What would happen if 25% of the population of Salt Lake reduced their water consumption by 10%?

Sounds like a good question for systems analysis.

My first question is, what is the system? Where does water come from, where does it go? What does it touch along the way?

Well, that’s it. No, you misunderstood. A well is where it comes from. Okay, city water comes primarily from mountain streams, but it is supplemented by well water in the summer.

So what would happen if around 75,000 of the city’s 300,000 residents used 10% less water? Nothing? Very little? A great deal? It does seem silly and naive to think nothing would happen, but maybe not so much to say, little of consequence.

Perhaps I am not thinking creatively enough about this, but I really can not imagine any major system perturbations resulting from such a modest reduction, that haven’t already been built into the system.

In fact, pertubations seem to be the norm for a system designed to accomodate expansion. With growth in Salt Lake accelerating, water demand is going to increase substantially in the coming years. The city has accounted for this in its planning, and the water treatment and delivery systems are able to handle the current need. A pipe that can deliver x gallons of water per day can also deliver 0.9x gallons.

But x is never static, because of growth.

According to the Tribune, “Salt Lake City saw around 725 market-rate apartments built from 2001 to 2010. In the past four years alone, that number jumped to 2,112, according to a new study. And the trend keeps climbing. More than 6,000 units are planned countywide during the next two years.”

Let’s suppose that the average resident uses 100 gallons a month. That’s 30 million gallons used. Now of 25% of residents used only 90 gallons each month, the total would fall to 29.25 million. That’s an average of 97.5 gallons per resident.

It is substantial, of course, but it would take just over 8,000 additional water conservers to bring the total back up.

Clearly the population growth in Salt Lake necessitates reduction in water usage by those currently living in the city to avoid major expansion of the physical delivery and treament systems.

The growth isn’t just near term. “The draft master plan envisions a quadrupling of the downtown resident population by 2040 — from about 5,000 people as measured in 2010 to 20,000 three decades from now.”

So no matter how much water 25% of the population leaves in the tap, demand will rise.

The classic model of uncontrolled urban growth is Los Angeles in the 1920s, when it grew 115%. A large water project was undertaken, which made the growing slightly less painful, but water availability has always strained the city. Still, in only two decades has the growth fallen below 10%.

Now, if the projections in Salt Lake are totally accurate, and the city has already planned for them to the decimal, then a 10% reduction might call for a 10% reduction in the future expanded workforce.

And since mountain water supply doesn’t always neatly match the demand for it in our beautiful valley, more wells will be required. So a corresponding 10% decrease in the increase of wells might be anticipated. But again, that all depends on accuracy of projections.

The better question to me is, what will be the consequences if residents don’t reduce water consumption? Then we can get to some interesting problems.

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