OCR Text |
Show Drains Approximately 30,200 acres of full and supplemental service lands in the Bonneville Unit presently have or would have deficiencies in subsurface drainage requiring correction with Unit development. With the application of Unit water, drainage distress would become more acute on present drainage deficient areas. In selecting lands to receive Unit water and Unit drains, those which have excessive salt content would be excluded. Total dissolved solids ( TDS) in drainage waters should be kept at a minimum. This does not eliminate the fact that drainage waters would generally contain higher concentrations of salt nitrates, and phosphates, etc. The total increase in salts entering Utah Lake and the terminus, the Great Salt Lake, cannot be determined until drainage requirements develop. The same situation would apply to the increase in salts entering the Colorado River. This has been estimated at 10 mg/ 1 at Hoover Dam as a result of the entire Unit, of which drainage would be but a part. Drainage problems of varying degrees would develop in those areas undergoing irrigation development. These problem areas are located on the lower lying lands of valley floors. These areas are: Spanish Fork area, Mona- Nephi area, Elberta- Mosida area, and the Duchesne River area. Determinations of exact locations and design of drainage systems would not be possible until the irrigation systems were in operation and problem areas became apparent. Ca) Provo Bay Area It is estimated that with Provo Bay development, more water would be returned to Provo Bay than is returned under the present operation. It is expected that the chemical quality of water pumped from the Bay under Unit operation would be similar to or better than that now leaving the Bay under natural conditions. The water now flowing into Utah Lake from Provo Bay averages about 550 mg/ 1 of total dissolved solids. Peripheral inflow to the Bay is of better quality than this, averaging about 300 mg/ 1 of total dissolved solids. The higher concentration of salt in the water 272 |