*2.1. Study Area*

The Mono River watershed occupies an area of 27,822 km<sup>2</sup> shared between two West-African countries, Togo and Benin. Specifically, it is located between the latitudes 06◦16 N and 09◦20 N, and the longitudes 0◦42 E and 2◦25 E (Figure 1). The major part of the basin lies in Togo's territory, totaling 21,750 km2, whereas that of Benin stretches to 6072 km2. The river serves as natural border between the two countries in the southern part. The climate is tropical (two rainy seasons and two dry seasons) downstream and subequatorial (one rainy season and one dry season) upstream.

**Figure 1.** Location of Mono watershed and considered rain gauges.
