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11" I.:? ,.:..> ;-:1 .' . . - CHAPTER II GRAND VALLI;Y RIVER BUDGET Ground Water The USGS river gag~ng stations are all well placed in narrow canyons where it is shallow to bedrock, and the ground water passing under these gages is insignificant compared to the measured streamflow. Any such ground water would be hydraulically connected to the surfac,e water and hence, have virtually the same quality. It was assumed that any river alluvial ground water inflows and outflows balanced out and could be ignored in the budgeting process. Ground water inflows from ungaged lands are discussed in the section on Ungaged Inflows. No non-alluvial ground wat<!r outflows are known to exist and by examining the geology of the valley, no significant ground water outflow would be expected. Ungaged Inflows The un gaged inflows represent the natural inflows and B,ssociated sal t entering the system boundaries in areas other than at the gaging stations. At first, a correlation was sought for monthly flow as a function of drainage area, mean basin elevation, and the 3D-year mean annual precipitation (published in the form of an isohyetal map as "Normal Annual Precipitation" by the Weather Bureau). Unfortunately, there were not enough data to develop the relationship, The only significant daily flow record of natural runoff in Grand Valley is for West Salt Creek near Mack. It should be noted that the East Salt Creek near Mack gaging station includes return flow from about 150 irrigated acres above the Government Highline Canal, and that the Badger Wash near Mack record includes water spilled by the Government Highline Canal. II-3