COUNTRY LIFE IN BC • MARCH 2020 Good ditches are critical for good drainage


Lower Mainland farmers face low land, high water by RONDA PAYNE


RICHMOND – Drainage issues cost farmers money through late planting, damaged equipment and lost crops. Whether it’s preparing for spring thaw or a fall downpour, farmers need help and input to manage their drainage systems. To help reduce losses and


improve crop yields, the Society Promoting Environmental Conservation (SPEC) has hosted workshops to help farmers understand the root causes. “A lot of times, when I talk to farmers, they forget they are part of this much bigger system,” says Yuko Suda, an engineer specializing in municipal sanitary sewers and a small-scale farmer herself. “You’re in a very delicate balance.”


This balance is especially


challenging for farmers in the Fraser Valley, who farm low- lying lands on the Fraser River delta with its high water table. A variety of factors can cause water to accumulate on a farm, whether it arrives as rain, surface run-off or overflow from adjacent bodies of water. Typically, excess water is caused by a high water table, ponding or flooding. When surface run-off, evaporation, evapotranspiration and infiltration can’t keep water


levels in check, other methods must be used to reduce water. “If the volume of water coming on the site is the same as the water going off, then you wouldn’t have a drainage issue,” she says. “You have to recognize what’s causing your problem. This determines how you’re going to deal with it.” She says clay soils usually cause ponding. Soil tests can determine if this is the issue on a site. If the soil further down isn’t saturated, tilling the soil and building up low- lying areas can help. Other issues are usually regional in nature and can’t be managed through on-farm tactics. If the soil is completely saturated it’s a high water table challenge. If the issue is flooding, the water is generally moving across the property. Suda outlined three ways to deal with drainage: ditches, cropping practices and drainage tiles. Ditches are the first solution she recommends as they’re the fastest way to get surface water off a property and assist with both drainage and irrigation. Some existing ditches run alongside roadways and are the responsibility of the municipality or the drainage district. Other ditches might be on-farm and are the property-owner’s responsibility.


Ditch maintenance is


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There’s no escaping the amount of water that comes down (or up) on Fraser Valley farms. But there are tools to manage it better, including ditch maintenance and using drainage tiles. RONDA PAYNE PHOTO


essential to ensure their proper function. In the winter, ditches should be kept as clear as possible to keep extra water moving off site. In the summer, more water is ideal to meet irrigation needs. “When ditches don’t get maintained well, that’s where you see drainage issues,” Suda says.


A lack of maintenance


allows grasses and swamp- loving plants to invade, and these can impede water flow and attract wildlife. Ditch sides should be fortified with


stones, grasses or other riparian plants to prevent sloughing of dirt into the ditch. Property owners should regularly watch for garbage and debris that can also lead to blockages. Growers should call their local municipality or drainage district to address issues affecting roadside ditches. Suda says ditch maintenance is a low priority for most municipalities, so farmers need to speak up. “When ditches are slowed or challenged along the line, it causes issues further up, away from where it’s draining,” she says.


Depending on the number and location of impediments, there may be a metre’s difference (or more) in water levels along the ditch system. However, a well-maintained ditch, where levels are stable along the route, is a good indicator of the water table


level.


Unfortunately, when ditch depth is affected by municipal projects, and water levels in them become lower than the level of outflow at the destination drainage point, brackish water can come into ditches and seep into fields, damaging crops. This creates even more of a need to ensure ditches are properly maintained and cleared of blockages. “That ditch is supposed to


intercept all that saltwater before it gets on your farm,” says Suda. “All of this information is available in the BC Drainage Manual. That is the go-to manual for BC and the Lower Mainland for drainage.”


Summer the best time for ditch maintenance, notes Suda, encouraging growers to be mindful of the dangers and take appropriate precautions.


Know your soils Soil tests can reveal many things to growers, but


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engineer Yuko Suda recommended a quick and dirty method to analyze soil for clay, sand and organics. Crush the soil sample to remove any clumps, then fill a jar about one-third with the soil sample, add a bit of dish soap and fill with water. Shake the jar and let it stand for a few hours to see the layers of soil composition. The heaviest soil components (clay and sand) drop to the bottom of the jar. Sand may sparkle. Organics will be a top layer or may float. To identify if the soil is clay or silt, Suda recommends adding water to a small soil sample and working the mixture like dough to create mud pies. Once combined, roll the soil into a log about a half-centimetre in diameter. Pick the piece up from one end. If the sample stays together it’s clay. If it breaks, it’s silt. Knowing the composition of soil is important because


clay soils can be problematic. “Before you look at any kind of drainage solution, you have to know what kind of soil you have,” she says.


—Ronda Payne


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