It might be time for Arizonans to rethink their water use as it may diminish Arizona’s fish supply.
Fish species native to Arizona watersheds could lose important parts to their habitat by 2050 as surface water flow is draining from the effects of climate change, a new study suggests.
“The more we look, the more we find a megadrought,” said Jonathan Overpeck, co-director of the Institute of the Environment in Tucson. “From the perspective of the past, we know that droughts in excess of 20 years have occurred so there is a possibility of it in the future.”
Most of the fish found in the Verde River Basin have already been endangered or threatened from the drought. These species include the speckled dace, roundtail chub and Sonora sucker. Their survival is primarily based on different nutrients and resources found in the watersheds.
A key component of these streams is hydrologic connectivity – allowing the dispersal of fish into river basins outside of their range, which enables fish to make use of the entire watershed as needed for eating, spawning and raising offspring, said Catherine Pringle, Institute of Ecology professor.
By the mid 21st century the basin network will experience a 17 percent increase in the frequency of stream drying events and a 27 percent increase in the frequency of zero-flow days, researchers found.
“We have portions of the channel that are going to dry more frequently and for longer periods of time,” said lead author in study Kristin Jaeger, assistant professor in Ohio State University School of Environment and Natural Resources. “As a result, the network will become fragmented, contracting into isolated, separated pools.”
If fish can freely flow throughout the entire watershed, the fish can make use of the resources available. But if the systems dry out or become small pools, fish are forced into crowded areas and lack of resources, said Jaeger.
The researchers used a rainfall runoff model to conduct this prediction, the Soil and Water Assessment Tool (SWAT), which incorporates the study basin’s elevation, terrain, soil, land use, vegetation coverage, and both current and future climate data, including precipitation and temperature.
Piecing together data from the SWAT, Jaeger found that flowing portions of the system would diminish between eight and 20 percent in spring and early summer, producing lengthier channels that will dry more frequently and over longer periods of time. These changes will reduce available habitat for fish and force them to travel longer distances for resources once channels rewet.
The fish already have a huge amount of stress put on them due to the surface and groundwater extraction for irrigation and drinking water, said Jaeger. The overall system is already compromised due to the extreme dry temperatures of the Southwest.
Of the 36 fish species native to Arizona in 1988, 21 are listed as threatened or endangered. Seventy percent of the native Arizona fish have been put on the Wildlife of Special Concern and over 50 percent federally listed as endangered or threatened. Most of the smaller rivers and creeks in Arizona are now dry except for periods of heavy rain, said officials with the Arizona Game and Fish Department.
“These fish are important cogs in the wheel of this greater ecosystem,” Jaeger said. “Loss of endemic species is a big deal in and of itself, and native species evaluated in this study are particularly evolved to this watershed. In this river network that currently supports a relatively high level of biodiversity, the suite of endemic fish species are filling different niches in the ecosystem, which allows the system to be more resilient to disturbances such as drought.
“If species are pushed over the edge to extinction, then what they bring to the ecosystem will be lost and potentially very difficult to replace.”
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Casey Woollard is a reporter for the Arizona Sonora News Service from the school of journalism at the University of Arizona. Reach her at caseyawoollard@email.arizona.edu