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Results for “Journal of Water and Climate Change”

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At least 253 records · Page 14Linked to original sources
USGS2016

Topobathymetric elevation model development using a new methodology: Coastal National Elevation Database

During the coming decades, coastlines will respond to widely predicted sea-level rise, storm surge, and coastalinundation flooding from disastrous events. Because physical processes in coastal environments are controlled by the geomorphology of over-the-land topography and underwater bathymetry, many applications of geospatial data in coastal environments require detailed knowledge of the near-shore topography and bathymetry. In this paper, an updated methodology used by the U.S. Geological Survey Coastal National Elevation Database (CoNED) Applications Project is presented for developing coastal topobathymetric elevation models (TBDEMs) from multiple topographic data sources with adjacent intertidal topobathymetric and offshore bathymetric sources to generate seamlessly integrated TBDEMs. This repeatable, updatable, and logically consistent methodology assimilates topographic data (land elevation) and bathymetry (water depth) into a seamless coastal elevation model. Within the overarching framework, vertical datum transformations are standardized in a workflow that interweaves spatially consistent interpolation (gridding) techniques with a land/water boundary mask delineation approach. Output gridded raster TBDEMs are stacked into a file storage system of mosaic datasets within an Esri ArcGIS geodatabase for efficient updating while maintaining current and updated spatially referenced metadata. Topobathymetric data provide a required seamless elevation product for several science application studies, such as shoreline delineation, coastal inundation mapping, sediment-transport, sea-level rise, storm surge models, and tsunami impact assessment. These detailed coastal elevation data are critical to depict regions prone to climate change impacts and are essential to planners and managers responsible for mitigating the associated risks and costs to both human communities and ecosystems. The CoNED methodology approach has been used to construct integrated TBDEM models in Mobile Bay, the northern Gulf of Mexico, San Francisco Bay, the Hurricane Sandy region, and southern California.

Journal of Coastal Research↗
USGS2025

The joint effect of changes in urbanization and climate on trends in floods: A comparison of panel and single-station quantile regression approaches

Estimates of annual maximum (peak) flow quantiles are needed for basins undergoing changes in both urbanization and climate. Most previous work on the effect of urbanization on peak flows has considered urbanization alone and only the spatial variation in flood quantiles or its mean temporal effect, and most work on the effect of nonstationarity in climate has focused on single-station analyses, which give uncertain results for extreme quantiles. To address these gaps, three approaches to the statistical estimation of the joint effects of changes in impervious cover and climate on the estimation of peak-flow quantiles were compared: single-station quantile regression; a fixed effect panel-quantile regression (pQR) method using a location (mean) shift to homogenize the panel; and a location-scale panel regression model (pQRmom), which accounts for both scale (variance) and location effects. The different approaches were applied to a dataset consisting of instantaneous annual peak flows from 127 minimally nested basins in the midwestern United States with at least 4 % change in imperviousness. The annual maximum daily discharge from a water-balance model was selected as the primary climate predictor; in addition, to provide a comparison of climate predictors, precipitation was also considered. The coefficients from single-station regressions were usually sufficiently certain to determine the effects of climate variation but usually too uncertain to estimate the effects of urbanization. The panel-quantile regression approaches give much more certain results, but their estimates of quantile dependence differ: although both indicate urbanization effects decreasing with decreasing annual exceedance probability (AEP), the pQRmom urbanization coefficients are insignificantly different from zero for AEPs less than 0.10, whereas the pQR coefficients remain positive and are significant except for AEP = 0.01, the smallest AEP value considered. Although the location-scale structure of the pQRmom approach has less flexible quantile dependence than the pQR approach, the pQRmom approach has somewhat lower overall error, and it is found that by subsetting the dataset to homogenize the scale effects, the pQR and pQRmom results become similar, indicating the insignificant urbanization coefficients for small AEPs of the pQRmom results are likely correct for the study dataset.

Arkansas, Illinois, Indiana, Iowa, Michigan, Minne↗
USGS2015

Climate change and water resources in a tropical island system: Propagation of uncertainty from statistically downscaled climate models to hydrologic models

Many tropical islands have limited water resources with historically increasing demand, all potentially affected by a changing climate. The effects of climate change on island hydrology are difficult to model due to steep local precipitation gradients and sparse data. This work uses 10 statistically downscaled general circulation models (GCMs) under two greenhouse gas emission scenarios to evaluate the uncertainty propagated from GCMs in projecting the effects of climate change on water resources in a tropical island system. The assessment is conducted using a previously configured hydrologic model, the Precipitation Runoff Modelling System (PRMS) for Puerto Rico. Projected climate data and their modelled hydrologic variables versus historical measurements and their modelled hydrologic variables are found to have empirical distribution functions that are statistically different with less than 1 year of daily data aggregation. Thus, only annual averages of the projected hydrologic variables are employed as completely bias‐corrected model outputs. The magnitude of the projected total flow decreases in the four regions covering Puerto Rico, but with a large range of uncertainty depending on the makeup of the GCM ensemble. The multi‐model mean projected total flow decreases by 49–88% of historical amounts from the 1960s to the 2090s for the high emissions scenarios and by 39–79% for the low emissions scenarios. Subsurface flow contributions decreased the least and groundwater flow contributions decreased the most across the island. At locations critical to water supply for human use, projected streamflow is shown to decrease substantially below projected withdrawals by 2099.

Puerto Rico↗
USGS1996

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

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

Journal of Geophysical Research B: Solid Earth↗
USGS2026

Mechanisms of Devils Lake’s responses to recent climatic wetting: Insights from a physically based hydrologic model

Study region Devils Lake Basin of the Northern Great Plains (NGP) region, North Dakota, USA Study focus Understanding the mechanism of Devils Lake’s responses and basin-wide hydrologic change under a wet-climatic regime using a process-based and cold region hydrologic model. New hydrologic insights Model results illustrate that three distinct hydroclimatic periods occurred during the study: Water Years 2002–05, 2006–11, and 2012–18. Following a brief time of contraction and growth, the latter two periods provide a complete picture of a wetting to drying cycle during an overall wetting regime. From 2006–2011, Devils Lake (DL) grew primarily due to lateral inflow, driven by strong precipitation and high frozen soil content leading up to the 2011 floods. In addition, during wet years, the snowmelt streamflow from the eastern and central parts of the DL Basin contributes significantly to lake growth compared to the western part. By contrast, from 2012 to 18, DL entered a contraction period, dominated by evaporation losses and anthropogenic flood control operations. Contributors to upstream drying included low precipitation, minimal snowpack accumulation, slightly lower frozen soil ratios, and minimal snowmelt runoff.

North Dakota↗
USGS2009

Detection and attribution of streamflow timing changes to climate change in the Western United States

This article applies formal detection and attribution techniques to investigate the nature of observed shifts in the timing of streamflow in the western United States. Previous studies have shown that the snow hydrology of the western United States has changed in the second half of the twentieth century. Such changes manifest themselves in the form of more rain and less snow, in reductions in the snow water contents, and in earlier snowmelt and associated advances in streamflow "center" timing (the day in the "water-year" on average when half the water-year flow at a point has passed). However, with one exception over a more limited domain, no other study has attempted to formally attribute these changes to anthropogenic increases of greenhouse gases in the atmosphere. Using the observations together with a set of global climate model simulations and a hydrologic model (applied to three major hydrological regions of the western United States_the California region, the upper Colorado River basin, and the Columbia River basin), it is found that the observed trends toward earlier "center" timing of snowmelt-driven streamflows in the western United States since 1950 are detectably different from natural variability (significant at the p < 0.05 level). Furthermore, the nonnatural parts of these changes can be attributed confidently to climate changes induced by anthropogenic greenhouse gases, aerosols, ozone, and land use. The signal from the Columbia dominates the analysis, and it is the only basin that showed a detectable signal when the analysis was performed on individual basins. It should be noted that although climate change is an important signal, other climatic processes have also contributed to the hydrologic variability of large basins in the western United States. ?? 2009 American Meteorological Society.

Journal of Climate↗
USGS2013

Historical groundwater trends in northern New England and relations with streamflow and climatic variables

Water-level trends spanning 20, 30, 40, and 50 years were tested using month-end groundwater levels in 26, 12, 10, and 3 wells in northern New England (Maine, New Hampshire, and Vermont), respectively. Groundwater levels for 77 wells were used in interannual correlations with meteorological and hydrologic variables related to groundwater. Trends in the contemporary groundwater record (20 and 30 years) indicate increases (rises) or no substantial change in groundwater levels in all months for most wells throughout northern New England. The highest percentage of increasing 20-year trends was in February through March, May through August, and October through November. Forty-year trend results were mixed, whereas 50-year trends indicated increasing groundwater levels. Whereas most monthly groundwater levels correlate strongly with the previous month's level, monthly levels also correlate strongly with monthly streamflows in the same month; correlations of levels with monthly precipitation are less frequent and weaker than those with streamflow. Groundwater levels in May through August correlate strongly with annual (water year) streamflow. Correlations of groundwater levels with streamflow data and the relative richness of 50- to 100-year historical streamflow data suggest useful proxies for quantifying historical groundwater levels in light of the relatively short and fragmented groundwater data records presently available.

Maine;New Hampshire;Vermont↗
USGS2017

Spatiotemporal variability of snow depletion curves derived from SNODAS for the conterminous United States, 2004-2013

Assessment of water resources at a national scale is critical for understanding their vulnerability to future change in policy and climate. Representation of the spatiotemporal variability in snowmelt processes in continental-scale hydrologic models is critical for assessment of water resource response to continued climate change. Continental-extent hydrologic models such as the U.S. Geological Survey National Hydrologic Model (NHM) represent snowmelt processes through the application of snow depletion curves (SDCs). SDCs relate normalized snow water equivalent (SWE) to normalized snow covered area (SCA) over a snowmelt season for a given modeling unit. SDCs were derived using output from the operational Snow Data Assimilation System (SNODAS) snow model as daily 1-km gridded SWE over the conterminous United States. Daily SNODAS output were aggregated to a predefined watershed-scale geospatial fabric and used to also calculate SCA from October 1, 2004 to September 30, 2013. The spatiotemporal variability in SNODAS output at the watershed scale was evaluated through the spatial distribution of the median and standard deviation for the time period. Representative SDCs for each watershed-scale modeling unit over the conterminous United States ( n = 54,104) were selected using a consistent methodology and used to create categories of snowmelt based on SDC shape. The relation of SDC categories to the topographic and climatic variables allow for national-scale categorization of snowmelt processes.

Journal of the American Water Resources Associatio↗
USGS2023

Drawdown, habitat, and kokanee populations in a western U.S. reservoir

Greater drought frequency and severity due to climate change will result in greater drawdown of water storage reservoirs. However, changes to oxythermal regimes due to drawdown are reservoir specific and interface with fish species-specific habitat requirements, producing varying effects on coldwater fish populations. We examined the effect of drawdown on the oxythermal habitat and relative abundance of kokanee Oncorhynchus nerka , a coldwater salmonid, in Island Park Reservoir on the Henrys Fork of the Snake River, Idaho. A measure of relative kokanee abundance was negatively, exponentially related to drawdown. Oxythermal patterns measured in the reservoir during 2021, a severe drought year, revealed that drawdown reduced kokanee habitat by increasing water temperatures and decreasing dissolved oxygen concentrations. Oxythermal refugia for kokanee appeared to relate to inflow from the spring-fed Henrys Fork and other groundwater inflows. However, we did not quantify groundwater flow or connections, and we did not study kokanee population demographics or mortality. Reducing these sources of uncertainty is a priority for future study. Still, our study highlights a potential mechanism connecting reservoir drawdown to fish populations and the unique yet predictable mechanisms by which reservoir drawdown interacts with reservoir morphometry to affect fish habitat availability.

Idaho↗
USGS2019

Timescales of water-quality change in a karst aquifer, south-central Texas

Understanding the drivers and timescales over which groundwater quality changes informs groundwater management, use, and protection. To better understand timescales of water-quality change over short (daily to monthly) and long (seasonal to decadal) timescales, the U.S. Geological Survey’s National Water-Quality Assessment (NAWQA) Enhanced Trends Network (ETN) program instrumented and sampled three wells in the Edwards aquifer in south-central Texas. The wells were instrumented to provide high-frequency continuous (subhourly) water-quality data (temperature, pH, specific conductance, and dissolved oxygen), which were augmented by the collection of discrete samples (about 6 per year) for a range of geochemical constituents (including selected isotopes and age tracers). ETN data (2013–2017) are considered with data from additional sites for the same time period, and also historical records (over more than 80 years) of climatic and hydrologic conditions. During the four-year study, hydrologic conditions transitioned from very dry to very wet. Sites in the updip/unconfined part of the aquifer showed notable changes in water level and geochemistry (1) in response to rainfall/recharge events, and (2) over the multiyear dry/wet cycle. Sites in the downdip/confined part of the aquifer showed changes in water level/spring discharge over similar timescales, although the response is more muted. Geochemistry at the downdip/confined sites, however, varied slowly and minimally, indicating that the geochemical response of the deeper aquifer is decoupled from recent hydrologic responses. Changes at the updip/unconfined sites reflect mixing with recent recharge, whereas the downdip/confined sites were dominated by mineral-solution reactions resulting from longer (decadal) residence times. Mean groundwater ages interpreted from measured age tracers and lumped parameter models range from 7 to >700 years (where mixed with premodern downdip water) but were mostly modern. The aquifer is characterized by updip-to-downdip trends in geochemistry with respect to water-rock interaction and groundwater age. Fourier spectral analysis of historical records indicate hydrologic variability has occurred at dominant periods of 30 and 15 years; in conjunction with age tracers, these results provide insight into timescales at which the aquifer’s public supply is vulnerable to changes in the water quality of recharge.

Texas↗
USGS2025

Ranking river basins for stream temperature research and monitoring in the contiguous United States

There is a need to prioritize research and data collection in river basins by integrating information from environmental, ecological, and socioeconomic datasets to maintain acceptable water quality for human uses and ecosystem health. Multiple anthropogenic and natural stressors are responsible for driving changes in stream temperatures that can alter ecosystems and degrade water quality. These stressors are variable spatially and temporally, which can be challenging for prioritizing monitoring and research. In this study, an evaluation of variables related to stream temperature was performed for 163 candidate basins of the contiguous United States to highlight potential focal areas. Thirty variables were combined in six components: anthropogenic forcing, natural forcing, climate change, ecological sensitivity, socioeconomic sensitivity, and data availability. The components were incorporated into three themes: vulnerability of streams to thermal change, vulnerability of ecosystems, and vulnerability of communities. By evaluating each theme separately, patterns of vulnerability and potential resiliency were identified as well as consistency in ranks within the themes. For example, results of the national scale ranking indicated the Southern California Coastal basin (within California-Nevada region) was the highest-ranking priority in vulnerability of streams to thermal change and vulnerability of ecosystems. The analysis also identified vulnerable basins with gaps in monitoring. For example, the Missouri-Oahe basin (within the Northern High Plains region) was the highest-ranking priority for vulnerable communities with limitations in data availability. The ranking approach provides insight into basins that are resilient and are ideal candidates for monitoring and research.

Journal of Hydrology↗
USGS2010

Importance of coastal change variables in determining vulnerability to sea- and lake-level change

In 2001, the U.S. Geological Survey began conducting scientific assessments of coastal vulnerability to potential future sea- and lake-level changes in 22 National Park Service sea- and lakeshore units. Coastal park units chosen for the assessment included a variety of geological and physical settings along the U.S. Atlantic, Pacific, Gulf of Mexico, Gulf of Alaska, Caribbean, and Great Lakes shorelines. This research is motivated by the need to understand and anticipate coastal changes caused by accelerating sea-level rise, as well as lake-level changes caused by climate change, over the next century. The goal of these assessments is to provide information that can be used to make long-term (decade to century) management decisions. Here we analyze the results of coastal vulnerability assessments for several coastal national park units. Index-based assessments quantify the likelihood that physical changes may occur based on analysis of the following variables: tidal range, ice cover, wave height, coastal slope, historical shoreline change rate, geomorphology, and historical rate of relative sea- or lake-level change. This approach seeks to combine a coastal system's susceptibility to change with its natural ability to adapt to changing environmental conditions, and it provides a measure of the system's potential vulnerability to the effects of sea- or lake-level change. Assessments for 22 park units are combined to evaluate relationships among the variables used to derive the index. Results indicate that Atlantic and Gulf of Mexico parks have the highest vulnerability rankings relative to other park regions. A principal component analysis reveals that 99% of the index variability can be explained by four variables: geomorphology, regional coastal slope, water-level change rate, and mean significant wave height. Tidal range, ice cover, and historical shoreline change are not as important when the index is evaluated at large spatial scales (thousands of kilometers). ?? 2010 Coastal Education and Research Foundation.

Journal of Coastal Research↗
USGS2008

Western juniper and ponderosa pine ecotonal climate-growth relationships across landscape gradients in southern Oregon

Forecasts of climate change for the Pacific northwestern United States predict warmer temperatures, increased winter precipitation, and drier summers. Prediction of forest growth responses to these climate fluctuations requires identification of climatic variables limiting tree growth, particularly at limits of free species distributions. We addressed this problem at the pine-woodland ecotone using tree-ring data for western juniper (Juniperus occidentalis var. occidentalis Hook.) and ponderosa pine (Pinus ponderosa Dougl. ex Loud.) from southern Oregon. Annual growth chronologies for 1950-2000 were developed for each species at 17 locations. Correlation and linear regression of climate-growth relationships revealed that radial growth in both species is highly dependent on October-June precipitation events that recharge growing season soil water. Mean annual radial growth for the nine driest years suggests that annual growth in both species is more sensitive to drought at lower elevations and sites with steeper slopes and sandy or rocky soils. Future increases in winter precipitation could increase productivity in both species at the pine-woodland ecotone. Growth responses, however, will also likely vary across landscape features, and our findings suggest that heightened sensitivity to future drought periods and increased temperatures in the two species will predominantly occur at lower elevation sites with poor water-holding capacities. ?? 2008 NRC.

Canadian Journal of Forest Research↗
USGS2018

El Niño increases high‐tide flooding in tidal wetlands along the U.S. Pacific coast.

Periodic oscillations between El Niño and La Niña conditions in the Pacific Basin affect oceanographic and meteorological phenomena globally, with impacts on the abundance and distribution of marine species. However, El Niño effects on estuarine hydrology and tidal wetland processes have seldom been examined rigorously. We used detailed wetland elevation and local inundation data from 10 tidal wetlands located along the Pacific coast of the United States to assess changes in flooding during the 2015–2016 El Niño and to determine decadal‐scale relationships between estuarine sea‐level anomalies and Pacific Basin climate indices for this region. During the 2015–2016 El Niño all sites experienced significant increases in high‐tide water levels exceeding those predicted by astronomical tides, and increased flooding frequency during at least one of the El Niño subperiods relative to pre‐El Niño conditions. The magnitude of positive sea‐level anomalies varied by site (4–15 cm), with local hot spots of high water in southern Oregon, northern California, and Pt. Mugu lagoon in the Southern California Bight. Furthermore, over the last three decades of historic tide records, there were positive relationships between high‐tide sea‐level anomalies and equatorial Pacific Basin sea surface temperature anomalies across the region, and negative relationships with the Northern Oscillation Index. Increases of 1 °C in equatorial sea surface temperature were associated with 3–5 cm of increased high‐tide flooding at the sites. Elevated estuarine flooding associated with future El Niños could impact important tidal wetland processes and could be an additive stressor for wetlands facing accelerating sea‐level rise.

California, Oregon, Washington↗
USGS2021

Tree mortality response to drought-density interactions suggests opportunities to enhance drought resistance

The future of dry forests around the world is uncertain given predictions that rising temperatures and enhanced aridity will increase drought-induced tree mortality. Using forest management and ecological restoration to reduce density and competition for water offers one of the few pathways that forests managers can potentially minimize drought-induced tree mortality. Competition for water during drought leads to elevated tree mortality in dense stands, although the influence of density on heat-induced stress, and the durations of hot or dry conditions that most impact mortality, remain unclear. Understanding how competition interacts with hot-drought stress is essential to recognize how, where, and how much reducing density can help sustain dry forests in a rapidly changing world. Here, we integrated repeat measurements of 28,881 ponderosa pine trees across the western US (2000-2017) with soil moisture estimates from a water balance model to examine how annual mortality responds to competition, temperature and soil moisture conditions. Tree mortality responded most strongly to basal area, and was elevated in places with high mean temperatures, unusually hot 7-year high temperature anomalies, and unusually dry 8-year low soil moisture anomalies. Mortality was also lower in places that experienced unusually wet 3-year soil moisture anomalies between measurements. Importantly, we found that basal area interacts with temperature and soil moisture, exacerbating mortality during times of stress imposed by high temperature or low moisture. Synthesis and Applications: Our results imply that a 50% reduction in forest basal area could reduce drought-driven tree mortality by 20-80%. The largest impacts of density reduction are seen in areas with high current basal area and places that experience high temperatures and/or severe multiyear droughts. These interactions between competition and drought are critical to understand past and future patterns of tree mortality in the context of climate change, and provide information for resource managers seeking to enhance dry forest drought resistance.

Journal of Applied Ecology.↗
USGS1998

Noble gases, stable isotopes, and radiocarbon as tracers of flow in the Dakota aquifer, Colorado and Kansas

A suite of chemical and isotope tracers (dissolved noble gases, stable isotopes of water, radiocarbon, and CI) have been analyzed along a flow path in the Dakota aquifer system to determine likely recharge sources, ground water residence times, and the extent of mixing between local and intermediate flow systems, presumably caused by large well screens. Three water types were distinguished with the tracers, each having a very different history. Two of the water types were found in south-eastern Colorado where the Dakota is poorly confined. The tracer data suggest that the first group recharged locally during the last few thousand years and the second group was composed of ground water that recharged earlier during a cooler climate, presumably during the last glacial period (LGP) and mixed aged water. The paleotemperature record archived in this groundwater system indicates that south-eastern Colorado was about 5??C cooler during the LGP than during the late Holocene. Similar temperature changes derived from dissolved noble gases in other aquifer systems have been reported earlier for the south-western United States. The third water type was located down gradient of the first two in the confined Dakota in western and central Kansas. Groundwater residence time of this water mass is on the order of 104-105 yrs and its recharge location is near the Colorado and Kansas border down gradient of the other water types. The study shows the importance of using multiple tracers when investigating ground water systems.A suite of chemical and isotope tracers (dissolved noble gases, stable isotopes of water, radiocarbon, and CL) were analyzed along a flow path in the Dakota aquifer system to determine likely recharge sources, ground water residence times, and the extent of mixing between local and intermediate flow systems. Three water types were distinguished with the tracers, each having a very different history. Two of the water types were located in south-eastern Colorado where the Dakota is poorly confined. The third water type was located down gradient of the first two in the confined Dakota in western and central Kansas.

Journal of Hydrology↗
USGS2017

Modeling summer month hydrological drought probabilities in the United States using antecedent flow conditions

Climate change raises concern that risks of hydrological drought may be increasing. We estimate hydrological drought probabilities for rivers and streams in the United States (U.S.) using maximum likelihood logistic regression (MLLR). Streamflow data from winter months are used to estimate the chance of hydrological drought during summer months. Daily streamflow data collected from 9,144 stream gages from January 1, 1884 through January 9, 2014 provide hydrological drought streamflow probabilities for July, August, and September as functions of streamflows during October, November, December, January, and February, estimating outcomes 5-11 months ahead of their occurrence. Few drought prediction methods exploit temporal links among streamflows. We find MLLR modeling of drought streamflow probabilities exploits the explanatory power of temporally linked water flows. MLLR models with strong correct classification rates were produced for streams throughout the U.S. One ad hoc test of correct prediction rates of September 2013 hydrological droughts exceeded 90% correct classification. Some of the best-performing models coincide with areas of high concern including the West, the Midwest, Texas, the Southeast, and the Mid-Atlantic. Using hydrological drought MLLR probability estimates in a water management context can inform understanding of drought streamflow conditions, provide warning of future drought conditions, and aid water management decision making.

Journal of the American Water Resources Associatio↗
USGS2013

Snow effects on alpine vegetation in the Qinghai-Tibetan Plateau

Understanding the relationships between snow and vegetation is important for interpretation of the responses of alpine ecosystems to climate changes. The Qinghai-Tibetan Plateau is regarded as an ideal area due to its undisturbed features with low population and relatively high snow cover. We used 500 m Moderate Resolution Imaging Spectroradiometer (MODIS) datasets during 2001&ndash;2010 to examine the snow&ndash;vegetation relationships, specifically, (1) the influence of snow melting date on vegetation green-up date and (2) the effects of snow cover duration on vegetation greenness. The results showed that the alpine vegetation responded strongly to snow phenology (i.e., snow melting date and snow cover duration) over large areas of the Qinghai-Tibetan Plateau. Snow melting date and vegetation green-up date were significantly correlated (p < 0.1) in 39.9% of meadow areas (accounting for 26.2% of vegetated areas) and 36.7% of steppe areas (28.1% of vegetated areas). Vegetation growth was influenced by different seasonal snow cover durations (SCDs) in different regions. Generally, the December&ndash;February and March&ndash;May SCDs played a significantly role in vegetation growth, both positively and negatively, depending on different water source regions. Snow's positive impact on vegetation was larger than the negative impact.

Qinghai-Tibetan Plateau↗