![]() For example, researchers working in Arizona have documented via videos how insects such as giant water beetles will climb up and away from streams as it begins to rain. Life in the region has adapted to these sudden fluctuations. Sudden desert thunderstorms can send a wall of water and boulders tumbling down river channels.Īnd the water can be gone almost as fast as it came, with floods followed days or even hours later by a placid trickle or no flow at all. The southwestern US is a land of hydrologic extremes. That could mean working to prevent losses at the most vulnerable sites or concentrating efforts around locations with a greater chance of persisting streamflow. More proactively, knowing the increased risk of intermittency for locations with lower, more variable minimum flows could help us to prioritize conservation efforts. ![]() But we can’t evaluate what we haven’t measured, and that cripples our ability to anticipate and adapt to changing water availability. Gages – including those with valuable long-term records – are being retired due to funding constraints. Well, these findings underscore the critical importance of continued streamflow monitoring. Perhaps most importantly, the data showed that streams with lower minimum flows and higher minimum flow variability are more vulnerable to the shift from perennial to intermittent. They found that zero flow days increased with drier values of the Palmer Drought Severity Index, a composite measure reflecting temperature, precipitation, soil moisture and evapotranspiration, and they found that the yearly average flow was a good predictor of the yearly minimum flow for both perennial and intermittent streams. Then, they related the number of zero flow days at a site to the climate features in the basin upstream as well as to the average and peak flows that we usually assess. To do this, the researchers from Colorado State University and the USGS gathered data from 115 river reaches in Arizona, Colorado, New Mexico, Utah and Wyoming. ![]() That is, from always having some flow to sometimes having none. This region, where life is tied especially tightly to water, is projected to see faster-melting mountain snow packs and longer, drier summers.Īnd a new study, out in the Journal of Hydrology, examined long-term records of stream flow throughout the Upper Colorado River Basin to explore how low flows might get lower and how some channels might switch from perennial to intermittent. Whatever name you prefer, get ready to use it more often when you’re talking about the western US. What do you call a stream with no water? A wash? A gulch? An arroyo? ![]()
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