Pondering a pond?
Resist the urge to excavate, and do some planning first

by Rupert Jannasch
A hot, dry summer lends itself to thinking about ponds. For a swim, maybe, or a basic necessity like watering the garden, or even a winter game of shinny. A water reservoir provides security against emergencies like a well gone dry, or a fire. It provides a drink for thirsty livestock, and a home for fish and waterfowl. Lastly, there are the calming and reflective qualities of an open sheet of water.
It’s tempting to start a pond simply because rural communities have an abundance of excavators capable of digging a massive hole all in one day. But actually completing a pond, with a reliable water supply and the means to retain it, can be a different story. Mud puddles and swamps are not on most people’s landscaping wish list; few things are more defeating than an empty pond. 
To begin with, the landowner needs to establish a source of water. Springs are ideal, as the water is usually clean and cool, with a constant flow. Sadly, springs tend to be hard to find, except perhaps in hilly terrain. A pond fed by a stream might seem like an obvious choice, except that silt can be troublesome, and obtaining permission from fish and environmental authorities can be difficult.
Surface run-off, although more seasonally variable than a spring or stream, is another option – if the landowner has some control over the catchment area. Water running over pasture land and forests is usually free of silt, and there are no regulations pertaining to water capture. The key is to have a catchment area large enough to fill a pond, but not so large that run-off from a heavy rain might overwhelm it. 
The fact sheet titled “Farm Ponds,” prepared by the Atlantic Committee on Agricultural Engineering in 1984, describes how to estimate the amount of water collected from catchment areas, according to the type of ground cover. (Follow the link at RuralLife.ca.) “Earth Ponds Sourcebook,” by Tim Matson (The Countryman Press, 1997), also contains a wealth of practical information about pond design and construction. 

DESIGN AND CONSTRUCTION
The appropriate style of pond construction depends on the terrain. On level land, the basin is usually excavated, whereas on slopes embankments are built to retain water. Sometimes a combination of the two methods is used. In any case, there are a few points about construction and design to consider before digging begins:

• A sound bottom is needed to hold water. The soil should be a minimum of 20 percent clay.

• It’s best if ponds are dug deep, to minimize seepage, evaporation, and weed growth.

• Steep sides help to discourage encroachment by invasive plants like bulrushes. However, lighter soils demand gentler slopes, to prevent caving in.

• Excavation yields a surprising volume of fill or debris. For instance, to build a small pond with a capacity of roughly 500 cubic yards, as depicted on the previous pages, about 25 tandem dump truck loads of fill would have to be removed, assuming 100 cubic yards was retained for the embankment. The landowner must either have a place nearby to dump it, or pay for trucking off site. 

• Bulldozers are more efficient than excavators at moving soil on large pond sites, and better suited to shaping and compacting embankments. 

• A pond should be built big enough for its intended use, but small enough to stay full most of the time.  The small pond shown in the photo is big enough to water a 1,000 square foot vegetable garden, but woefully undersized to irrigate an acre – even if more efficient drip lines were used instead of overhead sprinklers. 

OVERFLOW
In pond design and construction, you must remember that when it rains, it sometimes pours. Run-off from prolonged rainfall or freak storms can flood a pond in minutes. An essential feature, therefore, is a good-sized overflow or spillway, sometimes even two. Spillway design is one aspect of pond construction where professional assistance may be a wise investment. “Providing a way to let the water out is probably more important than letting it in,” says Laurie Cochrane, a Nova Scotia agricultural engineer.
Cochrane believes overflows work best if kept simple. Culverts through the front of an embankment, or tubular risers extending from the water surface to a drain running through the base of a dam, may leak around the edges, get plugged, or be too small to handle floods. Metal structures should be avoided entirely, he says, because they rust. 
The alternative is to place a spillway at a low point in the embankment, so excess water flows over and down the side of the pond. A liner made of waterproof geotextile should be used to prevent erosion, with rip-rap, or armor rock, placed on the liner to break the force of the water. 
In some cases, the spillway can be located at the same point where water enters the pond. This keeps water from going in and avoids the cascading effect of water flowing down an embankment. The outlet should be situated at a level that provides one or two feet of freeboard between the pond surface and the top of the bank. Whenever possible, overflows should spill onto the natural gradient where the soil is well-sodded, rather than onto an artificial embankment where the soil may be more prone to erosion. An emergency spillway set slightly higher than the main one is a wise investment, in case of blockages. 

MAINTENANCE
In order for a completed pond to remain useful and attractive for many years, a certain amount of maintenance is in order. Overflows need to be checked for leaks and blockages, and vegetation growing on embankments should be held in check. 
Letting trees grow on embankments is a risky business, because roots, dead or alive, can pierce the soil and cause leaks – or worse, a washout. Trees are best set well back from the banks. And beware of the gracious Weeping willow! This elegant menace can send out countless suckers in the course of a growing season. They must be pruned back each year.
Occasionally, silt might have to baled from the pond with an excavator. This is a messy job, and sometimes an expensive one. Muskrat, too, can muddy the waters and put a damper on swimming plans. Beavers have been known to bore holes through dams. Should the wildlife be removed? If so, how? Invariably, such questions will arise, and you will need to come up with good answers to ensure the integrity of your pond is not put in jeopardy. 
When things are done right, however, a well placed pond, brim full of water, should seem like it belongs – a permanent and essential part of the landscape.

(Rupert Jannasch grows vegetables and Highbush blueberries and raises sheep on his farm in Summerville, Hants Co., N.S. )

Ducks Unlimited
Ducks Unlimited (DU), the U.S.-based wetland conservation and waterfowl hunting organization, has constructed ponds, built fishways, and improved wetlands in Atlantic Canada since the 1960s. But Tom Duffy, the group’s regional manager, says the number and size of projects diminished in the 1990s as environmental regulations related to watercourses became more restrictive and costs increased. DU’s emphasis shifted to maintaining the original projects and excavating smaller ponds and wetlands in agricultural areas.
Joy Elliott and Doug Brown had two such ponds dug by DU on their farm in Belleisle, in Nova Scotia’s Annapolis County, in the late 1990s. Elliott says they were allowed to pump water for irrigation, and didn’t have to allow hunters to access the ponds. She credits DU for maintaining the ponds, including removing silt, but notes that the edges gradually filled in with alders, and “once the alders came in, the birds stopped coming.” 

Call before you dig
Constructing a pond to collect surface water – essentially a hole in the ground that is not in close proximity to an existing watercourse – is generally considered to have minimal environmental impact, and is generally subject to minimal regulatory oversight. However, it is advisable to call local environmental authorities to find out if there are any permitting requirements for digging a pond on the site you have in mind.
“If a pond is on upland then it wouldn’t need a permit from our department, provided it is not connected to a stream,” says Chris O’Connell, with the Nova Scotia Department of Environment.” But O’Connell cautions that although an alder swamp might appear to be a good pond site, it could be designated a wetland. In that case, he says, “permits are needed for removal of material, and often the landowner must compensate for the area destroyed by creating new wetlands elsewhere.”
Applicants for farm pond funding under Nova Scotia’s Growing Forward 2 program (which covers 25 percent to a maximum of $10,000) must work through the Department of Environment even when no permit is needed. For example, where a pond is to be located on a ditch with moving water six months of the year, the Department of Agriculture will insist on a letter from Environment stating that a permit is not needed, providing a paper trail to eliminate any future concerns over liability.

Aquatic plants
A variety of native aquatic plants can be used to create attractive borders along the shorelines of ponds. Pickerel weed (Pontederia cordata) is found naturally along the sides of lakes and marshes, and its purple flowers provide habitat for pollinators active in agricultural areas. Establishment of Swamp milkweed (Asclepias incarnata) is being promoted by conservation authorities as habitat for the Monarch butterfly. 
Native Water lilies such as the white Nymphaea oderata are another attractive option. Unlike plants that hug the shores, this species is known to migrate out from pond edges and colonize water up to 15 feet deep. 
It may take some years after constructing a new pond before conditions at the bottom are mucky enough for aquatic plants to take hold. Aquatic plants can be transplanted from the wild, but it is wise to assess the risk of any species becoming invasive. 
Shorelines that fall off steeply into deep water serve to control plants that grow in shallows. But botanist Nick Hill, founder of Fern Hill, a consultancy specializing in wetland and plant conservation, near Berwick, N.S., says aquatic plants usually won’t overrun a pond “unless it’s full of nutrients.” Still, he advises against introducing some plants such as cattails or bulrushes (Typha sp.). These, he says, are “native invaders.”