Monsoon flood pulse mobilizes selenium through impaired desert reach
July 20, 2026
In the span of two weeks, streamflow here surged from less than half a cubic foot per second — a channel barely alive — to 231 cubic feet per second, driven by summer monsoon pulses moving through the upper watershed. That kind of whipsaw hydrology is among the most ecologically disruptive sequences a high-desert stream can experience: it is not a gradual rise but a wall of energy that reorganizes the channel almost instantaneously. For a reach already carrying a burden of contamination, the timing could not be more consequential.During low-flow periods, fine sediments settle and contaminants concentrate in the shallow thalweg and streambed deposits — essentially pooling their toxicity in the one thin ribbon of water that aquatic life depends on. When the flood pulse arrives, all of that material mobilizes at once, flushing downstream in a single concentrated slug. Cottonwood Creek, which drains into this reach, carries an official federal impairment designation, and the conditions upstream have made that designation urgently relevant.The gravel pit operation known as Tri County Pit has exceeded its selenium discharge limits in each of the last four consecutive quarters, with the most recent exceedance running more than three times its permitted level. Four straight quarters of exceedance, with the most recent violation at over three times the permitted selenium concentration, directly upstream of a federally impaired waterway now experiencing its largest flow event in weeks. That convergence — chronic noncompliance meeting a high-magnitude flood pulse — is precisely when selenium loading to a downstream system becomes most dangerous.Selenium is insidious in aquatic systems because its toxic threshold sits just slightly above background concentrations, and it bioaccumulates through the food web with particular efficiency. Invertebrates absorb it from sediments; fish and waterbirds concentrate it further up the chain. The documented endpoint is reproductive failure: skeletal deformities in fish larvae, early embryo death in nesting waterbirds. Research following the Kesterson Reservoir disaster in California in the 1980s established the template — selenium at elevated but sub-lethal concentrations in adults produces catastrophic outcomes one generation later, and the damage is often not visible until breeding season reveals it.This corner of the Colorado Plateaus has always been shaped by the rhythm of monsoon pulses — the Ute and their predecessors understood these summer floods as agents of renewal, scouring channels, redistributing nutrients, and triggering spawning runs in native fish. In an unimpaired watershed, that reading holds. But when the channel carries a legacy of contamination from operations like those upstream, renewal and redistribution become the same event. What to watch for next: invertebrate communities in the weeks following this pulse, the behavior of any nesting waterbirds in the canyon corridor, and whether selenium monitoring data from downstream sampling points shows the spike this flood event would predict.
Bold jumping spiders hunt at summer peak
June 28, 2026
The days near Paonia right now are as long as they get. Heat builds off the sagebrush flats by mid-morning, insects are everywhere, and if you look closely at a fence post, a rock face, or the broad leaf of a cottonwood, you may find a bold jumping spider looking back at you.Bold jumping spiders are compact, heavy-bodied hunters, black with white and sometimes iridescent green markings, and rarely longer than a thumbnail. What sets them apart is their eyes. The front-facing pair is enormous relative to their body, and the visual acuity those eyes provide is exceptional among spiders. They can resolve detail and judge distance with enough precision to stalk and pounce on prey from several body lengths away. Unlike web-building spiders, which wait for prey to come to them, bold jumping spiders actively move through their environment: pausing, pivoting, tracking. When a fly lands within range, the spider turns to face it directly, fixes it with those forward eyes, and creeps closer before launching. The jump is controlled and short, and the spider drags a silk safety line as it goes, so a miss does not mean a fall.This is peak season for them. Long days mean more insect activity across more hours, and the spiders track that activity. Around Paonia, they hunt across the sagebrush scrub and the drier rocky margins where insects concentrate on warm surfaces. Ten-lined June beetles are out now, large enough that a bold jumping spider would not attempt one, but the smaller flies, beetles, and moths that share this landscape are fair targets. The cottonwood stag beetle is similarly too large, but its presence signals the kind of decaying wood habitat that also shelters the small insects the spiders do take. Where the invasive broad-leaved sweet pea and purple crownvetch have established themselves along roadsides and disturbed margins, they draw in pollinators, and the spiders hunt at the edges of those patches too, taking whatever arrives. The spiders are not specialists. They take what they can catch.Breeding activity is running alongside all of this hunting. Male bold jumping spiders court females with a precise visual display: the male faces the female, raises and waves his front legs in a specific pattern, and moves side to side. The female watches. Her response determines whether courtship continues or ends abruptly. Vision is the medium of the whole interaction, which makes sense given how much of their lives depend on seeing accurately. Females lay eggs in a silk retreat, often tucked under bark or behind a loose stone, and guard them until they hatch. The young spiders that emerge this summer will spend the rest of the season hunting and growing, overwintering as subadults, and reaching maturity the following year.
