Streamflow Alteration Active
Flow Modification of the Nation’s Streams and Rivers
Natural flows are critical to healthy ecosystems—learn how flows have changed and why
Humans, just like aquatic organisms, need water. Flood control, urban infrastructure, irrigation of agriculture, and myriad other ways we manage water affect the natural flow of streams and rivers. How do the ways we manage land and water affect the natural patterns of streamflow that ecosystems depend on?
Featured: Projecting future flow in Southwest streams
Streamflow in the Southwestern U.S. is projected to decrease by as much as 36–80% by the end of this century, reports a new study by the U.S. Geological Survey. These decreases could challenge our ability to meet future water demand in this region.
Civilizations sprang up where water was available. In modern times, humans have harnessed freshwater around the world for drinking, agriculture, industry, hydropower, and many other benefits. Human actions that can change streamflow patterns include dam building, stream diversion, pumping of shallow groundwater, and covering the landscape with impervious surfaces such as pavement and roofs.
Changes in climate also can alter flow by altering timing and amount of precipitation. And in most areas, changes in streamflow pattern caused by climate are superimposed on streamflow modifications caused by land and water management.
Human activities and management of water, as well as climate, can affect many aspects of streamflow. How high are the highest high flows, and how low are the lowest low flows? When do those high flows and low flows occur, and how often? Changes to these naturally occurring patterns can have ecological consequences, causing species loss and the diversity of species present to change.
An analysis of streamflow data for 1980–2014 compiled from more than 3,000 streamgaging sites across the U.S. found that low flows now are more frequent but occur for a shorter duration than they would naturally. High flows also are more frequent, but are lower in magnitude and shorter in duration than they would be naturally. Such changes have contributed to the deterioration of stream and river ecosystems. That's because aquatic species have evolved strategies to live with the streamflow regime that has existed for thousands of years. When that streamflow regime changes it can reduce their ability to survive and reproduce.
Climate also has induced changes in streamflow, as assessed at 600 streamgaging sites where influences from land and water management are minimal. Climate factors that affect streamflows include air temperature, whether precipitation falls as rain or snow, and the timing of precipitation and snowmelt. However, human management of land and water resources over the last 3 decades have modified streamflows more than variation in climate has over the same period.
A previous assessment of streamflow at 2,888 sites across the United States found that natural streamflow patterns have been altered at more than 85 percent of the stream sites. There were marked differences in the occurrence, type, and severity of streamflow alteration depending on whether the climate was arid or wet. The more that flow magnitude—how high the highest and lowest flows are—in a stream had diminished, the more likely that the ecological community of the stream was impaired.
Damage to ecosystems from streamflow modification has been successfully mitigated in some cases. Efforts to address streamflow modification can focus on a key streamflow characteristic, such as low-flow magnitude, or can address the entire flow regime—streamflow magnitude, variability, duration, frequency, and timing. The choice depends on specific ecological needs and the flexibility of other goals, such as water supply or energy production. All of these approaches require the scientific analysis and long-term monitoring of ecological and hydrological systems.
The links to the web pages below are a gateway to additional information in the ecology of streams.
Access our most recent flow-alteration data. Explore more data releases at ScienceBase.
Below, you’ll find the latest in peer-reviewed journal articles and USGS reports on flow alteration and its effects. For more publications on this and other water-quality topics, search the USGS Publications Warehouse. Look here for help using the Pubs Warehouse.
Biological relevance of streamflow metrics: Regional and national perspectives
Design tradeoffs for trend assessment in aquatic biological monitoring programs
River flow changes related to land and water management practices across the conterminous United States
Predicting the likelihood of altered streamflows at ungauged rivers across the conterminous United States
The quality of our Nation’s waters--ecological health in the Nation's streams, 1993-2005
Predicting thermal reference conditions for USA streams and rivers
Relations between altered stramflow variability and fish assemblages in Eastern USA streams
The relative importance of physicochemical factors to stream biological condition in urbanizing basins: Evidence from multimodel inference
Causes of systematic over- or underestimation of low streamflows by use of index-streamgage approaches in the United States
Alteration of streamflow magnitudes and potential ecological consequences: A multiregional assessment
GAGES: A stream gage database for evaluating natural and alteredflow conditions in the conterminous United States
- Overview
Humans, just like aquatic organisms, need water. Flood control, urban infrastructure, irrigation of agriculture, and myriad other ways we manage water affect the natural flow of streams and rivers. How do the ways we manage land and water affect the natural patterns of streamflow that ecosystems depend on?
Featured: Projecting future flow in Southwest streamsStreamflow in the Southwestern U.S. is projected to decrease by as much as 36–80% by the end of this century, reports a new study by the U.S. Geological Survey. These decreases could challenge our ability to meet future water demand in this region.
Civilizations sprang up where water was available. In modern times, humans have harnessed freshwater around the world for drinking, agriculture, industry, hydropower, and many other benefits. Human actions that can change streamflow patterns include dam building, stream diversion, pumping of shallow groundwater, and covering the landscape with impervious surfaces such as pavement and roofs.
Changes in climate also can alter flow by altering timing and amount of precipitation. And in most areas, changes in streamflow pattern caused by climate are superimposed on streamflow modifications caused by land and water management.
Human activities and management of water, as well as climate, can affect many aspects of streamflow. How high are the highest high flows, and how low are the lowest low flows? When do those high flows and low flows occur, and how often? Changes to these naturally occurring patterns can have ecological consequences, causing species loss and the diversity of species present to change.
An analysis of streamflow data for 1980–2014 compiled from more than 3,000 streamgaging sites across the U.S. found that low flows now are more frequent but occur for a shorter duration than they would naturally. High flows also are more frequent, but are lower in magnitude and shorter in duration than they would be naturally. Such changes have contributed to the deterioration of stream and river ecosystems. That's because aquatic species have evolved strategies to live with the streamflow regime that has existed for thousands of years. When that streamflow regime changes it can reduce their ability to survive and reproduce.
Climate also has induced changes in streamflow, as assessed at 600 streamgaging sites where influences from land and water management are minimal. Climate factors that affect streamflows include air temperature, whether precipitation falls as rain or snow, and the timing of precipitation and snowmelt. However, human management of land and water resources over the last 3 decades have modified streamflows more than variation in climate has over the same period.
A previous assessment of streamflow at 2,888 sites across the United States found that natural streamflow patterns have been altered at more than 85 percent of the stream sites. There were marked differences in the occurrence, type, and severity of streamflow alteration depending on whether the climate was arid or wet. The more that flow magnitude—how high the highest and lowest flows are—in a stream had diminished, the more likely that the ecological community of the stream was impaired.
Damage to ecosystems from streamflow modification has been successfully mitigated in some cases. Efforts to address streamflow modification can focus on a key streamflow characteristic, such as low-flow magnitude, or can address the entire flow regime—streamflow magnitude, variability, duration, frequency, and timing. The choice depends on specific ecological needs and the flexibility of other goals, such as water supply or energy production. All of these approaches require the scientific analysis and long-term monitoring of ecological and hydrological systems.
- Science
The links to the web pages below are a gateway to additional information in the ecology of streams.
- Data
Access our most recent flow-alteration data. Explore more data releases at ScienceBase.
- Publications
Below, you’ll find the latest in peer-reviewed journal articles and USGS reports on flow alteration and its effects. For more publications on this and other water-quality topics, search the USGS Publications Warehouse. Look here for help using the Pubs Warehouse.
Biological relevance of streamflow metrics: Regional and national perspectives
Protecting the health of streams and rivers requires identifying ecologically significant attributes of the natural flow regime. Streamflow regimes are routinely quantified using a plethora of hydrologic metrics (HMs), most of which have unknown relevance to biological communities. At regional and national scales, we evaluated which of 509 commonly used HMs were associated with biological indicatoAuthorsDaren Carlisle, Theodore E. Grantham, Ken Eng, David M. WolockFilter Total Items: 22Design tradeoffs for trend assessment in aquatic biological monitoring programs
Assessments of long-term (multiyear) temporal trends in biological monitoring programs are generally undertaken without an adequate understanding of the temporal variability of biological communities. When the sources and levels of variability are unknown, managers cannot make informed choices in sampling design to achieve monitoring goals in a cost-effective manner. We evaluated different trend sAuthorsMartin E. Gurtz, John Van Sickle, Daren Carlisle, Steven G. PaulsenRiver flow changes related to land and water management practices across the conterminous United States
The effects of land and water management practices (LWMP)—such as the construction of dams and roads—on river flows typically have been studied at the scale of single river watersheds or for a single type of LWMP. For the most part, assessments of the relative effects of multiple LWMP within many river watersheds across regional and national scales have been lacking. This study assesses flow alterAuthorsKen Eng, David M. Wolock, Daren CarlislePredicting the likelihood of altered streamflows at ungauged rivers across the conterminous United States
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 thAuthorsKen Eng, Daren Carlisle, David M. Wolock, James A. FalconeThe quality of our Nation’s waters--ecological health in the Nation's streams, 1993-2005
This report summarizes a national assessment of the ecological health of streams done by the U.S. Geological Survey's (USGS) National Water-Quality Assessment Program (NAWQA). Healthy functioning stream ecosystems provide society with many benefits, including water purification, flood control, nutrient recycling, waste decomposition, fisheries, and aesthetics. The value to society of many of theseAuthorsDaren Carlisle, Michael R. Meador, Terry M. Short, Cathy M. Tate, Martin E. Gurtz, Wade L. Bryant, James A. Falcone, Michael D. WoodsidePredicting thermal reference conditions for USA streams and rivers
Temperature is a primary driver of the structure and function of stream ecosystems. However, the lack of stream temperature (ST) data for the vast majority of streams and rivers severely compromises our ability to describe patterns of thermal variation among streams, test hypotheses regarding the effects of temperature on macroecological patterns, and assess the effects of altered STs on ecologicaAuthorsRyan A. Hill, Charles P. Hawkins, Daren CarlisleRelations between altered stramflow variability and fish assemblages in Eastern USA streams
Although altered streamflow has been implicated as a major factor affecting fish assemblages, understanding the extent of streamflow alteration has required quantifying attributes of the natural flow regime. We used predictive models to quantify deviation from expected natural streamflow variability for streams in the eastern USA. Sites with >25% change in mean daily streamflow variability compareAuthorsMichael R. Meador, Daren CarlisleThe relative importance of physicochemical factors to stream biological condition in urbanizing basins: Evidence from multimodel inference
Many physicochemical factors potentially impair stream ecosystems in urbanizing basins, but few studies have evaluated their relative importance simultaneously, especially in different environmental settings. We used data collected in 25 to 30 streams along a gradient of urbanization in each of 6 metropolitan areas (MAs) to evaluate the relative importance of 11 physicochemical factors on the condAuthorsDaren Carlisle, Wade L. BryantCauses of systematic over- or underestimation of low streamflows by use of index-streamgage approaches in the United States
Low-flow characteristics can be estimated by multiple linear regressions or the index-streamgage approach. The latter transfers streamflow information from a hydrologically similar, continuously gaged basin ('index streamgage') to one with a very limited streamflow record, but often results in biased estimates. The application of the index-streamgage approach can be generalized into three steps: (AuthorsK. Eng, J.E. Kiang, Y.-Y. Chen, D.M. Carlisle, G.E. GranatoAlteration of streamflow magnitudes and potential ecological consequences: A multiregional assessment
Human impacts on watershed hydrology are widespread in the US, but the prevalence and severity of stream‐flow alteration and its potential ecological consequences have not been quantified on a national scale. We assessed streamflow alteration at 2888 streamflow monitoring sites throughout the conterminous US. The magnitudes of mean annual (1980–2007) minimum and maximum streamflows were found to hAuthorsDaren Carlisle, David M. Wolock, Michael R. MeadorGAGES: A stream gage database for evaluating natural and alteredflow conditions in the conterminous United States
Stream flow is a controlling element in the ecology of rivers and streams. Knowledge of the natural flow regime facilitates the assessment of whether specific hydrologic attributes have been altered by humans in a particular stream and the establishment of specific goals for stream-flow restoration. Because most streams are ungaged or have been altered by human influences, characterizing the naturAuthorsJames A. Falcone, Daren Carlisle, David M. Wolock, Michael R. Meador