HOME ON THE FLOOD PLAIN
Riverbank-lowering projects help boost the odds for native fish, trees on the river
Just south of Paseo del Norte on the east bank of the Rio Grande, three men in hip waders wrangled a large net last week in search of endangered silvery minnows.
Their work paid off when they scooped dozens of squirming fish out of the net.
“A lot of fish — looks like lots of red shiners,” said Jason Kline, a biologist with SWCA Environmental Consultants, which is under contract with a state agency to help monitor fish populations in the Rio Grande.
Most of the fish, in fact, were red shiners, named for their distinctive red fins. But the catch also included a handful of silvery minnow, which were classified as an endangered species in 1994.
“We’re seeing good numbers of silvery minnow coming on to the floodplain in Albuquerque,” said Grace Haggarty, a hydrologist with the state Interstate Stream Commission, the agency that hired SWCA.
This site is an example of what biologists call a restoration area, where heavy equipment was used to lower the riverbank, allowing river water to flood the sandy bank.
The warm, slow-flowing nutrient-rich water in overbanked areas provide ideal nursery habitat for tiny larval minnow to grow into young adult fish, said Michael Porter, fishery biologist for the U.S. Army Corps of Engineers.
“Sometimes, they spawn on the flood plain, sometimes they spawn in the channel,” Porter said of the minnow. “But the larvae have to get on the flood plain to survive.”
Porter estimated that various state and federal agencies have built at least 50 restoration areas on the Rio Grande
between Cochiti Dam and Elephant Butte Lake.
Various state and federal agencies have funded the projects over the years. This 20-acre site, within eyesight of the Paseo del Norte bridge, was built by the Albuquerque Bernalillo Water Utility Authority in 2014.
Restoration areas do more than provide silvery minnow habitat.
“See all these little seedlings coming up?” Porter said.
Thousands of tiny cottonwood seedling pepper the dried mud, which had been underwater just days earlier. Most of the sprouts will dry out and die, but a few will send down roots that find water.
“The roots have to chase the water down as it recedes,” he said.
Also growing in some abundance here are willow seedlings. When they mature, willows provide vital habitat for the Southwestern willow flycatcher — a bird listed as an endangered species in 1995.
Cottonwoods and willows, both native to the Rio Grande bosque, have been muscled out of many areas by invasive species — especially salt cedar, Russian olive and Chinese elm.
Dozens of young cottonwood trees here are surrounded by chicken-wire cages.
“They put chicken wire around the cottonwoods because they’re valuable, and beaver love them,” Porter said.
Beavers cut down the cottonwoods and eat the bark, he said.
A healthy snow pack delivered plenty of water to the Rio Grande this year. The river overbanked this year in many areas that normally remain bone dry.
The Rio Grande has had the highest sustained flows this year since at least 2010, U.S. Geological Survey data shows.
Flows in Albuquerque peaked May 17 at about 5,000 cubic feet per second. Flows on that date in 2016 were about 1,500 cfs. They dropped rapidly last week, from about 3,800 cfs Tuesday to about 1,800 cfs Friday at Paseo del Norte.
In recent years, the Rio Grande has entered a drier period, with peak flows often topping out at 2,000 cfs or less, said Todd Caplan, restoration program director at GeoSystems Analysis Inc.
Restoration areas are typically designed with those lower flows in mind, said Caplan,who has designed and built restoration areas for several agencies.
A recent project at the Sevilleta National Wildlife Refuge north of Socorro was designed to begin filling with water at 800 cfs and become fully inundated at 2,000 cfs, he said.
This year, biologists have observed larval fish in the flood plain since it became inundated in May, Haggerty said.
“We will probably see a lot of fish next year that were spawned this year in the flood plain,” she said. “I think everybody feels pretty positive about how (the silvery minnow) are doing this year.”