 Farther south, particularly in Assaba and the northern portion of Guidimaka regions, rainfall is high enough to support forms of sedentary agriculture.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.