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(Simon. 1994), tracks the river surface elevation. which is a function of the river bed elevation, for a specified discharge. Use of this method can return more frequent values and also provides an analysis based on a cross section of the river rather than a single point in the cross section. Even though the method may be based on a cross section rather than a point, it still describes the river bed only at that cross section and cannot be applied to a river reach without additional supporting informinion. The results of this analysis are listed in table 4. The results indicate that the elevation of the river bed has generally increased throughout the study period. The changes in river-bed elevations, unlike the changes in most of the factors previously discussed in this section, [Ire relatively steady. The total increase, from 1960 to 1995, is aboUl 1.76 feet. Between 1996 and 1997 the records indicated an increase of about 1.1 feet. which is a much greater increase than has occurred historically and may be a short-term phenomenon. The information used as part of this study does not provide definitive findings about why the elevation of the river bed has increased, The changes could be the result of relatively large-scale processes that may affect several miles of the river or they could be the result of local processes related to the maintenance of sediment in the Fort Lyon Canal. Interrelations of Ground-Water Levels and Affecting Factors Ground-water levels and factors that Mfect them can be compared graphically. For this comparison, records were transformed and expressed as a fraction of their range (fig. 7). This transformation facilitates comparisons between factors that are sometimes expressed In different units and generally experience different ranges than ground-water levels that are expressed as depths to water in feel. A comparison of ground-water levels for two wells (one lowland well and one upland well) with the elevation of the Arkansas River bed, diversions 10 the Fort Lyon Canal flow from the winter- and project- water programs related to Pueblo Reservoir operation, diversions to the Fort Lyon Canal (annual total flow), flow in the Arkansas River (annual total and daily mean flow), ground-water withdrawals. and surface- ~.ater applications is shown in figure 7. There are some qualifications that need to be made concerning such a comparison, First, all factors, exc:ept ground- water levels, daily mean discharges, and the river-bed elevations are annual values and are represented as he given annual value for the entire year in figure 7. Second, most factors represent data measured at a specific geographic point. The hydrographs for ground-water withdrawals and surface-water applica- tions are exceptions; they represent the overall study area. The areal nature of the withdrawal and applies" tion data means that they may be Insensitive to local phenomena. Even though the curves in figure 7 require some qualifications, the figure still allows for observations of the interrelations being discussed, Some simple relations are readily apparent. One of the most promi- nent features of the smoothed curves for depths to ground water in figure 7 is that ground-water levels are high in the 1980's. Three of the hydrologic factors, surface-water applications, ground-water withdrawals, and flow in the Fort Lyon Canal, all show e1ear, either direct or inverse, relations to the high water levels observed in the 1980's. The levels of flow in the FOr[ Lyon Canal and surface-water applications are both greater than long-renn means during this period and represent recharge to the locsl aquifer. The levels of ground-water withdrawals are less than long-tenn means and represent a decrease in aquifer discharge. Thc combination of increased recharge and decreased aquifer discharge result in the higb ground-water levels observed in the 1980's. A prominent feature of the smoothed curve for ground"water levels in well 1 in figure 7 is the rela- tively steady decrease during the 1970's. Even though the records for ground-water withdrawals and surtace- water applications do not include all of the 1970's, their records. along with those for flow in the Fort Lyon Canal. portray the opposite of conditions observed in the 1980's when ground-water levels w~re high. Recharge to the aquifer from diversions to the canal and surface-water applications is low, and discharge from the aquifer from ground-water with- drawal, is high; these conditions combine to affect a decrease in water levels. The smoothed curves for both wells in figure 7 indicate a tendency for modest increase from about ! 990 on. During this time, surface-water applications are relatively constant but are at levels less than, but comparable, to the long-term meatl. Ground-water withdrawals ate also cotlstant duritlg this period, 'I I I , .1 ? Al'lEdys;;: of Hydrologic Factors That Affect Ground-Water Levels in the Arkansas River Alluvial Aquifer Near La Junta, Colorado, 1959-99