Abstract. In Indonesia, water is public goods so it is necessary to control water allocation. Inequity of water allocation between water users is expanding largely, including irrigation as the largest user, while the density of headworks in the river are getting higher. Considering that water is limited, the practice of irrigation water allocation needs to be refined, from the traditional equity to volumetric equity. MEQAA (Model Equalisasi Alokasi Air/Equalization Model of Water Allocation) plays a role in determining water sharing between headworks in order to meet the maximum-equal K-factor in river. MEQAA-Generic is a calculation machine with: analog-deterministic dynamic model; network equation according to mass balance and linear optimization; independent-based system; sustainability-efficiency-equity constraints; Ms. Excel-VBA. The inputs are: scheme system, local inflow, and irrigation demand. The outputs are: K-factor, release and ecosystem quote. The model performance is identified by comparing the output to the class of K-factor based on treatment of water distribution. The model test is performed in an uncontrolled and complicated system in Kukusan Tanggek watershed with 24 headworks in Lombok river basin. As long as it is adequate for water sharing, MEQAA-G can always produce maximum-equal K-factor. The output model is used to operation control.

Limitation and inequality of water in interspace and time opposite to the increased water demand indicated from the density of headwork nodes in the river system. It requires proportional-equal water allocation determined by the model. Existing models are not based on water as a public good and not using the sustainability-efficiency-equity criteria despite irrigation is the biggest use. The Water Allocation Model Equalization or in Indonesian it is called “Model Ekualisasi Alokasi Air” (MEQAA) is proposed. MEQAA modeling system is inspired by the shortage of irrigation water for a quite extended period of time and the complexity of the water allocation system in the Lombok river basin. MEQAA is assisted by MS Excel-VBA 2016 that can be tracked automatically on an independent river system scheme to create a network equation with mass balance principle and operation rule. This model is based on the dynamic-deterministic, so the performance test can be used with synthetic data. This experiment was compared with the output from the equalization method and the “first-come, first-served” (FCFS) method. The conclusions of this experiment are: (a) MEQAA can build a specific model according to a network-flow configuration for optimization-simulation with iteration of K-factor (release portion) and C-factor (storage portion) in order to get a maximum and equal and (b) the FCFS method can be detrimental to the river system. MEQAA is suggested as a decision support tool for water allocation planning or real-time operation.