Rain to Table

Get off Colorado River water —and go local with rainwater.

March 11, 2017

HomesteadIssue 23: March/April 2017

As foodies, we want fresh, local food that is produced as part of a food system that cares both for people and the planet. But do we hold the same standard for the water that comes out of our tap? Is it local? Is it part of a sustainable water system that protects our groundwater supply and our creeks and rivers? The short answer to these questions for Tucson’s municipal water supply is no.

Eighty-five percent of Tucson’s water supply comes from the distant Colorado River, and is transported with energy from a dirty coal-burning power generation plant on the Navajo reservation. Forty percent of the City of Tucson’s electricity demand is for transporting and treating water. Not only have we wreaked havoc on Tucson’s rivers, but since the late 1990s we’ve been helping diminish the mighty Colorado River by diverting water that reduces the river’s flow. With all the diversions from Western cities, the Colorado River stopped reaching the sea in 1988. The once lush and large Colorado River Delta is now a barren dustbowl.

Shortages in Colorado River supplies are quickly increasing with extended drought, climate change, and overuse. The situation is so dire, municipal and agricultural water providers across Arizona are sitting down to create a Drought Contingency Plan that will look at ways to reduce Arizona’s demand on the Colorado River. Our water utility, Tucson Water, is looking at ways to help with this effort, as well as offering some of the most robust water harvesting and water conservation rebates in the country.

Here’s the kicker: Colorado River water is actually not necessary for us to live in the Sonoran Desert. We have an abundance of local water from the sky—through both a winter and a summer rainy season. More rain falls on Tucson than we use through our municipal water supply annually. As citizens, we don’t need to wait for the government to act; we can take action today.

Rainwater harvesting is the simple act of collecting the rain that falls on site to use as water supply. By conserving water and implementing green infrastructure, we can also restore groundwater levels and our rivers at the same time. If you’ve heard about rainwater harvesting, maybe a big tank pops into your mind. Yes, collecting rainwater in a tank is one way to go. But there are much more basic and inexpensive steps you can take. First, you can start by creating a local water budget. Then, you can install a rain garden with organic mulch and native plants. After that, tap into graywater for irrigating fruit trees. And finally, install tanks to grow food or meet indoor water demands.

The first step down the path of independence from unsustainable Colorado River water is to create a local water budget (see sidebar).

You can also make hydrosustainability happen by joining the Rain to Table campaign, which runs from World Water Day (March 22) to Earth Day (April 22), and taking real action to harvest local water. Keep your eye on the Edible Baja Arizona blog to learn how to create a local water budget for your home, figure out how much water can be used from renewable sources, and take action to harvest local water. Join the campaign on social media by posting with the hashtag #raintotable. This campaign is a collaborative effort of Edible Baja Arizona, Watershed Management Group, and the Community Food Bank of Southern Arizona.

You can start small, and it can be as simple as creating a basin for some native plants or directing your laundry graywater to a fruit tree. I’ll be sharing tangible steps in upcoming issues to help you along your journey. In the meantime, here are seven simple ideas to get you started:

  • Watch how water moves through your yard when it rains.
  • Direct runoff into your yard. Make sure your gutters go into your yard, not down your driveway.
  • Get out a shovel and dig some simple depressions where rainwater flows to capture and sink water.
  • Add organic mulch. Leave tree trimmings and leaves in your yard, or get wood chips from a tree trimming company. Apply mulch liberally in basins and all dirt surfaces in your yard.
  • Do an audit of your landscape—and create a plan to replace non-natives with native plants over time.
  • Attend a free rainwater harvesting rebate class, currently offered by Pima County Cooperative Extension/Smartscape Program and Watershed Management Group. After attending the class, you will qualify for up to a $500 rebate for rain gardens and up to $2,000 for rain tanks.
  • Attend a free, hands-on workshop to learn about water harvesting and help install an actual system at someone’s home through WMG’s Co-op program. Visit WatershedMG.org for the workshop and class schedule.

So what if serious water conservation actions were adopted by all of Tucson? Watershed Management Group created a water budget for the entire Tucson Basin and found that if Tucsonans bring their average gallons per person per day down to 40, this community can meet its water needs with local, renewable groundwater supplies and reclaimed water.
(This does not factor in water harvesting as a supply.)

Water harvesting is powerful, but even stronger is the sense of purpose you’ll get from being a steward of this resource in your community. Our actions have consequences, and when we live locally we can be conscious of them. ✜

Lisa Shipek is the executive director of Watershed Management Group.

Create your own local water budget

Step 1: Supply.

Rainwater:

Calculate the renewable supply of rainwater that you could capture from your roof and landscape in one year. Let’s assume 12 inches of rain a year (1 foot); a 2,000-square-foot home; and 4,000 square feet of landscape.

6,000 feet² (roof & yard)
× 1 foot of rain × 7.48 gal rain/foot³
44,880 gallons of rain/year

Graywater:

We’ll assume 1 person uses 30 gallons of water/day for laundry, bathroom sink and shower. (Tucson Water customers use an average of 80 gallons per person per day. About 40 percent of that is for outdoor uses, leaving 48 gallons/day for indoor use. After subtracting water used for flushing toilets, dishwasher, and kitchen sink, we have about 30 gallons of potential graywater to harvest.)

30 gallons/day
× 365 days
10,950 gallons of graywater/year/person

Step 2: Demand.
Determine your monthly demand
by looking at your water bill.

How many gallons per month did you use in January? In July? Take the average of those two numbers, to capture both winter and summer water use, and multiply by 12. For our calculations, the average water use for a Tucson Water customer is 80 gallons per person per day. 80 gallons/day × 365 days = 29,200 gallons/year.

Step 3: Local Water Balance

For 1 person living in a typical midtown Tucson lot:

55,830 gallons rainwater and graywater supply
29,200 gallons of water demand
26,630 gallons left for local infiltration

The water budget tool is powerful; you can quickly see the possibilities for using local, renewable water as a principal water supply. Start by meeting your outdoor water needs with local water. Then you can start a rain-fed veggie garden or scale up and go completely hydrolocal, meeting all your indoor and outdoor needs with rainwater.

Note: To use rainwater harvesting for a Sonoran Desert native landscape, throw the above math out the window. If you go for a hike in the desert, you will see a wide diversity of plants surviving on rainfall alone. So, all you have to do is contour your yard to give your plants a leg up. Create basins and swales to slow and capture rain instead of mounds that shed water.







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