Hatches on any river will vary quite a bit from year to year and stretch to stretch. Typically on the Yakima hatches of most small Mayflies, small Caddis and Summer Stones will be stronger in the lower river and Green Drake, Golden Stone and Salmon Fly hatches will be stronger in the upper river. March Browns and Cahills tend to be more prolific in the middle stretch and October Caddis stronger in the middle and upper river.
Low water flows in the faster, freestone section below the lower hatchery diversion have significantly hurt the hatches in this stretch, this includes Sulfers, Tricos, BWOs, PMDs, Caddis and Mahogany Duns. Slow water Hatches above the diversion remain strong, this includes Callibaetis, Midges and Damsels.