Evaluation of some practical methods of estimating evapotranspiration in arid climates at low latitudes

A comparison is presented of monthly evapotranspiration data obtained by various methods for the valley of the Ruzizi (Eastern Congo Republic). Best agreement was noted for evaporation, as measured with a pan and calculated with Penman's equation. The Blaney‐Criddle and the Thornthwaite methods did not have an adequate response to changes in evaporation potential, since temperature and day length varied little. Some improvement was observed with the Blaney‐Morin method, which includes a humidity factor.