Has New Mexico passed “peak water”?
Water for household use peaked in 1995 and has been declining ever since, according to state data. Farm irrigation, which makes up the bulk of the state’s water use, has been declining since the 1970s.
For domestic water use, both from municipal water systems and domestic wells, conservation has so far been able to pick up most of the slack, with total water use dropping over the last 15 years even as the state’s population has continued to grow.
But farmers have had a tougher time of it, according to state data, responding with a combination of water efficiency and simply taking land out of irrigation.
Consider Curry County, on New Mexico’s eastern plains, where farmers are using less water because they have no choice.
They have taken land out of production and switched to sorghum, which is less thirsty than corn, according to county extension agent Luther Dunlap. They depend on water from the Ogallala aquifer, the great underground reservoir that fuels agriculture on the High Plains, and the Ogallala is dwindling.
“It’s been dropping significantly,” said Dunlap. “That’s our main source of water.”
According to a Journal analysis of new and historical data from the New Mexico Office of the State Engineer, water use in Curry County has dropped 29 percent since the mid-1990s. And Dunlap’s farmers are not alone. The state’s latest water use report, completed last month, suggests the same thing is happening across New Mexico. Total water use in the state, including all farms, businesses and cities, has dropped 14 percent from its peak in the mid-1990s, even as New Mexico’s population has grown by 22 percent.
While the success in reducing water use may look like a water conservation success story, the reasons behind it are not encouraging. Groundwater across the entire state, especially on New Mexico’s east side, is dwindling, according to research by the University of California’s Jay Famiglietti, who uses satellites to measure changes in the aquifer, the fresh water underground that is pumped up for use on farms and in cities.
“The trend is pretty significant,” Famiglietti said. Meanwhile, drought and warming temperatures have sapped the amount of surface water in the state’s rivers since the late 1990s.
In measuring how much water New Mexicans use, the state’s water use report is really tracking how much water we have, said John Longworth, head of the state’s Water Use and Conservation Bureau. While conservation efforts and reductions in mining and some industrial activity have reduced our water use, part of the explanation for the decline is simply that less water is available, Longworth said in an interview.
“This is about a lack of water resources,” said Sandia National Laboratories water researcher Mike Hightower.
Climate experts expect the decade-plus drought to eventually relent, though none can predict when. But the longer term warming trend, according to climate scientists, means future wet spells won’t be as wet and future droughts will be drier, leading to less river water on average in the long run.
The New Mexico data matches national trends. Hightower and others point to U.S. Geological Survey data showing that U.S. water use peaked in the 1980s and has flattened out or declined since, despite growing populations. The Arizona Department of Water Resources concluded that Arizona’s water use peaked in the 1980s, and the U.S. Bureau of Reclamation recently reported that overall water use in the Colorado River Basin, some of which lies in New Mexico, peaked in the late 1990s.
Peter Gleick, head of the Pacific Institute, a water policy think tank in California, has labeled the phenomenon “peak water.”
In the case of groundwater, according to Gleick, the “peak” comes when water users can no longer economically pump out as much water as they used to, forcing them to switch to alternative supplies or reduce their use. In New Mexico, there are examples of both. Albuquerque has reduced its groundwater pumping, switching to water imported from the Colorado River Basin. In Curry County, by comparison, farmers have simply had to reduce their use.
In the case of river water, which is renewable via rain and snow each year, the “peak” comes when human users take out the maximum available and then sometimes overshoot during drought times when less precipitation fails to replenish supply.
“More and more watersheds appear to have already passed the point of peak water,” Gleick wrote in 2010 in the Proceedings of the National Academy of Sciences.
That forces increased conservation, innovation in areas like water use, and difficult choices about how to allocate increasingly scarce supplies, Gleick wrote.
Agriculture is by far New Mexico’s largest water user, making up 79 percent of the water diverted from the state’s rivers and pumped from its aquifers in 2010, according to the Office of the State Engineer. Municipal systems and domestic wells for New Mexico homes represented 9 percent of the water that year.
Both groups of users have substantially reduced their water use since the 1995 peak, according to the state’s water use reports, which are done every five years.
State officials acknowledge some shortcomings in the data. The latest report only considers water diverted from the state’s rivers or pumped from the ground. It does not take “return flows” into consideration – irrigation water that soaks into the ground to recharge an aquifer, or return flows from a municipal sewage treatment plant to a river. Despite that shortcoming, the state’s approach is sufficient to provide a clear picture of the New Mexico’s water use trends, Hightower said.
Farm efficiency has played a major role in the water use reduction, with a shift away from flood irrigation to sprinklers and drip irrigation. In addition, total irrigated acreage decreased 9 percent since 1995, according to the state.
“Farmers get efficient when there’s shortage, no question,” said Longworth, whose staff produces the water use reports.
Municipal water use dropped consistently from 1995 to 2010, according to the state data. Albuquerque’s conservation success dropped water usage from 251 gallons per person per day in 1995 to 157 in 2010. Overall, municipal water use in the state dropped 9 percent since 1995 while population grew 22 percent.
Part of the municipal reduction is a result of 1992 legislation that standardized low flush toilets. “You can no longer buy 6 gallon per flush toilets after 1994,” Longworth noted. In the years since, appliance efficiencies followed, so that a typical home with the latest appliances uses 22 percent less water than an older home.
The peak and decline coincide with the first wave of an enduring drought that began in the late 1990s, according to David Gensler, water manager for the Middle Rio Grande Conservancy District. “We transitioned from a very wet period, with almost unlimited water and the reservoirs spilling every year, to a drought,” Gensler said. Driven by both drought and the requirements of the Endangered Species Act, Gensler’s agency began reducing its diversion of water from the Rio Grande in the early 2000s.
At the same time, dropping aquifers caused cities and farmers depending on groundwater to adjust their behavior to increasingly scarce and expensive supplies, Gensler noted. He called the resulting reduction in water use “a pretty practical human response to the situation.”
Whether the use might rise again if and when the drought eases is an open question. Gensler noted that requirements for environmental rivers flows will not go away, nor will the groundwater problems substantially lessen, even if rainfall patterns shift and the state gets wetter.
“It’s not going to go back,” he said.