Facts About the Lake Pontchartrain Basin
- Another name for the Lake Pontchartrain Basin is the Lake Pontchartrain Watershed.
- The basin, or watershed, is home to 1.5 million people.
- The watershed drains the land in 16 parishes in Louisiana and 4 counties in Mississippi.
- The Louisiana parishes in the Lake Pontchartrain Watershed are: Ascension, East Baton Rouge, East Feliciana, Iberville, Jefferson, Livingston, Orleans, Plaquemines, Tangipahoa, St. Bernard, St. Charles, St. James, St. John the Baptist, St. Helena, St. Tammany, and Washington.
- Lake Pontchartrain, formed 5000 years ago, is the largest feature of the Lake Pontchartrain Basin.
- Lake Pontchartrain is not a lake; it is an estuary, or an area in which fresh water from rain and rivers measurably dilutes the salt water from the Gulf of Mexico.
- Lake Pontchartrain is an entire ecosystem with great biodiversity. An ecosystem is made up of all the living and nonliving components of the environment.
What is a Water Shed?
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- A watershed is the total land area that contributes runoff to a specific body of water.
- The runoff is the water which flows off the land surface.
- The elevation and slope of the land determines which way the surface water will flow.
- The lowest areas in the watershed that act as collecting basins include rivers, bayous, canals, ditches, streams and lakes.
Lake Pontchartrain Basin
The Lake Pontchartrain Basin is a large watershed covering
700 square miles. In Louisiana the northern border is the Louisiana/Mississippi state line. The basin continues south to the Gulf of Mexico along the east bank of the Mississippi River. The western border of the Basin is the east bank of the Mississippi River, and the
eastern boundary is the Pearl River from Washington Parish to Breton Sound.
Where Does the Water in the Watershed Come From?
- Precipitation: Precipitation may be in the form of normal rainfall up to 60 inches per year or excessive ainfall events. Other forms of precipitation include sleet, freezing rain, or light snow.
- Groundwater: Groundwater infiltrates/percolates from surface waters, surrounds sedi-ment particles, and filters through the soil. Trapped groundwater may collect in aquifers, or it may move to the surface by way of wells drilled into aquifers or by seeping from springs.
- Land Drainage: Precipitation may land on non-absorbent surfaces. This surface runoff drains to lower areas from the streets, down the storm drains, and eventually gets pumped into the lowest area, Lake Pontchartrain.
- Waterbodies: Canals, lakes, and bayous are some of the water-collecting areas that hold and nnel water in and out of the watershed.
- Human use: Each person uses approximately 100 gallons of water each day. This water is brought from a water source by pipes. Careless actions by citizens, however, often allow water that is intended for human use to become surface runoff; examples include open or leaky faucets and old cracked pipes.
- Gulf of Mexico: Waters from the Gulf of Mexico move in and out of the Lake Pontchartrain area on each high and low tide and are blown in by strong easterly winds.
How does precipitation affect the watershed?
The water from rain runs off the land after heavy rainfall or small showers. This rainwater reaches the surface of the earth and enters the water cycle.
- The water cycle is an exchange of water molecules through the processes of evaporation, condensation, infiltration and precipitation.
- Evaporation is the loss of water molecules from the land surface and waterbodies; it supplies the moisture in the atmosphere.
- This moisture content is known as humidity.
- Moisture droplets gather together in the atmosphere where they condense around particles of dust or other
- Droplets become heavy, and eventually precipitation (rain) occurs.
How does groundwater affect the watershed?
- Precipitation soaks into the ground and becomes ground water.
- Surface water filters through soil and rock before reaching an aquifer.
- Water in the spaces/openings surrounding soil particles (interstitial) is used for the biological needs of many plants and animals.
- Aquifers are impounded or enclosed areas which hold the water underground. Many aquifers are tapped by communities for drinking water. Surface waters that become contaminated or polluted may seep into underground aquifers, deteriorating the quality of the water in the watershed.
How does surface runoff affect the watershed?
- Surface runoff is water that either does not have time to sink into the ground or is produced in such quantity (e.g., floods) that the normal soakingup process cannot take place.
- Water in the form of precipitation runs off the land surface from either grass, soil, or paved areas.
- The runoff may also drain from open hydrants or hoses.
- Surface runoff, either from the "first flush," the first inch of a heavy rainfall, or from water draining for a longer time (e.g., a garden hose) carries pollutants, such as motor oil or pesticides, to the waterbodies in the watershed.
- Responsible actions on the part of citizens can prevent contamination in the watershed. For example, each of us should recycle used motor oil, pick up pet wastes, and properly use pesticides, fertilizers, and herbicides.