Modeling the water balance of a ruminant production system in the semi-arid region

In the Brazilian semi-arid region, most cattle properties that use small dams as a source of water are unaware of the water balance of this system, which makes it difficult to plan and use this resource rationally. In this context, the objective was to demonstrate the impact of water consumption from a ruminant production system in a small reservoir. The water use model was developed using the Vensim PLE™ software for a hypothetical farm located in Petrolina, Pernambuco State, Brazil. The reservoir capacity and evaporation, infiltration and runoff rates were estimated from the literature and rainfall was estimated using the probability density function in the @RISK© software. The use of irrigation, water consumption of the family and farm, and water consumption by goats, sheep and cattle were estimated from the literature. In the horizon of 30 years, in only five of these the maximum capacity of the reservoir was reached. In the most demanding water scenarios, years are observed in which the reservoir dries up completely, making animal production unfeasible. Using the proposed model, it was possible to estimate, using real indicators, combinations to find the best way to use water, depending on the type of herd and the use of irrigation.