South Platte at 110 cfs: Caddis Window Opens as Drought Looms Upstream

What's Biting

What's Next

With the South Platte running 110 cfs as of the pre-dawn May 4 reading at USGS gauge 06701900, both rivers are in their most fishable pre-runoff window. Flows at this level keep the main channel accessible on foot, with trout stacked in the seams between fast water and slow and in the calmer water behind mid-channel boulders. No weather data accompanied this gauge pull — check the local forecast before heading out, particularly as afternoon convective storm activity begins to increase across Colorado's mountain corridors through May and can push flows upward quickly.

The next two to three days look like a prime caddis-watch period. Hatch Magazine's piece on caddis emergences notes how these insects can trigger an abrupt shift in trout behavior — from subsurface nymphing to aggressive dry-fly feeding — once water temperatures climb into the right range. On both the South Platte and Arkansas tailwaters, that transition typically develops through the first two weeks of May. Carry elk hair caddis in sizes 16–18, along with soft-hackle wets and emerger patterns, to bridge the moment when fish begin looking up.

Midges will continue to dominate early-morning sessions. Per MidCurrent's Tying Tuesday this week, sparse midge patterns designed specifically for "the clear, pressured water of stillwaters and tailraces" are the right tool for this phase. A two-nymph rig with a midge larva or pupa fished near the bottom in two to four feet of water is the most consistent morning approach at these flows. Field & Stream's recent guide to aquatic insects for trout anglers confirms that midges, alongside mayflies and caddisflies, form the core of a trout's spring diet — all three are in play to varying degrees on these rivers right now.

The waning gibbous moon (May 4) provides meaningful overnight illumination. Trout that feed hard under a bright moon can arrive at dawn slightly less aggressive than on dark nights — plan your arrival before first light to catch the window when midges cluster in the surface film and fish move into tailouts to feed. Blue-winged olive activity, more likely when skies cloud over, can extend good fishing from mid-morning into early afternoon.

One item worth tracking for the longer season: MidCurrent reports that the Tolland Ranch acquisition in Colorado is expanding fly-fishing access to previously private water in 2026 — new public beats that may shift angling pressure across the state's trout rivers as the season develops.

Context

Early May is historically one of the most deliberate target windows on Colorado's tailwater fisheries. Flows at 110 cfs on the South Platte sit within the normal mid-spring range — below the runoff push that typically arrives with peak snowmelt in late May and June — making this a stable pre-runoff window that experienced Colorado trout anglers often prioritize specifically. The Arkansas tailwaters tend to hold steadier regulated flows through the season by comparison, offering a secondary option if the South Platte begins to rise with snowmelt.

The Antero Reservoir news from Hatch Magazine is genuinely unusual in the recent history of Colorado fishing. The reservoir sits in South Park at the top of the South Platte River drainage, and Denver Water's announced plan to completely drain it represents a loss of one of the region's more storied trophy trout destinations. While the direct hydraulic effect on the main tailwater sections is buffered by additional impoundments, the loss of that fishery will likely shift angler traffic toward the remaining tailwater beats over the coming seasons — a pressure change worth anticipating.

On the hatch calendar, early May is typically the inflection point when the midge-dominated late-winter pattern begins yielding to a more complex sequence. Blue-winged olive hatches are often already established by now, and the first caddis activity typically builds through mid-May at the elevations common to both corridors. Field & Stream's recent aquatic insects primer covers this seasonal transition clearly. No local shop or on-the-water source was available in this data pull to confirm precise hatch timing for this specific week on either river, so treat the entomology framing as typical seasonal context rather than direct on-the-ground testimony.