The topography of Ukraine consists mainly of fertile plains (steppes) and plateaus. Mountains (Carpathians) are found only in the west and in the Crimean Peninsula in the extreme south. Abut 57% percent of the land in Ukraine is arable with approximately 4% under irrigation. The most important river in Ukraine is the Dnipro (Dneiper), the third longest river in Europe. It serves as a major source of hydro-electric power. Other major rivers include the Danube, Western Buh, the Tisza, the Pripyat, and the Desna.