Technology (drip irrigation) and environmental impact (SWAT modeling) components of "Agroforestry and Sustainable Vegetable Production in Southeast Asian Watersheds" project

Abstract

Over the past twelve (12) months of year 3 of project implementation, significant progress has been made on the drip irrigation technology and environmental impact (SWAT modeling) components of this project in the Philippines. Laboratory experiments on drip irrigation were conducted at the College of Engineering and Agro-industrial Technology, University of the Philippines Los Baños from October to December 2007 to determine the effect of slope and head on the water distribution uniformity of a 100 sq. m IDE drip irrigation system. The drip system was operated at pre-specified heads of 1 m, 2 m and 3.0 m from the reservoir outlet for slopes of 0%, 10%, 20%, 30%, 40% and 50% for the sub-main and 0% slope for the laterals. Results showed that the water distribution uniformity of the low-cost drip irrigation kit developed by the International Development Enterprises (IDE) is influenced by hydraulic head and slope. The coefficient of uniformity UC and the emission uniformity EU generally increase with increasing heads and decrease with increasing slope. The coefficient of uniformity generally followed a linear relationship with either head or slope. The UC and EU decrease substantially at submain slopes steeper than 30%. For level surface, a head differential of 0.5 m does not cause significant change in either UC or EU. For all slopes, a head of 3.0 m with respect to the junction of the most upstream lateral may be considered to be optimum from both hydraulic and practical standpoints. Linear regression models relating UC and either head or slope may be used for predicting water distribution uniformity for heads between 1.0 m and 3.0 m and for slopes between 0% and 50%.