Irrigation has a number of potential adverse impacts on freshwater systems. Irrigation can abstract water from natural systems and prevent or delay its return through diversions and storage; allow the conversion of natural lands into agricultural crops and infrastructure; disturb natural drainage systems through the construction of canals and drains, and pollute freshwater sysems with agricultural wastewater. An analysis of the total area equipped for irrigation within each ecoregion gives an indication of the relative degree of threat posed by irrigation to freshwater systems. Data come from the FAO and University of Frankfurt\'s Global Map of Irrigation Areas.