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Katholieke Universiteit Leuven (2018)

Estimation of evaporation and transpiration in the semi-arid Makanya catchment in Tanzania from measurements of soil water balance components in the field

Buluma, Melinda Nyangu

Titre : Estimation of evaporation and transpiration in the semi-arid Makanya catchment in Tanzania from measurements of soil water balance components in the field

Auteur : Buluma, Melinda Nyangu

Université de soutenance : Katholieke Universiteit Leuven

Grade : Master of Water Resources Engineering 2018

Résumé
The agricultural production in the semi–arid Makanya catchment, Tanzania is predominately rainfed alongside supplementary irrigation. The rainfall patterns experience inter- and intra- seasonal variability inducing water scarcity. The area also experiences excessive unproductive water losses through soil evaporation and deep percolation. Therefore, the estimation of evaporation and transpiration is fundamental to determine the best management practices to increase crop productivity under water scarcity. Estimation of evapotranspiration on maize plots for three different agricultural management practices was carried out using the soil water balance method in Bangalala village during March-April, 2018 through field measurements. The treatments were : flat cultivation with mulching, double digging and flat cultivation. The estimated evapotranspiration was partitioned into evaporation and transpiration. The evaporation was estimated using measurements from microlysimeters. Using the Darcy-Buckingham equation, deep percolation losses were estimated from tensiometry data and measured soil hydraulic properties. The results showed that there was variability in rainfall across the maize season and the dry period was during the beginning of May. The total seasonal rainfall at the field was 133 mm. However, the variability in the seasonal evapotranspiration mimicked that of rainfall. The seasonal actual evapotranspiration estimated on the maize plots for the three treatments was : 181 mm for flat cultivation with mulching ; 195 mm for double digging and 187 mm for flat cultivation plots. Across treatments, the plots with mulching had the least soil evaporation and highest transpiration throughout the season. The partitioning of ET into its components was also influenced by agricultural crop management. The E and T in the treatments were : E= 41 mm, T= 139 mm for flat cultivation with mulching ; E= 62 mm, T= 133 mm for double digging and E= 62 mm, T= 125 mm for flat cultivation.

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Page publiée le 10 décembre 2018