tailieunhanh - Potential evapotranspiration estimation and its effect on hydrological model response

The approach requires data on the land cover and related-vegetation parameters based on AVHRR and LDAS information, which are available in recent years. The Nong Son basin, a sub-catchment of the Vu Gia-Thu Bon basin in the Central Vietnam, is selected for this study. | V ietna m Jo urnal of Mechanics, VAST , , No . l (2008), pp. 20 - 32 POTENTIAL EVAPOTRANSPIRATION ESTIMATION AND ITS EFFECT ON HYDROLOGICAL MODEL RESPONSE Vu Van Nghi 1 State Key Laboratory of Hydrology, Water Resources and Hydraulic Engin eering, Hohai University, no. 1 Xikang Road, Nanjing 210098, China Do Due Dung, Dang Thanh Lam Southern Institut e for Water Resources Planning, 271/3 An Duong Vuong Street, District 5, Ho Chi Minh City, Vietnam Abstract. Potential evapotranspiration can be directly calculated by t he Penman-Monteith equation , known as the one-step method. The approach requires data on the land cover and related-vegetation parameters based on AVHRR and LDAS information, which are available in recent years. The Nong Son basin, a sub-catchment of t he Vu Gia-Thu Bon basin in the Central Vietnam, is selected for t his st udy. To this end , NAM model was used; the results obtained show that the NAM model has the potential to reproduce the effects of potential evapotranspiration on hydro logical response. Th is is seemingly manifested in t he good agreement between model simulation of discharge a nd the observed at the stream gauge. Keywords: Potential evapotranspiration, Penman-Monteit h method, Piche evaporation, Lea f area index (LAI) , Normalized difference vegetat ion index (NDVI) 1. INTRODUCTION One of the key inputs to hydrological modeling is potenti al evapotranspiration, which refers to maximum ~eteoro lo gically evaporative power on land surface. Two kinds of potential evapotranspiration are necessary to be defined: either from the interception or from the root zone when the interception is exhausted but soil water is free ly available, specifically at fi eld capacity (see [10], [32]) . The actual evapotranspiration is distinguished from the potenti al through the limitations imposed by the water deficit. Evapotranspiration can be directly measured by lysimeters or eddy correlation met hod but expensively and practically only in