdued, reworked sediments constitute lowstand deposits, causing the strongest, most extensive seismic reflections. Despite a primary eustatic control on sequence boundaries, New Jersey sequences were also influenced by changes in tectonics, sediment supply, and climate. During the early to middle Eocene, low siliciclastic and high pelagic input associated with warm climates resulted in widespread carbonate deposition and thin sequences. Late middle Eocene and earliest Oligocene cooling events curtailed carbonate deposition in the coastal plain and slope, respectively, resulting in a switch to siliciclastic sedimentation. In onshore areas, Oligocene sequences are thin owing to low siliciclastic and pelagic input, and their distribution is patchy, reflecting migration or progradation of depocenters; in contrast, Miocene onshore sequences are thicker, reflecting increased sediment supply, and they are more complete downdip owing to simple tectonics. We conclude that the New Jersey margin provides a natural laboratory for unraveling complex interactions of eustasy, tectonics, changes in sediment supply, and climate change.

New Jersey↗

USGS2016

State-and-transition models: Conceptual versus simulation perspectives, usefulness and breadth of use, and land management applications

State-and-Transition Simulation Modeling (STSM) is a quantitative analysis method that can consolidate a wide array of resource management issues under a “what-if” scenario exercise. STSM can be seen as an ensemble of models, such as climate models, ecological models, and economic models that incorporate human dimensions and management options. This chapter presents STSM as a tool to help synthesize information on social–ecological systems and to investigate some of the management issues associated with exotic annual Bromus species, which have been described elsewhere in this book. Definitions, terminology, and perspectives on conceptual and computer-simulated stochastic state-and-transition models are given first, followed by a brief review of past STSM studies relevant to the management of Bromus species. A detailed case study illustrates the usefulness of STSM for land management. As a whole, this chapter is intended to demonstrate how STSM can help both managers and scientists: (a) determine efficient resource allocation for monitoring nonnative grasses; (b) evaluate sources of uncertainty in model simulation results involving expert opinion, and their consequences for management decisions; and (c) provide insight into the consequences of predicted local climate change effects on ecological systems invaded by exotic annual Bromus species.

Book chapter↗

USGS1988

Sedimentary biomarker and isotopic indicators of the paleoclimatic history of the Walker Lake basin, western Nevada

Walker Lake, a terminal saline lake in western Nevada, has experienced major fluctuations in its water level due to changes in the regional climate during Quaternary times. As part of a paleo-climatological study of western Nevada, we have investigated organic matter δ 13 C and C/N values and lipid biomarker contents of sediments deposited at various periods over the past 150 thousand years of lake history. Surficial sediments from two cross-lake transects contain mostly lake-derived organic matter. Diagenetic losses of organic matter are evident in deeper sediments, and the proportion of aquatic and terrigenous organic materials changes in response to variations in preservational factors. Source identification of organic matter is complicated by the probability that Walker Lake has experienced desiccation at various times in its history which impacts the degree of preservation of organic substances.

Nevada↗

USGS2019

Coastal wetlands: A synthesis

This book and this synthesis address the pressing need for better management of coastal wetlands worldwide because these wetlands are disappearing at an alarming rate; in some countries the loss is 70%–80% in the last 50 years. Managing requires understanding. Although our understanding of the functioning of coastal wetland ecosystems has grown rapidly over the past decade, still much remains to be learned and understood. We have gained insight into the roles of geomorphic processes, hydrologic dynamics, biotic feedback, and disturbance agents in creating and molding a variety of coastal wetland ecosystems across climatic gradients. The variety is expressed not so much in the more obvious differences in vegetation cover, but rather how physical processes both facilitate and constrain a diversity of plant and animal communities. At one level, coastal wetlands are the product of tidal forces and freshwater inputs at the margin of continents. At another level, the plants control the water currents in the tidal creeks draining the wetlands by generating a tidal current asymmetry that controls sediment transport and results in a deep tidal creek surrounded by shallow vegetated wetlands. The vegetation also influences the physics of water and sediment through several other processes including biofilms, bioturbation of sediments, the buffeting of currents and waves, organic enrichment of sediments, and the closing of nutrient cycles. Few ecosystems provide us with so many clear examples of such feedback controls. What we do understand about the structure and functioning of coastal wetlands should provide the theoretical underpinnings for effective management in protecting them for their many contributions to ecosystem goods and services. What we do not understand should compel us to focus our attention and energies toward seeking optimal solutions to some of the most perplexing and urgent problems facing natural resource management.

Book chapter↗

USGS2011

Status and management of moose in the northeastern United States

Moose (Alces alces) populations have recolonized much of their historic range in the northeastern United States in the past 30 years, with their southern range edge extending to southern New England and northern New York. This southerly expansion occurred when certain other populations in the United States were in decline along the southern range edge, with climate change often cited as a probable cause. The areas that moose have recently occupied in the northeastern United States are some of the most densely human populated in moose range, which has raised concern about human safety and moose-vehicle collisions (MVC). We conducted a literature search about moose in the northeastern United States, and distributed a questionnaire and conducted phone interviews with regional biologists responsible for moose management to determine the status of moose, management activity, and research deficiencies and needs. Moose numbers appear stable throughout much of the region, with slow population growth in northern New York. Management activity ranges from regulated harvest of moose in Maine, New Hampshire, and Vermont, to no active management in southern New England and New York. The combined annual harvest in Maine, New Hampshire, and Vermont is >3,000. MVCs are a widespread regional concern with >1,000 occurring annually involving several human fatalities. Research should address impacts of parasitism by winter tick (Dermacentor albipictus) and brain-worm (Parelaphostrongylus tenuis) on productivity and mortality of moose, influence of climate change on population dynamics and range, and conflicts in areas with high human population density.

Alces↗

USGS2012

Influence of disturbance on temperate forest productivity

Climate, tree species traits, and soil fertility are key controls on forest productivity. However, in most forest ecosystems, natural and human disturbances, such as wind throw, fire, and harvest, can also exert important and lasting direct and indirect influence over productivity. We used an ecosystem model, PnET-CN, to examine how disturbance type, intensity, and frequency influence net primary production (NPP) across a range of forest types from Minnesota and Wisconsin, USA. We assessed the importance of past disturbances on NPP, net N mineralization, foliar N, and leaf area index at 107 forest stands of differing types (aspen, jack pine, northern hardwood, black spruce) and disturbance history (fire, harvest) by comparing model simulations with observations. The model reasonably predicted differences among forest types in productivity, foliar N, leaf area index, and net N mineralization. Model simulations that included past disturbances minimally improved predictions compared to simulations without disturbance, suggesting the legacy of past disturbances played a minor role in influencing current forest productivity rates. Modeled NPP was more sensitive to the intensity of soil removal during a disturbance than the fraction of stand mortality or wood removal. Increasing crown fire frequency resulted in lower NPP, particularly for conifer forest types with longer leaf life spans and longer recovery times. These findings suggest that, over long time periods, moderate frequency disturbances are a relatively less important control on productivity than climate, soil, and species traits.

Ecosystems↗

USGS2020

Use of boosted regression trees to quantify cumulative instream flow resulting from curtailment of irrigation in the Sprague River basin, Oregon

A boosted regression trees (BRT) approach was used to estimate the amount by which streamflow is increased when irrigation is regulated (curtailed) upstream of a streamgage on the Sprague River in southern-central Oregon. The BRT approach differs from most other approaches that require baseline conditions for comparison, where those baseline conditions are determined from past observations by searching for hydrologically similar years when irrigation was not regulated. Such baseline conditions are always imperfect estimates of the true baseline conditions. The BRT approach instead estimates unique baseline conditions for any year in which irrigation is regulated by calculating the baseline condition based on measurements of precipitation and weather observations that determine evapotranspiration, and other measurements that are proxies for the effects of climate and regional groundwater pumping on water-table elevation, using a model that has been trained in years of no regulation. The amount by which streamflow is increased by regulation is then calculated by subtracting the estimated baseline conditions from the measured streamflow. The approach is challenged by the fact that the streamflow increase may be a small fraction of the total streamflow; nonetheless, during 2 years in which regulation was started early and was implemented consistently through the season, the increased flow made up about one third of the flow past the streamgage during the regulation period. An advantage of this approach is that with rigorous model testing with holdout data, the threshold for detecting streamflow increase and intervals around the estimates of increase at a desired level of confidence can be quantified. The model relies on datasets that are readily available and updated continuously and therefore can be used operationally to inform resource management.

Oregon↗