2007-12-20_INSPECTION - M1984154

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south of Well No. 4 was suggested and recharge to this area was recently completed during August and September of 2006. Hershey's studies indicated recharge of the Clay Creek aquifer is successful in raising the water table and enhancing well yields. A recharge monitoring program was completed by Hershey at the main recharge site and indicated that for the April 1979 through July 1979 study period, the water table rose as much as 19 feet in some areas of the aquifer as a result of the recharge program. Water levels rose up-gradient of the recharge pond as far south as Well No. 8 and down-gradient of the recharge pond as far north as Well No. 20. Hershey also discussed the potential for degradation of the portion of the aquifer receiving recharged water due to the lower quality of water diverted from the Arkansas River by the Fort Bent Ditch compared to the ground water which originates in the Clay Creek basin. The 1979 study completed by Wheeler stated: "In the early 1970's the TDS content of water pumped from the Clay Creek Aquifer averaged about 600 mg/I. However, in the late 1970's the average salinity level increased to about 700 my/I. At least part of the increase can be attributed to the use of more saline Arkansas River diversions in the recharge program. Hardness is about 450 mg/I as CaCOs." "The quality of Arkansas River water at Lamar varies considerably depending on the quality of water in the river, the source of the water, the time of the year, the operation of John Martin Reservoir, and irrigation return flows. The TDS of the river water at Lamar generally varies from about 400 mg/I to about 4,400 mg/I. Arkansas River quality varies seasonally and is generally best during the summer months." A water quality analysis of a composite sample from the Clay Creek well field could confirm the trend identified by Wheeler in the 1970s. Deliveries of Arkansas River water to the Clay Creek aquifer recharge site should be made when higher quality water is available. A monitoring program of water quality at individual wells, the recharge site, and Fort Bent Ditch diversions would assist the City with understanding the long-term effects of the recharge program on the water quality of the north part of the Clay Creek aquifer. The City maintains a monthly water level measurement program in most of the Clay Creek wells. Hydrographs of water level changes were prepared for the 1996-through- 2006 period. The hydrographs for all of the measured wells are enclosed in Appendix D. Selected hydrographs are shown on Appendix B Plate 3. There are no meters on individual wells; therefore, it is difficult to discern whether the water level changes shown on the hydrographs are due to either pumping or recharge events or seasonal and annual changes in the aquifer. For example, Well No. 26 is the southern-most well in the Clay Creek aquifer and is not affected by the operation of the recharge program. The hydrograph for Well No. 26 illustrates "typical" changes in the water table in an alluvial aquifer. The water table rises in the winter months during periods of lower water demands and well pumping, and the water table declines during the summer months 28 - _.