摘要 : The first step in evaluating the input of agrochemicals to a watershed was to estimate land use using aerial photographs, fields observations, and data from the French National Agricultural Census (RGA). Secondly, the input of agr... 展开 The first step in evaluating the input of agrochemicals to a watershed was to estimate land use using aerial photographs, fields observations, and data from the French National Agricultural Census (RGA). Secondly, the input of agrochemicals on eachcrop was estimated, since 1970, from a survey at the farm level. These data were confirmed by local marketing technicians. Finally, the total quantity of agrochemicals was computed as the product of the input of agrochemicals on each crop and the surfacearea of each type of land use. Provided that a suitable evaluation procedure of land use is used, this method could be applied to other types of agricultural pollutants. 收起