THE IRRIGAGE: A NON?EVAPORATING IN?FIELD PRECIPITATION GAGE

Construction details and measurement data associated with a non-evaporating, in-field precipitation gage (the IrriGage) are presented. IrriGages are fabricated using standard pieces of PVC pipe and fittings. A plastic bottle is used to store collected water and is attached to the bottom of the collection barrel. Collected water is only exposed to the atmosphere through the collection barrel via a 9.5-mm drain hole. Evaporative losses from IrriGages were compared to losses from other precipitation collection devices in an in-field device evaporation study during the 2001 summer. During the study period, air temperatures often exceeded 38.C and daily grass-reference evapotranspiration rates exceed 8 mm/day. Evaporation losses from IrriGages were negligible over several weeklong measurement periods, while substantial evaporation losses were associated with standard rain gages and other collection devices.