The Lake Pontchartrain Basin Foundation (LPBF) began producing Pontchartrain Basin Hydrocoast maps in February 2012. Today, LPBF produces biweekly Pontchartrain Basin Hydrocoast maps with a salinity, biology, water quality, habitat and weather monitoring component assessing basin conditions. You can also view Pontchartrain Basin archived maps and methodology.
Pontchartrain Basin Hydrocoast Map Series Summary
The Hydrocoast maps for the week of April 3 to April 9, 2017 were produced using field data, MODIS, satellite imagery, precipitation data, wind data and permanent monitoring stations in the basin (USGS buoys, Coastwide Reference Monitoring System (CRMS), etc.). Salinities for this Hydrocoast period were slightly lower, when compared to the last Hydrocoast period. Discharges decreased for all Mississippi River outlets, and increased for the Pearl River and rivers flowing into Lakes Pontchartrain and Maurepas. Average daily discharge difference between last Hydrocoast and the current was:
- Pearl River = 6,785 to 21,875 cfs
- Tangipahoa = 457 to 2,837 cfs
- Tickfaw = 235 to 2,281 cfs
- Amite = 1,505 to 11,937 cfs
- Caernarvon Diversion = 2,932 to 1,980 cfs
- Mardi Gras Pass = 5,575 to 5,350 cfs
- Violet Siphon = Closed
- Bohemia Spillway = 0 to 0 cfs
- Bonnet Carré Spillway = 0 to 0 cfs
- Bayou Lamoque = 723 to 683 cfs
- Fort St. Philip = 72,561 to 69,825 cfs
- Baptiste Collete = 59,708 to 57,945 cfs
- Grand and Tiger Pass = 48,286 to 46,773 cfs
- Main Pass = 47,012 to 45,691 cfs
- West Bay = 28,716 cto 27,869 cfs
- Pass A Loutre = 40,339 to 39,253 cfs
- Southwest Pass = 191,626 to 186,464 cfs
- South Pass = 56,189 to 54,675 cfs
The first map (Hydrocoast map without precipitation) shows the salinity contours and freshwater discharge across the Pontchartrain Basin. The solid line salinity contours are at 1 ppt salinity increments. The salinity is highest out past the Chandeleur Islands (red lines, 32 ppt) and decreases to fresh conditions (dark blue lines) in the basin. Sea water generally has a salinity of 32 ppt. Green asterisks represent salinity leak points, usually in the form of gates in storm surge protection features but also in passes, portions of roads that are raised, canals, and bayous that are holes in the salinity barriers (pink lines) in the form of levees, roads, natural ridges and canals (with associated spoil banks). Salinity contours that are close together represent an area where salinity changes quickly over a short distance, which is seen slightly offshore throughout the basin during this Hydrocoast period. Contours that are farther apart represent a more gradual change over longer distances which can be seen in throughout the interior of the basin, in Lake Pontchartrain and Lake Maurepas.
The second map shows the salinity contours laid on top of a habitat/land-use map, showing where fresh to salt marsh and swamps are found in the basin. This map also shows soil water salinity contours across the land masses. Also on this map are benthic ecozones, which show the major species assemblages that occupy the water bottoms across the estuary. The third map shows the salinity contours in conjunction with weekly rainfall and wind roses in the Pontchartrain basin. During this Hydrocoast period there was some rainfall throughout the basin, with amounts ranging from 0.25 to near 7 inches. Resultant winds were mostly from the southwest. Wind speeds ranged from 2 to more than 11.1 m/s (4 to more than 25 miles/hr).
The fourth "Water Quality" shows the results of LPBF's water quality sampling around Lake Pontchartrain, reporting the fecal coliform counts. There were elevated fecal coliform counts for Laketown and Fountainebleau Beach, and high fecal coliform counts for Bonnabel Boat Launch, Tchefuncte River, Bayou Castine, and Northshore Beach. The water quality map also shows the impaired water bodies for Primary Contact (swimming, immersion likely) and Secondary Contact (boating wading, immersion unlikely) in the basin as prepared by the Louisiana Department of Environmental Quality under the EPA 305(b)/303(d) guidelines.
The fifth “Biological Map” shows oyster harvest area closure, as determined by the Louisiana Department of Health and Hospitals and the location of the public oyster seed grounds. During this Hydrocoast period oyster harvest area 8 was closed. The results of an aerial survey for actively fishing oyster boats in the Basin are shown. The flight was conducted on 04-04-2017 at 7 am. The survey counted were 53 oyster boats, with the majority in the Biloxi Marsh north of Bayou La Loutre. The biological map also shows the impaired water bodies for fishing and oyster propagation in the basin as prepared by the Louisiana Department of Environmental Quality under the EPA 305(b)/303(d) guidelines.