Characterization of Agropastoral Dam Lakes in the Bounkani Region, Côte d’Ivoire

Abstract

The North-East region (Bounkani) of Côte d'Ivoire is the least watered region of the country with an average annual rainfall of 945 mm. The rainfall deficits observed in Côte d'Ivoire since 1970s could constitute a real threat to the environment and to water resources in general, and to dam lakes in particular. The main aim of this study was to follow the evolution of the dam lakes in the region over the years, i.e,(1986, 2002 and 2017) with reference to their spatial distribution (their densities and their limnological ratios). The approach adopted consisted of mapping and monitoring through remote sensing technology which involves processing satellite images for automatic extraction of these agropastoral structures on the various images. The results showed that these dam lakes were unevenly distributed both at the level of the departments and the watersheds, with 73.43% in the Black Volta and 28.57% in the Comoé. The density was higher in Doropo and varied from one department to another from 1986 to 2017, for the department of Bouna, it ranged from 9.34.10-4 to 3.74.10-3 per km2. The departments of Doropo and Tehini showed 1.51.10-3 to 1.01.10-2 per km2 and 1.05.10-3 to 4.53.10-3 per km2 respectively. Nassian department displayed a value of 1.42.10-3 per km2 and remained constant from 2002 to 2017. Like the density, Doropo Department had the highest limnological ratio which changes from 7.09.10-5 to 2.71.10-4 per km2 over the same period. The mapping of these agropastoral structures showed 18 agropastoral structures where 57 (28.07%) were functional or even contained water in the dry season in the region in 2017 including 2 in Nassian; 4 in Tehini; 9 in Doropo and 3 in Bouna.