TITLE:
Influence of Potential Evapotranspiration on the Water Balance of Sugarcane Fields in Maui, Hawaii
AUTHORS:
Javier Osorio, Jaehak Jeong, Katrin Bieger, Jeff Arnold
KEYWORDS:
Evapotranspiration, Water Balance, Hydrological Modeling, Sugarcane, SWAT
JOURNAL NAME:
Journal of Water Resource and Protection,
Vol.6 No.9,
June
26,
2014
ABSTRACT: The year-long warm temperatures and other climatic characteristics of the
Pacific Ocean Islands have made Hawaii an optimum place for growing sugarcane;
however, irrigation is essential to satisfy the large water demand of
sugarcane. Under the Hawaiian tropical weather, actual evapotranspiration (AET)
is the primary mechanism by which water is removed from natural and
agricultural systems. The Hawaiian Commercial and Sugar Company (HC&S), the
largest sugarcane grower of the Hawaiian Islands, has developed a locally
optimized AET equation for the purpose of water management on its 184.3 km2 sugarcane plantation on the Island of Maui. In this paper, in order to assess
the influence of AET on the hydrological water balance of the HC&S’
sugarcane cropping system, the performance of the HC&S method was compared
with three physically-based methods: Penman-Monteith, Priestley-Taylor, and
Hargreaves, as well as, to a set of historical pan evaporation data. A Soil and
Water Assessment Tool (SWAT) project was setup to estimate the water balance in
two sugarcane fields: a windy lowland field and a rocky highland field on a
hill slope. Under Hawaiian weather conditions, wind speed was found to be the
most influential climatic parameter over potential evapotranspiration (PET);
therefore, the results with both Hargreaves and Priestley-Taylor underpredicted
PET by approximately 30%, presumably because these methods do not take wind
speed into account. The HC&S method was demonstrated to be the most
accurate PET method compared to the other commonly used PET equations, with
less than 10% error. Of the annual total water supply of 3400 mm, AET accounted
for 75% - 80% of the total water consumption. These findings can be used to
improve the irrigation efficiency as well as other management scenarios to
optimize water use on the Island of Maui.