Broomfield's Thirstiest Question Is About the Future, Not the Present
Somewhere in a filing cabinet or, more likely, a shared drive at Broomfield's Water Resources Department, there is a number that nobody can verify yet. It is an estimate of how many gallons of water this city will need on a hot Tuesday in July 2055. Nobody alive today will be able to check that number against reality for another three decades, and yet the city is paying an engineering firm, Carollo, right now to keep refining it as part of an amended water resources master plan moving through council this week.
This is a strange kind of science. Most of what gets covered in a column like this one involves observing something that already happened, a fossil, a virus, a weather pattern, and explaining how it works. Water demand forecasting runs the other direction. It tries to describe something that has not happened yet, using the tools of hydrology, demography, and statistics braided together, and it has to be right enough that a city doesn't run short, without being so conservative that it spends millions building capacity nobody ends up using.
The basic method is not exotic. Planners start with how much water people and businesses currently use per person, per acre of lawn, per industrial process, and multiply that by how many more people and acres and processes they expect to have. Along Colorado's Front Range, that second part is the hard one. Growth doesn't arrive on a smooth curve. It comes in bursts tied to housing starts, interest rates, and employer decisions made in boardrooms nowhere near Broomfield. So the forecasts are built less like a single prediction and more like a cone of possibilities, a low-growth case and a high-growth case bracketing a middle path, the same technique meteorologists use when they show a hurricane's possible tracks as a spreading fan rather than one confident line.
Layered on top of that is climate. Colorado's Front Range sits in a semi-arid zone where snowpack, not rainfall, does most of the heavy lifting for water supply. Snow that falls in the mountains over winter melts gradually through spring and summer, acting like a slow-release reservoir. Climate models suggest the Front Range will keep getting hotter, which means more of that water evaporates or gets pulled up by thirstier plants, a process hydrologists call evapotranspiration, before it ever reaches a tap. So the same population growth projected for 2055 has to be matched against a supply side that is itself uncertain, shifting with weather patterns nobody can forecast precisely that far out either.
One of the strategies cities use to hedge against that uncertainty is reuse, which is the subject of the separate water utilities agreement also on this week's agenda. Reuse means treating water that has already been used, in sinks, showers, and toilets, cleaning it to a high standard, and putting it back into the system for things like irrigation or industrial use, rather than drawing an equivalent amount fresh from a river or reservoir every single time. It does not create new water out of nothing, but it stretches the water already claimed by the city, effectively lowering the demand side of that big equation planners are always balancing.
What makes all this worth paying attention to is not the specific gallon figures, which will be revised again next year and the year after that, but the method itself. A water master plan is really a formal admission that a city is betting on an uncertain future and trying to hedge that bet with the best modeling available, then checking the model against reality every few years and nudging it closer to true. It's not so different from a farmer deciding how much seed to buy based on a forecasted growing season, just stretched across decades instead of months, and with a city's entire water utility riding on getting the slope of that growth curve approximately right.
The amendment working its way through council this week won't settle the question of 2055. Nothing will, not for a long time. But it is a reminder that behind a line item about an engineering contract sits a genuinely hard scientific problem, one where meteorology, demographic forecasting, and plumbing all have to agree with each other, at least closely enough that nobody in Broomfield notices the difference thirty years from now.