Skip to main content
Advanced Search

Filters: Tags: dams (X) > Types: Citation (X)

36 results (41ms)   

Filters
Date Range
Extensions
Types
Contacts
Categories
Tag Types
Tag Schemes
View Results as: JSON ATOM CSV
A substantial increase in fluvial sediment supply relative to transport capacity causes complex, large-magnitude changes in river and floodplain morphology downstream. Although sedimentary and geomorphic responses to sediment pulses are a fundamental part of landscape evolution, few opportunities exist to quantify those processes over field scales. We investigated the downstream effects of sediment released during the largest dam removal in history, on the Elwha River, Washington, USA, by measuring changes in riverbed elevation and topography, bed sediment grain size, and channel planform as two dams were removed in stages over two years. As 10.5 million t (7.1 million m3) of sediment was released from two former...
An approach is presented in this study to aid water-resource managers in characterizing streamflow alteration at ungauged rivers. Such approaches can be used to take advantage of the substantial amounts of biological data collected at ungauged rivers to evaluate the potential ecological consequences of altered streamflows. National-scale random forest statistical models are developed to predict the likelihood that ungauged rivers have altered streamflows (relative to expected natural condition) for five hydrologic metrics (HMs) representing different aspects of the streamflow regime. The models use human disturbance variables, such as number of dams and road density, to predict the likelihood of streamflow alteration....
The upper Colorado River system is the habitat of several endangered fish: Kendall Warm Springs dace, Colorado squawfish, humpback chub, and bonytail chub. The single most important factor contributing to the decline of these species has been the construction and operation of dams and reservoirs, which have effected flow, temperature, chemistry, biota, and migration routes. Water depletion amounting to about 25% of the total has also had similar effects, particularly by eliminating the backwater nursery areas. A predicted decrease in agricultural use and increase in energy development use would decrease the amount of used irrigation water percolating back into the groundwater and streams. In addition, water allocated...
thumbnail
This dataset contains values of normal reservoir storage in units of acre-feet per km2, for three time periods: 1992, 2002, and 2012. Values are derived from a slightly-modified version of the National Inventory of Dams (NID) 2013 dataset, for which approximately 10% of records had the dam completion date estimated.
The style and degree of channel narrowing in aggrading reaches downstream from large dams is dependent upon the dominant geomorphic processes of the affected river, the magnitude of streamflow regulation, and the post-dam sediment transport regime. We measured different magnitudes of channel adjustment on the Green River downstream from Flaming Gorge Dam, UT, USA, that are related to these three factors. Bankfull channel width decreased by an average of about 20% in the study area. In reaches with abundant debris fans and eddy deposited sand bars, the amount of channel narrowing was proportional to the decrease in specific stream power. The fan?eddy-dominated reach with the greatest decrease in stream power narrowed...
Abstract (from http://www.sciencedirect.com/science/article/pii/S1470160X15005518): Although localized effects of individual dams on stream fish assemblages have been relatively well-studied, less is known about the effects of multiple dams within a stream network on fishes and the patterns that emerge when the combined effects of individual and multiple dams are viewed across entire river basins, ecoregions, and states. This study evaluated multiple stream network fragmentation metrics representing localized (e.g., distance-to-dams) and cumulative (e.g., total upstream reservoir storage) dam influences on streams in Michigan, Wisconsin, and Minnesota, developing an approach for identifying suitable fish indicators...
thumbnail
The National Hydrography Dataset (NHD) is a feature-based database that interconnects and uniquely identifies the stream segments or reaches that make up the nation's surface water drainage system. NHD data was originally developed at 1:100,000-scale and exists at that scale for the whole country. This high-resolution NHD, generally developed at 1:24,000/1:12,000 scale, adds detail to the original 1:100,000-scale NHD. (Data for Alaska, Puerto Rico and the Virgin Islands was developed at high-resolution, not 1:100,000 scale.) Local resolution NHD is being developed where partners and data exist. The NHD contains reach codes for networked features, flow direction, names, and centerline representations for areal water...
Categories: Data; Types: Citation; Tags: Administrative watershed units, Area of Complex Channels, Area to be submerged, Basin, Bay/Inlet, All tags...
By using the established hydraulic relationships among flood frequency, flood magnitude, and river-channel capacity, we develop a scale-independent assessment of the hydrogeomorphic impacts of 21 dams across the United States that have broad ranges in function and contributing drainage area. On the basis of generalized extreme value (GEV) analysis of pre- and post-dam hydrologic records, our analysis indicates that the 2 yr discharge has decreased ~60% following impoundment, exceeding the magnitude of climatically triggered discharge reductions occurring during the Holocene. Reductions in the frequency of the pre-dam 2 yr discharge have been equally profound. The pre-dam 2 yr flood has occurred on average twice...
thumbnail
This CSV file contains 21 dam metrics representing stream fragmentation and flow alteration for nearly 2.3 million stream reaches in the conterminous USA. Dam metrics fall into four main categories: segment-based, count and density, distance-based, and cumulative reservoir storage (described below). These data were developed using spatially verified large dam locations (n=49,468) primarily from the National Anthropogenic Barrier Dataset (NABD) that were spatially linked to the National Hydrography Dataset Plus version 1 (NHDPlusV1). These dam metrics have been summarized using the unique identifier field native to the NHDPlusV1 (COMID) which can be used to join this table to spatial layers and data tables of the...
Categories: Data; Types: Citation; Tags: 2015 National Assessment, 2015 National Assessment, 2015 National Assessment, Alabama, Arizona, All tags...
Wavelet analysis is a powerful tool with which to analyse the hydrologic effects of dam construction and operation on river systems. Using continuous records of instantaneous discharge from the Lees Ferry gauging station and records of daily mean discharge from upstream tributaries, we conducted wavelet analyses of the hydrologic structure of the Colorado River in Grand Canyon. The wavelet power spectrum (WPS) of daily mean discharge provided a highly compressed and integrative picture of the post-dam elimination of pronounced annual and sub-annual flow features. The WPS of the continuous record showed the influence of diurnal and weekly power generation cycles, shifts in discharge management, and the 1996 experimental...
Tributaries may either ameliorate or exacerbate the geomorphic and ecologic impacts of flow regulation by altering the flux of water and sediment into the flow-regulated mainstem. To capture the effects of tributary influences on a flow regulated river, long-term discharge and cross-sectional data are used to assess the geomorphic and hydrologic impacts of impoundment. In addition, the use of the short-lived cosmogenic radioisotope 7Be (half-life 53·4 days) to link sediment transport dynamics to benthic macroinvertebrate community structure is evaluated. It is found that the 7Be activity of transitional bed load sediment is highly seasonal and reflects both variations in activity of sediment sources and limited...
thumbnail
The High Resolution National Hydrography Dataset Plus (NHDPlus HR) is an integrated datset of geospatial data layers, including the most current National Hydrography Dataset (NHD), the 10-meter 3D Elevation Program Digital Elevation Model (3DEP DEM), and the National Watershed Boundary Dataset (WBD). The NHDPlus HR combines the NHD, 3DEP DEMs, and WBD to create a stream network with linear referencing, feature naming, "value added attributes" (VAAs), elevation-derived catchments, and other features for hydrologic data analysis. The stream network with linear referencing is a system of data relationships applied to hydrographic systems so that one stream reach "flows" into another and "events" can be tied to and...
Types: Citation; Tags: Administrative watershed units, Area of Complex Channels, Area to be submerged, Basin, Bay/Inlet, All tags...
thumbnail
Conclusions: Watersheds with low indices of biotic integrity (IBI) have been heavily developed. The biggest factors contributing to low IBIs were the presence of large dams, introduced fish, and road density. Dams at low to middle elevations had the greatest effect on IBI. Thresholds/Learnings: Dams at low to middle elevations had the greatest effect on IBI. Synopsis: Researchers developed a watershed index of biotic integrity to evaluate the biological health of 100 watersheds in the Sierra Nevada of California. In general, watersheds with low indices of biotic integrity (IBI) have been heavily developed by hydraulic mining, agriculture, and hydroelectric dams. The biggest factors contributing to low IBIs were...
The hydrology and geomorphology of large rivers in America reflect the pervasive influence of an extensive water control infrastructure including more than 75,000 dams. One hundred thirty-seven of the very large dams, each storing 1.2 km3 (106 acre feet) of water or more, alter the flows of every large river in the country. The hydrologic effects of these very large dams emerge from an analysis of the stream gage records of 72 river reaches organized into 36 pairs. One member of each pair is an unregulated reach above a dam, whereas the other is a regulated reach downstream from the same structure. Comparison of the regulated and unregulated reaches shows that very large dams, on average, reduce annual peak discharges...
American geomorphologic research related to dams is embedded in a complicated context of science, policy, economics, and culture. Research into the downstream effects of large dams has progressed to the point of theory-building, but generalization and theory-building are from this research because (1) it is highly focused on a few locations, (2) it concerns mostly very large dams rather than a representative sample of sizes, (3) the available record of effects is too short to inform us on long-term changes, (4) the reversibility of changes imposed by dam installation and operation is unknown, and (5) coordinated funding for the needed research is scarce. In the scientific context, present research is embedded in...
Closure of Glen Canyon Dam in 1963 transformed the Colorado River by reducing the magnitude and duration of spring floods, increasing the magnitude of base flows, and trapping fine sediment delivered from the upper watershed. These changes caused the channel downstream in Glen Canyon to incise, armor, and narrow. This study synthesizes over 45 yr of channel-change measurements and demonstrates that the rate and style of channel adjustment are directly related to both natural processes associated with sediment deficit and human decisions about dam operations. Although bed lowering in lower Glen Canyon began when the first cofferdam was installed in 1959, most incision occurred in 1965 in conjunction with 14 pulsed...
thumbnail
Conclusions: Summarizes findings from a review of literature intended to identify critical thresholds for conservation based in empirical studies of landscape fragmentation. Presents a conceptual overview of landscape fragmentation and habitat loss, as well as guidelines and thresholds relating to landscape indicators such as patch size, habitat amount, edge effects, riparian buffers, and habitat connectivity. Thresholds/Learnings: Many. See Kennedy et al. 2003. Synopsis: This report summarizes findings from a review of literature intended to identify critical thresholds for conservation based in empirical studies of landscape fragmentation. In presenting a conceptual overview of landscape fragmentation and habitat...
Samples were taken year-round at eleven sites along the altitudinal profile (2900-1400 m a.s.l.) of the Gunnison River, a 329 km tributary of the Colorado River, to document the distribution of the Plecoptera and to evaluate responses to hypolimnial-release dams in the headwaters and middle reaches. Twenty-two species were present, with the greatest species richness occurring in an unregulated segment upstream of the middle reach dams; average nymphal biomass over the study period (175 organisms, 395 mg dry mass m?2) was also greatest in this segment. Only four species (58 organisms, 48 mg m?2) were present in the tailwaters of the headwater dam and values were greatly reduced (nine species; 35 organisms, 180 mg...
thumbnail
Canyon riparian zone vegetation is vulnerable to effects of upstream river regulation. We studied box elder (Acer negundo) dominated canyon riparian forests intensively on the Green and Yampa rivers in Dinosaur National Monument, Colorado, and extensively in four other major rivers of the upper Colorado River Basin to determine the effects of river regulation on riparian tree establishment patterns. We: 1) aged individuals to determine if establishment was correlated with high annual peak flows, 2) mapped cohorts to determine if the areal extent of post-regulation cohorts was reduced on regulated compared to unregulated river reaches, and 3) measured the floodplain position of cohorts in regulated and unregulated...
Aim A regional analysis was used to explore the influence of river regulation on the dominance of non-native, invasive shrubs and trees. We addressed the following questions: (1) How do large dams affect hydrological parameters that influence riparian vegetation? (2) How do flow regimes affect the dominance of non-native woody species? (3) How do changes in flow regimes affect the dominance of non-native woody species? Location South-western USA. Methods We sampled the canopy cover of woody species on 179 point bars along seven non-dammed and thirteen dammed river segments. Wilcoxon rank sum tests were used to determine differences between flow parameters in dammed and non-dammed rivers. We used correlation analyses...
map background search result map search result map Effects of river regulation on riparian box elder (Acer Negundo) forests in Canyons of the upper Colorado River Basin, USA National Hydrography Dataset (NHD) - USGS National Map Downloadable Data Collection Conservation Thresholds for Land Use Planners Evaluating the biotic integrity of watersheds in the Sierra Nevada, California. National Hydrography Dataset Plus High Resolution (NHDPlus HR) - USGS National Map Downloadable Data Collection Reservoir storage for selected Chesapeake Bay watersheds Dam Metrics Representing Stream Fragmentation and Flow Alteration for the Conterminous United States Linked to the NHDPLUSV1 Evaluating the biotic integrity of watersheds in the Sierra Nevada, California. Reservoir storage for selected Chesapeake Bay watersheds Dam Metrics Representing Stream Fragmentation and Flow Alteration for the Conterminous United States Linked to the NHDPLUSV1 National Hydrography Dataset (NHD) - USGS National Map Downloadable Data Collection National Hydrography Dataset Plus High Resolution (NHDPlus HR) - USGS National Map Downloadable Data Collection Conservation Thresholds for Land Use Planners