Characteristic of Evapotranspiration from Ground Surface for Cool Dry Seasoi on Zambezi River Flood Plain, Zambia

Abstract

Meteorological observations were made for the Feasibility Study on Rural Development carried out Namushakende area which is situated on the Zambezi River Flood Plain, Western Province, Zambia. On the basis of on the observed findings, evapotranspiration rates from ground surface were estimated in the cool-dry season. The results are summarized as follows;
(1) Hourly evapotranspiration rates calculated using the Bowen Ratio Method required modifications due to unstable results. On the contrary, potential evapotranspiration rates calculated from the Penman equation were quite stable.
(2) At Namushakende, the ratio of daily evapotranspiration rates calculated from the Bowen Ratio Method on daily evapotranspiration from the Penman equation was 0.33. This ratio, which was calculated using meteorological data observed in the dry season, could be judged as a proper value for this period.
(3) It was clear that both values of daily evapotranspiration rates at Namushakende and Mongu Meteorological Station, showed a good correlation. According to the investigations described above, a result of estimation for mean daily evapotranspiration rates at Namushakende for 100 days from March to June was 1.4mm/d.
(4) From the daily fluctuations of the estimated evapotranspiration at Namushakende, it was verified that the evapotranspiration rate at Namushakende did not decrease rapidly at the end of the rainy season and in the cool-dry season. This phenomenon seems to be related to the existence of a springing water source flowing into the eastern plateau, which influence the evapotranspiration rate. Therefore, the role of this underground water can be important for water use planning.