New Mexico's Ancient Irrigation Systems Help Protect Scarce Water Supply
The major rivers of the Southwest are hurting as snow becomes increasingly scarce in the Rocky Mountains. Scientists who study climate change warn such conditions are the new normal.
But there’s encouraging news in northern New Mexico, where an ancient irrigation system has survived for hundreds of years.
Spring marks an annual ritual on the farms of the upper Rio Grand Valley in New Mexico. It's when communities gather to clean out their local irrigation canals. In the town of Dixon a team of 32 workers in bandanas and work boots shovel dry grass and leaves from the bottom of a dirt ditch. A supervisor stands above them and hollers a roll call.
These hand-dug ditches are called acequias. It's a style of irrigation that has survived since the arrival of the first Spanish settlers. The network of canals branch out from neighboring rivers like arteries. Cottonwood trees taller than telephone poles grow beside them. Workers clear out debris the same way their ancestors did, with shovels and biceps.
Once clean, the acequias can receive river water. This year, supervisor Donald Atencio says the preparation is happening two to four weeks earlier than usual.
"We are one of the last acequias cleaning out this year already," Atencio said. "The other seven ditches already have water."
The reason for the early start is the early snow melt. Crowning this arid valley are the Sangre de Cristo Mountains. These silent giants feed the rivers below, but lately the rivers are going hungry. A quick trip up a nearby peak reveals why.
On a mountainside west of Taos in the center of New Mexico ski country the ground is more brown than white. This is one of many sites visited by Wayne Sleep, a hydrologic technician with the Natural Resource Conservation Service. A major part of his job is to measure snow pack.
"The 2013 snow season was terrible," he said. "Normally this time of year the canyon would still be snow-packed."
The last three years in New Mexico have been the driest on record, with snowpack readings at 30 percent of normal. And it's not just this state — snowpack is down across the Southwest
"We look at 30-year periods of records for our averages," Sleep said. "There's been some good years in there but the overall trend is dry."
Climate studies show the rate of global warming has accelerated in the last 30 years. In the Southwest, mountain snow melts into rivers like the Rio Grande and the Colorado and ends up in open air reservoirs like Elephant Butte in New Mexico or Lake Mead in Nevada. On hot, windy days these reservoirs act like a pot of boiling water.
"We measure evaporation directly from the surface of the water," said Salim Bawazir, an engineering professor at New Mexico State University. He and a team of students study evaporation at Elephant Butte reservoir.
"We can say we are losing about five feet per year," Bawazir said.
Five acre feet of water is enough to grow an acre of alfalfa. In times of drought, Bawazir said, reservoirs are not the ideal place to store water.
This is where the acequias of northern New Mexico may provide some relief. Because they are dug into the earth, they allow water to seep underground where it can be stored for up to three months.
"Hydrologically it's better to store water underground in northern areas because it's cooler and, you don't have evaporation," said Sam Fernald of New Mexico State University.
Fernald teaches water management and is currently leading an ongoing study of acequias that shows they are helping mitigate the effects of climate change.
"We can learn from these systems that have been adapted to water scarcity for hundreds of years how to have our own sustainable water management," he said.
Fernald and his team of researchers have installed water monitors in multiple acequia sites. Their data shows that crops use only 7 percent of acequia water. The rest eventually returns to the river through surface run-off or groundwater. In parts of northern New Mexico the groundwater and rivers are connected, Fernald said. That's no longer the case in other parts of the state.
But despite their potential benefits, the future of acequias is not guaranteed. Many farmers are struggling to make a living off the land. To survive, farmers are finding new ways to market their produce and ensure the future of their beloved irrigation system.