资源环境科技发展态势分析平台

Different formulas have been developed to estimate the mean annual evapotranspiration ratio (E/P) from the mean annual aridity index (E-p/P) based on the Budyko framework. A major challenge in using the Budyko framework for the interannual behaviors of a catchment is the missed storage. Here we develop a null-parameter formula of the storage-evapotranspiration relationship based on the simplified proportionality hypothesis, which takes the storage in the soil-plant-atmosphere continuum as the accessible water for the evapotranspiration processes. In this formula, the annual E/P depends on the annual E-p/P and S/P values where S is the soil-plant-atmosphere continuum storage. An annual water balance model including groundwater storage is required to estimate the annual runoff and S/P. We develop a new conceptual hydrological model with only three parameters in addition to the null-parameter formula. The model performs well in the case study of the North Loup River Basin in Nebraska. It is found that the annual E/P increases with the increasing E-p/P around a path that is different from conventional Budyko curves. For mean annual water balance, the triparameter model results in one-parameter formulas to estimate both of the mean annual E/P and S/P so that the status of storage can be included in the Budyko framework. This study presents a new simple approach to investigate the interannual variability of catchments with varying dryness.