The Do’s and the Don’ts of waterway stewardship…how can a rookie begin to get it right? That’s what this article’s about. Let’s start with Don’ts in this case, just in the event you face a water stewardship challenge as we speak.
1. dig a hole and fill it with water, until you know what’s in your inflow water and understand how to cycle it into something better than algae or wall to wall aquatic vegetation.
2. take a single measurement and think you know what’s in your water. Do…measure several times, especially just after water events. Chemical and nutrient insults are variable. Here’s what you measure for…(1.)
3. design your waterway around a smooth bottom. Do add surface area, particularly inert surface area. This can include rock, cobble, sand. Other forms of surface area, not necessarily totally inert, like dried, deciduous branches and deadheads can be valuable as well. A well designed waterway bottom will result in nutrients cycling into fish instead of algae. A poorly designed bottom is a recipe for pea soup. Do not line your waterway bottom with clay or dirt. If that’s all you have, or all you can afford, then cover it up with screened gravel or cobble. Know that there are life forms like specific minnows (carp are in the minnow family), other fish like suckers and some chubs, crawfish, and a range of invertebrates for whom turbid water is preferential. Thus they work very hard to make it so. You don’t want to fight them.
4. Smooth waterway bottoms are ideal if your goal is to grow free floating algae. If instead you prefer clear and highly productive water, add surface area on top of such a bottom. The surface area is technically called substratum. What grows on it is called substrate. That substrate is made up of biofilm, diatoms, and whatever else is suspended in your water. The blend is called periphyton, and it’s the base of the freshwater food chain. It will be an ongoing source of dissolved oxygen, and when it dominates a waterway will not experience the peaks and deficits of dissolved oxygen that prevail in an algae based waterway. Periphyton is a zooplankton factory. It is how to grow fish.
(SIDEBAR…Nature uses surface area, circulation and biofilm generating microbes to cycle organic nutrients up the food web. Human waste water facilities do the same thing. About half the lakes in the U.S. are now septic, because they don’t do this sufficiently…at least not relative to the inflow of nutrients they now receive. If you want a waterway that is highly productive, maximize for nature’s wetland effect. It’s easy…surface area and circulation. No, you don’t have to add microbes. They are already there, just waiting for that surface area and circulation. In fact those native microbes can and will double their population in the space of hours. They are even more prolific than algae. Just give them what they need…surface area and circulation.)
Here’s the MAGIC of waterway design. If you have enough surface area and circulation, you can even cycle the FREE nutrients, the ones that you’ve measured in your water, into fish. On the other hand, if your existing waterway is instead in the pea soup category, you might consider emptying it and start over.
Be smart about circulation and surface area. If gravity flow happens where you are, take advantage of it. Water has this fairly consistent habit of moving downhill, and if you can design for it to move over, around and through your inert surface area, and maybe even spend a little residence time doing so, why that’s a great way to grow fish.
Today there are vertical aerators, horizontal aerators, directional air diffusers, pumps, and fountains, all of which will happily help you circulate water. There’s even a bit of aeration that comes with the package. This is a good thing for your waterway. Incidentally, the more you circulate around your sticky, biofilm coated surface area, the clearer your water will be. Beyond clear water being preferential over turbid water, it also sets the stage for diatoms to grow onto biofilm at depth. This is a very good thing. Fish love it! Keep in mind, your waterway’s LATENT surface area may need to be bolstered in the event of nutrient insults.
For those of us who are charged with stewarding an existing waterway:
1. Circulate/aerate aggressively and consider prevention of stratification, which extremely efficient directional air diffuser technology has now made practical. Water will stratify in the event circulation systems shut down. When that happens phosphorus will be released from where it’s accumulated on the bottom. This is not good. Unless you are in the pea soup business. However, if you have enough surface area and circulation you can allow that inventoried phosphorus to resurrect. In fact, when you do so, given sufficient wetland effect, you can cycle phosphorus into biofilm and from there into diatom based periphyton and fish. But here’s the key…you want to have modeled your solution beforehand. If you don’t, you are just guessing and you can easily guess your way into a Harmful Algae Bloom or a toxic cyanobacteria condition.
2. Find a way to incorporate surface area within your waterway. Aggressive surface area and circulation/aeration can actually cause the organic fraction of sediment to cycle back into the food web. This could be a way forward. But just aeration and a waterway’s smooth bottom is rarely sufficient. Think adding surface area…cobble on the ice in the winter, dropping into place in the spring. Variations on this.
Concentrated animal feeding, which includes waterfowl and fish, will result in concentrated nutrients and sets the stage for an opportunistic life form, like algae, to take advantage of the condition. Last winter, here on Fish Fry Lake in Montana, a concentration of wild Ringneck Ducks, numbering as many as 300, frequented an open water area associated with operating air diffusers. These diving ducks roosted on the lake, and certainly deposited urine and feces in volume. However, they also foraged on underwater macrophytes, including northern milfoil and chara. The stewardship response was to allow some hunting during season, and to otherwise tolerate their presence. Alternatively, the diffuser could have been shut down which would have resulted in ice over of the open water. We consider this an experiment and are tracking the nutrient load, dissolved oxygen and turbidity status of the 6.5 acre waterway.
Even a mistreated waterway can be brought back. Fish Fry Lake started as a nutrient laden pond and was destined to be an algae dominated mosquito factory. Today, it is among the most productive fisheries in Montana. The lesson is clear. Base your stewardship on science. We have the science, and you can learn how to cycle unintended nutrients into something better than toxic algae and cyano bacteria blooms or massive underwater plant beds, or total coverage of duck weed. You can actually have clear water, safe water, water you will feel good about swimming in and letting the dogs drink from. But you need to operate from science.
The “Do’s and Don’ts” of Waterway Stewardship – how can a rookie get it right? – By Bruce Kania
April 10, 2013