The Lake Pontchartrain Basin Foundation (LPBF) produces biweekly Pontchartrain Basin Hydrocoast maps with a salinity, biology, water quality, habitat and weather monitoring component assessing basin conditions.
Pontchartrain Basin Hydrocoast Map Series Summary
The Hydrocoast maps for the week of October 29th to November 4th, 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 decreased in the northeast Lake Pontchartrain, Lake Borgne, Biloxi Marsh, and Mississippi Sound. Salinities increased around the eastern Bird’s Foot Delta, Breton Sound, and Chandeleur Sound. Discharges increased in all Northshore Rivers and Mississippi River outlets, with the exception of the Davis Pond Diversion. The Violet Siphon, Pointe a la Hache Siphon, Bohemia Spillway, and Bonnet Carré Spillway remained at zero discharge. Average daily discharge differences between the last Hydrocoast and the current Hydrocoast period are listed below in Cubic Feet per Second (cfs).
- Pearl River = 2,297 to 3,677 cfs
- Tangipahoa = 436 to 510 cfs
- Tickfaw = 97 to 114 cfs
- Amite = 1,154 to 1,257 cfs
- Bayou Lafourche, Donaldsonville = N/A
- Bonnet Carré Spillway = 0 to 0 cfs
- Davis Pond Diversion = 1,393 to 1,227 cfs
- Caernarvon Diversion = 544 to 555 cfs
- Naomi Diversion Canal = N/A
- Mardi Gras Pass = 11,650 to 13,700 cfs
- Pointe a la Hache Siphon = 0 to 0 cfs
- Violet Siphon = Closed
- Bohemia Spillway = 0 to 0 cfs
- Bayou Lamoque = NA
- Fort St. Philip = 81,111 to 89,953 cfs
- Baptiste Collete = 65,072 to 70,411 cfs
- Grand and Tiger Pass = 52,920 to 57,574 cfs
- West Bay = 31,296 to 33,864 cfs
- Main Pass = 52,080 to 55,035 cfs
- Pass A Loutre = 43,608 to 46,804 cfs
- South Pass = 60,742 to 65,193 cfs
- Southwest Pass = 207,154 to 222,333 cfs
- Sum of Reported MS River Discharges = 656,649 cfs
- MS River at Baton Rouge = 648,729 to 717,474 cfs
- MS River at Belle Chasse = 619,738 to 670,553 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. Seawater generally has a salinity between 32 - 35 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 and Mississippi 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 6.0 inches. Winds were mostly from the southeast and southwest. 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 high fecal coliform counts at Bogue Falaya. Fecal Coliform counts were elevated at Bonnabel Boat Launch and Tchefuncte River. 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 was conducted on October 29th of the Shrimp and Oyster fleets. 22 Shrimp boats and 46 Oyster boats were observed actively fishing. The Oyster fleet was observed in the Biloxi Marsh and Mississippi Sound, while the Shrimp fleet was observed mostly in Lake Borgne, Biloxi Marsh, and on the east side of the Mississippi River delta. 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.