A Comparison of Trends in Potential and Pan Evaporation for the Canadian Prairies

Abstract

Comparisons are made between potential evaporation trends and pan evaporation trends for a collection of sites on the Canadian Prairies. Trends are analyzed using the non-parametric Mann-Kendall test. There are many similar trend results, but most of these indicate no trend for either measure of evaporation. Seven cases (out of 53 in total) show matching significant trends, six of which are decreasing trends. One case shows opposing significant trends with an increasing pan evaporation trend and a decreasing potential evaporation trend. Despite the opposing trends, time series plots of pan and potential evaporation show similar timing of maximum and minimum values. Wind speed exerting an influence on potential evaporation and not on pan evaporation was the most common explanation for discrepancies between pan and potential evaporation trends.