Albuquerque’s ecosystem may benefit from this year’s heavy water flow and flooding in areas around the Middle Rio Grande.
Although the water levels are past their peak for this year, the average discharge in the Rio Grande in Albuquerque rose to nearly 6,000 cubic feet per second in June. Last June the discharge rate rarely surpassed 1,000 cfs.
On June 18 the discharge rate outside of Cochiti dam, an hour north of Albuquerque, was at its peak flow at a rate of 6,279 cubic feet per second, according to the U.S. Army Corps of Engineers at the Albuquerque District.
Areas surrounding the Rio Grande had good snowpack this year. Kim Eichhorst, an associate research professor of biology at UNM and co-director of Bosque Ecosystem Monitoring Program (BEMP), said the snowpack earlier this year melted, and sublimated – or evaporated straight from the snow. A dust layer on the snow also allowed the snow to evaporate faster.
“It was just this really perfect year where the snowpack was just over our long-term average, and as the snow was melting, we would get another storm that would replace the snow that had melted,” Eichhorst said.
BEMP has 17 monitoring sites in Albuquerque, over half of which experienced flooding this year. Eichhorst said some of the sites haven’t flooded in 20 years, even during the high-water flows in 2017.
Eichhorst said in a flood event like this, especially when sites haven’t flooded in a long time, the year following the flood may look bad for the ecosystem. In the following years, the ecosystem will often rebound and will have benefited from the floods.
“This is a flood driven system, so the plants and animals are well adapted, and they do really well with these flood events,” she said.
Eichhorst said there is a chance that next year the ecosystem will look great because of the more recent floods in 2017.
Following this year’s flood, there could be cottonwood and willow tree population increases -- more new trees to replace the old ones.
Walking through the bosque, most of the cottonwood and willow trees people see are at the end of their life cycle, and there are currently no new trees to replace them.
To germinate, Eichhorst said cottonwood seeds need open and saturated soil and a steady decrease in the water table.
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In 2017 the water table dropped at a stark rate – up to 20 meters a day. Cottonwood roots need on average a 5 centimeter per day decline.
The US Army Corps of Engineers control many of the dams along the Rio Grande, including Cochiti Lake. The Corps is currently operating under flood control and are stepping down the river flow at many of their dams, creating a less steep drop in the water levels.
Michael Porter, a Fishery Biologist at the Albuquerque district of the Corps, said slowing down the water levels could benefit many species living near the Rio Grande, including the silvery minnow and cottonwood seedlings.
“Through the years we’ve recognized that having a slower recession rate of the flows coming out of Cochiti affect the ecosystem,” Porter said. “If you have the flows at a much faster rate you tend to get floods at the feet of the banks, which brings more sediment to the river.”
Eichhorst explained that if there are still seeds floating around, there is a chance they could germinate if the river flows decrease at a slow and steady rate because seedlings will have a chance to put their roots in the ground.
BEMP will use vegetation monitoring in August and early September of this year to see if cottonwood trees start to bud and will continue to monitor them to see if they become established plants.
