EDEN: A Decade of Daily Water Maps for the Everglades

From a U.S. Geological Survey fact sheet by Eduardo Patino, Paul Conrads, Eric Swain and James Beerens, prepared under the USGS Greater Everglades Priority Ecosystems Science programme with the U.S. Army Corps of Engineers' RECOVER programme for the Comprehensive Everglades Restoration Plan. Version 1.1, January 2018.

The Everglades Depth Estimation Network (EDEN) gives scientists and resource managers daily maps of water level and water depth across the freshwater part of the Greater Everglades. Its area covers all or part of five Water Conservation Areas, Big Cypress National Preserve, the Pennsuco Wetlands and Everglades National Park.

Figure 1. EDEN water-level and water-depth surfaces for August 1, 2017. USGS.

How the maps are made

Each day's water-level map is interpolated from readings at monitoring gages, and depth is then estimated from a digital elevation model of the land surface. Online datasets also give the daily water level at each gage, and rainfall and evapotranspiration data, at https://sofia.usgs.gov/eden/.

The current model, the EDEN surface-water model version 2:

• Gages: takes continuous water-level readings from 247 stations — in freshwater marshes, on canals and on the tidal coast — run by Big Cypress National Preserve, Everglades National Park, the South Florida Water Management District and the USGS.
• Interpolation: builds the daily surface from the daily median level at 223 of those stations, keeping the other 24 for quality checks and for filling in missing or faulty data.
• Improvements over the original model: adjusted input data, a better understanding of how water flows, a network of elevation benchmarks, an area extended to cover part of southern Big Cypress and northwestern Everglades National Park, and separate models for five subareas.

The subarea models better capture the sudden jumps in water level between Water Conservation Areas; their surfaces are then merged into one for the whole network.

Figure 3. Five subareas merged to represent the whole EDEN model area (modified from Telis and others, 2015). USGS.

Many of today's gages were not running before 2000, so past water levels had to be reconstructed. Levels and depths at these gages were hindcast back to 1991 using 214 empirical models.

Field water-level monitoring gage EDEN 13. Michael Oliver, USGS.

What the data are used for

Scientists and managers use EDEN to guide large field operations, describe changes in water, and assess how the ecosystem responds as the Comprehensive Everglades Restoration Plan is carried out. EDEN water data have been used, for example, to study:

1. the health of American alligators in relation to water depth;
2. how landscapes change after fire, in relation to water depth;
3. habitat quality for wading birds that shift where they feed;
4. the habitat of the Cape Sable seaside sparrow.

Two web tools

EDEN has grown from a map service into a set of tools for analysing and presenting how the environment responds to changes in water, and for assessing management strategies across the system.

Explore and View EDEN (EVE)

EVE (https://sofia.usgs.gov/eden/eve/index.php) lets users view and download water-level, rainfall and potential evapotranspiration data as graphs or tables, for up to five gages at a time. Water levels are available daily from 1991 or hourly from 2000; daily rainfall and evapotranspiration are also available.

The Cape Sable Seaside Sparrow Viewer

The endangered Cape Sable seaside sparrow is one of eight remaining subspecies of seaside sparrow. It is now known only from seven separate subpopulation areas (A–F and AX) in Everglades National Park. Studies have shown clear links between water depth and the number of sparrows, and successful nesting depends on particular water conditions.

The viewer (https://sofia.usgs.gov/eden/csss/index.php) tracks water depth in the sparrow's habitat, past and present. Its animated maps show flooded and dry ground and calculate, for each subpopulation area:

• the percentage of the area that is dry;
• the percentage with water 17 centimetres deep or less — a critical depth for the sparrow;
• the percentage that has been dry for 40 days or more, and for 90 days or more.

Managers use it daily to judge how water depths may affect nesting and to guide their decisions.

The next decade

EDEN will keep producing its maps while developing new real-time tools for analysis and visualisation, including forecasts of water levels using statistical and numerical methods, and more specialised applications like the sparrow viewer as scientists need them.

EDEN was created in 2005, realising the vision of Aaron Higer for an internet-based, real-time, quality-checked source of water information for the whole Everglades.

Sources

• Eduardo Patino, Paul Conrads, Eric Swain and James Beerens, Everglades Depth Estimation Network (EDEN) — A Decade of Serving Hydrologic Information to Scientists and Resource Managers, U.S. Geological Survey Fact Sheet 2017–3069, version 1.1, January 2018. https://doi.org/10.3133/fs20173069 — three USGS figures recovered from the PDF.
• The fact sheet's map of gages, drawn on an Esri base map, and its photograph of a Cape Sable seaside sparrow, by a New Jersey Audubon photographer under a Creative Commons licence, are not reproduced.
• Rewritten in hubnx's own words.