The Senegal River Valley, sometimes known as the Chemama or the pre-Sahel, is a narrow belt of land that extends north of the Senegal River. Before the droughts of the 1960s, 1970s, and 1980s, the belt ranged from north of the river. By the late 1980s, desertification had reached the northern bank of the river in some parts of the valley. The valley is wider in Guidimaka Region and is completely dominated by the seasonal cycle of the river. Almost all of the valley's economically active population engages in sedentary agriculture or fishing along the Senegal River and its main tributaries—the Karakoro, the Gorgol, and the Garfa. This area supplies most of the country's agricultural production.