7750 - Laserfiche WebLink

Home Browse Search

CHAPTER III GAINS ALONG THE REACH Administrative spills are an operational tool used to level the demand placed on the canal and lateral systems with irrigation demand. This leveling is required due to the time lag between when the water is diverted from the river to when the water is delivered to the irrigator. This lag approaches 36 hours for the extreme reaches of some of the canal systems. To meet peak demand, the irrigation entities maintain full river diversions throughout most of the irrigation season. Administrative spills are then necessary whenever there is a reduction in the demand below the peak. The attached Features Map shows the configuration of the irrigation systems in the Grand Valley. For purposes of this report, the canal marked Grand Valley Canal is called the East GVIC Mainline. The Mesa County Ditch has been combined with the East GVIC Mainline. The canal marked. Grand Valley Mainline is referred to as the West GVIC Mainline. In the east end of the Grand Valley, all irrigation water delivered upstream of Indian Wash was assumed to influence the return flows along the Reach. These irrigation systems from north to south are: the Stubb Ditch, the East End of the Government Highline Canal (Highline) above Indian Wash, the Price Ditch, and the East GVIC Mainline Canal above Indian Wash. To estimate the amount of irrigation water returning to the Reach the following assumptions were made: 1) All of the seepage components enter the local ground-water system and are transported back to the Reach. 2) Administrative spills and irrigation return flows in the Stubb Ditch service area flow into the Highline Canal and thus do not return to the Reach. 3) The first administrative spill for the Highline Canal is at Indian Wash so those spills, if any, would return to the downstream end of the Reach. 4) One-half of the administrative spills and irrigation return flows from the Highline laterals service area flows into the Price Ditch and the other half returns uniformly to the Reach. 5) One-half of the administrative spills and irrigation return flows from the Price Ditch laterals service area flows into the East GVIC Mainline and the other half returns uniformly to the Reach. 6) Under most operating conditions, the GVIC does not spill water from the East GVIC Mainline Canal along the Reach. With a canal system about 100 miles long, it is not possible for the GVIC to anticipate a surplus amount of water 12.5 miles into 16