The Virgin and Santa Clara rivers had a combined streamflow of just over 112,000 acre-feet of water in the 12 months ending in September. This is more than the median streamflow of 96,000 acre-feet a year since 2006. And it’s more than all but seven of the nineteen years we’ve collected data for.
At first glance, this sounds promising, until we factor in the 50% population growth in Washington County since 2006. And the commercial growth. And the growth in tourism…
What’s An Acre-Foot & What does It Mean to Me?
The Washington County Water Conservancy District (WCWCD) says the typical household in the county uses about 0.75 acre-feet of water a year indoors and outdoors. There are 325,851 gallons in one acre-foot. So, countywide, each of us uses close to 240 gallons a day. We use less in Ivins. Last year we averaged 166 gallons a person a day.
What’s Your Acre-Footprint?
You can find your own usage on your monthly Ivins utility bill. The graph on your bill shows water use for the prior 13 months. The number shown above each month is how many thousands of gallons of water you used that month. So, add up the past 12 months, multiply by 1,000, then divide by the number of people in your household, and finally divide by 365 days. Voila! The result is your home’s use in gallons per person per day.
Our Personal Journey
Here’s our water use over the past five years. We’ve made an effort to conserve water. And it has worked, sort of. The dotted line (“adjusted”) shows our monthly usage dropped from over 120 gallons per person per day in late 2019 to about 80 last month.
But that excludes the four “water surprises” (leaks) we’ve had. When you add those in, the actual monthly usage has still gone down. But not as much. Those leaks wasted 81,000 gallons of water. Our leaks have been sinister. They choose to happen when we’re away. If we can get by without leaks on 80 gallons a day, that wasted water would have supplied the two of us for almost a year and a half.
Technology To The Rescue
The City is planning to install a city-wide Advanced Metering Infrastructure (AMI) system that uses smart meters to collect and transmit daily water usage data. That way, if you have a leak, you will know about it almost right away. Had we had that, it would have saved most of those 81,000 gallons from going down the drain.
The Challenge of High Flows
That was an interesting diversion from a discussion of river trends. Now let’s get back on topic and look at a different type of diversion. The average streamflow since 2006 is higher than the median, at 122,000 acre-feet. This is due to a few years with exceptional monsoon rains. However, these high flows are not as beneficial as they might seem. When river flows surge, the Quail Creek Diversion Dam sends excess water downstream instead of sending it to our reservoirs. That’s done to prevent sediment from clogging the pipeline or filling the reservoirs.
I took this video at the dam in April 2023 showing Virgin River water cascading over it. Every drop of that overflow was headed for Lake Mead, unused by us. (My tears are streaming in from the lower right.) The 66-inch pipeline just before the dam was working at full capacity, directing all the water it could swallow to Sand Hollow and Quail Creek reservoirs.
What Can We Rely On?
So, even though our rivers give us close to 100,000 acre-feet of water in most years, water managers focus on “reliable” usable flow rates. For the Virgin River, WCWCD estimates this reliable usable flow at about 64,000 acre-feet annually. That’s what we should be able to capture and use. WCWCD is using almost all of this reliable flow to quench our county’s thirst.
Reservoirs: Storing our Liquid Assets
Washington County’s five reservoirs (Quail Creek, Sand Hollow, Gunlock, Kolob, and Ivins) collectively have the capacity to hold nearly 109,000 acre-feet of water. By 2026, the new Chief Toquer Reservoir will add another 3,700 acre-feet of capacity. Beyond surface reservoirs, approximately 100,000 acre-feet of water have seeped into the aquifer beneath Sand Hollow, accessible via pumps for emergencies.
As of October, our largest reservoirs—Quail Creek, Sand Hollow, and Gunlock—held nearly 70,000 acre-feet, about 70% of their total 103,000-acre-foot capacity. Reservoir levels typically fluctuate with the seasons, rising in winter and spring and falling in summer and fall.
To better track water trends, a 12-month moving average offers a clearer picture. Thanks to a wet 2023, the downward storage trend of 2021 and 2022 reversed. Unfortunately, 2024 has been drier, and the moving average is once again heading downward. Now we wait to see what Mother Nature delivers in the way of snowpack this winter. That’s the drama of desert living.
A Peek Into 2025 Water Conditions
You can monitor how we’re doing in Southwestern Utah this winter, which gives us clues for what to expect from our rivers next year, at the USDA National Water and Climate Center website. The plot the “snow water equivalent” every day and compare it to the annual median. you can also compare this year’s to any prior year, going back to 1982.
Balancing a Growing Thirst with Limited Supply
The wet 2023 provided a boost to our water resources that worked for us in 2024. But it’s clear that natural variability and growing demand present challenges. Although we rely heavily on the Virgin River, there are other water sources. These include existing and potential new groundwater wells, reuse of wastewater, conservation, and shifting agricultural water use to residential users.
Will our rivers and these other water sources produce enough water to meet the needs of all the new development planned in the county? I have written about that before and have a lot of concerns (check out the 40+ past “water” articles). I am updating a lot of the information in those articles now and will post the results of my new research in a couple of weeks.
Let me know about Ivins issues that are important to you. Please email me with your concerns, ideas, suggestions, and recommendations. Sign up for monthly updates (click here)
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