The opener of Follow the Water: a rusted spoked iron wheel lying in the cobbles of the exposed lakebed, with the remaining water and the forested ridge behind it. It states the subject at once, what the falling water uncovered.

A large rusted iron wheel with eight spokes lying flat among rounded cobbles on a dry lakebed, a strip of blue water and a dark forested ridge behind it under a clear sky

Follow the Water

A hot, dry summer

My family camps over my birthday each summer. This year we returned to Arapaho Bay on Lake Granby, where we had camped 6 years before. The water had fallen far enough to walk out across the lakebed, and there we found Monarch, a mining town that went bust and was flooded when the Bureau of Reclamation built the Colorado-Big Thompson Project. The next day I built a quick app with Claude to explore it, then a presentation following the water from that lake to the people who depend on it.

Road map of northern Colorado with driving routes in blue looping around the mountains from Boulder and Denver to a campground on Lake Granby, the northern route 2 hours 51 minutes and the southern 2 hours 47 minutes

Map of Grand Lake, Shadow Mountain Lake and Lake Granby in blue among green forest, with a red pin at the far eastern end of Arapaho Bay

This story starts at our first camping trip 6 years ago, oddly with the van in the exact same camping spot. We canoed, fished, and splashed at the beach. The lake was exactly as you would expect.

A forested campground above a lake, a white van with a blue roof box parked on a dirt loop among pines, with a circular locator map at lower right

The sun setting through cloud behind a dark ridge, reflected orange in a full lake edged with pines, with a circular locator map at lower right

The bow of a canoe on rippled blue water, wooded shore and snow-streaked peaks ahead under a long smooth cloud, with a circular locator map at lower right

A person in a sun hat holding a leash on a sandy beach at the edge of a full lake, a black and white dog beside them, with a circular locator map at lower right

June 20, 2020

A black and white photograph looking down over dark pines onto scattered snow-covered buildings in a valley, on a dark ground, with a circular locator map at lower right

But in 1905, Lake Granby had not yet been dammed and there existed a small town called the Monarch Consolidated Gold and Copper Mining and Smelting Company on the bank of Arapaho Creek. The town had a railroad, cottages, a hotel, stores, a bowling alley, a theater, and a dance hall. The mine produced only $150 in copper per year, the box factory burned down, and the town slowly went bust.

Three people, one standing and pointing, at a heavy log-framed Arapaho National Forest sign, black and white

A large pale frame building and timber structures on a rocky flat below mountains, black and white

A rusted upright boiler and winch gears standing abandoned among tall trees, black and white

A printed U.S. Department of the Interior, Bureau of Reclamation map headed Colorado-Big Thompson Project, showing Lake Granby, Shadow Mountain, the Alva B. Adams Tunnel, Estes Park and Horsetooth Reservoir either side of the Continental Divide

In the early 1940s the US Department of the Interior began the Colorado-Big Thompson Project, whose goal was to manage water resources on the Western Slope of the Rockies. Lake Granby was dammed to create a working reservoir, and the remains of the town of Monarch disappeared underwater.

CreditMap: U.S. Department of the Interior, Bureau of Reclamation.

Steel reinforcing and concrete formwork laid into a steep excavated slope, black and white

A worker in a pith helmet leaning over a railing above the works, in hard shadow, black and white

Aerial view of a rock-faced earth dam holding back a blue reservoir, white water running down a long concrete spillway at its side — Granby Dam spillway into the Colorado River.

The same road map of northern Colorado with a dotted orange line running straight between two circled points across the mountains that the driving routes loop around — The project also included one of the most ambitious civil engineering projects of the century. Two teams drilled a 9-foot-high, 13-mile-long tunnel from Grand Lake under Rocky Mountain National Park to deliver water to the eastern side of the Continental Divide. Despite some delays due to World War 2, the teams met on June 10, 1944, to within an inch of each other's bore holes.

A crew in hard hats riding small rail cars out of a rough tunnel portal under a Bureau of Reclamation sign, black and white

Four miners in hard hats standing around a drilling machine at the rock face of a tunnel, sepia

Men in overcoats reaching through a ragged opening in a rock wall to shake hands with hard-hatted miners on the other side, black and white

A long tunnel lined with arched steel ribs, rail tracks running to a vanishing point and a figure far along it, black and white

A man in a green shirt and khaki shorts standing on a grassy shore among yellow flowers, one arm out toward a reservoir and a concrete building beyond it — Rivers of the Rockies Clip - Alva B. Adams Tunnel, Rocky Mountain Channel

A map of the Colorado River basin from Wyoming to the Gulf of California, with a circular enlargement of Grand Lake, Shadow Mountain Lake and Lake Granby labeled with the tunnel, the Colorado River, pumping, two dams and the camp site

Municipal

~40m people

Los Angeles, San Diego, Phoenix, Tucson, Albuquerque, Tijuana

Irrigation

~5.5m acres

Lettuce, spinach, broccoli, onions, carrots, cauliflower, herbs, kale

Energy

~1,600 MW

4 dams supplying electricity for ~700,000 people

CreditBasin map: Shannon1, CC BY-SA 4.0.

The river supplies every American eating a salad between November and March.

A dark table headed The Colorado Mainstem, readings 15–16 August 2026, listing seven lakes from Grand Lake to Lake Havasu with full-pool elevation, volume and depth, Lake Granby highlighted in orange at 59 percent

A shallow river braiding across a wide bare lakebed of gravel and silt between forested mountains, with a circular locator map at lower right

From a canoe, rippled blue water filling a valley to its wooded shores under a long smooth cloud — June 20, 2020

The same valley with the water gone, a shallow river running through bare gravel below the same mountains — August 6, 2026

A wide lakebed of silt, boulders and pale gravel running to the far mountains, water only at the edge of the frame, with a circular locator map at lower right

Pale cobbles and red brick fragments on bare silt, a straight line of stones running through them toward low green growth, with a circular locator map at lower right

A large rusted iron wheel with eight spokes lying flat among rounded cobbles, its hub full of sand, with a circular locator map at lower right

A low square pier of fitted stones standing in pale sand with a few plants growing at its foot, with a circular locator map at lower right

Two dark rough blocks on the lakebed with rows of iron bolts standing out of their tops, mountains and green growth beyond, with a circular locator map at lower right

A line of large rounded stones curving away across bare lakebed toward a gap in the mountains, with a circular locator map at lower right

A straight row of dark stones across the lakebed with a gap in it and a second line turning toward the camera, forested ridge behind, with a circular locator map at lower right

A wide lakebed of dark gravel, boulders and low green growth, a strip of water at far left below a forested slope and a pale sky

A wide band of pale exposed lakebed below pines and a long valley, the water a thin line far off, with a circular locator map at lower right

Pale exposed lakebed beyond the tops of pines, with brown mountains behind under haze, with a circular locator map at lower right

A dirt road and bridge beside a concrete tower on a rock-faced dam, a low reservoir at right, with a circular locator map at lower right

Sitting back at camp, I researched the history of the area and used Claude to build an app that would let me explore the lakebed in context and record my findings. The app overlays a historic USGS topo on satellite imagery, tracks live GPS, has a "waterline" slider that cross-fades past and present, and lets me drop pins on physical remains I find, with JSON export.

Open prototype

Phone screen of the app titled Monarch, Beneath Lake Granby: satellite imagery of a dark lake and forest, the waterline slider at its right end, Water, Today

The same phone screen with the slider at its middle, a historic topographic map half faded over the satellite image

The same phone screen with the slider at its left end, 1900s, Lakebed: the 1919 topographic map in full, showing Monarch, Monarch P.O., a railroad and Strawberry Lake

CreditHistoric map: U.S. Geological Survey, Rocky Mountain National Park sheet, 1919. Satellite: Esri World Imagery.

Introduction to the app.

A screen headed Get the historic map onto the ground offering two choices, Load it automatically, marked Recommended, and Use a screenshot, marked Manual

Select the historic map to overlay.

A historic map floating semi-transparent over the satellite view, with controls headed Align the old map, drag, pinch, twist, an opacity slider and buttons Cancel and Pin it

Pin the old and new maps to one another.

A sheet headed Mark a find, with a text field whose placeholder reads Stone foundation, about 4 by 6 m, and buttons Cancel and Save find

Record the location of interesting finds.

The GPS dot shows two rings, one for GPS accuracy (~5 m) and one for historic map drift (~65 m). This makes it easier to spot potential correlations between the modern high-res map and the historic low-res map.

Phone screen with the 1919 topographic map nearly opaque over the satellite image: 17 white diamond markers in the same places as on the map beside it, along a railroad line and a blue creek, an orange position dot among them inside a dashed ring, and the status line reading GPS plus or minus 5 m, dashed ring equals the old map's own plus or minus 65 m drift

The app's map on today's satellite image: 17 white diamond markers spread across dark water below a green shore, where the imagery still shows the lake full

The app's screen headed My finds, cropped to phone height with its middle rows cut: 10 of the 17 finds with their coordinates, from Rock wall corner to Long Big Rock Wall, then Large Foundation, Wagon Wheels, Entry Sign Pylons, Land of Pillars and More Rock Wall, each with a Remove link, and buttons Close and Copy as JSON at the foot

CreditHistoric map: U.S. Geological Survey, Rocky Mountain National Park sheet, 1919. Satellite: Esri World Imagery.

I found two competing Mark Twain quotes that spoke to me in this moment. The optimist who is sometimes wrong is hopeful, and hope leads to change. And knowing too little is an ageless problem, especially if you just turned 49. So in the face of drought and climate change, I choose learning and leading efforts for change. I take inspiration from humanity's audacious efforts like the Colorado-Big Thompson Project and its modern equivalents. I choose optimism.