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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 June 25th to July 1st, 2018 were produced using field data from the Louisiana Department of Wildlife and Fisheries (LDWF) water quality data, MODIS satellite imagery, precipitation data, and wind data from the permanent monitoring stations in the basin (USGS buoys, Coastwide Reference Monitoring System (CRMS), etc.). During the Hydrocoast period, salinities increased in the Mississippi Sound, northeast Lake Pontchartrain, Chandeleur Sound, Biloxi Marsh, and Breton Sound. Salinities remained similar in Lake Borgne. Discharges decreased in all Northshore Rivers and Mississippi River outlets, except for the Caernarvon Diversion. Average daily discharge differences between the last Hydrocoast and the current Hydrocoast are listed below in Cubic Feet per Second (cfs).

  • Pearl River = 3,263 to 2,581 cfs
  • Tangipahoa = 723 to 566 cfs
  • Tickfaw = 200 to 141 cfs
  • Amite = 1,599 to 933 cfs
  • Caernarvon Diversion = 304 to 385 cfs
  • Mardi Gras Pass = 9,750 to 7,950 cfs
  • Violet Siphon = Closed
  • Bohemia Spillway = 0 to 0 cfs
  • Bonnet Carré Spillway = 0 to 0 cfs
  • Bayou Lamoque = NA
  • Fort St. Philip = 61,130 to 54,640 cfs
  • Baptiste Collete = 52,181 to 47,703 cfs
  • Grand and Tiger Pass = 41,855 to 38,067 cfs
  • Main Pass = 41,371 to 38,014 cfs
  • West Bay = 25,096 to 22,943 cfs
  • Pass A Loutre = 35,654 to 32,812 cfs
  • Southwest Pass = 169,370 to 155,867 cfs
  • South Pass = 49,663 to 45,704 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 (orange lines, 35 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 in Breton Sound during this Hydrocoast period. Contours that are farther apart represent a more gradual change over longer distances which can be seen throughout the interior of the basin, in Lake Pontchartrain and Lake Borgne.

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 rainfall across the basin that ranged from 0.25 to greater than 6 inches. Winds were mostly from the south and southeast. Wind speeds ranged from 0.5 to 8.8 m/s (1.11 to 19.68 mph).

The fourth "Water Quality" shows the results of LPBF's water quality sampling around Lake Pontchartrain, reporting the fecal coliform counts. During this Hydrocoast period there were elevated fecal coliform counts at the Fontainebleau Beach, and Bogue Falaya. Hypoxia was observed in the Chandeleur Sound and Breton Sound on June 14th, 2018. 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 closures, 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. An aerial survey conducted on June 26th of the Shrimp, Oyster, and Pogy fleets observed 11 active Shrimp boats, 29 Oyster boats, and two Pogy boats. The oyster fleet was observed in and around the Biloxi Marsh, while the Shrimp fleet was observed mostly in Chandeleur Sound, Breton Sound, and the Bird’s Foot Delta. The two Pogy boats were observed in Chandeleur Sound. 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.