University of Twente Student Theses


Influence of Different Reference Evaporation Methods on the Estimated Soil Moisture for Agriculture in the Netherlands during Drought Periods

Habimana, Claude (2020) Influence of Different Reference Evaporation Methods on the Estimated Soil Moisture for Agriculture in the Netherlands during Drought Periods.

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Abstract:Different methods for assessing reference evaporation (ETo) can significantly affect the performance of land surface models in estimating the soil water dynamics. An accurate understanding of the influence of different reference evaporation methods is crucial for agriculture management decisions. Three ETo methods are discussed: One is based on the reference evapotranspiration presented in FAO-56 paper and is denoted FAO-Penman Monteith (FAO-PM). It is internationally recognized and ranked as the best method for the all-weather condition. The second is the modified Makkink reference evaporation based method. It is the standard method of the Royal Dutch Meteorological Institute (KNMI). The last one is DeBruin Method (here referred to as DeBruin-2016), it is a new remote sensing-based evapotranspiration method which is intended to present an estimate of the reference evapotranspiration from the reference area of grass growing in a wide field. In this study, these methods have been used to estimate the reference evaporation on 30 stations around The Netherlands for the period of 2018. The result indicated significant differences between these methods. In dry conditions, FAO-PM tends to overestimate the reference evaporation compared to the other two methods. The Makkink and De Bruin-2016 methods systematically showed almost the same estimation values of ETo. These different reference evaporation (ETo) forces the hydrological models. However, the national hydrological model (LHM) requires gridded data map of ETo. Therefore, Inverse Distance Weighting (IDW) interpolation method was applied to estimate the grid map. Furthermore, the national hydrological model (LHM) couples MetaSWAP and MODFLOW to simulate the rootzone soil moisture based on the three types of reference evaporation. The result indicated that the simulated soil moisture values for both Makkink and DeBruin method are higher than that of Penman-Monteith, except some months of the winter period (January and February). The soil moisture simulated based on Penman-Monteith depleted faster in the dry season than that of the other two methods. In comparison with the in situ measurement of the Raam soil moisture network, the result indicated that the soil moisture simulated based on the Penman-Monteith are in closer agreement with the in situ measurement at 20 cm depth during the growing season defined from April 1 to October 31, 2018.
Item Type:Essay (Master)
Faculty:ITC: Faculty of Geo-information Science and Earth Observation
Programme:Geoinformation Science and Earth Observation MSc (75014)
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