Lake Pontchartrain's Problems
LAKE PONTCHARTRAIN'S PROBLEMS
There seem to be two predominant schools of thought regarding Lake Pontchartrain. One that is reminiscent: "Gee, I remember when we could swim in da lake and, my gawd, did we eva catch da specks and da crabs!" These comments are usually followed by despair, a general feeling that those days are gone forever.
The other is no less genuine in its importance. It is that "I wish the lake could still be like it was when I was a kid, but we can't go back. Too many of the cures would cost jobs and tax money, and we don't have enough of either in this poor economy."
Our beloved lake got into this fix rather slowly. European peoples settled the area in the early eighteenth century since it provided, via Bayou St. John and the lake, a sheltered path to Mobile. Even though people were moving through the lake, their dwellings and impact on the habitat were centered along a narrow stretch of the river. Slowly, they moved into outlying areas, but the numbers were so low that the healthy lake easily absorbed their waste. By the early 1960s, it appeared as though a "Jefferson Parish Gold Rush" was on. This was followed by the invasion of St. Tammany and Tangipahoa parishes. The ever expanding population set the stage for the demise of the lake. Yes, we can list many specific activities that have had or are having deleterious effects on the lake's quality, but the basic problem is a human population base that grew too quickly without proper planning for the future. Our "problem" is that the "future" is finally here and we are ill prepared!
The many people required an improved shipping system, so the Mississippi River Gulf Outlet was meshed with the Gulf Intercoastal Waterway and the Industrial Canal, thus providing a new, unexpectedly efficient conduit for saline water into the lake. The many people needed quicker transportation out of New Orleans, so we built an elevated interstate whose construction techniques changed the hydrology of the LaBranche Wetlands. The many people caused more land to be covered with concrete that would shed water with every rain. The many people needed more roads, so we put more shell dredges, with advanced technology, into the lake to provide the required shells for the roadbeds, thus suspending more solids. The many people required an extensive sewerage system. In order to save non-existent tax dollars, corners were cut and the system leaked and polluted the lake. Since it is "expensive" to treat run-off water, the many people allowed their sewers to flow directly into the lake, thus "infecting" it with fecal coliform bacteria, oil, pesticides, fertilizers, etc. On north shore, all the same things were happening as that population enlarged, but they added agricultural run-off to the problem. All the while, various small industries contributed with their effluents that contained heavy metals, organics, creosote, and more. And then there was ballast flushing from vessels, contamination from particles in the air, over fishing, . . .
None of these activities has been solely responsible for the demise of the lake. Targeting one will not clean the lake. So what do we do? Succumb to despair? Give up because we can't afford the solution?
Our only answer is to experience "attitude adjustment." To some, that means having a beer and kicking back. Not so here! We need to become proactive and develop a self-assured sense of destiny for our lake.
Our citizens must be educated to the true negative economics of tolerating a disturbed lake. We need to fully understand the positive impact that a clean lake will bring. Undoubtedly, as we clean the lake there will be short-term economic casualties, but we must develop a long-term mentality. Think of the renewed commercial fisheries, and commercial developments that might be fed from sport fisheries, sailing, skiing, swimming, and even bird watching, a national craze that Louisiana has yet to fully capitalize on. And don't minimize the purely aesthetic value to humans of watching waves lap onto a beach, seeing pelicans feeding, and smelling the fresh scent of the breeze from a clean lake.
There is a sense that a sleeping giant is awakening. That giant is a citizenry that is saying "Enough is enough and too much is too much!" Once that giant is convinced that no price is too great to provide a high quality of life around the lake for its descendants, then (and only then) will the painful first steps be taken to correct past sins.
The standard that has been set by our Lake Pontchartrain Basin Foundation is to be able to swim in the lake by the year 2000. We would hope that the next standard, and certainly one of more import, will be to have a sustainable management plan for the lake that serves the needs of the citizens and their environment.
Let's list and briefly define the primary causes of trouble for the Lake Pontchartrain Basin. The following is primarily from Houck et al. (1989), the recent summary of known and inferred information on the lake.
1. Municipal runoff. A major portion of the lake's problems stem from all the substances that drain into the lake from the surrounding land. This section deals with runoff from cities and their environs. On South Shore, this enters the lake via the pumping stations that lift water and its contents from the canals into the lake or its adjacent marshes. On North Shore, municipal runoff flows directly into sewers and/or creeks and then into the lake. Municipal runoff consists of a myriad of potential contaminants:
a. hydrocarbons from automobile operation that settle on the streets during dry weather.
b. fecal material (dogs and cats in yards; rats, raccoons, opossums, nutria, squirrels, in yards and in sewers; leaking sewerage systems).
c. fertilizers and herbicides used on lawns.
d. oil and other substances poured down drains.
e. dirt, grease, and grime that washes from roofs, parking lots, garages, etc.
All of these and more accumulate during dry weather. When the rain hits, it washes concentrated amounts into the canals and they are then rapidly flushed into the lake.
2. Sewage systems. For years, one of the major problems was that Jefferson Parish put raw sewerage into the lake. This has been stopped, that waste now going to the Mississippi River. There are still hundreds of sewage systems pouring effluents into the lake or its tributaries, including the camps at Little Woods (eastern New Orleans) and Irish Bayou that dump raw sewerage into the lake. There is still a considerable amount that enters the lake from poor septic tank systems and from leaking sewage lines. The latter is especially true on South Shore. It is alleged that, in the old days, many (probably thousands) houses in Orleans Parish hooked their sewage lines directly into the street sewer system. Nobody knows who or how many, so this will be a very difficult problem to solve.
3. Industrial discharges. This does not seem to have been a major problem, but it has potential on a localized level. There is always a potential problem at the Seabrook Bridge where the Inner Harbor Navigation Canal (IHNC) empties into the lake. If and when a diversion canal is built in the Bonnet Carré Spillway area, then the lake will be vulnerable to contaminants from the petrochemical corridor on the river.
4. Shell dredging. Shell dredging was long considered one of the chief threats to the lake. The product sought was clam shells (Rangia cuneata). At one time, there were seven dredge boats working the lake 24 hours per day, 7 days per week. Each dredge had a 30 in diameter suction pipe that extended down into the bottom of the lake.
It caused three principal problems:
a. The dredge boat sucked up a 30 in wide and deep trough of lake-bottom, spit the shells onto a barge and spewed the remains (soil, worms, sponges, fish, etc.) back into the lake. The result was that a large portion of the lake bottom was covered with a layer of ooze that would not support the benthic fauna that normally run about on the lake's bottom or burrow into it. In effect, the shell dredgers strip mined the lake bottom. The benthic (bottom dwelling) fauna are important for cleansing the lake and they are important elements in the food web; without them, the lake ecosystem is weakened.
b. The dredging operations caused the suspension of much sediment into the water column, thus increasing turbidity markedly. More turbid water prevents light penetration, so photosynthesis and productivity decrease (in phytoplankton, algae, and rooted grass beds along the lake's margins).
c. They resuspended heavy metals and other pollutants.
Shell dredging was halted in 1990, not because it was the right thing for the lake nor because most people wanted it to. It was stopped because it caused the resuspension of certain chemicals that violated water quality standards..
INTERESTING POLITICS AND TRADE-OFFS. During the debate over closure of the shell dredging industry, each and every group had its mantra. The shell dredgers constantly talked of the economic loss to the region if they were closed down. Those who did not directly or indirectly support the economics of the shell dredgers felt that the benefits would out weigh the costs. No one seemed to question why the politicians from north of the lake appeared united against the shell dredgers. It is normal for politicians to support business. It was not until after the issue settled that it became apparent that the north shore politicians wanted the shell dredgers to stop because the shell dredgers where based in New Orleans, and, in the absence of shells for construction, gravel pits on north shore would flourish. In fact, many beautiful areas were soon clear-cut for new and expanding gravel pits, and murky run-off caused otherwise clear streams to become turbid (which virtually eliminates the presence of many species). Also, insurance agents reported huge increases in filings for cracked windshields resulting from hundreds of gravel trucks speeding along highways and pelting cars with rocks. Tradeoffs, always tradeoffs. Do we want a less turbid lake, or clear streams, woodlands, and many fewer broken windshields that cost money and create non-degradable waste? Certainly we wanted a less turbid lake, but how many people (including environmentalists) even know now about the tradeoffs?
5. Agricultural discharges. This primarily refers to fecal contamination from dairies and horse farms that runs into tributaries of the lake (such as the Tchefuncte, Tangipahoa, and Amite Rivers). There is much activity now to have farms develop treatment facilities for these waste products.
6. Saltwater intrusion. This is due to saltwater moving from the Gulf via the MRGO and IHNC. It has long been thought that this has caused the salinities of the lake to increase, but this was not evident in the analysis of 36 years of data by Sikora and Kjerfve (1985). They found that in the Little Woods area of eastern New Orleans, the salinity increased by a mean of 2%. There was very little change in the western end of the lake near Maurepas. They found that these changes were less than the total range of variability of salinity in the lake (0.06-15.18 ppt at Little Woods alone) and much less than the seasonal changes that are seen in the lake (less during rainy season, more during dry season). What this means is that, though the IHNC has occasional local impact, there are no data to support its long term impact. It has been suggested that a sill be constructed near the Seabrook Bridge that would keep the denser salt water from entering the lake.
Most people assume that an increase in salinity in the lake is responsible for the dying of the cypress trees at the western end of the lake (especially those easily seen from the I-10). In fact, it is contact with too much salt that is negatively impacting the cypress trees, but it is not abnormal salinities, just the "normal" brackish levels of the lake. What does this mean? Over the years, the marshes and ridges around the lake have been receding due to subsidence. As they recede, brackish water encroaches on plants that were once buffered by either land or marsh. The trees gradually weaken, then die. So it's not an increase in salinity, but contact with too high salinities due to subsidence (Sikora and Kjerfve, 1985:180).
7. Dead zones. There was a scare that huge dead zones, i.e., areas without life, were expanding in the lake. After careful study by scientists from UNO, they were identified as occurring around the Seabrook Bridge area. As in the hypoxic zones discussed for the Gulf of Mexico, they were caused by salinity stratification (saltwater wedging under freshwater) resulting in oxygen deficiency in the lower saltier stratum. This occurs because 1) organic material near or on the bottom rots and consumes oxygen and/or 2) algal blooms consume abnormal amounts of oxygen. Remember, little oxygen is exchanged between the different salinity strata. In late August or early September, storms mixed the water and eliminated the problem.
8. Vessels. The main concern here is all the grease, gasoline, oil, and grime that gets in the water from boat operation. One boat doesn't necessarily matter, but there are zillions of boats moving about in the lake.
9. Upland flood control and diversion. These concerns center around the impact on water quality from controlling water flow, especially by the Corps of Engineers. All sorts of things could make their way into the water and turbidity would increase from more soil flowing more rapidly toward the lake.
10. Diversion of Mississippi River water via the Bonnet Carré Spillway. For years, the Army Corps of Engineers has been studying several sites for diverting freshwater from the Mississippi River into stressed wetlands areas. There has been such a diversion proposed in the Bonnet Carré Spillway area. The water would be shunted through a concrete-lined channel; it was designed to carry water only, the sediment load being trapped and removed before it reached the lake.
The primary purpose for this diversion is to affect the salinity in Mississippi Sound in such a way as to encourage the oyster industry in that area. Many people think that the impact on Louisiana's portions of the Basin will be negative. They especially fear that contaminants from the river will hurt the lake and its use by humans.
This plan has finally been put to rest. The Corps proposed that they go ahead with the project. The environmental community said that, although they had supported the diversion while shell dredging was underway (with the belief that the diverted water would flush the lake), they now oppose the project. The Department of Natural Resources agreed, and killed the diversion. Stay tuned here. There are always those who will try to reactivate.
There are still a group of people who support diverting Mississippi River water into the lake, but by having it flow through the LaBranche wetlands instead of through a straight channel as had been proposed. Before the European invasion, natural overflows of the river during the spring deposited nutrients and sediment in the wetlands before flowing into the lake, so this interest is based on the desire to return the LaBranche wetlands to its natural system.
A FEW COMMENTS ON THE EFFECTS OF BONNET CARRÉ SPILLWAY OPERATION ON THE FAUNA AND FLORA OF LAKE PONTCHARTRAIN
The following data were acquired after the 1973 opening of 75 days (April 8-June 21) at a rate of 195,000 cfs.
For the flora in the Bonnet Carré Spillway, the annuals were virtually wiped out, but they revegetated quickly. Perennials did well except dew berries (Rubus), elderberry, groundsel, and marshelder (Iva frutescens). Seedlings of pecan, honey locust, live oak, and hackberry were killed. Seedlings of cottonwood, willow, greenbriar (Smilax), and peppervine were not killed.
For terrestrial fauna, there was much displacement. Snakes and nutria were washed out to the middle of the lake; most probably escaped onto adjacent levees. Many animals drowned.
Of the lake's epifaunal biota (animals living above the soil), five species were eliminated, three species had their abundance and distribution altered, and 21 species were basically unaffected.
Impact of Bonnet Carré Spillway on Epifaunal Invertebrates
Table I. List of epifaunal invertebrates indicating those affected by the 1973 Bonnet Carré Spillway opening.
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PHYLUM PORIFERA PHYLUM COELENTERATA PHYLUM PLATYHELMINTHES
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PHYLUM ENTOPROCTA PHYLUM NEMATODA PHYLUM BRYOZOA PHYLUM ANNELIDA |
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PHYLUM MOLLUSCA
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PHYLUM ARTHROPODA
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* Abundance or Distribution Affected
** Absent
From Michael A. Poirrier and Maureen M. Mulino. 1975. The effects of the 1973 opening of the Bonnet Carre Spillway upon epifaunal invertebrates in southern Lake Pontchartrain. Proc. Louisiana Acad. Sci. 38:36-40.
When the spillway is first opened, there are drastic changes in distributions of economically important species. The freshwater moves them about, but the long-term impact is very positive due to the introduction of large quantities of nutrients. It was surprising to find 21 species unaffected. It is possible that since Mississippi River water is high in total dissolved solids, this may be perceived physiologically by euryhaline organisms (these that can move between waters with differing salinities) as saline waters. It has been reported that waters high in calcium allow penetration by marine organisms.