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35 <br />30 <br />ALA.3 <br />25 <br />ALA.2 <br />20 <br />15 <br />10 <br />5 <br />0 <br />1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 20002001 <br />Figure 5. Water levels in wells ALA.2 and ALA.3. <br />The decrease in flow at a depth of 1,422 ft is due to the <br />diameter from land surface to a depth of 51 ft and <br />change in casing diameter at that depth. The two 12.0-inch diameter from 51 to 735 ft. The intervals <br />outflow zones may result because the annular space <br />containing torch-cut slots (from 446 to 537 ft and from <br />allows flow into lithologic layers below the clay layer <br />555 to 735 ft) are open to lithologic layers containing <br />from a depth of 290 to 440 ft that are cased off. Thus, <br />(1) sand, gravel, or cobbles; (2) clay with some sand or <br />outflow into the zones from 885 to 930 ft and 540 to <br />gravel; or (3) clay (fig. 7). The lithologic layers open <br />690 ft may occur to equalize the head differences <br />to the well are below a thick clay layer from 34 to 92 ft <br />among the flow zones below 930 ft and above 930 ft <br />and a predominantly clay layer from 92 to 401 ft. <br />that may have been created during free-flowing condi- <br />The temperature log and free-flowing and shut- <br />tions, or it may occur due to natural head differences <br />in stationary flowmeter measurements indicate inflow <br />that exist among the different flow zones of the <br />occurs in three zones: (1) 446 to 475 ft, (2) 500 to <br />confined-aquifer system. <br />530 ft, and (3) 670 to 728 ft. The small decreases in <br />The water level measured in this well is a <br />flow through the flowmeter of about 0.019 gal/min <br />composite of heads in the confined-aquifer system <br />observed in the shut-in stationary measurements from <br />because the 1,433-ft interval contributing flow to this <br />280 to 440 ft and 470 to 520 ft are likely measurement <br />well penetrates several different lithologic layers. <br />errors or diameter effects. Thus, both the free-flowing <br />and the shut-in flowmeter measurements show that <br />Well ALA.6 <br />flow increases as the depth decreases in the well. The <br />decrease in flow observed in both flowmeter logs at 51 <br />Well ALA.6 was constructed in 1957 for irriga- <br />ft is due to the change in casing diameter at that depth. <br />tion use and is a flowing well. The casing is 17.2-inch <br />12Geophysical Logging to Determine Construction, Contributing Zones, and Appropriate Use of Water Levels Measured in <br />Confined-Aquifer Network Wells, San Luis Valley, Colorado, 1998?2000 <br />