Appendix A is a compilation of the combined evaluative and monitored, where available, assessments for all assessed waterbodies in Louisiana. In cases where a waterbody is both monitored and assessed the worse of the two assessments is used under the heading "Degree of Support." "Waterbody Subsegment Code" and "Waterbody Description" provides the LDEQ code number for each subsegment and the physical description of the subsegment, respectively. The column under the heading "Type" indicates if a waterbody is either a river (R), lake (L), estuary (E) or wetland (W). "Size" refers to the total size of a waterbody subsegment, with rivers reported in miles, lakes in acres, and estuaries and wetlands in square miles.
"Degree of Support" represents the waterbodies overall degree of use support based on the numerical average of values assigned to the individual use support statements. Designated uses include: primary contact recreation (PCR), secondary contact recreation (SCR), fish and wildlife propagation (FWP), outstanding natural resource (ONR), drinking water supply (DWS), shellfish propagation (SFP), and agriculture (AGR).
For the 1998 assessment, overall degree of support uses the levels of fully, threatened, partially and not supporting designated uses. Levels of use support used for individual use support statements and their corresponding numerical value include fully supporting (F,4), fully supporting but threatened (T,3), partially supporting (P,2) and not supporting (N,1). Average support values from 3.5 to 4.0 are given an overall degree of support rating of fully supporting. Average values from 2.5 to 3.49 are rated as threatened, 2.49 to 1.5 are rated as partially supported, while values less than 1.5 are rated as not supported. If a designated use was considered to have insufficient data for a defensible assessment an "I" was placed in the column and no numerical value was assigned for overall support determination. Likewise, if a designated use did not apply to a particular waterbody a "." was placed in the column and no numerical value assigned.
The final two columns, "Suspected Causes" and "Suspected Sources", lists those causes and sources that are suspected of being responsible for waterbody impairment. Causes and sources printed in bold are heading categories with subcategory causes and sources, where appropriate, printed in normal type. For example, "Industrial point sources" is a heading category while "Major industrial point sources" and "Minor industrial point sources" are subcategories. Under this arrangement, "Industrial point sources" should not be considered a separate and independent source listing. Rather, it indicates that at least one subcategory is present. Therefore, when determining the size extent of waterbodies impacted by "Industrial point sources", or any other heading category, one should only add the miles for that category, not the miles for all subcategories below it.
Listings of suspected sources and suspected causes are not arranged in priority order, and no determination can be made as to which source or cause is primarily responsible for impairment. It is important to note that any single suspected cause or source of impairment cannot be considered the direct and only cause/source of use impairment. Rather, all cited causes and sources must be considered as a whole because in most cases they are interrelated. If monitoring data was available for assessment purposes, causes such as low DO or high fecal coliform levels could be more accurately determined. Monitoring information of this type is available in Appendix B. However, sources of these problems are generally less well defined, and are based on field staff evaluations. A complete listing of potential sources and causes can be found in Appendix F.
ATCHAFALAYA RIVER BASIN (01)
The Atchafalaya River Basin is located in the south central part of Louisiana. The Atchafalaya River is a distributary of the Red, Black, and Mississippi Rivers, presently carrying about 30 percent of the Mississippi's flow. The basin is well defined by a system of levees which surround it on the north, east and west. The entire basin serves as a major floodway for Mississippi River floodwaters. It encompasses approximately 1,806 square miles. The Atchafalaya Basin is predominantly wooded lowland and cypress-tupelo swamp with some fresh water marshes in the lower distributary area. It constitutes the largest contiguous fresh water swamp in the United States.
BARATARIA BASIN (02)
The Barataria Basin lies in the eastern coastal region of the state. This basin is bounded on the north and east by the lower Mississippi River, on the west by Bayou Lafourche and on the south by the Gulf of Mexico. The major receiving Waterbody in this basin is Barataria Bay. The Barataria Basin consists largely of wooded lowlands and fresh to brackish marshes, having some saline marsh on the fringes of Barataria Bay. Elevations in this basin range from minus two feet to four feet above sea level.
CALCASIEU RIVER BASIN (03)
The Calcasieu River Basin is located in southwestern Louisiana and is positioned in a north-south direction. The drainage area of the Calcasieu Basin comprises approximately 3,910 square miles. Headwaters of the Calcasieu River are in the hills west of Alexandria. The river flows south for about 160 miles to the Gulf of Mexico. The mouth of the river is about 30 miles east of the Texas-Louisiana state line. The landscape in this basin varies from pine forested hills in the upper end to brackish and salt marshes in the lower reach around Calcasieu Lake.
LAKE PONTCHARTRAIN BASIN (04)
The Lake Pontchartrain Basin, located in southeastern Louisiana, consists of the tributaries and distributaries of Lake Pontchartrain, a large estuarine lake. The basin is bounded on the north by the Mississippi state line, on the west and south by the east bank Mississippi River levee, on the east by the Pearl River Basin and on the southeast by Breton and Chandeleur Sounds. This basin includes Lake Borgne, Breton Sound, Chandeleur Sound and the Chandeleur Islands. The northern part of the basin consists of wooded uplands, both pine and hardwood forests. The southern portions of the basin consist of cypress-tupelo swamps and lowlands and brackish and saline marshes. The marshes of the southeastern part of the basin constitute the most rapidly eroding area along the Louisiana coast. Elevations in this basin range from minus five feet at New Orleans to over two hundred feet near the Mississippi border.
MERMENTAU RIVER BASIN (05)
The Mermentau River Basin is located in southwestern Louisiana, and encompasses the prairie region of the state and a section of the coastal zone. The Mermentau River Basin is bounded on the north and east by the Vermilion - Teche River Basin, on the west by the Calcasieu River Basin, and on the south by the Gulf of Mexico.
VERMILION-TECHE RIVER BASIN (06)
The Vermilion-Teche River Basin lies in south central Louisiana. The upper end of the basin lies in the central part of the state near Alexandria, and the basin extends southward to the Gulf of Mexico. The basin is bordered on the north and northeast by a low escarpment and the lower end of the Red River Basin. The Atchafalaya River Basin is to the east, and the Mermentau River Basin is to the west.
MISSISSIPPI RIVER BASIN (07)
The upper Mississippi River which flows south forms the boundary between Louisiana and Mississippi. The lower Mississippi River flows southeasterly through the southeast section of Louisiana. The upper stretch of the Mississippi does not get any tributary flow from the Louisiana side, which is leveed. Tributaries do enter from Mississippi, including the Yazoo River, the Black River, the Homochitto River, the Buffalo River and Bayou Pierre. The stretch of the Mississippi River between the Old River Control Structure and Baton Rouge does receive tributary flow from Thompson's Creek, Bayou Sara, Tunica Bayou and Monte Sano Bayou. The river is leveed on both the east and west banks from Baton Rouge below Monte Sano Bayou to Venice. This stretch of the river is also heavily industrialized, receiving numerous industrial discharges from Baton Rouge to New Orleans. The birdfoot delta of the Mississippi, where it flows into the Gulf, consists of fresh and intermediate marshes.
OUACHITA RIVER BASIN (08)
The Ouachita River's source is found in the Ouachita Mountains of west central Arkansas near the Oklahoma border. The Ouachita River flows south through northeastern Louisiana and joins with the Tensas River to form the Black River, which empties into the Red River. The Ouachita Basin covers over 10,000 square miles of drainage area. Most of the basin consists of rich, alluvial plains cultivated in cotton and soybeans. The northwest corner of the basin is forested in pine, which is commercially harvested.
PEARL RIVER BASIN (09)
The Pearl River Basin lies along the southeastern Louisiana southwestern Mississippi Border. This basin is bordered on the north by the Mississippi state line and on the west and south by the Lake Pontchartrain basin. Elevations in the basin range from 350 feet above mean sea level in the northwest portions to sea level at the southern end. Correspondingly, the vegetation varies from pine forests to brackish marsh.
RED RIVER BASIN (10)
The Red River has its origin in eastern New Mexico and flows across portions of Texas, Oklahoma and Arkansas before entering northwestern Louisiana. The river flows south to Shreveport, where it turns southeast and flows for approximately 160 miles to its junction with the Atchafalaya River. From the Arkansas state line to Alexandria, the Red River is contained within high banks which range from 20 to 35 feet above low water level. Below Alexandria, the river flows through a flat alluvial plain which is subject to backwater flooding during periods of high water. The Sabine River Basin lies to the southwest of the Red River Basin, and the Ouachita River Basin lies to the east. The Calcasieu, Vermilion - Teche, and Atchafalaya River Basins lie south of the Red River Basin. The Red River drains approximately 7,760 square miles within Louisiana.
SABINE RIVER BASIN (11)
The Sabine River Basin lies along the Texas - Louisiana border, encompassing more than 2,900 square miles of drainage area within Louisiana. The basin stretches from the Texas state line near Shreveport to the Gulf of Mexico. It is bounded on the east by the Red River Basin and Calcasieu River Basin. Characteristic vegetation ranges from mixed forests in the upper basin to hardwoods in the mid-section and brackish and saline marshes in the lower end.
TERREBONNE BASIN (12)
The Terrebonne Basin covers an area extending approximately 120 miles from the Mississippi River on the north to the Gulf of Mexico on the south. It varies in width from 18 miles to 70 miles. This basin is bounded on the west by the Atchafalaya River Basin and on the east by the Mississippi River and Bayou Lafourche. The topography of the entire basin is lowland, and all the land is subject to flooding except the natural levees along major waterways. The coastal portion of the basin is prone to tidal flooding and consists of marshes ranging from fresh to saline.