Environmental water studies refer to understanding the quantity, timing, and quality of water flows, as well as the water levels and storage required to sustain freshwater and estuarine ecosystems and the human livelihoods that depend on these ecosystems. The concept of ‘environmental flows’ in stream ecology are the basis of these studies, but they go beyond the understanding of surface flows and include the understanding of variations in water levels in other aquatic systems such as lakes, springs, wetlands, and aquifers.
Water Census • Streamflow • Groundwater • Water Use • Environmental Flows • Evapotranspiration • Focus Area Studies
Environmental Water Studies
Advances in ecological water studies rely on the development of techniques that can be used to link elements of hydrologic regimes to estimates or indicators of how a range of aquatic organisms living in the ecosystem will biologically respond. Developing accurate and reliable metrics requires studying biological responses – such as how different types of aquatic habitats respond to hydrologic changes and researching how aquatic organisms respond to key hydrologic variables – in order to identify indicator species which can be used to draw broader inferences about how the full community is likely to be affected. In a stream ecosystem, this includes aspects of the stream's hydrograph – for example, the seasonality, timing, and frequency of low and high flows, as well as the speed (or rate) at which hydrologic processes occur. It could also include water-quality characteristics, such as dissolved oxygen, temperature, or other factors that are known to influence the occurrence and distribution of aquatic organisms.
Baseline Hydrographs
The USGS is developing innovative tools and resources that provide stakeholders and environmental water science practitioners with the hydrologic and ecological information necessary for comparing natural and altered hydrologic regimes and determining the effects of streamflow alteration and water withdrawals on aquatic ecosystems. The goal is to build stakeholders' capacity to use science to develop their own management metrics and guidelines. At the national scale, this includes developing stream simulation and modeling tools for building a national foundation of baseline streamflows that will ultimately produce hydrographs from which a suite of ecologically important hydrologic statistics for all ungaged stream locations in the U.S can be calculated. Baseline hydrographs provide a hydrologic reference point by which hydrologic alterations can be considered.
Stream Classifications
A national streamflow classification structure and set of flexible tools developed for the National Water Census will give stakeholders the capability to evaluate stream characteristics and ecological parameters at regional and local scales. This builds stakeholder capacity to use science to develop management metrics and guidelines. At the national scale, this includes stream simulation and modeling tools for building baseline streamflow estimates, which are derived from a suite of ecologically important hydrological statistics at un-gaged stream location in the United States. Baseline hydrographs provide a reference point by which hydrologic alterations can be considered.
Ecological Effects of Hydrologic Alteration
In addition to the national-scale ecological water studies, the USGS is performing ecological water studies at the large-river basin scale in Focus Area Studies. These studies emphasize development of modeling tools that are highly transferable to other large-river basins. Several of these studies are incorporating components of a scientific framework for evaluating ecological water needs at multiple spatial scales known as the Ecological Limits of Hydrologic Alteration (ELOHA). ELOHA is a flexible framework for supporting water management decisions based on scientific information about ecological responses. The USGS role is to provide background scientific information that stakeholders can use to develop and test their own scenarios.
The Apalachicola-Chattahoochee-Flint, Delaware, Coastal Carolinas, and Red River Focus Area Studies have incorporated ecological water science components.
Below are other science components of the National Water Census.
National Water Census
National Water Census: Streamflow
National Water Census: Groundwater
National Water Census: Water Use
National Water Census: Evapotranspiration
National Water Census: Focus Area Studies
Below are publications associated with the National Water Census.
Evaluating and managing environmental water regimes in a water-scarce and uncertain future
Recent advances in environmental flows science and water management—Innovation in the Anthropocene
Measuring and evaluating ecological flows from streams to regions: Steps towards national coverage
Using regional scale flow–ecology modeling to identify catchments where fish assemblages are most vulnerable to changes in water availability
A comparison of hydrologic models for ecological flows and water availability
An objective and parsimonious approach for classifying natural flow regimes at a continental scale
- Overview
Environmental water studies refer to understanding the quantity, timing, and quality of water flows, as well as the water levels and storage required to sustain freshwater and estuarine ecosystems and the human livelihoods that depend on these ecosystems. The concept of ‘environmental flows’ in stream ecology are the basis of these studies, but they go beyond the understanding of surface flows and include the understanding of variations in water levels in other aquatic systems such as lakes, springs, wetlands, and aquifers.
Water Census • Streamflow • Groundwater • Water Use • Environmental Flows • Evapotranspiration • Focus Area Studies
Environmental Water Studies
Example output from REFDSS showing a “Flow Versus Habitat Chart”, which is a means of visualizing the habitat area as a function of streamflow (discharge). Advances in ecological water studies rely on the development of techniques that can be used to link elements of hydrologic regimes to estimates or indicators of how a range of aquatic organisms living in the ecosystem will biologically respond. Developing accurate and reliable metrics requires studying biological responses – such as how different types of aquatic habitats respond to hydrologic changes and researching how aquatic organisms respond to key hydrologic variables – in order to identify indicator species which can be used to draw broader inferences about how the full community is likely to be affected. In a stream ecosystem, this includes aspects of the stream's hydrograph – for example, the seasonality, timing, and frequency of low and high flows, as well as the speed (or rate) at which hydrologic processes occur. It could also include water-quality characteristics, such as dissolved oxygen, temperature, or other factors that are known to influence the occurrence and distribution of aquatic organisms.
Baseline Hydrographs
The USGS is developing innovative tools and resources that provide stakeholders and environmental water science practitioners with the hydrologic and ecological information necessary for comparing natural and altered hydrologic regimes and determining the effects of streamflow alteration and water withdrawals on aquatic ecosystems. The goal is to build stakeholders' capacity to use science to develop their own management metrics and guidelines. At the national scale, this includes developing stream simulation and modeling tools for building a national foundation of baseline streamflows that will ultimately produce hydrographs from which a suite of ecologically important hydrologic statistics for all ungaged stream locations in the U.S can be calculated. Baseline hydrographs provide a hydrologic reference point by which hydrologic alterations can be considered.
Stream Classifications
A national streamflow classification structure and set of flexible tools developed for the National Water Census will give stakeholders the capability to evaluate stream characteristics and ecological parameters at regional and local scales. This builds stakeholder capacity to use science to develop management metrics and guidelines. At the national scale, this includes stream simulation and modeling tools for building baseline streamflow estimates, which are derived from a suite of ecologically important hydrological statistics at un-gaged stream location in the United States. Baseline hydrographs provide a reference point by which hydrologic alterations can be considered.
Ecological Effects of Hydrologic Alteration
In addition to the national-scale ecological water studies, the USGS is performing ecological water studies at the large-river basin scale in Focus Area Studies. These studies emphasize development of modeling tools that are highly transferable to other large-river basins. Several of these studies are incorporating components of a scientific framework for evaluating ecological water needs at multiple spatial scales known as the Ecological Limits of Hydrologic Alteration (ELOHA). ELOHA is a flexible framework for supporting water management decisions based on scientific information about ecological responses. The USGS role is to provide background scientific information that stakeholders can use to develop and test their own scenarios.
The Apalachicola-Chattahoochee-Flint, Delaware, Coastal Carolinas, and Red River Focus Area Studies have incorporated ecological water science components.
- Science
Below are other science components of the National Water Census.
National Water Census
The USGS National Water Census (NWC) is designed to systematically provide information that will allow resource managers to assess the supply, use, and availability of the Nation’s water. The goal of the NWC is to provide nationally-consistent base layers of well-documented data that account for water availability and use nationally.National Water Census: Streamflow
The USGS National Water Census complements the USGS national network of more than 8,000 streamgages by estimating streamflow for ungaged locations throughout the country, by analyzing streamflow records, and by providing tools for analysis of streamgage data to end users. The USGS National Water Information System (NWIS) makes the actual streamgage data available to the public, most of it in "near...National Water Census: Groundwater
The National Water Census (NWC) is leveraging a long history of groundwater studies and is accelerating ongoing regional studies to assess the Nation's groundwater reserves, studies that formerly were conducted under the USGS Groundwater Resources Program. The NWC is also increasing the ability to integrate groundwater and surface-water analyses into watershed-level assessments of water...National Water Census: Water Use
Through the National Water Census, USGS will provide national information on withdrawal, conveyance, consumptive use, and return flow by water-use category at spatial and temporal resolutions important for risk-informed water management decisions. Water-use data provide a foundation for water managers to analyze trends over time, plan more strategically, identify, and ultimately quantify...National Water Census: Evapotranspiration
No water budget would be complete without accounting for evaporation and related processes, such as transpiration and sublimation. Evapotranspiration, or "ET," refers to the combined flux of plant transpiration and evaporation from the adjacent soil. It is especially important for understanding water used by irrigated crops, and is related to crop productivity. Consumptive water use for irrigation...National Water Census: Focus Area Studies
Focus Area Studies are stakeholder-driven assessments of water availability in river basins with known or potential conflict. They contribute toward ongoing assessments of water availability in large watersheds, provide opportunities to test and improve approaches to water availability assessment, and inform and ground truth the National Water Census with local information. Common to each of the... - Publications
Below are publications associated with the National Water Census.
Evaluating and managing environmental water regimes in a water-scarce and uncertain future
While the number of environmental flows and water science programmes continues to grow across the globe, there remains a critical need to better balance water availability in support of human and ecological needs and to recognise the environment as a legitimate user of water. In water‐stressed areas, this recognition has resulted in friction between water users in the public and private sectors. ARecent advances in environmental flows science and water management—Innovation in the Anthropocene
The implementation of environmental flow regimes offers a promising means to protect and restore riverine, wetland and estuarine ecosystems, their critical environmental services and cultural/societal values.This Special Issue expands the scope of environmental flows and water science in theory and practice, offering 20 papers from academics, agency researchers and non‐governmental organisations,Measuring and evaluating ecological flows from streams to regions: Steps towards national coverage
Living aquatic communities are largely determined and maintained by the volume and quality of flowing waters, both within lotic systems and in receiving waters of coastal systems. However, flow is one of the most frequently and extensively altered features of rivers and streams; alteration effects are likely to be exacerbated by climate change. Lotic systems vary and different fish species need diUsing regional scale flow–ecology modeling to identify catchments where fish assemblages are most vulnerable to changes in water availability
Streamflow is essential for maintaining healthy aquatic ecosystems and for supporting human water supply needs. Changes in climate, land use and water use practices may alter water availability. Understanding the potential effect of these changes on aquatic ecosystems is critical for long-term water management to maintain a balance between water for human consumption and ecosystem needs.Fish speciA comparison of hydrologic models for ecological flows and water availability
Robust hydrologic models are needed to help manage water resources for healthy aquatic ecosystems and reliable water supplies for people, but there is a lack of comprehensive model comparison studies that quantify differences in streamflow predictions among model applications developed to answer management questions. We assessed differences in daily streamflow predictions by four fine-scale modelsAn objective and parsimonious approach for classifying natural flow regimes at a continental scale
Hydro-ecological stream classification-the process of grouping streams by similar hydrologic responses and, by extension, similar aquatic habitat-has been widely accepted and is considered by some to be one of the first steps towards developing ecological flow targets. A new classification of 1543 streamgauges in the contiguous USA is presented by use of a novel and parsimonious approach to unders