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The agricultural and environmental functionality of irrigation districts is sometimes controversial, with salinity as a frequent argument in the arid countries. In the 20th century, the Spanish Ministry of Agriculture studied the degree and extent of salinity and other facets of irrigated districts in Spain by conducting soil surveys and land evaluations from the 1940s to the early 1980s. This article presents a--probably partial--list and the available details of these studies for the Ebro Basin. We had access to some of these studies, although for most of them we only have indirect information; we also indicate the existence of these kinds of studies for other regions of mainland Spain. However, updated systematic estimations of the extent and degree of soil salinity are unavailable for most of the irrigated lands in Spain and for many other dry countries. A feasible task, as shown further in the article, is screening the value of the still readable studies and selecting the irrigation districts whose past documentation and present status allow for a new evaluation of soils, or at least measuring their actual salinity for comparison with the previous data. The results will help irrigators, government agencies, and other stakeholders in the appraisal of the effects of agricultural practices--chiefly the application of water--and to re-design them if needed. We advocate for the collection and critical review of the surviving soil studies, and for their rescue through scanning and digitalization. This task is compelling due to the decay of the existing paper documents. [ABSTRACT FROM AUTHOR]