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At least 1,153 records · Page 64Linked to original sources

USGS2017

Hydrologic and geomorphic changes resulting from episodic glacial lake outburst floods: Rio Colonia, Patagonia, Chile

Glacial lake outburst floods (GLOFs) are a prominent but poorly understood cryospheric hazard in a warming climate. We quantify the hydrologic and geomorphic response to 21 episodic GLOFs that began in April 2008 using multitemporal satellite imagery and field observations. Peak discharge exiting the source lake became progressively muted downstream. At ~40–60 km downstream, where the floods entered and traveled down the main stem Rio Baker, peak discharges were generally < 2000 m 3 s −1 , although these flows were still >1–2 times the peak annual discharge of this system, Chile's largest river by volume. As such, caution must be applied to empirical relationships relating lake volume to peak discharge, as the latter is dependent on where this observation is made along the flood path. The GLOFs and subsequent periods of free drainage resulted in > 40 m of incision, the net removal of ~25 × 10 6 m 3 of sediment from the source lake basin, and a nonsteady channel configuration downstream. These results demonstrate that GLOFs sourced from low‐order tributaries can produce significant floods on major main stem rivers, in addition to significantly altering sediment dynamics.

Cachet‐Colonia‐Baker Valley, Patagonia, Rio Coloni↗

USGS2016

On the deterministic and stochastic use of hydrologic models

Environmental simulation models, such as precipitation-runoff watershed models, are increasingly used in a deterministic manner for environmental and water resources design, planning, and management. In operational hydrology, simulated responses are now routinely used to plan, design, and manage a very wide class of water resource systems. However, all such models are calibrated to existing data sets and retain some residual error. This residual, typically unknown in practice, is often ignored, implicitly trusting simulated responses as if they are deterministic quantities. In general, ignoring the residuals will result in simulated responses with distributional properties that do not mimic those of the observed responses. This discrepancy has major implications for the operational use of environmental simulation models as is shown here. Both a simple linear model and a distributed-parameter precipitation-runoff model are used to document the expected bias in the distributional properties of simulated responses when the residuals are ignored. The systematic reintroduction of residuals into simulated responses in a manner that produces stochastic output is shown to improve the distributional properties of the simulated responses. Every effort should be made to understand the distributional behavior of simulation residuals and to use environmental simulation models in a stochastic manner.

Water Resources Research↗

USGS2021

Modeling the impacts of hydrology and management on carbon balance at the Great Dismal Swamp, Virginia and North Carolina, USA

The impact of drainage on the stability of peatland carbon sinks is well known; however, much less is understood regarding the way active management of the water-table affects carbon balance. In this study, we determined the carbon balance in the Great Dismal Swamp, a large, forested peatland in the southeastern USA, which has been drained for over two hundred years and is now being restored through hydrologic management. We modeled future net ecosystem carbon balance over 100 years (2012 to 2112) using in situ field observations paired with simulations of water-table depth. The three scenarios used in the model were baseline conditions, flooded/wet conditions, and drained/dry conditions, which represent a range of potential management actions and climate conditions at the Great Dismal Swamp. In the Baseline scenario, results show a carbon sink of 0.7 Tg, or an average annual rate of 0.23 Mg C/ha/yr. The Flooded/Wet scenario produced a net ecosystem carbon balance of 4.6 Tg C or an average annual rate of 1.06 Mg C/ha/yr. For the Drained/Dry scenario, under which no management was conducted, and typically dry conditions were assumed, the Great Dismal Swamp becomes a net carbon source at –2.07 Tg C or an average annual rate of –0.38 Mg C/ha/yr.

North Carolina, Virginia↗

USGS2022

Hydrologic modification and channel evolution degrades connectivity on the Atchafalaya River floodplain

The Atchafalaya River Basin is the largest remaining forested wetland in the contiguous United States. Since 1960, dredging and channel erosion in the Basin have resulted in changes to the hydrologic connectivity that have not been quantified. Analyses were conducted to determine the hydraulic and geomorphic factors that have changed since discharge became controlled that may have decreased river/floodplain connectivity. We examined: (1) stage/discharge relationships from 1960 to 2014; (2) hydroperiods across the floodplain; (3) discharge distribution to the floodplain by comparing discharge measurements from 1959–1968 to 2005–2012; and (4) channel cross-sections and floodplain elevations. Our results indicate that much of the floodplain no longer receives headwater discharge (upstream to downstream, > 200 km 2 ) or receives too little discharge to alleviate stagnancy and hypoxia in the forested wetland at lower stages. Large portions of the Basin (400 km 2 ) have low water levels controlled by channel geomorphology and sea-level rise that inundate the forested floodplain for more than 50% of the calendar year. This extended duration of inundation contributes to hypoxia and likely reduces nutrient retention. The confinement of discharge to a large efficient channel compromises the ability of this system to respond to sea-level rise and subsidence. This study provides insight to the effects of flood management projects along Coastal Plain rivers and deltas.

Louisiana↗

USGS2006

Evaluation of gridded snow water equivalent and satellite snow cover products for mountain basins in a hydrologic model

The USGS precipitation-runoff modelling system (PRMS) hydrologic model was used to evaluate experimental, gridded, 1 km2 snow-covered area (SCA) and snow water equivalent (SWE) products for two headwater basins within the Rio Grande (i.e. upper Rio Grande River basin) and Salt River (i.e. Black River basin) drainages in the southwestern USA. The SCA product was the fraction of each 1 km2 pixel covered by snow and was derived from NOAA advanced very high-resolution radiometer imagery. The SWE product was developed by multiplying the SCA product by SWE estimates interpolated from National Resources Conservation Service snow telemetry point measurements for a 6 year period (1995-2000). Measured SCA and SWE estimates were consistently lower than values estimated from temperature and precipitation within PRMS. The greatest differences occurred in the relatively complex terrain of the Rio Grande basin, as opposed to the relatively homogeneous terrain of the Black River basin, where differences were small. Differences between modelled and measured snow were different for the accumulation period versus the ablation period and had an elevational trend. Assimilating the measured snowfields into a version of PRMS calibrated to achieve water balance without assimilation led to reduced performance in estimating streamflow for the Rio Grande and increased performance in estimating streamflow for the Black River basin. Correcting the measured SCA and SWE for canopy effects improved simulations by adding snow mostly in the mid-to-high elevations, where satellite estimates of SCA are lower than model estimates. Copyright ?? 2006 John Wiley & Sons, Ltd.

Conference Paper↗

USGS2022

A hydrologic perspective of major U.S. droughts

Drought is a recurring natural hazard that has substantial human and environmental impacts. Given continued global warming and associated climate change, there is concern that droughts could become more severe and longer lasting. To better monitor and understand drought development and persistence, it is helpful to understand the development and climatic drivers of past droughts. In this study we use monthly runoff percentiles to identify five major drought events in the conterminous United States (CONUS) from 1901 through 2020. For each drought event we examined spatial patterns of departures of mean monthly precipitation, temperature, soil moisture storage, and runoff for 2,107 hydrologic units (HUs) across the CONUS. Results indicated that precipitation deficits have been the primary driver of past major-drought events and temperature a secondary driver, even of the most recent drought event (September 1999 through September 2015) when positive temperature anomalies occurred over most of the CONUS. Additionally, negative soil moisture storage departures were more negative than runoff departures during the five drought events we examined, which emphasizes the importance of measuring both runoff and soil moisture to monitor drought conditions. We also examined the use of statistical persistence to develop short-term (i.e., 1 month) forecasts of runoff drought conditions in the CONUS by developing autoregressive integrated moving average (ARIMA) models for each HU. Results indicated that persistence can be used to predict short-term changes in the spatial pattern of drought and the areal extent of drought, but that predictions of runoff magnitude for any particular site are often poor.

International Journal of Climatology↗

USGS2021

A stable isotope record of late Quaternary hydrologic change in the northwestern Brooks Range, Alaska (eastern Beringia)

A submillennial-resolution record of lake water oxygen isotope composition (δ 18 O) from chironomid head capsules is presented from Burial Lake, northwest Alaska. The record spans the Last Glacial Maximum (LGM; ~20–16k cal a bp ) to the present and shows a series of large lake δ 18 O shifts (~5‰). Relatively low δ 18 O values occurred during a period covering the LGM, when the lake was a shallow, closed-basin pond. Higher values characterize deglaciation (~16–11.5k cal a bp ) when the lake was still closed but lake levels were higher. A rapid decline between ~11 and 10.5k cal a bp indicates that lake levels rose to overflowing. Lake δ 18 O values are interpreted to reflect the combined effects of changes in lake hydrology, growing season temperature and meteoric source water as well as large-scale environmental changes impacting this site, including opening of the Bering Strait and shifts in atmospheric circulation patterns related to ice-sheet dynamics. The results indicate significant shifts in precipitation minus evaporation across the late Pleistocene to early Holocene transition, which are consistent with temporal patterns of vegetation change and paludification. This study provides new perspectives on the paleohydrology of eastern Beringia concomitant with human migration and major turnover in megafaunal assemblages.

Alaska↗

USGS2021

Hydrologic effects on growth and hatching success of age-0 Channel Catfish in the Tallapoosa River basin: Implications for management in regulated systems

We assessed the effects of hydrology on growth and hatching success of age‐0 Channel Catfish Ictalurus punctatus in regulated and unregulated reaches of the Tallapoosa River basin, Alabama. Age‐0 Channel Catfish ( N = 91) were collected from sites in both the Coastal Plain and Piedmont regions in fall 2003 and fall 2005. Lapillus otoliths were used to estimate the daily ages of age‐0 Channel Catfish, for which hatch dates were back‐calculated. We performed growth analysis to determine growth histories of each fish at 20‐d increments from hatch. Across the 2 years of sampling, Channel Catfish hatches were documented from June 7 to September 15. Ages and growth rates of age‐0 Channel Catfish ranged from 20 to 126 d and 0.60 to 1.5 mm/d, respectively. In general, growth was highest among age‐0 Channel Catfish from unregulated sites in the lower Coastal Plain, lowest among fish from unregulated sites in the Piedmont, and intermediate from regulated sites in the Piedmont. Successful hatching typically occurred during periods when mean discharges were in the upper two quartiles of flows for each site but not during exceptionally high peaks in flow. Physiographic province, the frequency of high pulses, and the number of flow reversals were the most important factors influencing the growth of recently hatched Channel Catfish. Results suggest that a low to moderate frequency of high pulses (25–150 pulses per 20‐d increment) and a moderate number of flow reversals (~100–175 reversals per 20‐d increment) enhances early growth of Channel Catfish in the Tallapoosa River system. Managing flow, when possible, to minimize large releases of water that result in exceptionally high pulses and providing minimal hydropeaking may improve hatching success during the Channel Catfish spawning season.

Alabama↗

USGS2009

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

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

California↗

USGS2006

The influence of major dams on hydrology through the drainage network of the Sacramento River basin, California

This paper reports basinwide patterns of hydrograph alteration via statistical and graphical analysis from a network of long-term streamflow gauges located various distances downstream of major dams and confluences in the Sacramento River basin in California, USA. Streamflow data from 10 gauging stations downstream of major dams were divided into hydrologic series corresponding to the periods before and after dam construction. Pre- and post-dam flows were compared with respect to hydrograph characteristics representing frequency, magnitude and shape: annual flood peak, annual flow trough, annual flood volume, time to flood peak, flood drawdown time and interarrival time. The use of such a suite of characteristics within a statistical and graphical framework allows for generalising distinct strategies of flood control operation that can be identified without any a priori knowledge of operations rules. Dam operation is highly dependent on the ratio of reservoir capacity to annual flood volume (impounded runoff index). Dams with high values of this index generally completely cut off flood peaks thus reducing time to peak, drawdown time and annual flood volume. Those with low values conduct early and late flow releases to extend the hydrograph, increasing time to peak, drawdown time and annual flood volume. The analyses reveal minimal flood control benefits from foothill dams in the lower Sacramento River (i.e. dissipation of the down-valley flood control signal). The lower part of the basin is instead reliant on a weir and bypass system to control lowland flooding. Data from a control gauge (i.e. with no upstream dams) suggest a background signature of global climate change expressed as shortened flood hydrograph falling limbs and lengthened flood interarrival times at low exceedence probabilities. This research has implications for flood control, water resource management, aquatic and riparian ecosystems and for rehabilitation strategies involving flow alteration and/or manipulation of sediment supplies. Copyright ?? 2006 John Wiley & Sons, Ltd.

River Research and Applications↗

USGS2013

Balancing practicality and hydrologic realism: a parsimonious approach for simulating rapid groundwater recharge via unsaturated-zone preferential flow

The impact of preferential flow on recharge and contaminant transport poses a considerable challenge to water-resources management. Typical hydrologic models require extensive site characterization, but can underestimate fluxes when preferential flow is significant. A recently developed source-responsive model incorporates film-flow theory with conservation of mass to estimate unsaturated-zone preferential fluxes with readily available data. The term source-responsive describes the sensitivity of preferential flow in response to water availability at the source of input. We present the first rigorous tests of a parsimonious formulation for simulating water table fluctuations using two case studies, both in arid regions with thick unsaturated zones of fractured volcanic rock. Diffuse flow theory cannot adequately capture the observed water table responses at both sites; the source-responsive model is a viable alternative. We treat the active area fraction of preferential flow paths as a scaled function of water inputs at the land surface then calibrate the macropore density to fit observed water table rises. Unlike previous applications, we allow the characteristic film-flow velocity to vary, reflecting the lag time between source and deep water table responses. Analysis of model performance and parameter sensitivity for the two case studies underscores the importance of identifying thresholds for initiation of film flow in unsaturated rocks, and suggests that this parsimonious approach is potentially of great practical value.

Water Resources Research↗

USGS2019

Understanding the central Great Plains as a coupled climatic-hydrological-human system: Lessons learned in operationalizing interdisciplinary collaboration

This chapter discusses an interdisciplinary and transdisciplinary project to understand the interactions of agriculture, climate, and water resources in the Central Great Plains as a coupled natural-human system. We focus on the Smoky Hills Watershed in Kansas, where we gathered socioeconomic, hydrological, and climatic data, along with ecological data on fish species. The project involved substantial stakeholder engagement, which was complicated by post-truth attitudes about climate science and environmental regulation by some groups. We discuss the challenges of team management, stakeholder engagement, and data integration for modeling, notably the incorporation of stakeholder support for environmental policy in the context of extreme climatic events. We conclude by offering a framework for good collaborative practice to manage the complications of crossing boundaries in transdisciplinary research and outreach.

Kansas↗

USGS2013

Assessing and measuring wetland hydrology

Virtually all ecological processes that occur in wetlands are influenced by the water that flows to, from, and within these wetlands. This chapter provides the “how-to” information for quantifying the various source and loss terms associated with wetland hydrology. The chapter is organized from a water-budget perspective, with sections associated with each of the water-budget components that are common in most wetland settings. Methods for quantifying the water contained within the wetland are presented first, followed by discussion of each separate component. Measurement accuracy and sources of error are discussed for each of the methods presented, and a separate section discusses the cumulative error associated with determining a water budget for a wetland. Exercises and field activities will provide hands-on experience that will facilitate greater understanding of these processes.

Book chapter↗

USGS2015

The influence of hydrology on lacustrine sediment contaminant records

The way water flows to a lake, through streams, as runoff, or as groundwater, can control the distribution and mass of sediment and contaminants deposited. Whether a lake is large or small, deep or shallow, open or closed, the movement of water to a lake and the circulation patterns of water within a lake control how and where sediment and contaminants are deposited. Particle-associated contaminants may stay close to the input source of contamination or be transported by currents to bathymetric lows. A complex morphology of the lake bottom or shoreline can also affect how contaminants will be distributed. Dissolved contaminants may be widely dispersed in smaller lakes, but may be diluted in large lakes away from the source. Although dissolved contaminants may not be deposited in lake sediments, the impact of dissolved contaminants (such as nitrogen) may be reflected by the ecosystem. For instance, increased phosphorus and nitrogen may increase organic content or algal biomass, and contribute to eutrophication of the lake over time. Changes in oxidation-reduction potential at the sediment-water interface may either release some contaminants to the water column or conversely deposit other contaminants to the sediment depending on the compound’s chemical characteristics. Changes in land use generally affect the hydrology of the watershed surrounding a lake, providing more runoff if soil binding vegetation is removed or if more impervious cover (roads and buildings) is increased. Groundwater inputs may change if pumping of the aquifer connected to the lake occurs. Even if groundwater is only a small portion of the volume of water entering a lake, if contaminant concentrations in the aquifer are high compared to surface water inputs, the mass of contaminants from groundwater may be as, or more, important than surface water contributions.

Book chapter↗

USGS1994

Hydrologic control of litter decomposition in seasonally flooded prairie marshes

The effect of seasonal inundation on the decomposition of emergent macrophyte litter ( Scolochloa festucacea ) was examined under experimental flooding regimes in a northern prairie marsh. Stem and leaf litter was subjected to six aboveground inundation treatments (ranging from never flooded to flooded April through October) and two belowground treatments (nonflooded and flooded April to August). Flooding increased the rate of mass loss from litter aboveground but retarded decay belowground. Aboveground, N concentration decreased and subsequently increased earlier in the longer flooded treatments, indicating that flooding decreased the time that litter remained in the leaching and immobilization phases of decay. Belowground, both flooded and nonflooded litter showed an initial rapid loss of N, but concentration and percent of original N remaining were greater in the nonflooded marsh throughout the first year. This suggested that more N was immobilized on litter under the nonflooded, more oxidizing soil conditions. Both N concentration and percent N remaining of belowground litter were greater in the flooded than the nonflooded marsh the second year, suggesting that N immobilization was enhanced after water-level drawdown. These results suggest different mechanisms by which flooding affects decomposition in different wetland environments. On the soil surface where oxygen is readily available, flooding accelerates decomposition by increasing moisture. Belowground, flooding creates anoxic conditions that slow decay. The typical hydrologic pattern in seasonally flooded prairie marshes of spring flooding followed by water-level drawdown in summer may maximize system decomposition rates by allowing rapid decomposition aboveground in standing water and by annually alleviating soil anoxia.

Manitoba↗

USGS1985

Hydrologic changes associated with the October 28, 1983, Idaho earthquake

Significant hydrologic changes were observed after the magnitude 7.3 earthquake that occurred on October 28, 1983, in central Idaho. Groundwater levels rose by as much as 3 meters near the epicenter. Discharge in many streams and springs increased, in some instances by more than 100%. One warm spring ceased flowing for several days; the flow then resumed and peaked at about nine times its original rate. Available data show no significant changes in water quality following the earthquake. ?? 1985 Birkha??user Verlag.

Pure and Applied Geophysics PAGEOPH↗

USGS1982

Hydrologic inferences from ring widths of flood-damaged trees, Potomac River, Maryland

Year-to-year variability in the ring widths of trees on flood plains along two reaches of the Potomac River near Washington, D.C., seems in large part to be related to differences in flood-flow regimes. Trees directly exposed to high flood velocities are damaged more often than sheltered trees and thus exhibit more variable ring-width patterns. The ring-width variability of unsheltered trees on low levels of flood plains is greater than that of trees on high levels, indicating that variability values are positively correlated with flood frequency. Sheltered trees, however, have less variable ring-width patterns than those of unsheltered trees, and variability is not correlated with flood frequency. As a result, ring-width variations may be used to estimate the probability of flood damage along local channel reaches of a stream. Growth responses after hydrologic catastrophies in 1948 and 1972 indicate that rings of flood-plain trees can be used to document the occurrence and crest altitude of high-magnitude floods. ?? 1982 Springer-Verlag New York Inc.

Environmental Geology↗

USGS1985

Disturbance in a cypress-tupelo wetland: an interaction between thermal loading and hydrology

The interaction between thermal loading and hydrology was examined in a forested wetland. As a result of flooding, portions of the wetland are periodically exposed to elevated water temperatures, resulting in progressive deterioration of the canopy. We chose three study sites along a gradient of canopy disturbance: most disturbed, intermediate disturbance and a least disturbed site. The timing of flooding has important effects on this wetland: floods which occur late in the growing season have greater impact on the timing of litterfall and the extent of tree mortality. Following a flood in May, there was no observed increase in litterfall, and woody detrital production (tree mortality) eliminated only o.4% and 1.1% of the aboveground woody biomass at the intermediate and least disturbed sites, respectively. In contrast. premature leaf senescence and literfall were observed at the intermediate site following an August flood, and tree mortality at the intermediate and least disturbed sites eliminated 10% and 8%, respectively, of the aboveground woody biomass. At the most disturbed site, where the majority of trees were already dead, no additional mortality was recorded during the study. Long-term effects of this disturbance regime are the loss of small stems and increased stem production of trees which remain. While stem production at the intermediate site (413 g.m −2 .yr −1 ) exceeded that at the least disturbed site (373 g.m −2 .y −1 ), total aboveground net primary production was highest at the least disturbed site (788 g·m −2 · yr −1 ), primarily because of the greater stem density. Portions of this wetland continue to deteriorate after more than 30 years of thermal loading.

Wetlands↗