Water erosion is an alarming threat to soils in Morocco. It has a direct impact on agricultural land and the country's infrastructure such as highways. In order to evaluate this effect, several studies take place in Northern Morocco, while very few concerned the watersheds of Central Morocco. This paper presents the results of a quantitative study on water erosion and loss of mineral elements in the Ben Ahmed watershed. Rainfall simulation was conducted with an erosive intensity of 60 mm/h, for sites representing the main soils of the watershed. It resulted that their detachability was between 19 and 34 g/l, erosion rates ranging between 4.3 and 12.3 t/ha; 38% to 73% rain turned into runoff depending on soil type. The laboratory analysis of the recovered sediments showed that soil loses 7.1 kg of organic matter, 1.1 kg of potassium and 0.062 kg of phosphorus per hectare in the watershed.
