news from the waterfront by Tim Matson
THE PONDKEEPER’S SEASONS: SUMMER
Three typical problems come up in summer ponds: overgrowth of aquatic vegetation and algae, low water levels, and dead fish.
The emergence of aquatic vegetation and algae is just about inevitable in an earth pond. In fact, a certain amount of vegetation can be good nourishment, producing oxygen and food for fish and other critters, as well as providing protective habitat, and preventing erosion.
But excess alage and weeds can make a mess. Clouds of algae foul up swimmers, tangle fishing lines, clog inflows and spillways and other pipes, and lure animals you may not want. Massive vegetation can drive up water temperatures and reduce dissolved oxygen, stressing or killing fish.
Good initial construction is the best maintenance
against these problems. A deep pond avoiding shallow slopes discourages weeds and algae. It’s important to maintain water levels to discourage weeds from getting a toehold in the edge areas, and to keep up conservation tactics, especially diverting nutrient rich runoff that could feed vegetation. Summer is the time to fix fences too; keeping farm animals away from the shoreline prevents trampling and erosion of the perimeter.
Drawdowns can help control unwanted edge plants.
By lowering the water level partially or by complete dewatering, the pond keeper can dry up and kill aquatic vegetation. This can be done if the pond has a drain, or by siphon hose or pump. Obviously a full drawdown is not an option if the pond is stocked with fish. Plants can be raked up or pulled during a drawdown. In truth, roots and seeds are likely to lead to reoccurance of the problem some time after the pond is refilled, but it’s a low cost technique that can yield benfits, if temporary.
Water quality problems, including weed growth, may also be helped by using aeration and/or circulators; biologicals to enhance nutrient decomposition, dyes to cut off photosynthesis, and introduction of aquatic life that feeds on plants, such as carp or crayfish, where legal.
Fallen water levels are another common summer problem. Usually it’s due to extreme dry weather,
structural leakage, or location in a site without
sufficient water supply – or a combination. The solution may involve finding one or more supplemental water supplies, or locating the source of the leak and fixing (often easier said than done).
Excerpted from Earth Ponds: The Country Pond Maker’s Guide to Building, Maintenance, and Restoration.
July 21, 2010