Disappearing Rio Grande

For two weeks, we have ridden a river so thick with mud we could watch it change the shape of the river channel.

Every afternoon rainstorm brought sediment pouring into the river from the side canyons and arroyos. The next morning, as the river level dropped, the banks would be coated with fresh mud the consistency of pudding.

We would sink down to our shins until our feet came to rest on the solid ground below the fresh mud. Or we would sink until our legs provided enough flotation.

That river of mud comes to end here at the Cochiti Reservoir.

Built as a flood control dam, this five-mile-long earthen dam is responsible for stopping the flooding of Albuquerque. The consequence was that it destroyed several thousand archeological sites as it inundated White Rock Canyon and submerged half of the farmlands the Cochiti Pueblo had used for the last 700 years.

But that’s a story for next week.  What we saw today was the reservoir’s greatest weakness:  it’s filling up with dirt.

As we entered the lake, the brown, silt-packed river was sliding in underneath the green water of the lake.  Two miles later, the water leaves the reservoir but the sediment stays behind and the reservoir keeps getting shallower.

If nothing is done, the delta the river is building at the head of the reservoir will reach the dam.  Then the river will do what it does best and start cutting away at anything that stands before it.

The Rio Grande has cut through volcanoes, lava flows and entire mountain ranges.  In the geologic time frame, the dam’s odds of sticking around are not good.

But today the dam is doing well and we hauled our boats over and through the mud of the delta when we could not find water deep enough to float us.

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