What is NAWQA? What are they doing in southern Louisiana?
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Land and Resource Uses of the Acadian-Pontchartrain NAWQALouisiana has abundant natural resources. These are some of the main types of land use, and issues that relate to water resources:
A general land-use map, showing agriculture, urban areas, and forest/swamp/marsh.
Rice is cultivated in a large portion of southwestern Louisiana. In some areas, rice is "double-cropped" with crawfish, where crawfish are collected with traps from ricefields flooded over the winter, before new rice is sown. Water for the fields is pumped from the ground or diverted from nearby streams, which may experience flow reversals. Draining ricefield water carries large amounts of sediment into nearby waterways.
Sugarcane, corn, and soybeans are grown in large areas of the Verret Basin, an area between levees of the Atchafalaya and Mississippi levees. Sugarcane is also grown around the City of Lafayette. The use of atrazine on sugarcane and corn, and its subsequent leaching to nearby waterways, exacerbates the problem of high dissolved atrazine concentrations in Mississippi River water. Atrazine is used in large portions of the midwest, drains into the Mississippi, and exposes aquatic organisms to chronic levels of atrazine.
Population is rapidly increasing in parts of the study unit, notably the North Shore of Lake Pontchartrain and the areas surrounding Baton Rouge. Most modern development is suburban and commercial, which affects large areas of land with changes in rain-runoff characteristics and quality.
Urban streams receive large amounts of water in very short spans of time during storms. When weather is clear, water levels can be very low. Urban streams in the Baton Rouge area are usually channelized, and cleared of woody vegetation to speed drainage during high water. While the channels may be initially V-shaped after channelization, a deep U-shape develops, along with natural meanders, after months or years of storm flows. This deep U-shape is characteristic of sticky-clay soils from ancient river deposits.
Parks, preserves, and wildlife management areas:
Fishing, hunting, and other recreational water uses are common in the Gulf region. Wildlife Management Areas are spread across Louisiana and Mississippi. Nutrient enrichment and high levels of bacteria can adversely affect options for swimming and fishing.
Oil and gas has been extracted and processed in this area for many decades. Oil refineries and pumps can often be found intermixed with rice fields and pastures, and along major waterways.
Sand and Gravel Mining:
Away from the coastal areas, sand and gravel may be mined from riverbeds. This mining destabilizes the channel, and can lead to greatly increased sedimentation downstream.
Marshes in south Louisiana are rapidly converting to open water. Natural sinking through subsidence and compaction of sediments are natural in this area of newly-formed land. However, with the modern levee and canal systems of southern Louisiana, water moves differently from the historical period when these marshes were established. Marshes may lack inputs of freshwater or sediment, or suffer too many nutrients and pesticides, resulting in plant death.
Introduced species, such as nutria, are changing the makeup of swamp communities. Nutria eat tree seedlings, changing swamp to open area. Other invasive species, such as Chinese Tallowtree, water hyacinth, and common carp change the ecological composition of animals and plants in Lousiana wetlands, competing with native species or changing the physical habitat.
Increases in available nutrients, as well as the importation and release of non-native aquatic plants, has led to many bayous being choked with aquatic vegetation. Dense growth of aquatic vegetation impedes shipping traffic and recreational boating. These invaders are easily transported to new waters by clinging to boat propellers. Aquatic vegetation may be physically removed with "harvesters" or poisoned with herbicides. These treatments usually offer only temporary relief.
Of particular importance in southern Louisiana is the spread of a non-native relative of duckweed called Giant Salvinia. Like water hyacinth, Giant Salvinia forms a dense coat of vegetation on the water's surface, shutting out light to phytoplankton and aquatic plants below. Unlike hyacinth, Giant Salvinia offers little surface or root area for aquatic invertebrates to live in, further reducing production at the bottom of the food chain. The problem has become so severe, the US Department of Agriculture has a Pest Alert to help people be aware of, and more readily identify this invasive species. Giant Salvinia resembles another Salvinia species called "Water Spangle" that has also invaded Louisiana waterways, but to a less noxious extent.