Redução de evapotranspiração em reservatórios artificiais.

Abstract

The objective of this work is to show a practical techinique capable of reducing water tosses by evaporation in a reservoir. The techinique consists in covering the evaporative surface with plastic screens. Solar radiation or heat reaching the water surface is reduced and, as a consequence, the water vapour pressure gradient too. The field experiment is dirided in two phases; from March 28 to Aphl 25 1999, using white screen, and from May 1st to May 13 1999, using green screen. Wind speed at 0.5 and 2.0 m above the evaporative surface and evaporative losses in thee tanks ( screen-covered, uncovered and class A) are measured in both phases. Water surface and air temperatures, global solar radiation over and under the plastic screen, net solar radiation and relative humidity are obtained using an automatic data acquisition system MICROLOGGERS 21x, at 3 - hour intervals ( 06:00, 09:00, 12:00, 15:00 and 18:00 SLT) during the first phase and at 6 - hour intervals during the second one. Results show reduction in potential evaporation (PE) to be 25% in the white screen case and 37% in the green one, thereby showing the technique to be successful in reducing PE in spite of the limitations of this study.