Water use inside inland valleys agro-systems in the Dano basin, Burkina Faso

Abstract

The hydrological behavior of inland valleys agro-systems is investigated in the Dano basin in South-Western Burkina Faso. Four inland valleys, two with irrigation reservoirs, one with contour bunds and the last with drainage canals were monitored during two hydrological years from June 2014 to May 2016 and compared. A set of indicators on their reliability, their productivity and on the impacts on their environment were assessed. The indicators were chosen to allow spatial and seasonal comparison among the schemes. The results showed a rather abundant rainy season in the four schemes allowing the rain-fed cultivation of rice, with more available water in the simply designed schemes. The irrigation frequency inside the reservoir-based schemes is found to affect their efficiency during the dry seasons. As for the productivity, the reservoir-based schemes perform better than the rest because of an improved control of the inflows and drainage system. In terms of impacts, three out of four schemes have low impacts on their downstream users with a drainage ratio over 60%, and 30% for the last one, which depicts also large amounts of unused water, especially for simple designed inland valleys. On the water quality aspects, the concentration of nitrates, nitrites, potassium, and orthophosphates in the four schemes respect the norms for drinking water, due in part to low fertilizer applications, although having a high potential for eutrophication. The study provides technical elements for comparison between different types of inland valley schemes and highlights their impacts on the water cycle.