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 August 7 to August 13, 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 incerased slightly across the basin since the last Hydrocoast period. In Lake Pontchartrain the salinity was below 3 ppt and reached 28 ppt in Chandeleur Sound. Discharges decreased at all northshore rivers, except Amite River. Average daily discharge difference between last Hydrocoast and the current was:
- Pearl River = 15,755 to 11,896 cfs
- Tangipahoa = 2,567 to 1,250 cfs
- Tickfaw = 718 to 423 cfs
- Amite = 3,469 to 3,703 cfs
- Caernarvon Diversion = 61 to 101 cfs
- Mardi Gras Pass = 7,100 to 7,050 cfs
- Violet Siphon = Closed
- Bohemia Spillway = 0 to 0 cfs
- Bonnet Carré Spillway = 0 to 0 cfs
- Bayou Lamoque = 673 to 807 cfs
- Fort St. Philip = 55,312 to 52,426 cfs
- Baptiste Collete = 48,174 to 46,136 cfs
- Grand and Tiger Pass = 38,464 to 36,749 cfs
- Main Pass = 38,368 to 36,840 cfs
- West Bay = 23,169 to 22,189 cfs
- Pass A Loutre = 33,112 to 31,808 cfs
- Southwest Pass = 157,297 to 151,098 cfs
- South Pass = 46,123 to 44,305 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 rainfall throughout the basin, with amounts ranging from 2 to over 8 inches. Resultant winds were mostly from the southwest and northwest. Wind speeds ranged from 0.5 to 8.8 m/s (1 to 20 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 at 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. Also shown are points where Hypoxia was observed in Chandeleur Sound.
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.