Water is by far the most limiting factor when designing for long-term, ecologically harmonious, self-reliant living in Joshua Tree. Few places on earth have as little average yearly rainfall (and yet, a gorgeous diversity of wildlife lives and thrives in this seemingly inhospitable climate). The groundwater is hundreds of feet underground, (a remnant of the last ice age!) and these reserves are being depleted by about one foot per year, with very little natural recharge taking place. For this reason, human settlement as we know it has only been a part of this desert ecosystem for a matter of decades—an experiment made possible by the era of cheap, abundant oil and industrial agriculture. For as long as the village of Joshua Tree has existed, all of the food and other human necessities have been trucked in from hundreds, and often thousands, of miles away meaning there is, at present, no local food culture alive here. Fortunately, as of the creation of this design, work is in progress to start importing water via the California Aquaduct from the Sacramento Delta, 600 miles to the northwest. And while that precious lifeline is deeply honored and appreciated, what this experiment seeks to find out is, can we, through design and appropriate technology, learn to live well and even thrive on the actual water budget that nature gives us? Towards this end, the central and primary strategy of this design is to try to capture, and wisely use (reuse, and then use again) every drop of water that finds its way onto this piece of land. This will be done in the following ways:
-Rainwater will be captured from all rooftops to be stored and kept clean in three large tanks around the property for drinking. It is conservatively estimated that once renovations are completed this system will yield 3,400 gallons of drinking water per average year of rainfall.
-All pumped groundwater that is used on the property (wastewater, cooking water, and evaporative cooler water) will be re-used appropriately as many times as possible before being lost to the system. This will be the primary source of irrigation for all zone 1 elements.
-The kitchen garden will utilize water-efficient wicking beds as well as sunken, in-ground beds that will be deeply mulched above, and lined with plastic or clay below to slow water loss (both to evaporation and also to rapid infiltration down through the course sandy soil). The zone 1 food forest (this will be described later) will also be located in a large sunken infiltration basin. Both of these elements will be further sheltered from evaporation by trellises, with deciduous vines shading them in the summertime.
-Every drop of rain that falls on the land will be encouraged to sink into the ground rather than running immediately off the property, and each small wash (wadi) that runs close enough to the land will be captured, and put to use by the system. This will be accomplished by the extensive use of swales, which are perfectly level trenches that follow the natural contours of the land. All of these swales will be deeply mulched and densely planted, holding moisture within the root zones of the plants for as long as possible.
-Sponge Swales will be installed next to many of the trees. These are short trenches and holes that are packed with absorbent, durable organic matter such as cardboard, paper and woody debris. When saturated with water, they retain moisture for a very long time, allowing the roots of plants nearby to sip from them.
-Each tree and shrub will also be planted with a deep watering tube, which allows irrigation to happen below the surface of the soil, reducing evaporation and encouraging deep root systems.
-As the main living systems in the design mature, it is intended that less and less irrigation will be needed, eventually achieving maximum productivity with only a modest and sustainable draw upon ground water reserves. It is our intention to begin to slowly wean all plants and trees off of ground-water irrigation once they are well established in (except for those within our greywater-fed “oasis zone” area in zone 1).