June 15 has been designated as the official beginning of monsoon season in Arizona. The calendar may state it will soon be time for the rainy season, but meteorologists are saying its accompanying storms may actually be late this year.
Desert ground water is alkaline and high in salts, whereas rainfall is neutral and nearly devoid of salts. Vegetation appreciates fresh rainfall much more than the processed water from irrigation systems.
During an average year, nearly 60,000 gallons of rain water will be received on a typical residential lot in our area. This water often runs down the street and into nearby arroyos because of installed plastic landscape fabric and drainage ditches.
From arroyos much rainfall runs into the Santa Cruz River where it later may spill over the desert floor somewhere near Tucson.
Water harvesting is one of the oldest known gardening methods. All that is needed is rain and a place to store it. Native American Tohono O’odham and Hopi still practice rainwater harvesting. These systems can be as simple as contouring the landscape so the water flows to the garden space, or creating mini-basins around plants. River rock cover in the channels prevents washing out of waterways, and is also aesthetically pleasing.
Simple to build mini-basins are shallow depressions around plants, with added rock to maintain the form. When constructing berms for plants, be careful to not accidentally damage hidden roots. Adding soil at the drip line is preferred instead of digging down within the drip line. Collection of water inside these basins will provide plants with a longer, deeper drink.
Gutters and downspouts on structures allow collection of rainwater that lands on the roofs. It can then be directed to the garden or stored for later use. There are sophisticated and expensive systems with above- and below-ground storage tanks, piping and pumps. However, for simplicity, old-fashioned rain barrels are still available, cost much less, and collect a fair amount of water.
Public tours and workshops on active and passive water harvesting are randomly presented by The Nature Conservancy, 1510 E. Fort Lowell Road, Tucson. For schedule, call 520-622-3861.
Although all vegetation responds to monsoon season storms, some plants are referred to as “barometer plants” reacting to rising humidity by producing early, bright blooms. For example, blossoms on Ocotillo, Arizona Rosewood, Texas Olive, and many varieties of Texas Rangers have recently been doing their best to forecast coming rains.
After the rainfall harvest system has been selected, river rock channels are installed, and mini-basins are created around plants, the landscape is prepared for another bountiful monsoon season… now bring on the rain!
Mary Kidnocker is a University of Arizona Master Gardener who lives in the Green Valley area. Her articles are featured weekly.