ESTIMATES OF MONTHLY AND ANNUAL EVAPORATION RATES AND EVAPORATED VOLUMES PER UNIT TIME IN THE TUCURUÍ-PA AND LAJEADO-TO HYDROELECTRIC POWER PLANT RESERVOIRS BASED ON DIFFERENT METHODS

ABSTRACT Evaporation rates in reservoirs influence the volume of water available for multiple uses. Thus, the objective of this study was to estimate the evaporation rates and the evaporated volumes per unit time in the Tucuruí-PA and Lajeado-TO reservoirs based on the methods in Linacre (1993), Kohler et al. (1955), Morton (1983), Bruin & Keijman (1979) and Penman (1948) method was adopted as the standard. The mean annual evaporation rates in the Tucuruí and Lajeado reservoirs, estimated by the Penman method, were similar, with values of 1,784 mm and 1,882 mm, respectively. None of the alternative analyzed methods could be used to estimate the mean annual evaporation in the Tucuruí and Lajeado reservoirs and could not replace the Penman method. However, the Linacre (1993) and Bruin & Keijman (1979) methods could be used to estimate monthly evaporation during the dry season in Tucuruí. The mean evaporated volume per unit time and the mean net evaporated volume per unit time in the Tucuruí reservoir correspond to 120% and 50%, respectively, of the total water demand in the Tocantins-Araguaia region, while the mean evaporated volume per unit time and the mean net evaporated volume per unit time in the Lajeado reservoir correspond to 120% and 50%, respectively, of the total water demand in the basin.

摘要 水库蒸发速率影响可用于多种用途的可用水资源总量。据此，本研究旨在以彭曼（Penman，1948）方法为标准方法，结合莱纳克（Linacre，1993）、科勒等（Kohler et al.，1955）、莫顿（Morton，1983）、布鲁因与凯伊曼（Bruin & Keijman，1979）提出的方法，估算图库鲁伊-帕拉州（Tucuruí-PA）与拉雅多-托坎廷斯州（Lajeado-TO）两座水库的蒸发速率及单位时间蒸发量。经彭曼方法估算，图库鲁伊与拉雅多水库的年平均蒸发速率分别为1784毫米与1882毫米，二者数值相近。本次分析的其余替代方法均无法用于估算两座水库的年平均蒸发量，亦无法替代彭曼方法。不过，莱纳克（1993）与布鲁因与凯伊曼（1979）提出的方法可用于估算图库鲁伊水库旱季的逐月蒸发量。图库鲁伊水库的单位时间平均蒸发量与单位时间平均净蒸发量，分别相当于托坎廷斯-阿拉瓜亚地区总需水量的120%与50%；而拉雅多水库的单位时间平均蒸发量与单位时间平均净蒸发量，则分别相当于该流域总需水量的120%与50%。