Farming is a major livelihood in Abra. In a desire to have sufficient harvest and higher crop production, the farmers depend mostly on irrigation. The study aimed to describe the operation of the irrigation system in Lagangilang, Abra, identify the constraints aﬀecting the system; and develop a mathematical model for the optimization of the irrigation system. The study utilized the developmental methods of research to formulate a mathematical model that will ecologically optimize irrigation water service in the municipality. The irrigation system supplies water to the farmlands and optimized as follow: 10.8 L/s is optimized to irrigate the total land area of Pawa-Presentar; 38 L/s for Nagtupacan headgate 1 and 2.47 L/s for its second headgate; 2.65 L/s for Dalaguisen headgate 1 and 3.05 L/s for its second headgate; and 0.8 L/s for Bio, San Isidro; (5) at the given maximum rates and land areas, Pawa-Presentar farmlands can be irrigated with 3.26days or 78.23hours; Nagtupacan within 0.71days or 17.02 hours; Dalaguisen within 70.17 hours in headgate 1 and 28.6 hours in headgate 2; and Bio, San Isidro within 4.30 days or 103.24hours.