In the western plains of Venezuela, was recently launched significant growth in intensive agriculture. Therefore, determining the availability of water to satisfy the demand for maize (Zea mays L.) is essential as a tool for the entities responsible for the management of this resource in the area. With the available information on studies and projects in the area related to climate, soil and water in the region, a methodology was established to assess the availability of water for growing crop (Zea mays L.) along rivers and Boconó Masparro in Barinas and Portuguesa. Net irrigation requirements (NIR) crop using CROPWAT were determined using information from weather and soil textural classification of the area. It was found that all NIR combinations tested did not exceed the 6 mm.mes-1. A map of the NIR was developed, resulting in these concentrated in the center of the map, near the river Boconó. According to the availability of water and NIR, we can say that the demand for water in the region of maize is satisfied.