Voice of the River

Balancing the Books: Using data for better water management

By David Tucker, communications manager

So far, the banner snow year promised by a La Niña weather pattern hasn’t quite materialized. While the recent storm cycle has greatly improved conditions, this summer’s water supply has still been on my mind lately.

Considering the fact that human water consumption continues increasing in the upper Gallatin River watershed, is this the year we see the first signs of a major shortage? And what impacts would a shortage have on the health of the Gallatin River?

If you read this column regularly—and you should—you likely know that 100 percent of our household water supply comes from underground aquifers. These aquifers are fed by precipitation, which in our neck of the woods comes primarily in the form of snowmelt. Less snow equals less snowmelt and less snowmelt equals less aquifer recharge. But what does that lack of recharge mean to the Gallatin, a surface water fed by runoff, rain, tributaries, and snow that melts directly into the stream?

It turns out, water under the ground also feeds our surface waters. The two sources are connected, and if aquifers are inadequately recharged, water quality in streams and rivers like the Gallatin can suffer greatly. Inadequate flows of clean water can’t dilute concentrations of harmful pollutants. At the Gallatin River Task Force, we’re trying to improve water quality in the Gallatin, so naturally we’re concerned about residential and commercial water supply and demand.

To this point, we haven’t seen major impacts to the water supply in the upper Gallatin watershed, but conditions are constantly evolving and projections for the future are ominous. The 2017 Montana Climate Assessment predicted less snow and in turn less available fresh water within 25 years.

In a 2015 Source Capacity Study commissioned by the Big Sky Water and Sewer District, researchers estimated a capacity deficit from water sources used by the district by 2023 at the latest. In case you’re keeping count, that’s two years from now.

All demographic studies predict more people moving to southwest Montana, with growth in Gallatin County outpacing all other similarly sized communities. When we consider these two realities taken together, we have to ask when will demand outpace supply, and what impacts will that demand have on cherished waterways like the Gallatin?

Getting a sense of current supply and demand is harder than you might think. In Big Sky, there are more than two dozen public water systems, from the Big Sky Water and Sewer District, which services about 40 percent of all water users, to small entities that service individual HOAs and individual systems at single-family homes. This decentralized system makes getting data difficult, but having everyone on the same page is essential for understanding how our community’s water needs influence our watershed’s water quality and quantity. In most instances, water usage isn’t even metered, making exact calculations impossible.

Coordination between all the public water system managers makes community-scale trends easier to understand and forecast and makes it possible to plan for catastrophic events like wildfire. This is the only way to implement a sustainable plan for Big Sky’s future water use, and without a comprehensive understanding of water use, we won’t be able to keep the Gallatin healthy for future generations to enjoy.

While some may say an easy solution is to limit all future development, Big Sky and the upper Gallatin tributaries already have quality problems exacerbated by uncertain water supply. The South Fork, the Middle Fork, and the West Fork are all impaired by state standards, meaning they exceed certain pollution thresholds. A contributing factor to that impairment is the volume of water in those streams. While we certainly must continue taking steps to limit pollutants reaching our waterways, we also must be taking steps to ensure adequate and increased flows now.

Knowing more about current supply and demand is a step in the right direction for forecasting future river health. Again, all signs point toward more people living in the upper Gallatin watershed and less snow—currently our primary source of fresh water—falling in the upper Gallatin watershed.

Without creative solutions driven by comprehensive data, this isn’t a sustainable combination. But by collecting and sharing information, we can make a plan to keep our waterways full of clean, cold water.

This article originally appeared in Explore Big Sky’s Water Wisdom column.


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