The Washington County Water Conservancy District (WCWCD) released a new Impact Study two weeks ago. It shows WCWCD is currently using more than 90% of its annual “reliable” water supply of 64,099 acre-feet per year.
The study expects WCWCD to add an additional 3,000 acre-feet of supply, but not until 2025 and 2026 with the Ash Creek and Sullivan Wells projects. Nothing before and nothing after, until 2035. That’s when WCWCD is still planning for the Lake Powell Pipeline to become a reality. Really?
The current “excess” capacity of about 660 acre-feet could service about 1,300 new homes. Ivins alone has more than that in the works.
The Impact Study reports that, “With no additional supply, existing sources will fall short of demand around 2023, even at the proposed reduction in the level of service for new users.” The study extends that date to 2028 if “the planned future water supplies excluding Lake Powell Pipeline are constructed in that timeframe.” Timeframe means the expected delivery dates of 2025 and 2026, but that still leaves an awkward gap in 2023 and 2024.
The additional supply of 3,000 acre-feet expected in a few years would hydrate about 6,000 “equivalent residential connections” (ERCs). But the Impact Study estimates there will be demand for 34,000 more ERCs in the next 10 years. What to do?
Well, a 1993 report, imaginatively titled “Utah State Water Plan: Kanab Creek/Virgin River Basin,” had some answers. It recommended low flow devices and fixtures, secondary systems to homes, xeriscaping for new construction, and increased water pricing, saying that current low water prices provide little, if any, incentive for the consumer to conserve water. That was almost 30 years ago.
Great advice! We really should do all of that, shouldn’t we? And hopefully not take another 30 years to think about it. In the meantime, let’s look at our current water supply to get a better understanding of how reliable it is.
Our Rivers
In the 12 months ending September 30th, the streamflow on the Virgin and Santa Clara rivers totaled just over 95,000 acre-feet. That beats the previous 12-month total of just under 72,000 acre-feet. And it is in-line with the median streamflow of 96,000 acre-feet since 2006.
Is being in line with the longer-term streamflow good? Karry Rathje, with WCWCD, points out that, “Although this water year may be similar to other water years in the last 15 years, we have about 40% more people relying on our supplies than we did in 2006.”
The average streamflow is higher than the median, at 122,000 acre-feet. That’s due to some years with exceptional monsoon rains. Those rains are not as helpful as you might think. Karry points out that high river flows must often be bypassed at the Quail Creek Diversion to prevent sediment from filling the transmission pipelines. So, the duration of high flow events affects how much water can be captured and made available for use. Because of this, annual average flow rates are not the best indicator of water availability.
The goal is to determine a “reliable” flow for the rivers. I met with Zach Renstrom at WCWCD last week and he’s using 60,000 acre-feet a year as the reliable flow for the Virgin River. That’s less than any 12-month period over the past 17 years. The closest we came was in June 2021 when the flow over the prior 12 months was just under 63,000 acre-feet. So, 60,000 acre-feet seems conservative and pretty reliable… as long as Mother Nature isn’t fickle.
Reservoirs
WCWCD’s five reservoirs in Washington County can hold almost 109,000 acre-feet of water. More are coming. On top of that potential capacity, WCWCD estimates 100,000 acre-feet have seeped into the aquifer below Sand Hollow. Pumps are in place to use that water if needed, but that’s a last straw event.
The amount of water in our local reservoirs has fallen by 5,000 acre-feet in the past 12 months. In the previous 12 months it fell an additional 4,000 acre-feet. Oops. It looks like we’ve been dipping into our savings account to balance our budget. That’s not good. I mentioned to Zach that I interpret those drops as a raid on our emergency savings account and it suggests that all of our water sources have been insufficient to meet even current demand, at least in the past two years. He didn’t disagree.
Reservoir levels bounce around a lot during any year, increasing in the winter and spring and decreasing in the summer and fall. A better way of looking at water trends in our reservoirs is on a 12-month moving average basis. That’s the chart below.
Karry told me that the amount of water stored in our reservoirs has been declining for four years. Similar declines occurred in the 2006-2009 and in 2011-2015 timeframes. She also noted that although it is early in the water year, which started October 1st, there are indications that it may be another average/below average year. She said that WCWCD is concerned that our reservoirs may end the year, next September 30th, at record low levels.
Next Steps
This won’t be my last post about water. There’s more coming soon, thanks to a lot of information I have received in the past few weeks from a number of people, including: Zach Renstrom, General Manager, Washington County Water Conservancy District; Karry Rathje, Communications & Government Affairs Manager, Washington County Water Conservancy District; Wayne Pennington, Dean of Engineering and Professor of Geophysical Engineering Emeritus; Michigan Technological University; Ryan Rowland, Data Chief, USGS Utah Water Science Center; Tom Marston, Investigations Chief, USGS Utah Water Science Center; Zachary Frankel, Executive Director, Utah Rivers Council; and Ed Andrechak, vice President, Conserve Southwest Utah.
Please share your comments on this topic and tell me about other Ivins issues
I have not addressed in recent posts. Email me at Mike@MikeScott4Ivins.com.
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