Pondology news from the waterfront by Tim Matson

 


DROUGHT BUSTERS PLUS: 2016 POND ROUNDUP
PART ONE

Starting the year I like to look at the past season for situations that can be instructive toward future improvements for pond owners and builders.

Here in Vermont, and across much of the country, we had a bad drought. The drought followed a rather dry previous summer, a low snowfall winter, and then the bottom dropped out. Many household wells, including mine, went dry or nearly so. Lake and river water levels hit record lows, with attendant water quality problems with algae and E. coli bacteria contamination. Many ponds were seriously distressed.

Droughts can trigger pond issues that may be solo problems or a mixture, usually the latter. Usually the first thing that goes wrong in a drought is low water levels. Low water can result in many problems: warming water, low dissolved oxygen levels, fish kills, filamentatious algae growth, turbid water (often algal bloom), and the low water itself.

The quickest remedy is to add water. Adding water can help offset many of the issues mentioned above, depending on the amount. Generally, the more the better. Adding water can cool the pond, boost oxygen levels, save fish, etc. If the water is cool and if it's splashed in (oxygen booster), all the better. Ideally you want to get the pond overflowing as much as possible.

Low water can also lead to pond structure damage. As the water drops, the previously submerged pond basin is exposed to sun and air. If the pond was lined with clay to help hold water, the exposed clay can crack and lead to future leaks when the water rises. Plants around the shoreline can die. One pond owner I know moved her potted water lillies downslope as the water dropped, to keep them in the water. If the water drop is significant, pond critters like frogs may leave for a new habitat.

Low water and its attendant poor quality may also discourage swimming. I know many pond owners last summer who quit using the pond for swimming, including me. If the pond is used for irrigation or livestock water, supply may be reduced or cutoff.

What's the cure for drought? You either wait it out and hope for rain, or consider water supply improvement options. Improving water volume is usually done by either adding water or improving pond water retention, or both.

How is water added? The ideal solution to a water deficit is to find a natural source of new water, preferably one that will flow to the pond under its own steam (gravity flow). These sources include streams, springs, shallow wells, roof runoff, and uphill runoff piped or ditched to the pond. Of course, depending on the severity of the drought, these sources may be minimal. But every drop helps.

Years ago, I found that hillside runoff to my pond increased when the hill was cleared of trees. In some cases accumulated sediment on the pond bottom can block off springs, and a cleanout may help free up supply.

Water sources that won't flow by gravity to the pond are often pumped. Usually this requires power from the electric grid, but solar pumps may be an option. Non-electric hydraulic rams are sometimes used for pumping.

Several of my clients own ponds supplied by drilled wells. Some of these wells are helpful, some not so much, depending on the capacity of the well, the severity of the drought, and how leaky the pond is. If you're thinking of having a well drilled for the pond, keep in mind that predicting well capacity is impossible, so it can be a gamble and a pricey one.

It may be possible to use your household well to feed the pond. But this usually requires a well of high volume and recovery. In some cases a second pump is installed in the well, to reduce wear on the house supply pump. Distance and/or lift to the pond can be a factor in well potential.

Some ponds troubled by drought may already have water level problems, which the drought worsens. In such a situation, you can add to the possible remedies above, options to reduce leaks. These options include installing a membrane liner to eliminate all seepage/leaks completely. Once filled, a lined pond will need only occasional topping off, even in a drought. This topping off water could come from any of the sources mentioned above. It might even include ground water from below the liner, recaptured and pumped back to the pond. Clay is also used to try to leak-proof a pond, but the requirements for good quality clay, and proper clay installation make this an iffy option.

Another remedy for a pond vulnerable to low water even before a drought is to re-think pond depth. This is especially true for embankment ponds. It may be that the dam was built higher than the natural water supply can consistently fill. I can't begin to count the number of ponds I see which are reported to fill in the fall, winter, and spring, but then drop. There can be numerous reasons for this situation, sometimes many reasons, but here's one you may never have considered: dam height. It's hard to calculate how consistently a new pond will fill to overflow level, unless the water supply is very generous or the pond is lined. If the pond seems reluctant to fill, consider shaving down the dam to match the water level you do have. This will of course reduce your depth, but hopefully not drastically.

Speaking of lower pond depth, this can trigger water quality problems. Luckily, there are many ways to improve water quality brought on by drought, or other factors. We will take a look at these water quality solutions in Drought Busters Plus: 2016 Pond Issues Roundup Part Two, in March.
    
As a follow up to the January Pondology about ice savvy, here is a link to more safety information from Bob Dill at Lake Ice. Thanks Bob!

February 1, 2017

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