Field scale quantification indicates potential for variability in return flows from flood irrigation in the high altitude western US

•29 % of irrigation water and precipitation returned to surface water, 18 % went to storage, 20 % went to riparian ET, and 23 % went to ET from hay crops.•18 % of return flows occurred after the cessation of irrigation; more than the median of 14 % across comparable studies.•Decoupling of return flow quantity, timing; comparatively lower total return flows (29 %) corresponded with higher late-season flows (18 %).•Flood irrigation via measured return flows supports three key hydrologic ecosystem services: soil water storage, riparian vegetation, and late-season baseflow.•Underscores potential for both benefits and tradeoffs in local and regional alterations to irrigation management in the intermountain west.