A water management approach commonly used by cotton growers in the Condamine - Lower Balonne catchment area is to divide farm storages into several cells. The strategy aims to reduce evaporative losses by minimising surface area for a given total volume. Cells are nominally 4 in high with a 3 in water depth. Water losses are further reduced by having cells of various sizes, so that water can be stored in the combination of cells that best minimises surface area. Cotton growers face a move towards deeper cells. Current storages can be deepened, but at a cost, or any new storages can be built for a greater depth. Through the use of computer modelling techniques, we have aimed to quantity the impact of water storage depth on cotton production in the study area. It explores the efficacy of different water management practices on increasing cotton production or decreasing water lost due to evaporation. This study explains some of the factors involved so that better decisions can be made regarding water management.