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Fresh and salt water How do coastal wetlands balance fresh and salt water?

Trace rivers, tides, salinity gradients, groundwater, wetland life, drought, storms, restoration, and monitoring through fresh and salt water balance.

5
lessons
~20 min
to learn
🔬 Science
subject
Adults
level
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What you’ll learn

  1. Freshwater meets the tideExplain how river flow and tides create a moving salinity gradient.Freshwater meets the tide maps the sources and mixing pathways that connect rivers, wetlands, and estuaries.
  2. Salinity moves through wetlandExplain how salt travels through surface water, soil, groundwater, and infrastructure.Salinity moves through wetland follows storage, exchange, residence time, and hidden water routes.
  3. Plants and animals manage saltConnect salinity exposure with wetland plant zones, animal movement, and food webs.Plants and animals manage salt shows how tolerance, microhabitat, and connectivity shape living communities.
  4. Weather and people change the balanceExplain how drought, rain, storms, withdrawals, and restoration alter fresh-salt water balance.Weather and people change the balance links events and decisions to altered water pathways.
  5. Monitoring a shifting gradientUse contextual measurements and models to evaluate changing salinity patterns.Monitoring a shifting gradient turns water-balance ideas into testable evidence and revisable explanations.

Questions this course answers

Why does the salinity boundary in an estuary move?

Freshwater input and tidal saltwater exchange vary through time and space.

Put the water-mixture pathway in order.

Inputs and movement create the chemical conditions organisms encounter.

Why can soil remain salty after surface water drains?

Pore-water storage and slow exchange can create a lag in soil conditions.

Why does residence time matter to a wetland?

Duration of exposure can matter as much as the peak salinity.

What best explains plant zones across a marsh?

Plant distribution reflects several interacting physical and biological conditions.

Match each feature with its role.

Different wetland structures shape pathways or exposure in different ways.

Grounded in trusted sources

  • NOAA National Ocean Service, What is an estuary? Estuaries Tutorial, https://oceanservice.noaa.gov/education/tutorial_estuaries/est01_whatis.html
  • NOAA National Estuarine Research Reserve System, What Is an Estuary?, https://coast.noaa.gov/nerrs/about/what-is-an-estuary.html
  • U.S. Environmental Protection Agency, Indicators: Salinity, https://www.epa.gov/national-aquatic-resource-surveys/indicators-salinity
  • U.S. Geological Survey, Freshwater-Saltwater Interactions along the Atlantic Coast, https://water.usgs.gov/ogw/gwrp/saltwater/gwflow.html
  • National Park Service, Wetlands and Marshes - Point Reyes National Seashore, https://www.nps.gov/pore/learn/nature/wetlands.htm
  • Wikimedia Commons MediaWiki API image records, https://commons.wikimedia.org/w/api.php

Every Wunder lesson is built from real, reputable sources — never invented.

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