Proxies Project | U.S. Geological Survey

The Proxies Project is a series of studies to improve our understanding of water contaminants and water quality hazards. These studies develop models and technical approaches for estimating concentrations and assessing risk associated with:

- harmful algal blooms (HABs)
- per- and polyfluoroalkyl substances (PFAS)
- 12 elements of concern (EoC)

Harmful Algal Blooms • Per- and Polyfluoroalkyl Substances • Elements of Concern

A ‘proxy’ (also known as a ‘surrogate’) is a measurement or model of one thing that helps us to understand some other thing that we’re interested in (like HABs, PFAS, or EoC). The proxy is typically simpler, cheaper, and (or) more rapidly measured than the direct measurement of the thing we’re interested in. In this project, the proxies we can readily measure or model are water constituents (like temperature, dissolved oxygen, turbidity, and salinity) and physical processes (like streamflow and runoff). The things we’re interested in are the water quality hazards and contaminants.

The three workgroups that make up the Project are taking a combination of approaches to develop proxy models for the three water contaminants (PFAS and EoC) and water quality hazards (HABs) noted above, although all workgroups are using:

Geospatial data
In-situ sensors (sensors that stay in the water)

In-situ sensors provide continuous, high-resolution data for a wide range of water quality metrics, which are necessary for proxy model development.

The specific studies are being conducted in hydrologic basins. A hydrologic basin is an area of land where all the precipitation drains into a specific river, like the Mississippi River Basin or the Columbia River Basin. The studies in the Proxies Project range from sub-basins (small drainage areas completely contained within larger basins) to multi-basins (independent large basins or groups of interconnected basins). This big range in spatial scale makes it easier to take the approaches and models developed by the Proxies Project and ultimately apply them to the whole country.

The three hydrologic basins for these studies include:

Delaware River Basin
Upper Colorado River Basin
Illinois River Basin

Additional PFAS-focused studies are also being conducted in Cape Cod and the Potomac River Basin.

Map showing the locations of the three primary Integrated Water Availability Assessment (IWAA) hydrologic basins (Delaware River, Illinois River, and Upper Colorado River). — Map showing the locations of the three primary Integrated Water Availability Assessment (IWAA) hydrologic basins (Delaware R., Illinois R., and Upper Colorado R.) where various Proxies project surface water studies and modeling efforts are taking place (blue insets). Additional PFAS specific studies (green insets) are being conducted in the Potomac R. basin and at the ‘USGS Cape Cod Groundwater Contamination Research Site’ (red star).

This webpage has links to all products resulting from the Proxies Project. The sections below provide more information on the goals, objectives, and approaches for each of the three workgroups, as addressed by this four-year effort (fiscal years 2021-2024).

Project Wide Product

Web Tool
Catalogue of Geospatial Datasets for the USGS Water Quality Program, Proxies Project

Harmful Algal Blooms (HABs)

USGS Hydrologist Collects a Water-Quality Sample at Henry, Illinois — USGS hydrologist Jessie Garrett collects a sample from a HAB on the Illinois River in 2021. Photograph by Katie Summers, USGS.

Harmful algal blooms (HABs) happen when naturally occurring algae become very abundant and (or) releases toxins that can be harmful to people, pets, and wildlife. We generally understand the major drivers of HABs, like high water temperature, slow water, and sunlight. But we understand less about how these factors interact to start a HAB at a particular place and time, particularly when and where HABs occur in flowing water, like rivers and streams.

The main goals of the HABs part of the Proxies Project are to:

Better understand the processes controlling HABs in rivers
Develop better approaches to identify and forecast HABs at different spatial scales

Specific objectives of the HABs studies include:

Assess existing metrics and thresholds used to define HABs
Develop proxy approaches for identifying HABs in rivers, using continuous monitoring
(in-situ sensor) data at the basin or sub-basin scale
Map rivers vulnerable to HABs across the conterminous U.S. (lower 48 states)
Use these new approaches to create a framework for forecasting HABs in river systems

The HABs workgroup is using existing data sources and a combination of geospatial analytics, machine learning, and modeling to meet these objectives.

Contact: Jennifer Murphy

HABs Products

Data Releases

Papers

Software or code

Per- and Polyfluoroalkyl Substances (PFAS)

A USGS scientist collects groundwater as it discharges into a lake in Cape Cod, Massachusetts. — USGS scientist Dennis LeBlanc collects groundwater as it discharges into a lake in Cape Cod, Massachusetts. The groundwater contains high concentrations of PFAS from a legacy fire training area. Photograph by Douglas Kent, USGS.

Per- and polyfluoroalkyl substances (PFAS) are a diverse group of chemicals that:

Last a long time in the environment (hence their nickname “forever chemicals”)
Occur in many waterbodies (and in both surface water and groundwater)
Are potentially harmful to human health and aquatic ecosystems

The current approach for measuring PFAS concentrations in natural waters, like rivers and lakes, is liquid chromatography-tandem mass spectrometry—an analytical method that is very good at detecting PFAS in water. However, this method is expensive and often involves long wait times for results. New proxy models and sensor-based technologies provide faster estimates of PFAS concentrations in water at a finer spatial scale. This information helps identify where we need to collect discrete water samples (samples of water collected at one point in time and taken back to a laboratory for analysis) and when we need to use traditional analytical approaches to quantify PFAS concentrations.

The main goals of the PFAS component of the Proxies Project are to:

Model PFAS concentrations in surface water and groundwater
Develop sensor-based approaches that provide proxy measurements for estimating PFAS concentrations in natural waters

Specific objectives of the PFAS studies include:

Develop a data exploration and visualization tool that shows the locations of potential PFAS sources in each basin, which will help inform PFAS modeling efforts
Develop surface-water models for PFAS concentrations at the basin spatial scale
Conduct field studies using various sensor technologies to develop proxy approaches for estimating PFAS concentrations in natural waters
Conduct field studies to better estimate PFAS concentrations in contaminated groundwater sites

To meet these objectives, the PFAS workgroup uses a combination of:

Existing and new data collected by both discrete sampling and in-situ sensors
Geospatial analytics focused on potential PFAS sources
Hydrodynamic modeling to predict concentrations

Contact: Larry Barber, Doug Kent

PFAS Products

Data Releases

Papers

Web tool

Interactive Map: Potomac Wastewater Mapper

Elements of Concern (EoC)

Graphic of twelve elements of concern identified by Basin Managers in the Delaware River Basin, Illinois River Basin, and Upper Colorado River Basin as part of a 2021 survey that are studied by the Proxies Project.. — Elements of Concern (EoC): The Proxies Project studies 12 EoC that Basin Managers in the Delaware River Basin, Illinois River Basin, and Upper Colorado River Basin identified as part of a 2021 survey. Of the 12 elements identified, there are: 7 transition metals (Cd, Cu, Cr, Fe, Hg, Mn, Zn) 2 post-transition metals (Al, Pb) 1 metalloid (As) 1 reactive non-metal (Se) 1 actinoid (U)

Elements of concern (EoC) are a group of elements that are monitored at the local, regional, or national level because of their known toxicity in aquatic systems. Traditional, discrete water sampling approaches for monitoring EoC concentrations require a lot of time and money, and often involve prolonged wait times for obtaining results. Continuous proxy measurement of EoCs in rivers allows for more rapid and (near) real-time estimates of EoC concentrations, which may reveal unhealthy levels of EoC sooner. Proxy approaches for estimating EoC concentrations across large spatial scales (sub-basins and basins) can help identify sources of EoC and show how far EoC travel.

The main goals of the EoC part of the Proxies Project are to:

Explore modeling approaches that provide high-frequency (rapid and near real-time), site-specific estimates of EoC concentrations in streams
Explore modeling approaches that provide sub-basin- to basin-scale spatial estimates of EoC concentrations in streams based upon specific landscape and geographic factors

Specific objectives of the EoC studies include:

Develop a data exploration and visualization tool for mapping concentrations of the 12 EoC in the three study basins (Delaware River Basin, Illinois River Basin and Upper Colorado River Basin) using existing data from the Water Quality Portal
Develop spatially explicit models (models where the specific locations of things matter) using a combination of machine learning and a long list of attributes for each basin (for example, geology and soil characteristics, mining areas, population centers, and infrastructure). These models show us which attributes affect how EoC vary across the landscape at different spatial scales, from small drainage areas to large basins.
Develop models that provide high-frequency estimates of EoC concentrations at USGS continuous water monitoring sites using commonly deployed in-situ sensors (pH, specific conductance, dissolved oxygen, turbidity, temperature, and streamflow)
Develop models that estimate EoC concentrations through time and across the landscape using new sensor technology and newly collected field data

To achieve these objectives, the EoC workgroup is using:

Existing data from the Water Quality Portal
New data collected in the field (including EoC concentration data and paired sensor data)
Geospatial approaches with machine learning and other forms of statistical modeling

Contact: Mark Marvin-DiPasquale, Blaine McCleskey

EoC Products

Data Release

Concentration Data for 12 Elements of Concern Used in the Development of Surrogate Models for Estimating Elemental Concentrations in Surface Water of Three Hydrologic Basins (Delaware River, Illinois River and Upper Colorado River)

Software or code

Code to Download and Harmonize Discrete Metals and Ancillary Data in Three Hydrologic Basins (Delaware River, Illinois River and Upper Colorado River)

Web Tool

Concentration data for 12 elements of concern in surface water of three hydrologic basins (Delaware River, Illinois River and Upper Colorado River) – A data visualization tool

Below are data associated with this project.

Below are publications associated with this project.

Proxies Project Active