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level. Shallowing of the water level coincides with the operation <br />of the irrigation ditches, usually between llpril and October. The • <br />water levels decline between November and April. If water levels <br />respond due to precipitation events, they ar•e masked by the effect <br />of recharge from the irrigation network. There is no evidence that <br />mining has ]owered the piezometric surface in the vicinity of these <br />wells. <br />2. Well GW-N3 -- Underburden <br />Water level measurements have been taken at this well on a <br />monthly basis since August, 1979. The water level hydrograph <br />for this well shows a maximum seasonal water level fluctuation <br />of about seven feet during the period between 1980 and 1983. <br />The fluctuation in static water level in 1984, 1985, and 1986 <br />is only about two_ feet. Shallowing of the static water level <br />generally occurs between May and September, coinciding with t:he <br />operation of the irrigation ditches. <br />3. Well GW-N4 -- Dakota Coal • <br />Water level measurements have been made' at this well on a <br />monthly basis since August, 1979. The water level hydrograph <br />for this well shows a maximum seasonal vaater level fluctuation <br />of about 2.5 feet. The water levels generally increase between <br />June and October and decline between November and May. It <br />appears that there is about a one-month lag between when the <br />irrigation system starts up in April and when the static water <br />levels in the coal seam respond. There are no discernable <br />water level responses to precipitation, nor can any effect from <br />mining be observed. <br />4. Shop Well GW-N5 -- Underburden <br />Well GW-N5 was intended to be used as the' mine supply well but, <br />because of its extremely poor quality, it was never used for <br />anything except a monitor we]l. The water level hydrograph for <br />this well shows seasonal water level fluctuations of a few feet <br />during the past two years. The reason for this trend is not • <br />74 <br />