Simplified Interception/Evaporation Model

Giorgio Baiamonte

doi:10.3390/hydrology8030099

Abstract

It is known that at the event scale, evaporation losses of rainfall intercepted by canopy are a few millimeters, which is often not much in comparison to other stocks in the water balance. Nevertheless, at yearly scale, the number of times that the canopy is filled by rainfall and then depleted can be so large that the interception flux may become an important fraction of rainfall. Many accurate interception models and models that describe evaporation by wet canopy have been proposed. However, they often require parameters that are difficult to obtain, especially for large-scale applications. In this paper, a simplified interception/evaporation model is proposed, which considers a modified Merrian model to compute interception during wet spells, and a simple power-law equation to model evaporation by wet canopy during dry spells. Thus, the model can be applied for continuous simulation, according to the sub hourly rainfall data that is appropriate to study both processes. It is shown that the Merrian model can be derived according to a simple linear storage model, also accounting for the antecedent intercepted stored volume, which is useful to consider for the suggested simplified approach. For faba bean cover crop, an application of the suggested procedure, providing reasonable results, is performed and discussed.

Highlights

Hydrology 2021, 8, 99. https://According to Brutsaert [1], the interception process is determined by the rainfall fraction that moistens vegetation and that is temporarily stored on it, before evaporating.When the vegetation cover is fully saturated, the interception storage capacity is achieved.In practice, the interception storage capacity is denoted as rainfall left on the canopy at the end of the rainfall after all drip has ceased [2]
We explored the rainfall partitioning in net rainfall and evaporation losses by canopy, by using a very simplified sketch of the interception process, which
In order to derive the evaporation losses by wet canopy, the suggested procedure combines a modified interception model proposed by Merrian, which is applied during rainfall wet spells, and a simple power-law equation to model evaporation during the dry spells

Summary

Introduction

Hydrology 2021, 8, 99. https://According to Brutsaert [1], the interception process is determined by the rainfall fraction that moistens vegetation and that is temporarily stored on it, before evaporating.When the vegetation cover is fully saturated, the interception storage capacity is achieved.In practice, the interception storage capacity is denoted as rainfall left on the canopy at the end of the rainfall after all drip has ceased [2]. According to Brutsaert [1], the interception process is determined by the rainfall fraction that moistens vegetation and that is temporarily stored on it, before evaporating. The water stored on the canopy may evaporate soon after, short-circuiting the hydrologic cycle. Most surfaces can store only a few millimeters of rainfall, which is often not much in comparison to other stocks in the water balance, interception is generally a significant process and its impact becomes evident at longer time scales [3]. Interception storage is generally small, but the number of times that the storage is filled and depleted can be so large that the evaporation losses by wet canopy may become of the same order of magnitude as the transpiration flux [4]

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Methods

Conclusion