Development of appropriate water management strategies in the context of projected air temperature increases under a changing climate necessitates assessing how increases in atmospheric demand for water might constrain future water availability. This is most easily assessed using estimates of potential evaporation (PE). Most temperature-based methods for estimating PE have been calibrated in different landscapes in more southern locations using a singular calibration coefficient. This study assessed whether regionally calibrated temperature-based models improve estimates of PE in Ontario and whether further improvements could be made by adjusting coefficients monthly to address a marked seasonality in Ontario or spatially to address the province’s size and varied landscape. Monthly calibration coefficients were calculated for four temperature-based methods (Thornthwaite, Blaney–Criddle, Hamon and Hargreaves–Samani) using climate data and evaporation estimates from 18 pan evaporation stations in Ontario. Calibrated models were then evaluated against an additional 19 pan evaporation stations by comparing estimates of PE calculated using the adjusted and literature-derived coefficients with pan evaporation estimates. Finally, PE estimated using adjusted coefficients was compared to evaporation (E) estimated using a water balance approach for 64 watersheds across Ontario. As anticipated, the regional calibration process increased the accuracy of the PE estimates relative to those calculated using published model coefficients. Use of monthly model coefficients addressed the marked seasonality of evaporation in Ontario and resulted in improved PE estimates. Adjusted model coefficients varied spatially but the paucity of measurement stations precluded further regionalization. PE estimates improved using adjusted coefficients, varied less between models, and were highly correlated with water balance estimates of E. The Hargreaves–Samani model produced the best estimates of PE using unadjusted and adjusted coefficients and was most highly correlated with long-term water balance estimates of E.

在气候变化的情况下预计气温升高的背景下制定适当的水管理策略，有必要评估大气对水的需求增加如何限制未来的水供应。最容易使用潜在蒸发量（PE）进行评估。大多数基于温度的PE估算方法已使用奇异的校准系数在更南部地区的不同景观中进行了校准。这项研究评估了基于区域校准的基于温度的模型是否可以改善PE的估计值在安大略省以及是否可以通过每月调整系数以解决安大略省明显的季节性问题或在空间上解决该省的规模和多样的景观来进行进一步的改进。使用来自安大略省18个蒸发皿蒸发站的气候数据和蒸发量估算值，对四种基于温度的方法（Thornthwaite，Blaney–Criddle，Hamon和Hargreaves–Samani）计算了每月校准系数。然后，通过将使用调整后的和文献得出的系数计算出的PE估计值与锅蒸发估计值进行比较，针对另外的19个锅蒸发站点对校准后的模型进行评估。最后，将使用调整系数估算的PE与蒸发量（E）使用水平衡方法对安大略省64个集水区进行了估算。如预期的那样，相对于使用已发布的模型系数计算出的PE估计值，区域校准过程提高了PE估计值的准确性。每月模型系数的使用解决了安大略省明显的蒸发季节，并提高了市盈率估计值。调整后的模型系数在空间上有所变化，但由于测量站的匮乏，无法进一步进行区域划分。PE估计值使用调整后的系数得以改善，模型间变化较小，并且与E的水平衡估计值高度相关。Hargreaves–Samani模型产生了最佳的PE估计使用未经调整和调整后的系数，并且与E的长期水平衡估算值高度相关。