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w o o en strong basis for evaluating the effectiveness of salinity control measures. Details of the demonstration area are shown in Figure 4. with all the available knowledge regarding the study area, a lateral including the associated lands served by the lateral water supply was used as a subsystem for evaluating the salinity reduction in the Colorado River resulting from the implementa- tion of a salinity control technology package. The study area was originally selected because it is fairly representative of the Grand Valley, and has five canals which traverse the area, thereby allowing greater participation by the majority of irrigation entities in the Valley. In order to facilitate the continued participation by the irrigation interests in the Grand Valley, the laterals were selected to cover as many canals as possible. The final selec- tion, as shown in Figure 5, had two laterals under the High- line Canal, one under the Price Ditch, three under the Grand Valley Canal, and three under the Mesa County Ditch. It should be pointed out that the lands served by the Highline Canal in the demonstration area are served under carriage contract with the Mesa County Irrigation District (Stub Ditch) and the Palisade Irrigation District (Price Ditch). Therefore, all the irrigation entities in the demonstration area are involved directly in the project. The laterals were selected to capitalize on previous work regarding canal and lateral lining, irrigation scheduling, and drainage studies. The hydrologic knowledge already gained in this demonstration area allowed routine surface water and groundwater monitoring to evaluate the overall effectiveness of the salinity control technologies. The lands which received treatment under this demonstration project (about 20 percent of the demonstration area), along with previously constructed channel lining and drainage facilities, provided a significant impact upon salinity leaving the demonstration area. The experimental design for the preevaluation was primarily aimed at providing specific information for the 330.7 hectares (817 acres) undergoing treatment listed in Table 1. The field data collection program allowed the design of irrigation and drainage facilities and provided sufficient data to allow pre- dictions of salinity benefits which resulted from each specific salinity control measure. Although the postevaluation included the monitoring of water and salts entering and leaving the demonstration area, the primary emphasis was the on-site evalua- tion of each specific salinity control measure. The on-site evaluation was then compared with the results of the total demonstration area hydro-salinity monitoring program. 8