The geostatistical method, formulated in the groundwater field, has been applied to identify contaminant sources in river pollution problems. The problem consists of recovering a contaminant source at a known location from a finite number of concentration measurements. It is an ill-posed problem, whose solution is nonunique and cannot be determined through standard techniques. The presence of dead zones has been considered because of their relevant influence on transport processes. The possibility of linear decay reactions in the main stream and in the dead zones has also been included. Applications to field data show that the method is efficient in recovering the release history of an arbitrarily distributed source as well as multiple independent point sources, given a finite number of observed concentrations at one or several downstream points. The influence of the degree of dispersion on the observations is stressed. Finally, the effects of measurement errors and of the number of measurement points have been investigated.