MISSOULA — How often do you think about where your water comes from? Or more importantly, how much water there is?
All of Missoula's water comes from one source — the Missoula Aquifer — and it's the mother load of aquifers. It’s one of the most unique and productive aquifers in the United States. So what makes it so special? How come it's one of the best in the United States? Why does this even matter?
To answer all of them we first have to take a step back in time to when Missoula was known by a slightly different name — Glacial Lake Missoula. About 13,000 to 15,000 years ago during the last ice age, Missoula was underneath 1,000 feet of water.
This was because there was a large glacial ice dam blocking the drainage of the Clark Fork River and with nowhere to drain, all of that water accumulated in the Missoula Valley. This kept happening until a breaking point was reached.
That breaking point was when the amount of water eventually became so much that it would force its way underneath the glacial dam, causing the glacier to uproot because, after all, ice does float. And when the glacier was uprooted there was no more dam, and all of that water that was contained rushed towards the Pacific Ocean creating catastrophic flooding.
To better understand the magnitude of the flooding, think about the Missoula area being under 1,000 feet of water again. A lot of water right? Now, imagine all of that water being gone in just 10 days. This is where the story of the aquifer begins to come in. So real quick, let’s go over what an aquifer is.
An aquifer is a collection of water underground, stored in the pockets that exist between rocks, gravel, sand and any other sedimentary material. The larger the individual rocks and bits of gravel are in the ground, the larger the amount of water that can be stored. This then also affects the flow rate, which is the rate at which water moves within the aquifer. This will come up later.
Back to the floods.
Soil, small rocks, and sand are what was taken away from the bottom of the lake during the floods. Left behind were larger rocks and course gravel, going about 30 to 40 feet down. By the time the ice age ended and Glacial Lake Missoula ceased to exist, those rocks and course gravel were what was left for the base of the ground that we walk on now.
Besides just the ground, the river bed of the Clark Fork River was also now made up of course gravel and rocks — again, going all the way down 30 to 40 feet around Missoula. This here is where the recipe for the aquifer lies.
With 30 to 40 feet of rocks and course gravel going straight down around the city, there’s nothing to stop some of the water from the river seeping straight down — and that’s exactly what it does.
All of that is what takes us up to the modern day where the story of trying to understand the aquifer begins.
Beginning in the 1960s researchers and scientists tried to figure out how the aquifer functioned. How much water went into the aquifer? How much water went out? How much was the city pumping out?
All of these questions were trying to be answered during this time to get a grasp on what the water budget of the town was. A water budget is essentially just the balance between how much water goes into the system and then how much is taken out by people.
The researchers were in large part unable to fully figure out how exactly the aquifer functioned for years, obtaining results that seemed full of error time and time again.
Then in the late 1980’s, the water utility company, the University of Montana and the City of Missoula all got together to try and figure out the aquifer once and for all. They put money towards a study headed by Ross Miller — a Master’s student who had a degree in geology.
With Ross Miller at the head and supported by numerous colleges and professionals, he got to work. The study first began by looking at how the water within the aquifer moved, it was important to understand how it moved to accurately measure the amount coming in and the amount going out.
Simple enough right? Dig a couple of monitoring wells, measure the water level throughout the day when pumps are running and then take those measurements from across the town to develop a model. Well, there was an issue. The water level was moving in such small amounts that the sensors that were being used were pretty much useless.
At a seeming dead end with data that seemed to be all wrong, Ross Miller came to a bold conclusion. They were entering uncharted territory. Textbook values and models at the time couldn’t be relied on as this aquifer seemed to be a whole different beast.
He went to the geology department at the University of Montana seeking help to develop and manufacture new sensors that could make more precise measurements — down to the 1/100th of an inch. And after a little bit of time, the new sensors were ready and the show was back on the road.
Miller and his team went to a monitoring well they had dug that was 100 feet away from one of the largest pumping wells in town. To make sure they got the correct results, they shut off the pump for a couple of days to make sure that the water in the surrounding part of the aquifer had time to settle and yield good data.
Then with the the well ready, they turned on the pump setting it to a maximum of 7,000 gallons of water per minute. They then let the pump run at this rate for eight hours. So, how much did the water level change? Well, after eight hours of continuous pumping at 7,000 gallons a minute, the water level only dropped 1/10th of a foot.
These results blew the preconceived notations of what the flow rates of an aquifer could be out of the water, or rather — out of the ground. No one else had ever seen an aquifer that had so much water and seemed to be indifferent to huge amounts taken out.
With this came the conclusion of the study. They had developed a model and figured out how much water came in and how much went out. What were those values?
Miller determined with accuracy that anywhere from 220,000 and 250,000 acre-feet of water went into the aquifer every year with 80% of it coming from the Clark Fork River, which is roughly the same amount that went out back into the Clark Fork River every year.
How much water is that? Well for reference, the people and City of Missoula were pumping out about 30,000 acre-feet a year in the late 1980s, representing 10% to 12% of what they could take out.
All of this now leads us to today. Let’s take a step back from thinking about aquifers and rocks and flow rates and pumping and glacial lakes and whatever else. Let’s take a second to think about today and the world we live in. Today is full of uncertainty about technology, the economy, geopolitics, and the changing climate.
This year we have seen a snowpack in Montana that is 70% of what it has historically been and warmer temperatures throughout the year. But still, we have it pretty good compared to other places, such as the Southwest United States.
In a region like the Southwest, there are larger issues than just warmer temperatures. There, the issue is that they may run out of water — and soon. If they do run out of water, where do these climate refugees go? Maybe to a place with an abundance of water? Well, Missoula has an abundance of water because of its mother load of an aquifer.
This is the situation that Missoula faces — the potential for massive growth due to climate refugees coming in from places that have a shortage of water. This is not a surprise, however.
The City of Missoula is already taking this into account as they plan for the future, they are currently planning a study to look into what sudden and massive growth could look like in the future — and how they would adjust to it.
