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 May 1 to May 7, 2017 were produced using field data, Louisiana Department of Wildlife and Fisheries (LDWF) water quality 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 increased for all rivers and outlets, except for Pearl River, the Bohemia Spillway, and the Caernarvon Diversion. Discharges decreased for the Pearl River and Caernarvon Diversion, and were the same for the Bohemia Spillway. Average daily discharge difference between last Hydrocoast and the current was:
- Pearl River = 15,166 to 10,659 cfs
- Tangipahoa = 583 to 1,472 cfs
- Tickfaw = 296 to 1,199 cfs
- Amite = 1,587 to 6,559 cfs
- Caernarvon Diversion = 1,980 to 122 cfs
- Mardi Gras Pass = 5,350 to 12,000 cfs
- Violet Siphon = Closed
- Bohemia Spillway = 588 to 588 cfs
- Bonnet Carré Spillway = 0 to 0 cfs
- Bayou Lamoque = 683 to 1,109 cfs
- Fort St. Philip = 69,825 to 99,774 cfs
- Baptiste Collete = 59,708 76,120 cfs
- Grand and Tiger Pass = 48,286 to 62,596 cfs
- Main Pass = 45,691 to 59,314 cfs
- West Bay = 27,869 to 36,610 cfs
- Pass A Loutre = 39,253 to 50,156 cfs
- Southwest Pass = 186,464 to 238,258 cfs
- South Pass = 54,675 to 69,863 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 2 to over 7 inches. Resultant winds were from the west. 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 Laketown, the Bonnabel Boat Launch, Pontchartrain Beach, and the 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.