The most important parameters regulating algal growth are nutrient quantity and quality, light, pH, turbulence, salinity and temperature. Light is the most limiting factor for algal growth, followed by nitrogen and phosphorus limitations, but other nutrients are required including carbon. Biomass is usually measured by the amount of chlorophyll a in the water column. Water temperature influences the metabolic and reproductive rates of algae. Most species grow best at a salinity that is slightly lower than that of their native habitat, The pH range for most cultured algal species is between 7 and 9, with the optimum range being 8.2-8.7. Through photosynthesis, algae produce oxygen in excess of respiratory requirements during daylight hours. Conversely, during low light or nighttime periods algae respire (consume) dissolved oxygen, sometimes depleting water column concentrations. Thus, high algae concentrations may lead to low dissolved oxygen concentrations.
A common solution for algae is copper sulfate. Copper Sulfate works to kill the algae, but when it dies, it settles to the bottom of the water body where it becomes a carbon source for bacteria and future algae. One will often see shallow ponds with rising algae. But there is significant concern about copper in coastal water bodies. Copper is toxic to marine organisms so USEPA and other regulatory bodies are considering the limits on copper use. Such a limitation would severely limit options in dealing with algal blooms near coastal waters.
Mixing is necessary to prevent sedimentation of the algae, to ensure that all cells of the population are equally exposed to the light and nutrients. So oxygenation can help (it also mixes the water. The depth of south Florida water bodies is problematic (shallow and therefore warmer than normal). But oxygen will help microorganisms on the bottom consume the carbon source on the bottom, which might slow algal growth. Analysis is ongoing.
Two other conditions work against controlling blue-green algae outbreaks: climate change and political/regulatory decision-making. Lake Okeechobee has routine algal blooms from the nutrients introduced from agriculture and runoff around the lake, which encouraged an artificial eutrophication of the lake years ago. It continues today. Warmer weather will encourage the algal blooms in the future. The decisions to discharge the water without treatment is a political one. From a regulatory perspective, algae is seen as a nuisance issue, not a public health or environmental issue. But algal blooms consume oxygen and kill fish, so the ecosystem impact is considerable – it is not a nuisance .
The term algae encompass a variety of simple structures, from single-celled phytoplankton floating in the water, to large seaweeds. Algae can be single-celled, filamentous or plant-like, anchored to the bottom. Algae are aquatic, plant-like organisms – phytoplankton. Phytoplankton provides the basis for the whole marine food chain. Phytoplankton need light to photosynthesize so will therefore float near the top of the water, where sunlight reaches it. Light is the most limiting factor for algal growth, followed by nitrogen and phosphorus limitations), but other nutrients are required including carbon, silica, and other micronutrients. These microscopic organisms are common in coastal areas. They proliferate through cell division.
A natural progression occurs in many water bodies, from diatoms, to green algae to yellow/brown to blue-green, with time and temperature. The environment is important. Southern waters are characterized as being slow moving, and warm. This encourages cyanobacteria – or blue green algae. The introduction of nutrients is particularly difficult as it accelerates the formation of the blue green algae. Blue-green algae creates the bright green color, but is actually an end-of-progression organism.
If cells are present in the water mass in large numbers an algal bloom occurs. An algal bloom is simply a rapid increase in the population of algae in an aquatic system. Blooms may occur in freshwater as well as marine environments. Colors observed are green, bright green, brown, yellowish-brown, or red, although typically only one or a few phytoplankton species are involved and some blooms may be recognized by discoloration of the water resulting from the high density of pigmented cells.
So the desire for development created the idea to drain the swamp, which led to exposure of dark, productive soil that led to farming, which lead to fertilizers, which led to too much water, and water pollution leading to algae. A nice, predictable progression created by people. So what is the solution?
We have all seen the stories about land in the Everglades agricultural Area thissummer. I was asked to give a presentation at a national conference in Orlando recently about water management in Florida. It was a fun paper and most of the people there were not from Florida, so it was useful for them to understand the land of water. Florida has always been a land shaped by water. Initially it was too much, which frustrated federal soldiers trying to hunt down Native Americans in the 1830s. In 1881, real estate developer Hamilton Disston first tried to drain the swamps with canals. He was not successful, but Henry Flagler came through a decade later and constructed the east coast railroad in the 1890s. It is still there, 2 miles off the coast, on the high ground. However water limited development so in 1904, Napoleon Bonaparte Broward campaigned to drain the everglades. Broward’s efforts initiated the first land boom in Florida, although it was interrupted in the 1920s by hurricanes (1926 and 1928) that sloshed water out of Lake Okeechobee killing people and severely damaging property in Miami and around Lake Okeechobee. A dike was built (the Hover dike – it is still there). However, an extended drought occurred in the 1930s. With the dike preventing water from leaving Lake Okeechobee, the Everglades became parched. Peat turned to dust, and saltwater entered Miami’s wells. When the city brought in an expert to investigate, he found that the water in the Everglades was the recharge area for the Biscayne aquifer, the City’s water supply. Hence water from the lake needed to move south.
Resiliency has always been one of Florida’s best attributes. So while the hurricanes created a lot of damage, it was only a decade or two later before the boom returned. But in the late 1940s, additional hurricanes hit Florida, causing damage and flooding from Lake Okeechobee prompting Congress to direct the Army Corps of Engineers to build 1800 miles of canals, dozens of pump stations and other structures to drain the area south of Lake Okeechobee. It is truly one of the great wonders of the world – they drained half a state by lowering the groundwater table by gravity canals. To improve resiliency, between 1952 and 1954, the Corps, in cooperation with the state of Florida, built a levee 100 miles long between the eastern Everglades and the developing coastal area of southeast Florida to prevent the swamp from impacting the area primed for development.
As a part of the canal construction after 1940, 470,000 acres of the Everglades was set aside for farming on the south side of Lake Okeechobee and designated as the Everglades Agricultural Area (EAA). However water is inconsistent, so there are ongoing flood/drought cycles in agriculture. Irrigation in the EAA is fed by a series of canals that are connected to larger ones through which water is pumped in or out depending on the needs of the sugar cane and vegetables, the predominant crops. Hence water is pumped out of the EAA, laden with nutrients. Backpumping to Lake Okeechobee and pumping the water conservation areas was a practice used to address the flooding problem.
There was an initial benefit to Lake Okeechobee receiving nutrients. Older folks will recall that in the 1980s , the lake was the prime place for catching lunker bass. That was because the lake was traditionally nutrient poor. That changed with the backpumping which stimulated the biosystem productivity. More production led to more biota and more large fish. This works as long as the system is in balance e- i.e. the nutrients need to be growth limiting at the lower end of the food chain. Otherwise the runaway nutrients overwhelm the natural production and eutrophication results. Lake Okeechobee is a runaway system – the algae now overwhelm the rest of the biota. Lunker bass have been gone for 20 years.
The backpumped water is usually low in oxygen and high in phosphorus and nitrogen, which triggers algal progressions, leading to toxic blue-green algae blooms and threaten lake drinking water supplies. Think Toledo. Prolonged back pumping can lead to dead zones in the lake, which currently exist. The nutrient cycle and algal growth is predictable.
The Hoover Dike is nearly 100 years old and while it sit on top of the land (19 ft according to the Army Corps of Engineers), there is concern about it being breached by sloshing or washouts. Undermining appears in places where the water moves out of the lake flooding nearby property. So the Corps tries to keep the water level below 15.5 ft. During the rainy season, or a rainy winter as in 2016, that can become difficult. If the lake is full, that nutrient laden water needs to go somewhere. The only options are the Caloosahatchee, St. Lucie River or the everglades. The Everglades is not the answer for untreated water – the upper Everglades has thousands of acres of cattails to testify to the problem with discharges to the Everglades. So the water gets discharged east and west via the Caloosahatchee and St. Lucie River.
The nutrient and algae laden water manifests as a green slime that washed onto Florida beaches in the Treasure coast and southwest Florida this summer, algae is actually a regular visitor to the coasts. Unfortunately memories often fail in temporal situations. The summer 2016 occurrence is reportedly the eighth since 2004, and the most severe since 2013. The green slime looks bad, can smell bad, kills fish and the 2016 bloom was so large it spread through estuaries on both coasts killing at least one manatee. One can see if from the air – try this link:
The reliability of the assets within the area of interest starts with the design process in the asset management plan. Decision-making dictates how the assets will be maintained and effective means to assure the maximum return on investments. Through condition assessment, the probability of failure can be estimated. Assets can also fail due to a growing area that may contribute to exceeding its maximum capacity. Operation and maintenance of the assets are important in reassuring a longer life span as well as getting the most out of the money to be spent. Prioritizing the assets by a defined system will allow for the community to see what areas are most susceptible to vulnerability/failure, which assets need the most attention due to their condition, and where the critical assets are located in relation to major public areas (hospitals, schools, etc.) with a high population.
So what happens when conditions change? Let’s say sea levels are rising and your land is low. What would the potential costs be to address this? Better yet, what happens if it rains? We looked at one south Florida community and the flood stage for each based on 3 storm events: the 1:10 used by FDOT (Assumes 2.75 inches in 24 hours), the Florida Building Code event that includes a 5 in in one hour event (7 in in 24 hrs), and the 3 day 25 year event (9.5-11 inches).
Of no surprise is that the flooding increases as rainfall increases. Subsequent runs assumed revisions based on sea level rise. The current condition, 1, 2 and 3 ft sea level rise scenarios were run at the 99 percentile groundwater and tidal dates and levels. Tables 2-5 depict the flood stage results for each scenarios. The final task was designed to involve the development of scenarios whereby a toolbox options are utilized to address flooding in the community. Scenarios were to be developed to identify vulnerabilities and cost effectiveness as discussed previously.
The modeling results were then evaluated based of the accompanying infrastructure that is typically associated with same. A summary of the timelines and expected risk reductions were noted in the tables associated with storm and SLR scenarios. This task was to create the costs for the recommended improvements and a schedule for upgrading infrastructure will be developed in conjunction with staff. Two issues arise. First, the community needs to define which event they are planning to address and the timelines as the costs vary form an initial need of $30 million to over $300 million long-term. Figure 1 shows how these costs rise with respect to time. The long-term needs of $5 million per 100 acres matches with a prior effort in Palm Beach County.
Figure 1 Summary of Costs over the 3 ft of potential sea level Rise by 2011, under the 3 storm planning concepts.
Curtailed water use and conservation are common topics of conversation in areas with water supplies limitations. As drought conditions worsen, the need for action increases, so when creating a regulatory framework, or when trying to measure water use efficiency, water supply managers often look for easily applied metrics to determine where water use can be curtailed. Unfortunately, the one-size-fits-all mentality comes with a potential price of failing to fully grasp the consequences decision-making based on such metrics.
One of the issues that water supply regulator like to use is per capita water use. Per capital water use is often used to show where there is “wasted” water use, such as excessive irrigation. However such a metric may not be truly applicable depending on other economic factors, and may even penalize successful communities with diverse economic bases. A heavy industrial area or dense downtown commercial center may add to apparent per capita use, but is actually the result of vibrant economic activity. Large employment centers tend to have higher per capital use than their neighbors as a result of attracting employees to downtown, which are not included in the population.
In south Florida, a recent project I was involved with with one of my students showed that while there was significant variability among utilities, but the general trend of increased economic activity was related to increased per capita use. Among the significant actors were health care, retail trade, food service and scientific and technical services. It appears to be these sectors that drive water use upward. As a result when evaluating the efficiency of a utility, an analysis should be conducted on the economic sectors to insure that water regulations do not stifle economic growth and jobs in a community. And conversely if you do not have these sectors, you water use should be lower. Something to think about when projecting or regulating water use. Limited water use may in fact be limiting economic activity in the area. Of course if you are water limited, limited new withdrawals may be perfectly acceptable if you want to encourage other options, like direct or indirect potable reuse, irrigation, etc.
It would be interesting to expand this study across the country to see what the national trends look like and how different tourism oriented South Florida might actually be.
Most water suppliers realize that the more natural their land is upstream of their water supplies, the less risk there likely is for their customers. Under the source water protection programs that state, local officials and water utilities implement, the concept is to keep people related activities out, and let the natural forests and landscapes remain. For the most part the natural areas support only a limited amount of wildlife (sustainable) and thereby there natural systems are attuned to compensate for the natural pollutant loads, sediment runoff, ash, detrital matter, etc., that might be created through natural processes. For thousands of years these systems operated sustainably. When people decide there needs to be changes, it seems like the unanticipated consequences of these actions create more problems. Now many of these same ecosystems do not work sustainably and water quality has diminished, increasing the need for treatment and the risks of contamination to the public. It would be better, but decidedly less popular on certain fronts, to provide more protection to natural systems that extend into watersheds (which is most of them), not less.
So this leads to a series of questions that go to the greater questions about natural environments:
Is it really necessary to cull the small Yellowstone bison herd by 1000? What do bison have to do with watersheds? Well, the bison create much less damage to grasslands and underlying soil than cattle due to the size of their hooves. An argument is that we need to cull the herd because they transmit disease to cattle, but Brucellosis has never been demonstrated to move from bison to cattle, so disease is not an answer. What is really happening is that there is competition between buffalo and cattle for grazing. Competition with cattle means that the cattle are on public property, not private ranch lands, and the cattle trample the public lands which creates the potential for soil erosion and sediment runoff. So I am thinking water folks should be siding with the bison. Of course without wolves, there is no natural predator for bison, which raises a different sustainability problem, so maybe instead of killing them, we move them to more of their native ranges – maybe some of those Indian reservation might want to restart the herds on their lands? That might be good for everyone, water folks included.
Part 2 – is it necessary to continue to protect wolves or should we continue to hunt them in their native ranges? Keep in mind wolf re-introduction efforts are responsible for most of the wolf populations in the US, specifically in the Yellowstone area. Without wolves, there is no control of large grazing animal populations (see bison above, but also elk and deer), and there is a loss of wetland habitat because the elk eat the small shoots used by beavers to build dams and trap sediment. Eliminating wolves has been proven to create imbalance. Wolves = sediment traps = better water quality downstream. Sounds like a win for everyone. (BTW there is a program in Oregon to protect wolves and help ranchers avoid periodic predation of calves by wolves so they win too).
Part 3 – Is it really necessary to kill off coyotes in droves? The federal government kills thousands of coyotes and hunters and others kill even more. This is a far more interesting question because it leads to one of those unintended consequences. !100+ years ago people decided wolves were bad (we still have this issue ongoing – see above). So we eradicated wolves. No wolves means more rodents, deer, elk, etc. which mean less grass, less aspens and less beavers, which means more runoff which does not help water suppliers. It also means more coyotes, because there is more food for the coyotes. Interesting that coyotes have pretty much covered the entire US, when their ranges were far more limited in the past. Coyotes are attracted to the rodents and rabbits. But the systems are generally not sustainable for coyotes because there is not enough prey and there is no natural control of the coyotes – again, see wolves above. A Recent Predator defense report indicates that culling coyotes actually increases coyote birth rate and pushes them toward developed areas where they find cats and small dogs, unnatural prey. Not the best solution – unintended consequences of hunting them on more distant land pushes them into your neighborhood. Not the consequence intended. So maybe we keep the small dogs and cat inside at daybreak and nightfall when the coyotes are out and let them eat the rats and mice that the cats chase and once consumed they go away. Coyotes need to eat grazers and rodents but you need the right mix or the grazers overgraze, which leads to sediment runoff issues – which is bad for us. That also seems like a win.
Everglades restoration is a big south Florida issue. The recharge area for the Biscayne aquifer is the Everglades. So water there seems like a win for water suppliers? So why aren’t we the biggest Everglades advocates out there? Still searching for that answer, but Everglades restoration is a win for us and a win for a lot of critters. Federal dollars and more federal leadership on restoration is needed. Which leads to ….
Do we need more, not less management of federal lands? Consider that the largest water manager in the west is the federal government, which has built entire irrigation systems to provide water to farmers who grow crops in places that are water deficient. Those farms then attract people to small towns that consume more of the deficient water. Then people lobby to let cattle graze on those public lands (see bison above), timber removal – which increases sediment erosion, or mining (what could possible go wrong there?). So since the federal government manages these lands, wouldn’t better regulations and control to keep the federal properties more protected benefit water users and suppliers? Contrary to the wishes of folks like the guys holed up in a federal monument in Oregon, or the people who have physically attacked federal employees in Utah and Nevada, more regulations and less freedom is probably better in this situation for the public good. If we are going to lease public lands (and most lands leased are leased to private parties for free or almost free), and there should be controls on the activities monitoring for compliance and requirements for damage control caused by those activities. There should be limits on grazing, timber and mining, and monitoring of same. Lots of monitoring. It is one of the things government really should do. And we need it to protect water users downstream. Again a win for water suppliers.
So as we look at this side issue, ecosystems, bison, wolves, coyotes and the Everglades seem very distant from our day-to-day water jobs. But in reality they are not. We should consider the impacts they might have on water supply, keeping in mind natural system decisions are often significantly linked to our outcomes, albeit the linkage is not always obvious.