When people find out I work at Denver Water, they ask me one question more than any other: “Why do we let water flow out of Colorado to California and other states?”

The short answer is: The Colorado River Compact mandates that California gets its share. But that leads to a longer explanation about the Colorado River Compact, one of many complex laws that govern how water is divided among western states.

Complicated or not, we should all understand how drought in California — and Gov. Jerry Brown’s mandate to cut water use by 25 percent — have a direct impact on the water we use in Colorado. With that in mind, I tried to boil this down for an audience with no prior knowledge or interest in the subject: My teenage daughter.

I’m changing her name to Abby so she doesn’t hate me for sharing her answers with the world.

Me: Sweetie, have you ever heard of the Colorado River Compact?

Abby: You mean a compact like for makeup?

Me: (Sighing) No, a compact is an agreement between states. The Colorado River Compact is an agreement between seven western states that share water from the Colorado River Basin.

Abby: Basin? And you say I talk in a foreign language!

Me: A basin is where water drains into a common area. The Colorado River Basin is the region where the Colorado River drains.

Abby: Wait. If it’s the Colorado River, how does it flow through other states? Isn’t it Colorado’s river?

Me: Good question. While the river originates in Colorado, the water does not belong to Colorado. All seven states have claims to the water. That’s how the compact came about.

Abby: How can other states claim water from Colorado? That’s not fair.

Me: Western water law is based on something called prior appropriation. It … STOP MAKING THAT FACE! It just means whoever puts the first claim on an amount of water for what is called “beneficial use” has the right to use it, regardless of the original location of the water. Think of it as “first in time, first in right.”

Abby: Speaking of time, you’re rambling again, Dad.

Me: Stay with me. Back in the 1920s, the states in the lower basin of the Colorado River — California, Arizona and Nevada — were growing rapidly, and they had the oldest rights to the water. The other four states in the upper basin — Colorado, Wyoming, New Mexico and Utah — got nervous about having enough water for their own futures. The seven states couldn’t agree on who would get how much of the Colorado River’s flows, so in 1922 they negotiated an agreement, or compact, that divided the region into those same upper and lower basins.

Abby: Cool. So they divided up the water evenly among the states and they all lived happily ever after. The end! Great story, Dad! Goodnight.

Me: It’s 4 in the afternoon. Get back here! Under the agreement, the upper basin states must allow a specific amount of Colorado River water to flow to the lower basin states over a running 10-year average. The upper basin states store that water in Lake Powell in Utah. The lake is like a big savings account of water to meet that obligation. But now we get to the problems.

Abby: Let me guess. There’s not enough water in the river for everybody.

Me: Exactly! It turns out the 1920s were a very wet period in the Colorado River Basin. Essentially, the compact allocated more water than the river would normally produce. Then you add in a lot more growth in the lower basin states and the drought in the region for the past decade or more, and you get … wait for it … one giant bathtub ring!

Abby: Finally! We get to some cool stuff!

Me:  See?! But it’s not really cool. I told you the upper basin states store water for the lower basin states in Lake Powell. But because of the drought and continued increased use by the lower basin states, the water levels at Lake Powell have dropped dramatically in the last decade. Just look at these photos. You see that white discoloring in the rock where the water levels used to be? Lake Powell is at only 45 percent of its capacity.

Abby: So what happens if the lake level continues to drop?

Me: It could trigger what’s called a “compact call.” If the upper basin states can’t supply the amount of water mandated in the compact to the lower basin states, the upper basin states would have to restrict their own usage of Colorado River water to fulfill their obligations.

Abby: And what happens to Colorado?

Me: Well, Denver Water gets about half of its water from the Colorado River. If we lose half of our water supply, you can see how that would cause significant problems.

Abby: Is there anything we can do about it?

Me: We’re trying. Denver Water is actually working with other water providers in the Colorado River Basin through an agreement called the Colorado River System Conservation Program.

Abby: None of these things have simple names, do they?

Me: Point taken. The program is trying to find temporary, voluntary ways to reduce demand on the Colorado River, so more water can go into our bank account in Lake Powell. It’s a much better alternative than having mandated reductions.

Abby: So is this why you yell at me for taking long showers?

Me: Sort of. Every little thing we can do to use water efficiently helps. Particularly in the western United States, we are all connected by our water use.

Abby: Congratulations Dad. Despite your best efforts, I think I learned something.

Me: Thank you … I think.