Simple tools and accessible information are needed by environmental planners to select sites for the restoration or creation of wetlands. A flexible suitability model for allocating wetlands is demonstrated in small (20–2,000 ha) agricultural catchments in the semiarid Ebro basin (NE Spain). The model used improved existing data layers (soil and geomorphology), simple geographical transformations (slope and distance to frequently flowing streams) and other created data layers (land use). Detailed scales of data layers (~1:5,000 and <30 m cell-size) are needed to work with small catchments. A deep knowledge of the study area is a requirement for reducing the subjectivity associated with experts’ decision. The studied cases proved that 31% of catchment areas were suitable to create wetlands, and another 12% were very suitable. In 11 out of 12 studied catchments 100% of their existing wetlands fell into the area selected by the model as suitable. Most of the suitable area was situated in the lower parts of the catchments examined in the study. There is enough very suitable area in all catchments to fulfil the functional requirements of the wetlands to improve water quality. The model is a simple and useful tool for environmental planning in areas degraded by irrigated agricultural use.