(CNN) — "Whiskey is for drinking; water is for fighting."
My old man loved that old quote, almost as much as he loved whiskey, water and the American West.
Bill Weir Sr. was a big-city detective with the soul of a cowboy.
After a particularly rough week of murder and mayhem, he tossed his badge on his captain's desk with indelicate instructions on where to put it.
He packed his saddle and skis and left Milwaukee for the mountains.
On "The Wonder List," Bill Weir remembers his late father by heading out West to complete a journey they dreamed about.
Once he was settled as a Coloradan, that old quote took on fresh significance.
Atop his horse alongside a dry ditch or knee-deep in a trout stream, he'd grouse about water rights and population growth and the inevitable day of reckoning.
"One day we're going to raft the Colorado, kid," he'd say. "Before it's gone."
That conversation echoed around my skull the day I borrowed his snowshoes and followed the instructions in his will. Dad wanted me to spread his ashes atop Mount Sopris.
From Denver to Los Angeles, almost 40 million people depend on the Colorado River to survive. Relentless Western drought and equally relentless growth are straining the river.
The mountain, and the rivers below it, were our favorite playground when I was a boy. I climbed to a perfect spot next to a lovely little lake and held a memorial service for one.
My dad is the inspiration for "The Wonder List." He lived in constant wonder of the world's wild places, and he constantly wondered about the fate of our planet.
So this one's for him ... and the 40 million people who depend on the Colorado River to survive.
It's thought that for the past 15 years or so, the Colorado has been at its lowest level since the 9th century.
As big cities take their share, the Colorado River is in peril. Bill Weir plunges in before it's too late on "The Wonder List."
Back then, a few native tribes were at risk. Today, it is countless families, farms and factories from Denver to Los Angeles.
One look at Hoover or Glen Canyon dam fills you with wonder at the kind of American might that built huge communities in the desert. But that wonder shifts when you notice the stark bathtub rings way above the water they hold.
Go behind-the-scenes as Bill Weir tracks, and gets lost, along the Colorado River between Denver and Las Vegas.
Lake Powell and Lake Mead are more than half-empty, and not even the heavy snows of this El Nino year can reverse the trends of climate change and population growth.
Like my dad before them, another 20 million are expected to "go West, young man" by midcentury.
But how much farming, ranching, floating, fishing, damming, building, drinking and fighting can one river take? How long can the Colorado flow?