Thursday, March 2, 2023

Lessons from Snow in our Urban Desert


I woke up to this view from my front door. Snow in Tucson!  This is the second time we have had snow this winter! This is the epitome of what Katherine Hayhoe termed "Global Weirding!" Maybe I'm exaggerating a bit. But it is weird. It is rare for it to snow in our desert town.  

I like to fancy myself a "citizen scientist" taking pictures to investigate what is happening in our garden and desert food forest. So out I went this morning with my cellphone to take pics of the snow. Here are the lessons I learned. 

The snow on the gravel or bare dirt has already melted. But where we have native plants (that some people call "weeds") or organic mulch in the catchment basin, the snow was still on the ground. I noticed that there was no snow left where our neighbors have gravel or just plain dirt in their yards. That demonstrates just how much heat gravel holds. But I already knew that from going barefoot when working on my yard in June. I walk on the horse purslane mulch to keep my feet from burning. 

I found a similar development in the easement behind our house. The snow is sticking to the desert mustard on the ground beside our garden. Notice that the snow isn't sticking to the ground in the garden perhaps because the palo verde branches that shelter it from the summer sun also shelter it from the cold. Note that there are no "weeds" in the garden. 

See the snow on the bunch grass in our jujube basin? As the snow melts it is another source of water for the plants and trees in our basins. 

Our native desert trees and bushes have adapted to the occasional freeze and snow storms. In fact, the hackberry in the mesquite guild (below) and our wolfberry in the right-of-way basin seem to be thriving in the snow. The organic mulch helps.  

Then I investigated what was happening in the backyard. The snow was already melting into the greywater basin supplying water for the heritage fruit trees there.

As anyone who has a cistern (rain tank) knows, we get lots of rain off of the roof.  Now our cisterns are overflowing from the snow melting off of our roof and the neighbors' roof. 

snow on our neighbors' roof

snow melting into the cistern

The cistern overflows into the garden...Sheltered by the branches of the palo verde, the chard is doing fine. 

Reminds me of how the snow melts on the Catalinas, rushing into our desert streams to nourish the surrounding trees and riparian habitat. 

view of the top of our watershed - the snowcapped Catalina Mountains

Here's what I learned from my little citizen science project this morning:

I learned that ground covered with gravel retains more heat so the snow melts. But without a catchment  basin to gather that water for a nearby tree, the water is often wasted. (Though the water can sink in under the gravel to water a nearby plant if there is no plastic preventing it.)  In our yard, the native grasses and organic mulch allowed the water to slowly melt into the catchment basin to the benefit of our native trees and bushes. I observed how the snow in our greywater basin melted into the basin to water our heritage fruit trees and how the snow on the roof melted into our cisterns filling them up to use on our garden and landscaping.

Who knew we had a "snow water harvesting" system?! In the desert! How great is that!?