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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 February 5th to February 11th, 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, salinity decreased in eastern Lake Pontchartrain and the Mississippi Sound. Salinity increased in Lake Borgne, and remained similar in Chandeleur Sound, Breton Sound, and the Biloxi Marsh. Discharges increased at all Northshore Rivers and Mississippi River outlets. Average daily discharge differences between the last Hydrocoast and the current Hydrocoast are listed below in Cubic Feet per Second (cfs).

  • Pearl River = 4,820 to 14,285 cfs
  • Tangipahoa = 1,243 to 2,933 cfs
  • Tickfaw = 815 to 1,644 cfs
  • Amite = 3,350 to 5,887 cfs
  • Caernarvon Diversion = 1,479 to 3,476 cfs
  • Mardi Gras Pass = 4,500 to 5,600 cfs
  • Violet Siphon = Closed
  • Bohemia Spillway = 0 to 0 cfs
  • Bonnet Carré Spillway = 0 to 0 cfs
  • Bayou Lamoque = NA
  • Fort St. Philip = 41,193 to 49,252 cfs
  • Baptiste Collete = 37,856 to 43,856 cfs
  • Grand and Tiger Pass = 29,841 to 34, 836 cfs
  • Main Pass = 30,634 to 35,131 cfs
  • West Bay = 18,207 to 21,092 cfs
  • Pass A Loutre = 26,418 to 30,337 cfs
  • Southwest Pass = 125,495 to 144,111 cfs
  • South Pass = 36,798 to 42,257 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 Mississippi and 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 8 inches. Winds were mostly from east, northeast, and southeast. Wind speeds ranged from 0.5 to 11.0 m/s (1.1 to 24.6 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 higher fecal coliform counts were reported at Bogue Falaya. 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.