Seleucid agriculture was the main economic activity in the Seleucid Empire. Irrigation was more common inland in areas that received less rainfall than coastal regions of the Mediterranean. The Tigris, Euphrates and Oxus rivers allows water to be distributed through canal networks controlled by the Seleucids. Taxes were levied on agricultural goods based on the productive capacity of the land, and so irrigated lands like Mesopotamia were more heavily taxed.