This study applies contingent valuation to assess farmers' willingness to trade irrigation water. We analyse farmers' willingness to pay for water and their willingness to accept the selling of water through a seasonal market, under both normal rainfall and drought conditions. A survey of 241 farmers (irrigators and non-irrigators) in the Guadalquivir River Basin and in the Mediterranean (Almanzora) Basin in southern Spain is used as a basis to construct the irrigation water supply and demand curves for both basins. Assuming that each basin operates as a single country, an international commerce framework is applied to study inter-basin trading. Results show that there is scope for both intra-basin and inter-basin markets. The equilibrium market price increases from 0.17 EUR/m3 in the baseline scenario to 0.21 EUR/m3 under drought conditions. These results are in line with observed market prices during 2006–2007. We also find a threshold volume under which start-up costs for irrigation infrastructure make it unprofitable for non-irrigators to enter the market. Finally, we conclude that farmers' ethical perspective of considering irrigation water as a non-tradable commodity constrains them from participating in such markets.