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Environmental Overview - Regional Description of the Lake Pontchartrain Basin Contributors: Penland, McCarty, Beall, Maygarden
The process of preserving and restoring water quality is complex (Stone et al., 1982; LPBF, 1995). Although there have been numerous studies and reports that address water quality in the Basin, not every scientist, regulatory agency or concerned citizen will agree on the true nature of the problem. At times it is difficult to establish clear cause-and-effect relationships between human activities and the deterioration of water quality.
There are, however, known sources of water pollution, both point (from a single source) and non-point (from diffuse sources) that need to be considered. Stormwater runoff is the largest contributor to the pollution in Lake Pontchartrain, followed by wastewater discharge and agricultural runoff.
Bacteria and viruses (pathogens) from warm-blooded animals and human wastes represent a major source of pollution that limits primary and secondary recreation in the Basin's water bodies. Because of the pathogen contamination, the Louisiana Department of Health and Hospitals (LDHH) advises against swimming within approximately one-quarter mile from the south shore of Jefferson and Orleans Parishes and within 183 m (600 ft) of the mouths of rivers and streams that flow into the Lake along the north shore. Several rivers in parishes that border the Lake have also been posted against swimming in recent years.
Some of the most severe water quality problems are found along the shorelines directly adjacent to Lake Pontchartrain in Jefferson, Orleans and St. Tammany Parishes. Much of this pollution originates from urban stormwater runoff, the largest single cause of water pollution in the Basin. In addition to pathogens, stormwater may contain elevated levels of heavy metals and elevated amounts of soil-derived suspended sediments.
Urban runoff is not the only source of municipal water pollution. In 1989, more than 500 communities were discharging treated and untreated wastewater into the Lake Pontchartrain Basin. These facilities ranged from individual package treatment systems for schools or subdivisions to large municipal systems discharging more than one million gallons of treated sewage daily. Wastewater from these facilities contains varying amounts of suspended solids, biochemical oxygen-demanding materials, nutrients (phosphorous and nitrogen) and pathogens.
In addition to larger treatment systems, tens of thousands of individual septic systems contribute to water quality problems. In some poorly sewered and non-sewered communities, untreated sewage is being directly discharged into the Lake and its rivers and bayous. Although water quality impacts from sewage have been lessened by system upgrades on the south shore, improved septic tank regulations and the diversion of wastewater to the Mississippi River, significant problems still remain, especially on the north shore.
Agricultural discharges also contribute significant pollution loadings to the Lake Pontchartrain Basin (LPB). Agricultural runoff, originating from farm practices such as animal operations, agrochemical applications and land-clearing activities contains pathogens, nutrients, toxic chemicals and sediments. Although pathogen contamination from large animal operations has led to the closing of some rivers to recreation, new cost-sharing programs have begun to address these problems. In addition to agricultural practices, tree-farming operations have impacted water quality in specific areas. In order to address the impacts of forestry operations, voluntary best management practices (BMPs) have been in effect since 1990.
Oil and gas production has also impacted the Lake. Produced water or formation brine is a by-product of oil and gas well operations. Produced water contains varying levels of salt water with organic, naturally occurring radioactive and heavy metal contaminants that can adversely affect receiving waters. The impact on water quality in a shallow confined lake, such as Lake Pontchartrain, would be far greater than on deep flowing seawater such as the Gulf of Mexico.
Currently, there is a moratorium on new drilling operations in the Lake itself, and state and federal regulations will phase out most discharges in the Basin. Some operations in high-flushing areas in the Basin, such as Breton Sound, will be allowed to continue discharging produced water into the Basin if permitted by the Louisiana Department of Environmental Quality (LDEQ).
The salinity in the Lake is also affected by saltwater intrusion from MRGO via IHNC and the Intracoastal Waterway. In the eastern end of the Basin, fresh water from the Pearl River can dilute some of the elevated salinity levels. Freshwater diversion projects can also offset the effects of saltwater intrusion. Diversions from the Mississippi River can provide much-needed sediments to replenish wetland areas. While diversions can be beneficial, they also have the potential to cause environmental harm. The Mississippi River contains toxic chemicals, pesticides, herbicides, excess nutrients and sediments. Any diversion project must be judged on both its merits and its potential to cause damage.
Both residential and commercial development of uplands and wetlands have also impacted water quality throughout the Basin. Dredging and filling of wetlands is often considered to be the most detrimental of these practices. Wetlands serve as natural filters for stormwater runoff. When the natural vegetation is destroyed, sediments, heavy metals and other contaminants are transferred to the Basin's surface waters. In addition, the impervious surfaces, resulting from the steadily increasing number of roads, parking lots and driveways, decrease the surface area available for filtering runoff through the soil. As development around the Basin increases, water quality problems are expected to escalate. The EPA Index of Watershed Indicators ( IWI ) provides a good environmental overview of the LPB (Figure 10). Using seven condition and nine vulnerability indicators, the IWI data provide an overall water quality assessment rank for the Basin. Of the ten watersheds that make up the Lake Pontchartrain Basin, only the Amite is designated as having Serious Water Quality Problems and High Vulnerability. Seven are designated as having Serious Water Quality Problems and Low Vulnerability and three as having Water Quality Problems with Low Vulnerability. In general, the watersheds draining the Florida Parishes are in poorer condition than the others in the Basin, with the exception of the Tangipahoa watershed. All of the watersheds rank poorly in the Designated Use Attainment, Ambient Water Quality Data - Four Conventional Pollutants, Wetland Loss Index and Aquatic/Wetland Species at Risk IWI indicators. The remaining IWI indicators vary among the watersheds. Figure 11 illustrates the IWI ranking of all watersheds in Louisiana, allowing a comparison of the Lake Pontchartrain Basin watersheds with others in the state.
As this overview demonstrates, the LPB has experienced serious decline since the middle of the last century and continues to face pressures and challenges. The good news is that due to the SAVE OUR LAKE initiative and the LPBF's leadership in this coordinated campaign to restore the Basin, the water quality and other ecological health indicators are improving. In addition, as a result of projects funded through the Coastal Wetland, Planning Protection and Restoration Act (CWPPRA), some critical wetland habitats that were rapidly disappearing are now recovering. The Lake Pontchartrain Basin Restoration Act of 2000 will provide greater resources to address the environmental restoration of the Basin. The successful restoration of the LPB must be based on the distribution of sound technical information to planners and decision makers. The Environmental Atlas of the Lake Pontchartrain Basin is a step toward restoring the Basin. « Previous | Next »