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4-17 <br />• Aquifers with a low yield to wells are developed in sandstone <br />strata and locally in the coal seams. The permeability of the <br />sandstone strata is a combination of primary (intergranular) and <br />secondary, (fracture) permeability. The coal seams have a sig- <br />nificant secondary permeability only locally where there is <br />significant fracturing; primary permeability is always very low. <br />The water flow may be highly variable in various directions and <br />at different locations, depending on the nature of fracturing <br />present. Because fracturing is localized and not continuous, <br />the coal seams do not appear to be significant aquifers. <br />Regional dip of the Mesaverde Formation strata is about three <br />degrees to the northeast and the main ground water flow direction <br />• is governed by this dip. The principal recharge to the aquifers <br />occurs where the aquifers are subcropping beneath the stream <br />beds filled with saturated alluvium. Direct infiltration of <br />precipitation and snowmelt on the outcropping areas of water <br />bearing formations is secondary. Due to the lithological char- <br />acter of Pdesaverde Formation - alternating sandstones, siltstones, <br />shales, claystones and coals - the vertical component of the <br />recharge due to primary permeability is minimal. The plastic <br />character of the fine-grained units also prevents the development <br />of a significant secondary (fracture) permeability, so that <br />vertical recharge due to secondary permeability is also minimal. <br />Local vertical infiltration can develop perched aquifers of <br />• limited extent above the stream beds. In areas where major <br />