In Turkey, the government initiated an irrigation project in the Southeastern Anatolia region, which is expected to irrigate an additional 1.07 million hectares of land. This study estimates the consequence of increased Turkish cotton production area on the world cotton market. We use a multi-market, multi-region partial equilibrium model to simulate the impact of increasing cotton harvest area in Turkey. Results suggest that with the increase in cotton production area in Turkey the world cotton price would decrease by about 9.5 percent. Effects on prices and area planted in other countries depend on whether the project converts non-agricultural lands to cotton, or re-allocates area currently planted to grains.