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Table 2. Frequency analysis for calculated depths to water [Depth to water was calculated for a grid of 98 X 98-foot cells; values for individual cells were assigned using an distribution method similar to inverse distance squared weighting] Frequency Interval Absolute Relative Cumulative (feet) (percent) (percent) 0-5 11,432 31.13 31.13 5-10 7,432 20.24 51.37 to-15 4.730 12.88 64.25 15-20 5,149 14.02 78.27 20-25 3,103 8.45 86.72 25-30 2,387 6.50 93.22 30-35 l.lX)9 2.75 95.97 35-40 683 1.86 97.83 40-45 511 1.39 99.22 45-50 287 0.78 100.00 Total 36,723 100.00 General Changes in Water Levels Some of the most useful information available from the historical records concerns how water levels have generally changed through time. For instance, have water levels remained about the same or have they changed substantially, and if they have changed, have the changes been steady or abrupt? A visual inspection of the records indicated that, in most repre- sentative cases, ground-water levels have generally had a net increase during the study period. Examples of these increases for the five wells in figure I are shown in hydrographs (fig. 4) For the purposes of this discussion, the wells shown in figure 4 are referred to as "well I" (SC02405503AAC), "well 2" (SC02305415DCC), "well 3" (SC0230542IBCC), "well 4" (SC02305428CCBI), and "wellS" (SC02305430DBD). Information concerning the period of record and the number of measurements for each of these five wells is listed in table 3. Water levels in all five wells have been measured for much of the study period, and water levels in all wells except well 5 have been measured more than 100 times; well 5 has only been measured 36 times. Wells I and 4 are located near the Arkansas River and the other three wells are either close to the Fort Lyon Canal or nearly centrally located between the canal and river (fig. I); wells I and 4 are referred to as "lowland," and wells 2, 3, and 5, are referred to as "upland" wells in this report. This simple geographic classification also fits the differences between t~e hydrographs for the lowland wells and the upland wells. The lowland wells have water levels that are relatively close to the land surface. Also, although both lowland wells have water-level records that are relatively fiat, their water levels stilI indicate a ~;eneral tendency to increase through time. In this report, water levels are referred to as "high" or "low", and high water levels correspond to shallow depths to water. In general, the difference between the shallowest and the deepest depth to water, or the difference between the highest and lowest water levels, measured at a given well and referred to as range in this report, is relatively small (table 3) for the lowland wells. However, each lowland well does have at least a few measurements that seem to represent short -term changes in water levels, for instance 1965 for well 4 (SC02305428CCB I) and 1987 for well I (SC02405503AAC). The three upland wells, wells 2, 3, and 5, have hydrographs with shapes that are very different Irom the hyclrographs for the wells near the river (fig. 4). All three wells have much greater ranges than the ranges from the wells near the river. In addition, the hydro- graphs for these upland wells each have much hIgher water levels at the end of the period of record than at the early part of the period, indicating a general tendency for increases in water levels that is much more apparent than in the hydrographs for the lowland wells. Although water levels the in upland wells exhibit long-term general increases in water levels, all three also have a period, from about 1967 through about 1979, during which they had a fairly steady decrease. The decrease is most apparent in wells 2 and 3 and least apparent in well 5. During the 1980s water levels were generally high, increasing in the early part of the decade and decreasing in the later part. Two of the three upland wells experienced the highest water levels measured in the mid-1980's. From aboUl1990, water levels in the wells began to increase slowl)T in a trend that continued for the remainder of the period of record. HISTORICAL WATER LEVEL:> 9