The study aimed to analyze, using chance constraint programming, the economic profitability of irrigation under hydrological risk at the level of two perimeters irrigated from two small dams located in various climatic conditions: Baldia dam in semi-arid Southern parts of the Dorsal and Charfi in sub-humid Northern parts. Two scenarios of water availability were simulated: a deterministic scenario where water is supposed available and a probabilistic scenario where water sup-ply is uncertainty. Under deterministic scenario, the suitable crops mix to meet monthly water availability in both sites consists to grow autumn vegetable crops and olive trees. For both sites, the economic return was increased by 256% and 486%, respectively for Charfi and Baldia Perimeters. Under probalistic scenarios, results showed that optimal cropping pattern and farmer’s income, strongly vary with the level of water risk supply and across regions, depending on whether the irrigated area is located in the northern or southern parts of the Dorsal. In the northern parts, there is 99% chance to meet monthly water requirement without significant impact on crops choices and farmer’s income. However, in Baldia perimeter, the cultivated area and farmer’s income are very sensitive to water uncertainty. Requiring the maximum reliability of water supply should reduce both the potential irrigated area and the farmer’s income, respectively by 80.5% and 93.5%. The investment in irrigation becomes in this case un-economic profitable. Based on these results, the planner should rethink the implantation of small dams in southern parts of the Dorsal, to develop irrigation activities.