Actual evapotranspiration and canopy resistance measurement of the savannah in the Kouilou basin (Congo-Brazzaville) /Nizinski, Georges /Galat, Gérard /Galat-Luong, Anh BIOCLIMATOLOGIE SAVANE EVAPOTRANSPIRATION CANOPEE SAISON HUMIDE SAISON SECHE EAU DU SOL BILAN HYDRIQUE HUMIDITE DE L'AIR TEMPERATURE METHODE D'ANALYSE MODELISATION MODELE MATHEMATIQUE ETUDE COMPARATIVE RADIATION The aim of this work is to study the actual evapotranspiration and surface resistance of the savannah using the Bowen-ratio method for two contrasted periods, dry and rainy season. The reliability of this method has been assessed by comparison with the Monteith equation and the soil-water balance method in a 90% Loudetia arundinacea dominated savannah (Pointe Noire, Congo). Our results relate to the period from 18 September to 11 October 1998 (24 days): (a) from 18 to 29 September (“dry season”), the soil-water content was less than 70% of the soil-water content at field capacity (63–70% of RFC; large soil-water stress; T/EP from 0.2 to 0.4); (b) from 30 September to 11 October (“rainy season”) soil-water content close to 90–92% of RFC; no soil-water stress; T/EP from 0.73 to 0.77). The mean daily surface resistance reulting from the Bowen-ratio method was 317 s m–1, 355 s m–1 during the “dry season” and 279 s m–1 during the “rainy season”. The total actual evapotranspiration (Ea) resulting from the Bowen-ratio method, Penman-Monteith equation and soil-water balance method were, respectively of 58.6–57.8 and 56.2 mm, with the mean daily Ea of 2.4–2.4 and 2.3 mm day–1 (2.4–1.5 and 2.2 mm day–1 in “dry season” and of 2.5–3.4 and 2.5 mm day–1 in “rainy season”). The Bowen-ratio method was used for the assessment of the actual evapotranspiration from the temperature and specific humidity differences, net radiation and the soil heat flux measurement: its advantages are a rapidity of installation, a temporal resolution of measurement in less than one hour and a good integration of the heterogeneousness of the savannah’s latent flux of vaporization. This method is adapted to ecophysiological studies in tropical conditions with reduced teams. 2014 text https://www.documentation.ird.fr/hor/fdi:010062733 fdi:010062733 Nizinski Georges, Galat Gérard, Galat-Luong Anh. Actual evapotranspiration and canopy resistance measurement of the savannah in the Kouilou basin (Congo-Brazzaville). 2014, 45 (5), 359-366 EN CONGO POINTE NOIRE