heron bird with fish in its mouth

Not All Algal Blooms Are Harmful

Warm temperatures and rainy Summer weather conditions often set the stage for algal blooms in our rivers, lakes, ponds, and canals. Like many people across the State, residents of the Lake Worth Drainage District (LWDD) may have concerns or confusion about these blooms. To help answer some frequently asked questions, we are providing the following information about algae.

Algae are simple organisms that grow through photosynthesis, a process by which sunlight is used to metabolize nutrients. Algae are a basic component of the food chain and are commonly found in marine, estuarine, freshwater lakes, canal systems, stormwater ponds and even swimming pools. Algae appear as green, red, or yellowish-brown particles that float on the water surface.

Although algae are a normal component of an aquatic ecosystem, nutrient-rich waters warmed by the sun provide a favorable medium for the overgrowth. This overgrowth is called an ‘algal bloom’. For algal blooms to occur two things must be present: high concentration of nutrients (nitrogen and phosphorus) and adequate sunlight. We cannot control sunlight, but we can limit our nutrient impact to surrounding waterbodies with proper maintenance of septic tank systems and limited use of fertilizers on landscapes and lawns. Currently approved herbicide or chemical treatments for the removal of algae uses a heavy metal compound that may adversely impact the waterbody. However, scientists are studying new treatments for the control of algae and safer alternatives may become available in the future.

While visually unappealing, most algae is not harmful to human health and provides a food source for aquatic life. However, some types, like “Blue-green” algae, which is a cyanobacteria, secrete toxins that may be harmful. The algae toxins can be inhaled by people living around the waterbody. It will aggravate respiratory illnesses like asthma. Symptoms of exposure to toxic algae include difficulty breathing, wheezing, skin rashes, headaches, and possible tingling in the fingers and toes. If water containing toxic algae is consumed potential liver damage may occur. It is important to keep humans and pets away from waterbodies that have toxic algal blooms and seek medical advice if symptoms appear.

Since most types of algae found within LWDD’s canals are non-toxic and do not impact flood control operations, LWDD does not regularly treat the canal system for algal blooms. Most algae growth in our canals is harmless and will dissipate on its own or will be flushed out of the canal system after a heavy rainfall.

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Water Flows Downhill: But Not Always In the Desired Direction

Stormwater management systems within the Lake Worth Drainage District (LWDD) area are required to provide both flood control and water quality mediation. There are two general types of stormwater systems that perform these functions – retention and detention. Both systems depend on proper grading of the land to successfully keep homes from flooding and ensure water quality. The relationship between land and stormwater management is inseparable.

swale area filled with water arrows are indicating the direction water will enter the swaleA retention stormwater system is designed so the grading or slope of the land helps to collect water in low lying areas. This helps to prevent flooding in undesirable areas and allows the water to slowly seep into the shallow groundwater aquifer. As the stormwater seeps into the ground, the grasses, sand, soils and rocks help filter out contaminants thus providing water quality treatment. The retention stormwater system can be man-made or a naturally occurring depression. There is no discharge to another water body such as a pond, lake or canal. This type of drainage system is often found in rural areas or large undeveloped areas.

Community lake with arrow indicating where the water will flow into a drain and then outflow to the lakeA detention stormwater system is used by most modern-day residential communities. The design directs and contains stormwater onsite in a pond. It is designed to allow pollutants in the water to settle to the bottom of the pond leaving cleaner water on top. Again, the grading of the landscape is vital to the success of the system as the water must flow toward and into the detention system. The detention system consists of pipes and catch basins to collect and direct the stormwater. Water moves away from homes via an overland drainage flow. Front, side, and back yards typically utilize overland drainage. Stormwater flows through the front or back yards and may cross four to five lots until it reaches a catch basin. The catch basin is connected to underground pipes that discharge the water to the community pond for storage and cleaning.

After a rainstorm, the water in the pond will rise and if the elevation is high enough, the cleaner water at the top will drain from the pond through an outflow structure and eventually into a LWDD canal. The overland flow of stormwater over a LWDD canal bank and into the channel is not allowed. The untreated stormwater can impact water quality and dangerous washouts in the bank can occur.

The LWDD designs its canal banks and rights-of-way to prevent stormwater runoff from directly entering the canal system. A typical LWDD canal right-of-way is graded so the canal berm is higher than the surrounding land and stormwater will flow away from the canal. Due to the regular maintenance activities of the LWDD like mowing, as well as the natural settling of the soils, regrading of the right-of-way is one of the important flood control operations performed by the LWDD.diagram of LWDD typical canal right-of-way

Over time, property owners may also have to regrade their front, side and back yards to match their original drainage design. Settling of the soiarrow depicting how the flow of water can be slowed by vegetation and fencingls or enhancements such as landscaping materials or installation of fences may impede the overland drainage flow. This disruption can cause soggy areas in yards and standing water during heavy rain events. In severe cases, patios, garages and homes can be adversely affected. Property owners should be aware that it is their responsibility to ensure the overland drainage flow is maintained to the design condition.

Development activities that effect how much rain can soak into the ground, how much water leaves a property, and where it will go are regulated by the South Florida Water Management District. Community drainage system permits and plans may be obtained through this agency at www.sfwmd.gov. Additionally, permits for the crossing and use of the LWDD canal right-of-way for the installation of drainage infrastructure such as culverts and outlets can be obtained by visiting LWDD’s online permit system at www.lwdd.net/right-of-way/permitting.