In this paper a model is proposed for analysing alternative policies that might be used in allocating water in Thailand. The model used is an integration of farm linear programming models with a spatial equilibrium model, using the so-called price-linked farm and spatial model (Batterham and MacAulay, 1994). A method of linking spatial equilibrium models and linear programming representations of farm models via the demand side as opposed to the supply side is outlined in this paper. A case study is made of the Chao Phraya Delta, an area that is progressively challenged by competing claims for water use and which needs to better allocate water resources.