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Pontchartrain Basin

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 February 20 through February 26, 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 higher, overall, when compared to the last Hydrocoast period. Discharges decreased across the Basin, except for at the Amite River and Caernarvon Diversion Discharges increased at all Mississippi River outlets and passes. Average daily discharge difference between last Hydrocoast and the current was:

  • Pearl River = 5,214 to 4,465 cfs
  • Tangipahoa = 830 to 599 cfs
  • Tickfaw = 505 to 327 cfs
  • Amite = 1,282 to 1,440 cfs
  • Caernarvon Diversion = 60 to 67 cfs
  • Mardi Gras Pass = 6,400 to 4,350 cfs
  • Violet Siphon = Closed
  • Bohemia Spillway = 0 to 0 cfs
  • Bonnet Carré Spillway = 0 to 0 cfs
  • Bayou Lamoque = 606 to 392 cfs
  • Fort St. Philip = 87,757 to 52,897 cfs
  • Baptiste Collete = 69,104 to 46,472 cfs
  • Grand and Tiger Pass = 56,430 to 37,031 cfs
  • Main Pass = 54,055 to 37,092 cfs
  • West Bay = 33,235 to 22,350 cfs
  • Pass A Loutre = 46,027 to 32,032 cfs
  • Southwest Pass = 218,641 to 152,121 cfs
  • South Pass = 64,111 to 44,605 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 bain, with amounts ranging from 0.25 to near 4 inches. Resultant winds were mostly from the northwest. 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 high fecal coliform counts for Bogue Falaya and Bayou Castine. 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 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.