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targeted 120 wells were never pleasured under finis task and are therefore not included in the <br />hydrographs in Appendix D. Of the 120 hydrographs, 18 are alluvial wells, 102 are wells <br />completed in bedrock aquifers. The period of record shown on the hydrographs for each well is <br />different since all of the measurements available for a given well are presented. Measurements <br />Have beep collected op an annual basis since the nnid 1980's for most of the wells >lncluded in <br />Appendix D, wifln bi-arunual measurements collected since 2003 as part of earlier phases of finis <br />task. <br />The annual spr>ingtiple measurements collected by the DWR since tlne mid-1980's provide a <br />valuable record of long-term changes in aquifer water levels. Though variations in water levels <br />from local pumping and other effects may be seen in these wells over only a few years of data, a <br />much more complete picture of water levels emerges when wells have been measured over an <br />extended period of time. The primary purpose of collecting autumn water levels under Task 39 <br />was to identify seasonal trends witln>ln the data. <br />Autumn water level measurements have been collected for three years under different phases of <br />the SPDSS and were evaluated for seasonal trends. While some wells show a predictable <br />seasonal variation (such as the autumn water levels are always lower than previous spring <br />water level), several wells do not demonstrate any seasonal trend u1 water levels. Several of <br />these wells are domestic or municipal wells that are actively pumped. The pumping history of <br />the measured well and of nearby wells and even whether the well is pumping at the time of <br />measurement is generally unknown. Therefore, it is possible that some of the water level <br />measurements are affected by pumping. As with long-term springtime measurements, autumn <br />measurements would likely show a general trend over an extended period of time. However, <br />with the linnited dataset of three years, the localized effects of pumping can be quite significant <br />and make trends indiscernible in some of the measured wells. <br />The hydrographs presented iln Appendix D show different types of seasonal trends that can be <br />grouped according to tlne one of the following descriptions: <br />A. Wells show a cyclical pattern where autumn water levels are always lower than tlne <br />previous springtime measurement and generally lower than tlne follownng spring's <br />measurement. This trend >lndicates that seasonal pumping has affected water levels in <br />tlne vic>lnity of the measured well. <br />B. Wells show continued long-term trends where autunnn measurements fall generally on a <br />trendl>lne between two sequential spring measurements. <br />C. In a few >lnstances, autumn water levels are higher than the spring levels. This trend <br />suggests that the aquifer has been recharged during the sunnmer by irrigation from a <br />surface water source. <br />D. A large portion of the wells show no discernible seasonal trend. <br />The fourth group of wells (Group D, those with no discernible seasonal variation) is the most <br />abundant in tlne hydrographs. An example of this type of water level trend can be seen in <br />Appendix D, Figure D-104, Meridian W&S LFH-1. Tlne next most abundant grouping of wells is <br />Group A (autumn water levels consistently below spring measurement). Figure D-1, well KB- <br />25A shows this seasonal behavior quite dramatically. This type of behavior is seen iln many of <br />the continuously monitored alluvial wells discussed iln Section 2.2 below. Many wells show no <br />seasonality and autumn measurements generally fall in lime with the long-term spring <br />SPDSS Phase 4 Task 39 Technical Memorandum-Final <br />O~i20%2008 <br />