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Swale well

Getting creative with water landscaping - photo by Teena Jo

swale
water conservation landscaping - photo by Teena Jo

By Erin Volheim

In the spring of 1998, Wolf Creek was flowing with water on farmer Tom Powell’s initial visit to the land his family now cultivates as Wolf Gulch Farm. This first glance at Wolf Creek could have led him to believe the land was blessed with water. Sun and water are optimum situations for growing most crops, but the seemingly plentiful water of 1998 was a seasonal apparition, drawing its strength from a high water table born from the floods of 1997. Subsequent years were mostly dry averaging around 11 inches a year, (comparable to a good year in the Sonoran Desert), while the past two years have averaged around 27 inches per year. Wolf Gulch Farm is situated in the Little Applegate Valley of Southern Oregon where moisture is drawn to the coniferous North-facing hillsides and drawn away from the South-facing oak, manzanita, and madrone woodlands. The terraced slopes of Wolf Gulch Farm are positioned in one of these South-facing bowls.

 

Historically, farmers have been at the whims of weather patterns. The 21st century bears the additional burden of human-influenced global warming and the subsequent bioregional climate changes; hotter temperatures, floods and regionally uncharacteristic cold snaps. Even the centuries-old Farmers Almanac is having a hard time predicting the weather of the future. Wisely, Tom foresaw that his first priority was to drought proof the farm as much as possible. Improving the natural water storage capacity at Wolf Gulch farm was not only important for the farm’s viability but for the surrounding wildlands and wildlife, as well. He chose to enact two general approaches to water storage, one at the surface level and the other subterranean.

 

The surface approach was to install cisterns and create two ponds. The 3,000 sq. ft. roof of the main house has a water catchment system that routes water to two 2,000 gallon cisterns that can be used in the summer to supplement irrigation for the kitchen garden around the house. The house has access to a five gallon per minute well. The rain water catchment system, when it’s managed in a more aseptic manner, can also be filtered for drinking and bathing water and provide back-up irrigation for the lower fields.

In the first year, Tom also built two ponds. Winter rains fill the ponds supplemented with seasonal water from Wolf Creek and the farm’s roads. These ponds are gravity-fed with one above the first set of higher fields and the other above the lower fields. The best pond is one in which water is naturally held by a clay soil layer, surrounded by non-invasive native vegetation which shades the pond from evaporation, filters the water and creates wildlife habitat while providing irrigation water.

 

Tom first tried a pond without a plastic liner, but since Southern Oregon summers are generally dry; it was hard to maintain the necessary water level that would prevent the natural clay bottom from cracking. As nature’s best is hard to imitate, he eventually had to install a black plastic liner that kept water in the pond. Initially, he started with open ditches that also exposed the water to the sun and absorption into the soil. Now the flow is funneled through pipes instead. An additional water source for the ponds, is channeled from access roads through the fields that are angled to divert water into a parallel ditch that directs run-off to the pond. On average, the first pond holds a half-acre foot of water while the second one holds three-acre feet. With his ponds, Tom was able to directly irrigate two acres of annuals the first year.

 

Another way to hold water is in the soil structure utilizing a keyline system. P.A. Yoemans of New South Wales, Australia, developed the keyline method to stretch water resources available on his ranch in its arid climate. The system uses various methods to spread water laterally, across slopes and also, to slow its movement off the farm. Utilizing gravity, this is achieved with ponds, swales, cultivation and roads that direct water. The practice has become a model for sustainable agriculture. Designing a keyline system for any property requires good initial planning. A contour map is essential in order to best understand the rise, fall and flow of water on the land.

 

Proponents of keyline design recommend the use of aerial photomaps because of their increased contour detail. With keylining, the three fundamental concepts that must be understood are keypoints, keylines and keyline cultivation patterns. A keypoint is a position located along the centerline at the base of the steepest part of a primary valley, the place where there is a change in a slope. A keyline is a contour line that runs through the keypoint and extends to where the curve of the valley start to become the sides of the ridge.

 

Tom maintains the keyline design on the farm by keyline cultivating annual fields two times a year, and the pasture and perennial fields once a year. Yoeman invented a special plow for cultivation in his pastures. The plow is a modified ripper designed to loosen soil without turning it over. Keyline cultivation is done across the slope, slightly off contour, on a line dropping in elevation as one moves from a valley to a ridge. The keyline rips absorb water and influence its flow across the slope, moving it from wetter areas (valleys) to drier areas (ridges).

 

The keyline plow that is used has three shanks, each with a tapered foot at the bottom and a wheel on each end. The wheel is what you use to adjust the depth of your shanks. This kind of plow breaks up clay without turning it over, thereby maintaining the soil structure while allowing air and water to penetrate. Simultaneously, this form of passive tillage adds organic matter to new depths. This approach, coupled with additions of organic matter results in the formation of more topsoil.

 

The first time Tom keylined at a shallow four inches because the soil was very compacted. Later, he went to 12 inches and now it’s 18 inches each time. Every spring in his annual fields, Tom turns in his cover crop, lets it decompose, keylines his contours and then rototills down six inches maximum while adding amendments to his annual fields. A second keyline ripping, just before sowing fall cover crop, breaks up any hardpan from use of the rototiller. It’s not recommended to plant small seeded annuals into the keylines, because the seed will be overwhelmed at that depth. Potatoes, onions for seed and garlic and other low water tubers and bulbs could be planted along with fruit and nut trees into the keyline rip.

 

A swale is a slight depression that runs along the contour of the land. That is to say, it is level all along its length. It can be deep, shallow or even hidden. The dirt from digging the swale is usually used to make a berm on the downhill side. Rainfall, instead of running straight down the slope runs to the swale. There it soaks in slowly, forming a lens of water underneath that is absorbed into the clay layer. This provides a plume of shallow subsurface water down slope from the swale where it is stored for a long time. A common-sized swale is two or three feet wide. Of course, you can make them any size you want. An important distinction is that a swale is not a drain. It is a water collection device. The cheapest way to store water is in the soil. And of course, by stopping the run-off it prevents erosion as well.

 

After five years of water storage in swales and keylining, Tom started planting his orchard hedgerows three years ago. He planted apple, plum and pear trees as as a hedgerow – or windbreak – which are flanked on one side by a row of native conifers like ponderosa pine. On the other side are native alder and ash, which are fast growing deciduous trees that will shelter the slower-growing fruit trees into maturity. This provides habitat for wildlife and for other pollinators, as well. Tom also planted chestnut trees which have a long taproot, very much like the native oaks and manzanita of this area.

 

In Southern Oregon, though the summers are dry, the winters can be very wet. So when planting trees in areas like these, he recommends not planting them too deeply, not only to prevent suckering at the graft point but because water-filled basins in a wet winter will easily rot the root systems of newly planted trees. He plants the trees with their fine upper roots above the soil line and then generously top dresses them with compost. For the first several years, it will be necessary for him to water in the dry season till the roots of these newly planted trees are established and can begin to take advantage of the water stored in the clay. He will also sheet mulch these hedgerows with cardboard to supress weeds.

 

Two other facets of being a water-wise farmer are utilizing low water irrigation methods and choosing the right crops. Conventional agricultural irrigation is one of the largest groups of consumptive water uses in Oregon state. Overhead sprinklers and big water guns result in excessive evaporation and deep percolation losses, it’s estimated at least 25 percent is lost to evaporation, even more if you water during the heat of the day. Tom switched to drip irrigation as soon as he could.

 

Tom has also built his farm around root crops and the more drought tolerant and heat loving Nightshade, Curcubitae and Allium families. His market field’s focus has been led away from fussy water-intensive Brassicas, except for those less water-intensive varieties that are closer to their wild relatives like cabbage, kale and collards. He also recommends growing income-producing seed crops. Seed crops conserve water because you need to stop watering in the hottest months, like August to convince them into producing seed and to let them dry out before the autumn rains.

 

One of the first signs that keylining was a success at Wolf Gulch Farm, was the immediate effect Tom saw on his parsnips and carrots. He can now direct seed without forking the soil and instead of harvesting small stunted, forked roots that hit hardpan; they are big, sweet and straight.

 

Perhaps one of the clearest signs of success, that doesn’t require a farmer’s wisdom, is being able to jump into a water-rich pond on a hot, global warming day in the 21st century.

 

Erin Volheim lives in the Little Applegate of Southern Oregon where she writes her award winning journalism.

 

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