Evaluation of the Sparse Gash interception model in a Pinus eldarica plantation located in a semi-arid climate zone

Research of the rainfall intercepted by trees is crucial in the management of water resources of afforestation in arid and semi-arid regions. The goal of this study was to evaluate the Sparse Gash model for estimation of rainfall interception (I) in a mature Pinus eldarica afforestation located in the Chitgar Forest Park in a semi-arid climate zone. Measurements of gross precipitation (P_G) and throughfall (TF) were recorded on an event basis from 2009, September to 2010, April. I was calculated as the difference between P_G and TF. Estimation of I was made by the Sparse Gash model, a powerful tool for estimating I, which uses canopy water storage capacity (S), free throghfall (p), and the ratio between evaporation rate from the wet canopy to the mean rainfall intensity (). For the measurement period, P_G totaled 164.8 mm during 30 rainfall events and rainfall interception loss totaled 61.2 mm. The model predicted I to be 62.19 mm for all the storms analyzed. This only differed from the measured I (61.2 mm) by 0.99 mm. A linear significant relationship (r² = 0.8772) was found between estimated I by the model and the measured I. Root mean square error (RMSE) of the estimation was 0.49 mm in a storm scale corresponds to 23.7% error. We concluded that the Sparse Gash model successfully predicted I for P. eldarica afforested regions of the semi-arid climate zone of Iran where a field measurement of rainfall interception is time-consuming and laborious.