Where Does All The Water Go?
Since the temperature is still high, the humidity still low, and the relentless wind continues to blow, I thought it appropriate to talk one more time about water conservation. Since there seems to be rekindled interest in saving this limited resource, let’s look at where it all goes. There are the obvious perpetrators such as business, golf courses, industrial users, farmers, and of course housing developments. I heard today that the complexes that house the computers to run AI will use about five million additional gallons of water per day in Phoenix. Not our problem up north. Or is it?
There is a measurable amount of freshwater in most places on the planet. With few exceptions, water can be found in underground aquifers. It’s only a matter of how deep one has to drill to tap into it. These aquifers are fed, and therefore filled, by surface water from runoff. Areas with more rainfall have more runoff, more recharge, but lower needs at the surface. Arid areas like the Southwest have lower amounts of rain and it comes bi-seasonally. In buckets and buckets sometimes. When the rain comes that fast, it has no time to percolate into the ground and instead makes its way to the ocean rather quickly. So, how do the aquifers get recharged in an arid area like ours? Snowpack. High elevation snowpack, to be more precise. At higher elevation, the snow tends to melt and soak in more than it does at lower elevations due to cooler temperatures and increased canopy. At the lower elevations, the snow often evaporates quickly and very little soaks in. That’s why it’s all gone in a couple days and the mud doesn’t last long after that. For instance, it’s been calculated that around 98% of all the moisture that falls in the Prescott Active Management Area is lost to evaporation.
Evaporation from the surface and evapotranspiration by plants accounts for tremendous moisture loss. How can we directly affect that natural process to help conserve water? Let’s start with the simplest technique. I call it “leave it alone.” Similar to “If it ain’t broke, don’t fix it.” This area was doing fine before we got here and started messing with the ecology. The more area we leave alone, the better. Stewardship demands this. The opposite of stewardship is greed, plain and simple. Using proper stewardship, a developer would create lots that preserved as much of the natural vegetation as possible. A greedy developer will bulldoze everything to create as many lots as possible in the smallest space possible. Look around. I’ll bet you can quickly identify both in a development near you.
Every new construction, commercial or residential has an area of disturbance around the building that will need to be treated in some way for a number of reasons. Erosion by wind or water is the first that comes to mind. Builders could be a bit more careful how much they disturb when they build and possibly hydroseed most of it with native plants of the area as a first line of defense. When the property becomes occupied, the new owner can decide how much or how little landscaping should be done. In our leave it alone concept, perhaps consider only landscaping the areas closest to the buildings and leave the rest alone.
The second technique is using native plants as much as possible. Okay, let the whining begin. “They’re ugly, they don’t grow very fast, they’re expensive.” They are also the best adapted, most water-conserving plants you can have in your yard! Trade-offs are tough sometimes. I’m always fascinated by the people who move here because they love the way it looks and the first thing they want to do is change it. Perhaps “fascinated” isn’t the word I was looking for. I understand most people want a shade tree or two in their yard and I’m very supportive of that when the most drought-tolerant species are used. Don’t put a guzzler in your yard. Also, if you live on the prairie like I do, where there are at least 25 species of grasses already, try just putting a little extra water on it a few times a year. You might be amazed at how good it looks!
Lastly, let’s look at using non-biological ground covers. Rock and gravel. For a couple reasons, I’m not a big proponent of this technique. For one, most people will scrape more native plants away to create a bigger space of “pretty” and then cover it with a weed control fabric before adding the rock. This permanently alters the ecology, but it does indeed act as a mulch and prevents some evaporation. Secondly, however, it is a big heatsink. This warms the soil beneath the gravel and reflects heat above. This increases heat overall and will often damage any plants you are trying to grow in these areas. A better option is the use of organic mulches such as wood chips or ground bark. A word of caution though, do not use weed barriers under organic mulches or you lose the benefit of creating good soil beneath that will hold more moisture, prevent runoff, and reduce evaporation.
Hopefully, I have provoked a little thinking about what is here already and how it has functioned efficiently for a very long time without our help. Studies have shown that even just scraping the native grass off the ground causes additional water loss and ground heating. So why do we keep doing that without repairing the damage? As a general rule, always keep the ground covered. Stay tuned.
See You On The Prairie!
The Horticoach