Calibration and comparison of forest canopy interception models

Author(s): Linhoss, A.; Siegert, C.; Levia, D.

Rainfall interception by the forest canopy plays an important role in the water budget by removing water from the terrestrial hydrologic cycle. Effective models of canopy interception are critical for simulating the water budget and river flows. Over the years, several models have been developed to simulate canopy interception. Few comparative studies have been conducted that assess how well these models simulate measured interception. The objective of this study was to compare five mechanistic canopy interception models including the Rutter, Rutter Sparse, Gash, Sparse Gash, and Liu models. Each model was calibrated independently using PEST, and automatic parameter estimation routine. The five models were calibrated for American beech and yellow-poplar stands as well as under leafed and unleafed conditions. Overall, the models behaved somewhat similarly. Cumulative error ranged between 0.0% and 14.9%. The models were also assessed for their ability to accurately simulate interception during individual rainfall events. The coefficient of determination (R2) between measured and modeled interception events ranged between 0.21 and 0.48. An important reason for the low R2 values is the fact that the models were unable to simulate very low or very high levels of interception. Measured interception ranged between 0.2 and 12.2 mm while modeled interception only ranged between 1.2 and 6.9 mm. These results indicate an important gap in our ability to simulate a substantial portion of the water budget.

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