Swale, berm, retention basin and gabion are all words which are becoming commonplace in the vocabularies of gardeners in the Rim country. Gardeners are learning new methods of water management in home and commercial landscapes through harvesting rainfall and runoff, and conserving water that comes out of the tap.
Official records show this area has had an appreciable increase in rainfall this winter, but meteorologists warn the drought isn't over. Without a snow pack, which melts slowly and fills streams for months, unseasonable warm temperatures and winds will dry out plants and soils very quickly.
Preparing now to capture spring and summer rainfall, and to use a drip irrigation system where necessary during dry weather will help to cut water bills and take the strain off the uncertain water supply in Rim communities.
Water harvesting offers benefits far beyond that of saving water now for use later.
- Swales are essentially dry creek beds carrying water from the source, such as a downspout, to the area it is needed, like a tree well.
- A berm is a small ridge, intended to contain water in a specific area.
- A gabion is a rock wall intended to prevent erosion.
- Retention basins are pits, ponds, or other depressions, dug into the ground and generally landscaped with rock and plants, which will allow runoff to pond up while absorbing into the ground.
Municipalities frequently require developers to install retention basins to prevent runoff into storm drain system, and to help prevent erosion. As erosion and runoff cause costly repairs to roads, retention basins help save some of those costs as well as helping to recharge ground water supplies as the water is reabsorbed into the ground.
All of these methods can be integrated into the overall landscape design and add interest as well as focal points to home gardens and commercial landscapes.
PAWS in the Park, in partnership with the town of Payson Parks Department and the High Country Xeriscape Council of Arizona, is engaging in a large water harvesting project. Swales are being placed to carry runoff from the east side of the dog park, along McLane Road into retention basins which will be filled with rip-rap and top dressed with finer granite.
Trees that are adapted to this climate zone, and will not need supplemental water after established, will be planted on the edges of the retention basins. Large boulders placed near the bases of the trees will offer shelter to the roots, keeping them cool and moist.
The boulders will also serve as seating for pet owners who are watching their dogs.
Installing swales to direct water to fill the retention basins will allow the water to be absorbed slowly into the ground, and be taken up by the tree roots. The rocks in the basins will prevent standing water, which breeds mosquitoes, and could be a safety hazard to children and pets.
Top dressing the rock with finer material makes the surface more comfortable for the dogs feet. The retention basins will be designed to allow simple "sheet flooding" or even disbursement of water in the event of extremely heavy rain. Sheet flooding solves the problem of gullies forming because the water is evenly spread over a larger area.
To see what a global issue rainwater harvesting has become, type in "rainwater harvesting" on an Internet search engine. Thousands of sites will come up, dealing with water crises all over the world. A good place to start for basic information would be one of these sites: www.dot.co.pima.az.us/flood/wh/bene.html; http://dmoz.org/ Science/Environment/Water_Resources/Rainwater_Harvesting/; www.xeriscapeaz.org
Garden tasks for April include:
Prune: As soon as buds begin to swell on roses and leaves appear on clematis, prune for spring growth. Remove protective wraps on young trees, and prune off any die back.
Plant: Perennials as they become available at the nurseries. Ask about drought-resistant varieties. Plant a native tree on Arbor Day, April 29. See www.arborday.org for more information.
Feed: Blood meal will add needed nutrients to perennial plants and also discourage invasion by neighborhood cats and rabbits.
Repair: Check drip-systems. Replace misters and sprinklers with drip emitters or lengths of laser-drilled soaker. Install a rain gauge and buy a moisture meter. When using a drip system, watering for a long period less frequently is far more cost efficient and better for the plants than watering frequently for just a few minutes.
When rainfall occurs, turn off the drip system, if it is on an automatic clock. Check the amount of precipitation with the rain gauge. Check soil moisture with the moisture meter and do not water until the top 3 inches of soil is dry. Three to 4 inches of mulch will drastically reduce the amount of moisture lost by the soil after deep, slow watering sessions.