AbstractChanges in montane meadow vegetation were examined in a previously ephemeral drainage that received flow augmentation as a mitigation measure for a transbasin diversion in southeastern Wyoming. After two years of elevated surface and groundwater levels, the herbaceous vegetation shifted toward more water‐tolerant species. Dry meadows became like moist meadows, moist meadows became more like moist‐wet meadows, and moist‐wet meadows became more like wet meadows. Sedge (Carexspp.) biomass increased from 337 to 456 g m−2in the wet meadows, while tufted hairgrass (Deschampsia cespitosa) biomass decreased from 18 to 3 g m−2in the moist‐wet meadows. Slimstem reedgrass (Calamagrostis neglecta) remained unchanged in the meadows with shallow standing water, but increased from 17 to 88 stems m−2in the dry meadows with an elevated water table. Bare ground also increased as much as 31 per cent in the meadows without a defined dra