Three months ago, Colin McDonald and Erich Schlegel found the source of the Rio Grande in the mountains of southern Colorado and started walking. Their destination: the Gulf of Mexico nearly 1,900 miles downstream.

When we caught up with McDonald last week, he’d made it to El Paso, Texas. The 33 year old reporter from Suquamish, Washington, estimates he has paddled and walked for 675 miles so far, stopping often to discuss the state of the Rio Grande with locals and river experts. Schlegel — a photojournalist born in Monterrey, Mexico, and raised in Brownsville, Texas — has split his time between the river and a support vehicle, documenting the journey with his camera. The pair raised money on Kickstarter to fund the expedition and to develop an expedition blog featuring McDonald's writing and Schlegel's photography. They hope to reach the sea by mid January.

Canoe & Kayak: It looks like low water on your trip has meant more walking than paddling at times. How are you holding up?

Colin McDonald: We expected low to no water in many of reaches and came ready to walk. We have actually been pretty lucky with the amount of water we have had. The biggest challenge has been to not walk or paddle so much that we can’t recover in time for the next day’s paddle or walk. Sometimes I do that well, others times I end up with too many blisters.

What percentage of the time have you been on foot?

Of the 675 miles we've done so far, the last 200 has been entirely dependent on what the rainfall was the day before. So I've probably paddled 500 miles and walked 150, and I'll walk 200 more before I hit the Rio Conchos.

Based on your blog, it's looks like you've had to switch craft often. In one picture you're in a canoe, the next a kayak, and then you're walking with your packraft.

Yeah, this system is remarkably variable. To put it in perspective, the Rio Conchos (a major tributary of the Rio Grande) is basically flooding with monsoon season water right now. It's flowing at 10,000 cubic feet per second (cfs), but a few weeks ago it was flowing at 40 cfs.

The crazy part about the Rio Grande is that it jumped from 120 to 1000 cfs in one day while we were on the water. That same place a year ago, it'd been flowing at 10,000 cfs, and the big floods of the past have been estimated to reach 100,000 cfs. The spectrum of the river is so broad, it's difficult to pin down what is normal. In fact, nobody knows what's normal anymore. Or maybe I should say normal is somewhere between flood and drought.

What made you want to follow the Rio Grande source to sea?

No other major river in the United States is going to change more than the Rio Grande as weather patterns shift. The snowpack is going to be smaller and melt earlier, the droughts are going to be longer, the monsoon floods bigger. I wanted to follow the river to understand how these changes are already impacting the people and places that depend on the river.

How long has this trip been in the works?

I’ve been dreaming of this trip for about five years and working directly on it since the spring of 2013.

What is your goal?

Public awareness about the state of the Rio Grande is decades behind public awareness about the state of other rivers in the Southwest like the Colorado River. (The Colorado has Will Ferrell advocating for it!) My goal is to share with a general audience what is happening to the Rio Grande so more people will want to become involved with deciding what its future will be.

What has surprised you most so far?

I am amazed at how manipulated the Rio Grande is and how easily it runs dry. You can have the biggest snow year possible in the Rockies and none of that water will make it to the Gulf of Mexico. But I’m also impressed by how resilient it is and how many people care about it. The river will run free again, it’s just a question of what century that will happen in.

What have been some of your biggest challenges?

Being away from my fiancee for this long is by far the hardest. The second is the constant effort needed to maintain the schedule and set up interviews as we travel.

Have you seen anything along the way that gives you hope for the future of the river?

River ecosystems, especially those of the Rio Grande, evolved with constant change and are therefore amazingly resilient when given a chance to bounce back. They're not like rain forests where once they're cut down, they're gone. It is amazing how much potential rivers have.

What are the most notable changes in the river you’ve encountered so far?

Every dam completely changes the nature of the river. So far the biggest dam and biggest change was at Elephant Butte. There the river goes from a relatively free-flowing system that often overtops its banks to relatively sterile reservoir. The only flow allowed to pass, outside of the irrigation season, comes from a pipe that collects the condensation from inside the cement dam.

What are the biggest unknowns still ahead?

We don’t know how the drug cartels will see us, what camping will be like along the border fence and where we will get drinking water in the Forgotten Reach between where we are now, El Paso, and Presidio, Texas.

The Forgotten Reach is itself is probably the biggest unknown. It hasn't had water since 1916. It's called the Forgotten Reach because it was basically forgotten when the waters of the Rio Grande were being divided up. Back then, the priority was agriculture and the thinking was: if any water reached the sea, it was a waste. Dams were built and 200 miles of the river ran dry.

Where does the Forgotten Reach end?

The Rio Conchos comes out of Mexico and that's the second Rio Grande. The odd part of the Rio Grande is that it's really two rivers. The upper Rio Grande is really a closed basin because no water flows out of it. For all intensive purposes, all the water that flows out of the mountains of Colorado and New Mexico ends at El Paso. Then there's the Forgotten Reach. When it starts to flow again, what's called the Rio Grande is really not the Rio Grande at all because its entire flow is supplied by the Rio Conchos flowing out of Mexico.

Anything else we should know?

If you would like an official expedition sticker or t-shirt please visit our kickstarter page.

–Follow the journey in real-time: Visit McDonald and Schlegel’s expedition blog here.

–How has the Rio Grande changed over the last 20 years? Read this story from the C&K vault to find out.