Geology topics
Publications and source records attributed to Jeff V. Phillips.
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A study was conducted during the summer of 2003 on Mapleton Lateral Canal near Mapleton, Utah, to determine gain or loss of flow in the canal from seepage. Measurements were made in May, June, July, and September of 2003. The uppermost reach of the canal had an apparent average loss of 2.6 cubic feet per second. The next reach downstream showed an apparent average gain of 1.4 cubic feet per second. The next three downstream reaches had apparent average losses of 2.4, 2.5, and 2.7 cubic feet per second. The apparent average net loss from the canal was 8.8 cubic feet per second, or a loss of 30 percent of the total discharge measured at the head of the canal.
Utah’s weather is prone to extremes – from severe flooding to multiyear droughts. Five major floods occurred during 1952, 1965, 1966, 1983, and 1984, and six multiyear droughts occurred during 1896-1905, 1930-36, 1953-65, 1974-78 (U.S. Geological Survey, 1991), and more recently during 1988-93 and 1999-2002. The areal extent of floods generally is limited in size from one to several watersheds, whereas droughts generally affect most or all of the state. Southern Utah, in particular the Virgin River drainage basin, began experiencing drought conditions during the winter of 1998-99. By 2000, drought conditions were evident throughout all of Utah. The current drought (1999-2002) is comparable in length and magnitude to previous droughts; however, with population growth and increased demand for water in Utah, the general effect is more severe. During 2002, the fourth straight year of nearly statewide drought conditions, some areas of Utah experienced record-low streamflows. Several record-low streamflows occurred in streams with records dating back to the 1900s. The U.S. Geological Survey (USGS) uses streamflow data from eight long-term streamflow-gaging stations for comparison of hydrologic conditions in Utah (fig. 1).
Potential errors were derived for individual discharge measurements and stage-discharge relations for 17 streamflow-gaging stations in Maricopa County. Information presented primarily consists of stage and discharge data that were used to develop the stage-discharge relations that were in effect for water year 1998. Accuracy of the discharge measurements directly relate to accuracy of the stage-discharge relation developed for each site. Stage-discharge relations generally are developed using direct measurements of stage and discharge, indirect measurements of peak discharge, and theoretical weir and culvert computations. Accuracy of current-meter measurements of discharge (direct measurements) depends on factors such as the number of subsections in the measurement, stability of the channel, changes in flow conditions, and accuracy of the equipment. Accuracy of indirect measurements of peak discharge is determined by the accuracy of discharge coefficients and flow type selected for the computations. The accuracy of indirect peak-discharge computations generally is less than the accuracy associated with current-meter measurements. Current-meter measurements, indirect measurements of discharge, weir and culvert computations, and step-backwater computations are graphically represented on plots of the stage-discharge relations. Potential errors associated with the discharge measurements at selected sites are depicted as error bars on the plots. Potential errors derived for discharge measurements at 17 sites range from 5 to 25 percent. Errors generally are greater for measurements of large flows in channels having unstable controls using indirect methods.
In the winter of 1997-98, the U.S. Geological Survey, in cooperation with the Flood Control District of Maricopa County, made six verification measurements for Manning's roughness coefficients at Skunk Creek above Interstate 17. Data from four floodflows were recorded and analyzed, three of these flows occurred in February 1998 when Arizona received precipitation from the El Nino weather phenomenon. Discharges ranged from 187 to 760 cubic feet per second and resultant verified values for Manning's roughness coefficient, n, ranged from 0.056 to 0.039. Skunk Creek above Interstate 17 - an ephemeral wash within a flood-control structure - is overgrown with desert brush throughout the main channel and the presence of the vegetation has a significant effect on n values throughout the reach. The results of this study are verified roughness coefficients that can be transferred to similarly vegetated channels in Maricopa County and other arid and semiarid environments where roughness factors must be assessed for flood management or other purposes.
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Physical and hydraulic characteristics are presented for 14 river and canal reaches in Arizona for which 37 roughness coefficients have been determined. The verified roughness coefficients which ranged from 0.017 to 0.067, were computed from discharges, channel geometry, and water-surface profiles measured at each of the sites. The information given for each stream segment includes bed and bank descriptions, data tables showing hydraulic components, a plan view, cross-section plots, and color photographs that can be used as a comparison aid in determining roughness coefficients for similarly channeled streams. Relations derived from the data presented relate Manning's roughness coefficient (n) to various hydraulic components. For gravel-bed streams, verified roughness coefficients are related to median grain size of the bed material and hydraulic radius resulting in an equation that can be used to transfer results to similar dry-land channels. The equation developed for base values of n for gravel-bed channels in Arizona is significantly different from similarly derived equations for other regions of the United States and the world.
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According to precipitation and streamflow data collected in the State, Arizona experienced one of the driest periods on record from January 1 to June 30, 1996. During this period, Arizona averaged less than -4.5 on the Palmer Drought Index (PDI); a widely used index that compares monthly rainfall to soil moisture for a given area. PDI values less than -4.0 indicate extreme drought conditions. PDI values for Arizona have ranged from less than -5 to greater than 7 since 1895. Governor Fife Symington declared a state of emergency for Arizona on May 3, 1996, because of the extremely dry conditions.