PHOTO: Meghan Hess/Flickr
Brien Darby
March 18, 2016

For the urban farmer who wants to create a closed-loop growing system, finding a natural supply of irrigation water is important. Many people know about using rain barrels, but in some areas of the country, but there are other methods you can put to use to catch and divert rain water or—especially in the case of areas where rain catchment is illegal—maximize the use of it. Here are some water strategies you can put into place this year to have a luscious and fruitful garden.

1. Implement Rainwater Catchment and Redirection Systems

Capturing rainwater is a passive method of garden watering that can either supplement regular watering or, in some cases, take care of all the water needs for a garden. Strategies for catchment and storage of rainwater vary widely from site to site, so it can be difficult to speak in general terms about the perfect rainwater system. These differences arise from variations in roof styles, garden design, plant selection and water-storage methods. Many states in the western U.S. have strict regulations regarding water catchment and storage that often prohibit the use of rain barrels, so check with your local ordinances before designing any rainwater catchment system.

Although rain barrels have become the poster child for water catchment, it’s important to remember that they are only one piece of a larger system. The five basic parts of any catchment system are:

  • the collection area (usually a roof)
  • a water transport system (gutters and downspouts)
  • a method of trapping debris (separate, sealed catchment tube next to a downspout; a p-trap before entering the storage tank; a mesh filter between the downspout and the storage tank)
  • storage tank or barrels; in all regions, storage tanks should be enclosed
  • a system for using the rainwater in the garden (gravity fed, pump-driven, a tap for filling watering cans)

In regions where water storage is prohibited, a catchment system can still be effective simply by directing water from the roof to the garden via the position and length of the downspout.

2. Dig A Passive Rain Garden

Almost all rain gardens rely on deep digging in order to catch and hold water. To design a bed that passively catches rainwater, dig the bed in a trough shape, 1 to 2 feet deep. Fill the bed with a loose soil mixture rich in compost or humus. Humus, or finished compost, aids greatly in retaining water, whereas sandy or rocky soils tend to drain rather quickly.

Additionally, water can be directed to the rain garden with the help of downspouts, hosing attached to catchment barrels, or trenches dug into the ground. Rain gardens can also be watered by hand, but a passive system will always create less work for the gardener!

3. Strategize Your Garden’s Position

Many gardens rely on gravity to maximize the watering potential of a single rainfall. In fact, designing a garden around the existing site elevation is a key permaculture concept. When planting on a hillside or slope, position plants with the least water needs at the top of the slope and those with the greatest water needs at the bottom. The bottom bed can resemble a traditional deeply dug, trough-shaped rain garden that will collect mostly gravity-fed rainwater. However, along the slope, swales can be incorporated to temporarily trap rain and water individual gardens.

A swale is a trench, a mound or both (with the trench on the uphill side and the mound on the downhill side), built along a contour line with the purpose of detaining water on its downhill journey. Often times, tall plantings, such as fruit trees or shrubs will also be planted on the downhill side of the swale.

4. Choose The Right Crops

In most rain gardens, plants are grown in trenches that are meant to fill with water. However, this means that the plants growing in these beds must be tolerant of wet conditions, as it can take up to 48 hours for a trench to fully drain after a heavy storm. The best plants for a rain garden in any region are ones that have deep root systems and are either native or well-adapted to grow in the climate.

The following are recommendations for perennial flower, shrubs and grasses that do well in a variety of climates:

  • yarrow (Achillea millefolium)
  • false indigo (Baptisia australis)
  • northern sea oats (Chasmanthium latifolium)
  • tickseed (Coreopsis verticillata ‘Moonbeam’)
  • purple coneflower (Echinacea purpurea )
  • Maxamilian sunflower (Helianthus maximiliani )
  • bee balm (Monarda didyma )
  • ruby muhly grass (Muhlenbergia reverchonii )
  • spring and fall obedient plant (Physostegia intermedia and P. virginiana )
  • blue-eyed grass (Sisyrinchium angustifolium)

Three tree species that often perform well in raingardens are:

  • Drummond’s maple (Acer rubrum var. drummondi )
  • swamp white oak (Quercus bicolor )
  • river birch (Betual nigra )

5. Terrace Gardening

Terrace gardening is a traditional method of altering a slope in order to capture rainwater. Some of the oldest terraced gardens can still be seen in the Incan ruins at Machu Picchu in Peru. Similar to these ancient beds, contemporary terrace gardens are built by excavating a portion of the slope, using rocks or lumber to create a retaining wall, and then backfilling with an appropriate soil mixture. The challenge then and now is to build the wall in such a way that it doesn’t collapse from the weight of the soil, especially after a heavy rain.

6. Waffle Gardens

One final method of using garden design to capture rain water comes from the native cultures of the American Southwest. The Zuni of New Mexico commonly built waffle gardens for their high-value crops, such as chili peppers and tobacco. The beds are designed with 2-foot squares dug below the surface of the ground that are separated by small berms made of unamended soil. From above, this arrangement resembles a waffle. The vegetable crops are planted inside the squares where rainwater will collect and water the plants slowly over time.



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