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. .-, . ~... I-\. ~ ..... SPECIAL STUDIES (continued) With these models the implication for water resources projects is that farm operation could be designed to use the least amount of water and return the smallest amount of salt to the river while permitting the farmer to obtain the greatest possible return from his farm. The salt load reductions expected from irrigation scheduling and management could also be verified on the Vernal Unit in the Uinta Basin. 2. Florida Project Area Study Flow and quality data were collected a~ several points in the Florida Project area beginning in 1958 before the project was constructed. A study of these data for the period 1958-63 shows the effect of irrigation of these lands on the quality of return flows leaving the area. Results show that there has been a very small amount of pickup mea- sured in the river downstream from the irrigated area. The concentration of total dissolved solids in the inflowing water ranges from 0.14 to 0.17 ton per acre-foot (103 to 125 mg/L). and that of the out flowing water ranges from 0.17 to 0.30 ton per acre-foot (125 to 221 mg/L). About 13,720 acreS (5550 ha) were irrigated at the time the measurements were made. Other areas in the Colorado River Basin with similar underlying aquifers would yield only minor amounts of salt. type soils and 3. Grand Valley Area Agricultural Research Service The Agricultural Research Service is doing a research study Grand Valley with regard to irrigation efficiencies. This is covered in Part VIII. in the further 4. Montezuma Valley The Soil Conservation Service has conducted a study of on-farm im- provements ~n ~he Montezuma Valley in Colorado. 5. Other Studies Considerable variation in the effects of irrigation return flow on water quality is to be expected. Differences arise due to the size of the irrigated areas, the number of times the return flow is reused, properties of the soils and drainage area, number of years land has been irrigated, nature of aquiferst rainfall, dilution, temperature, irrigation methods, storage reservoirs, vegetation, and type of return flow channels. Consumptive use, ~eturn flow, salinity, and pollution studies are continually being made by universities such as Utah State and Colorado State and by Federal agencies in cooperation with State and local agen- cies. Some of the study areas are purposely held small to achieve better control, but they will be as representative as possible of existing proj- ects. The results pertaining to the quantity of return flow wi 11 be very 104