The report discusses a project to evaluate the salinity control effectiveness of canal and lateral linings for reduction of seepage losses into the ground water. Grand Valley in the upper Colorado River Basin was used as a model. A detailed evaluation of the necessary hydrologic and salinity parameters in the principal demonstration area was made. A hydro-salinity model has been prepared, which has allowed the itemizing of the various segments of the dual flow system into water and salt budgets for the periods prior to and immediately after the construction of the linings. In addition, the results were employed to derive some generalized valley-wide water and salt budgets. The salinity control benefits exceeded the costs of the canal lining program. (Author)