A section of Rapid Creek just west of Silver City in the Black Hills. (Seth Tupper/South Dakota Searchlight)
As recently as nine years ago, I thought Rapid City had enough water for decades to come.
I got that idea from covering an event in 2014 where then-Mayor Sam Kooiker spoke.
“Unlike many other cities in the West, Rapid City does not have a water supply problem,” he said, adding that the city of 73,000 had “enough water in this area to serve more than 170,000 people.”
Time and new developments have altered that impression.
Four years ago, I reported on a study commissioned by the West Dakota Water Development District. Experts at South Dakota Mines considered the broader Rapid City area and determined that the region had enough water for the next 100 years under average precipitation; however, the study also indicated that demand for water could already exceed supply during a prolonged drought.
That caught me — and I think a lot of other people — by surprise.
After all, the city’s water supply includes Rapid Creek and the Deerfield and Pactola reservoirs in the Black Hills. From the looks of it, there’s plenty of water.
But the city also uses wells, and the surface water ultimately depends on underground sources. Rapid Creek and its tributaries start as high-elevation springs in what’s known as the Limestone Plateau region of the western Black Hills. The springs emanate from underground pockets of water called aquifers, and aquifers are not inexhaustible resources.
When wells dropped ‘all around the Black Hills’
Mark Anderson made that last point abundantly clear at the Western South Dakota Hydrology Conference last month in Rapid City. He’s the retired former director of the U.S. Geological Survey’s Dakota Water Science Center.
During a presentation at the conference, Anderson said something notable happened between 2000 and 2007 to wells that pull from the Madison aquifer: their levels fell, anywhere from a few feet to more than 100 feet.
It’s not unusual for well levels to fluctuate, especially as people use the water, and as varying levels of precipitation filter down to recharge aquifers. But this drop in well levels was interesting for a couple of reasons, Anderson said.
First, it happened during a period that was dry, but not historically so.
“I think most of us probably don’t really think about it as really a significant drought,” Anderson said.
Second, the phenomenon happened “all around the Black Hills.” Anderson showed data reflecting drops of 134 feet in a well near Rapid City, 80 feet near Tilford, and 7 to 9 feet in the southern Black Hills.
The level of an observation well near one of Rapid City’s underground water-supply sources dropped 37 feet and “was only about 10 feet from going pretty close to zero flow,” Anderson said.
The wells have recovered since then, but Anderson said the lesson from the data is clear: “I don’t think we should just think we can sustain the growth in the Black Hills area for the next 20 to 40 years on groundwater, without unacceptable consequences.”
Anderson said he’s “not saying the Madison is going to dry up.” But he said the consequences could include drawing the aquifer down so far in the Black Hills that wells start pulling in much poorer-quality water from the aquifer’s eastern reaches.
Changing water needs
In another presentation, Jay Gilbertson, manager of the East Dakota Water Development District, framed water problems more broadly. He explained that for much of South Dakota’s history since statehood, it consisted of water users with small needs — independent farmers and ranchers with their own (often poor quality) wells, small towns drawing from local rivers or lakes or aquifers, and small industries with moderate water needs.
In recent decades, those circumstances have changed. Farmers, ranchers and other rural residents have increasingly demanded water systems to improve the availability and quality of their water. As agriculture has consolidated and birthed factory farms, feedlots and ethanol plants, the industry’s water needs have grown exponentially. The proliferation of housing developments in Sioux Falls and other cities has sent them searching for additional water sources.
And when South Dakotans need more water, they all eventually go to one place: the Missouri River and its vast reservoirs, the only source big enough to accommodate all the demand. The sprawling Mni Wiconi and Lewis & Clark pipelines are two of the best-known projects already capitalizing on the Missouri’s largesse.
According to Gilbertson, projects like those are the model for the future.
“Where we’re heading,” he said, “is big, regional systems.”
Multiple efforts to build additional Missouri River pipelines have recently gotten underway around the state, including the Western Dakota Regional Water System. The nonprofit sprang up in Rapid City from concern about the 2019 study I mentioned earlier.
Unfortunately, as we know from the examples of Mni Wiconi and Lewis & Clark, water pipelines are massive undertakings that require decades of lobbying, congressional funding and construction.
All of which is to say that nine years ago, when I got the impression from listening to Rapid City’s then-mayor that there was no need for additional water supplies, the city and the region probably should have already been deeply involved in talks about a Missouri River pipeline.
As it is, current efforts got a late start, leaving open the possibility of those “unacceptable consequences” that Mark Anderson mentioned.
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