Interstate Collaboration in the Arkansas River Compact Compliance Process: The "Nuts and Bolts" of Developing PET for Canal Service Areas for Input to the H-I Model

The Hydrological-Institutional (H-I) Model is a computer model used to determine compliance with the Arkansas River Compact. The States of Kansas and Colorado complete an annual update of the model to compute the effects of well pumping on Stateline river flows. The annual update process requires the two States to agree on the crop mix, weather data and potential evaporation (PET) estimates for the canal service areas (among other things). The H-I Model is highly sensitive to the crop evapotranspiration input, so the update of this input data set is given particular attention by both States. This paper describes the evolution of the PET estimates over time, and the steps involved in the annual update process, emphasizing the collaboration and cooperation that occur in order to reach a final PET data set.