Wichita water statistics update

With adequate river flow every day, the Wichita ASR water project produced water equivalent to six days design capacity during July 2016.

Since this article was written, the city has changed the way it determines the availability of water in the river. This may change some of the conclusions made below, but I believe the changes are minor.

An important part of Wichita’s water supply infrastructure is the Aquifer Storage and Recovery program, or ASR. This is a program whereby water is taken from the Little Arkansas River, treated, and injected in the Equus Beds aquifer.^{1 2} That water is then available in the future as is other Equus Beds water.

With a cost so far of $247 million, the city believes that ASR is a proven technology that will provide water and drought protection for many years. In 2014 the city recommended that voters approve $250 million for its expansion, to be paid for by a sales tax.³ Voters rejected the tax in the November 2014 election.

July 2016 production

In July 2016, the ASR project recharged 158,770,175 gallons of water.⁴ The design capacity for ASR is 30,000,000 gallons per day, so production for the entire month of July was about six days design capacity. For other context, in 2015 the Wichita Water Utility produced 18,942 million gallons of water.⁵ The water recharged in July 2016 is 0.84 percent of this.

The ASR project is able to draw from the Little Arkansas River when the flow is above 30 cfs. As shown in the chart of the flow of the river, there was adequate river flow for ASR to operate every day of the month for July 2016. This is counting only those days when the flow was above 30 cfs for the entire day.⁶

ASR project background and production

According to city documents, the original capacity of the ASR phase II project to process water and pump it into the ground (the “recharge” process) was given as “Expected volume: 30 MGD for 120 days.” That translates to 3,600,000,000 (3.6 billion or 3,600 million) gallons per year. ASR phase II was completed in 2011.

At a city council workshop in April 2014, Director of Public Works and Utilities Alan King briefed the council on the history of ASR, mentioning the original belief that ASR would recharge 11,000 acre feet of water per year. But he gave a new estimate for production, telling the council that “What we’re finding is, we’re thinking we’re going to actually get 5,800 acre feet. Somewhere close to half of the original estimates.” The new estimate translates to 1,889,935,800 (1.9 billion) gallons per year.⁷

Based on experience, the city has produced a revised estimate of ASR production capability. What has been the actual experience of ASR? The U.S. Geological Survey has ASR figures available here. I’ve gathered the data and performed an analysis. (Click charts for larger versions.)

I’ve produced a chart of the cumulative production of the Wichita ASR project compared with the original projections and the lower revised projections. The lines for projections rise smoothly, although it is expected that actual production is not smooth. The second phase of ASR was completed sometime in 2011, but no water was produced and recharged that year. Further, 2013 was a drought year, so to present ASR in the best possible light, I’ve prepared a chart starting in July 2013. That was when it started raining heavily, and data from USGS shows that the flow in the Little Arkansas River was much greater. Still, the ASR project is not keeping up with projections, even after goals were lowered.

On the chart of monthly production, the horizontal line represents the revised annual production projection expressed as a constant amount each month. This even rate of production is not likely, as river flow varies. In the three years that ASR phase II has been in production, that monthly target been exceeded in six months.

Two nearby charts give an idea of the efficiency of operation of the ASR project. (Click charts for larger versions.) For each month, I counted how many days had a river flow above 30 cfs at every measurement for the day. (The flow is measured many times each day.) If a day had all measurements above 30 cfs, I counted that as a day of adequate river flow. I then calculated the number of days of work actually accomplished using the water produced each month, the number of days of adequate river flow for the month, and the ASR design capacity.

As can be seen in the charts, the ASR project is operating far below its design goal.

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Notes