Almost every day I am asked to outline a water treatment plan. New clients and old friends expect the answer to be simple, but there are many ‘It Depends’ caveats. Each body of water is unique, responding best to a slightly different approach. Even if the dosage is simple, the application is as important as the products used. These conversations often reveal that the owner is unsure of site-specific details, the deeper challenges presented and the nuances of water treatment. Setting all that aside, the following is a simplified approach to aquatics.
The best management practice for water is to use the least amount of chemicals. This is balanced against the need to control unwanted and invasive species, while minimizing labor. Ecologic diversity is the long-term goal. Below a certain dosage, chemicals have a negligible effect. Therefore, an aquatic program generally first increases toxicity, then ramps down chemical usage. Ultimately the aquatic plant growth becomes acceptable, costs are reduced, and the water ambience/function is near maximum.
The following factors affect water treatment estimates:
Water Volume: What is the surface area and average depth?
Water Source:
Does the lake fill with water from an aquafer, a deep well, city water, or reclaimed water? The less pristine the source, the higher the nutrient loading, and thus the more product needed for the same level of control. This also applies to landscaping and nearby animals, especially uphill and upwind.
Dissolved Oxygen:
Does the water have enough dissolved oxygen (DO) available, both for the fish and other oxygen-consuming creatures? Generally, 4ppm is poor DO, 6+ppm is good, whereas 3ppm or lower will see fish kills. Higher DO will discourage the growth of algae and cyanobacteria, as these excrete oxygen. Lower temperature waters can hold more DO; more salinity can reduce DO; more wind increases DO and evaporation. A lake often requires mechanical aeration to have sufficient DO, such as diffusers, fountains, and waterfalls.
Depth Max and Average: Water depth is important to know for application calculations, but also to estimate biologic functions. Comparing the current depth profile with the lake’s original design, the difference is the muck accumulation, which is a combination of dirt/clay and biologic material. Bottom diffusers are less effective at DO introduction at depths less than 6 feet; depths greater than 40’ see less DO despite the lower temperatures at those depths.
Mixing and Circulation:
Moving water is healthy water. How long does it take for the entire volume to recycle? Healthy water turns over a few times a day. Circulation implies mixing, which is enhanced by bottom diffusers at all depths. Large bodies of water often have coves and fingers, which have lower circulation. The larger a lake, the less likely it has good circulation, especially at the deepest points.
Effluent:
Where does the water flow when it leaves your lake/property? EPA and State laws limit pesticides and other products in water. A property owner should not add any product before understanding the laws governing their property and the property downhill receiving effluent.
Changing the Environment: Peripheral trees and other high nutrient sources may need to be moved or eliminated. Increased light will result in more algae growth. Increased wind from tree removal will help the DO% but will also increase evaporation. More evaporation will increase the cost of water replacement, so dissolved solids in the water may increase. Some lakes are devoid of aquatic grass. The introduction of fast-growing aquatic grass can address this problem. In later years this grass could take over 50% – 80% of the lake surface, requiring a huge annual expense to cut back. Before adding or subtracting to an aquascape, including the nearby landscaping, consider the long-term outcomes carefully.
Goals and Limitations: Clearly define what is the highest priority, and who may disagree with this goal, or wish to amend the process. Water management is not intuitive, often having capital and recurring costs. Many companies offer different products and processes, promising similar outcomes. Some prefer killing everything for maximum control in the short-term, minimizing labor and short-term cost. Others prefer the ecologic approach, using subtler products that ‘turn the big ship’ around. A reservoir owner wants a maximum volume with toxicity just below the legal limit. A mixed-use HOA wants fish and no algae blooms, with butterflies and birds coming back each year. Depending on the property either can be correct.
CALCULATIONS
Step One is usually control of algae/cyanobacteria, which may be at the advanced stage of a Harmful Algae Bloom. Copper (Cu) products are the most effective, coming in several forms. Using a double-chelated product, which is a liquid, is the most efficient. Commonly we use F-30 Algae Control, which introduces 0.1ppm Cu for each gallon applied to 1 Acre-Foot of water; persisting for about 21 days. Control generally begins at 0.2ppm; 1.0ppm Cu is the EPA limit for potable water. Using these concepts, we can make a plan to address the owner’s goal.
Example:
- Volume of Water 300’ x 700’ x 11’ average depth = 2,310,000 Cubic Ft
- A closed system with average water source quality and no effluent issues
- The surface is 4.82 acres, or 210,000 Ft Sq., so a fairly large lake. Air Temp Day Avg ~ 85 F
- Circulation is not good; Wind is high from the west; trees and brush surround the entire lake.
- The lake was built in 1975 as a reservoir for cattle and crops, plus flooding protection. Original depth was 25’. The bottom layer is 60% mud/40% bio muck, reducing the original volume by about half. The abundance of minerals makes this ‘hard’ water, known to precipitate out copper in lower quality algaecides. The water is very turbid with a planktonic alga, plus a top matting of Lyngbya. There is no aeration. A new owner has finished building a home on the lake; the big family has moved in; they like fishing and being outdoors with their dogs.
Solution:
The family wants a fast fix, but years of damage and a weak biosphere will take 1-2 years to address, assuming the best approach. Because they just made a big move, funds are tight and big investments for the lake are not in the budget. A middle ground solution is needed now. For safety until the HAB is eliminated, forbid any swimming, and pets should be kept from the water.
Even though they should not be in the water, it is being used to water crops and fill troughs. The cows seem healthy. Sheep are very susceptible to copper, so they should be watered from another source. Now that the family is safer, the application can be considered. Maximum Cu for potable water should be approached, so calculate for 0.8ppm for a strong initial control.
53 (Acre-Feet) x 8 (.1 per Gal) = 424 gallons of F-30
The Mfg. says that 4 parts F-30 Algae Control with 1 part F-55 Bio Zyme is very effective, so the owner orders 400 gallons of F-30 AC and 100 gallons of the beneficial bacteria enhancer.
If another control dosage is needed, begin 30 days after last application, for 0.5ppm
Follow label instructions on all products
Despite budget issues, the owner installs one multi-head diffuser in the deepest spot, increasing DO and mixing. The water column is so unhealthy no enzyme will diffuse to the bottom. 10 gallons of F-55 BZ are repurposed to drip-drag lines, injecting directly into the muck layer. Two months later a 5-pound bucket of F-51 Muck Reducing Pellets is purchased for bottom treatment, to reclaim depth and further boost the beneficial bacteria colony. Multiple advantages are slowly observed as the ecosphere reacts over the first six months.
The next year, applications are reduced in half, then in half again. A long-lasting aquatic-blue dye with a UV blockers is added to the process (F-40 Enviro Blue). The family likes the color, but it is the reduction of photosynthesis that is sought. Then a clarifier is added to the treatment, dropping nutrients into the muck, which is now being eaten by the diverse bacteria. The ugly and smelly matting has not returned; fish are abundant and healthier.
Other important applications can be incorporated, like more instruments in a song. Clarifiers bind and drop particles from the water column, so their nutrients are unavailable to algae. A defoamer will break down unsightly bubbles. Two different quality dyes can mix for a preferred look, while not compromising the UV-blocking performance of the blue/yellow product. Pure bacteria and vital minerals replace those missing and absorbed by struggling water.
Finishing our story… More aeration is installed in 2-3 years. At this stage, synthetic chemicals are mostly replaced with biologic products. The family includes a waterfall built with local rocks, which pushes surface currents against the prevailing winds, clearing out the last stagnant region. Only in especially hot years, when pollution overwhelms the balanced and healthy water, does the family resort to a control treatment. But now the lake recovers quickly. Maintenance is sufficient for many years and fish thrive.
Patrick Simmsgeiger is the President of DWI, a lake management company based out of Southern California. He is a Certified Lake Manager (CLM) with over 40 years of experience in the field. [email protected]
