The Senegal River Valley, sometimes known as the Chemama (see Glossary) 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 sixteen to thirty kilometers 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.

The climate of the Senegal River Valley contrasts with that of the Saharan and Sahelian zones. Rainfall is higher than in other regions, ranging from 400 millimeters to 600 millimeters annually, usually between May and September. This rainfall, combined with annual flooding of the river, provides the basis for agriculture. Temperatures are cooler and subject to less annual and diurnal variation than in other regions.

The Senegal is the only permanent river between southern Morocco and central Senegal. From its source in Guinea, it flows north and west 2,500 kilometers, reaching the Atlantic Ocean at Saint Louis, Senegal. From its mouth, the river is navigable as far as Kayes, Mali, during the rainy season and Podor, Senegal, during the rest of the year. Heavy rains, beginning in April in Guinea and May and June in Senegal and Mali, bring annual floods. These floods cover the entire valley up to a width of twenty-five to thirty-five kilometers, filling numerous lakes and sloughs (marigots) that empty back into the river during the dry season. When the waters recede from the bottomlands, planting begins.

The Senegal River Valley, with its rich alluvial and clayey soil, is comparatively abundant in flora. Moreover, higher rainfall, irrigation, and abundant side channels and sloughs tend to produce a lush, near-tropical vegetation, with baobab and gonakie trees and abundant rich grasses. Ddounm and barussus palms are also found here. Much of the flood plain is cultivated.

Data as of June 1988