Potentiometric surface of the Ozark aquifer in northern Arkansas, 2004

Hydrogeology and hydrologic conditions of the Ozark Plateaus aquifer system

“…Evapotranspiration is generally greatest during the summer and lowest during the winter, following the pattern of solar radiation (Brye and others, 2004); therefore, any potential recharge from precipitation during the summer is greatly reduced by evapotranspiration; water levels in shallow wells across the Ozark Plateaus generally increase during the winter to early spring wet season, but cease any increase or decline as the growing season begins. Surface topography also controls recharge because the position of the water table tends to reflect topography (Imes and Emmett, 1994;Schrader, 2005), and surface runoff is generally greater (that is, recharge is less) where slopes are steeper (Dugan and Peckenpaugh, 1985;Stieglitz and others, 1997). Recharge rate is dependent on surficial geology and soil type: permeable soils and fractured and karsted carbonate units exposed at the surface enhance recharge, whereas lowpermeability soils, thick, clayey regolith, and low-permeability bedrock exposures impede recharge.…”

“…Shallow and unconfined parts of aquifers receive this recharge directly from infiltration of precipitation or surface runoff. Deeper aquifer zones, where the aquifer is confined by overlying confining units, receive recharge via vertical leakage through fractures and faults (Imes and Emmett, 1994;Schrader, 2005;Czarnecki and others, 2009). The shallow groundwater system is closely connected to surface water in the Ozark Plateaus.…”

“…Losing sections of streams are common and contribute to groundwater recharge, and groundwater can reemerge and discharge to springs and gaining sections of streams. Recharge to the deeper confined groundwater-flow system depends on the geographic extent of where the aquifer formations crop out at the surface (Schrader, 2005) and the permeability of overlying confining units (MacDonald and others, 1977); therefore, the rate of recharge to the Ozark system is generally greater where the aquifer is shallow and unconfined and less for the deeper confined aquifer areas (Imes and Emmett, 1994). Recharge rates for the Ozark system range from 0.04 to 15 inches per year (in/yr)-which constitutes zero to 30 percent of annual precipitation-generally across outcrop areas of the Springfield Plateau aquifer and Ozark aquifer (table 5).…”

Water levels of the Ozark aquifer in northern Arkansas, 2013

“…In western Benton and western Washington Counties, the groundwater flow is generally to the west and northwest. Lamonds, 1972;Imes, 1990;Imes and Smith, 1990 In most of the study area, the general altitude and shape of the potentiometric surface of the Ozark aquifer has changed little since predevelopment or as was mapped in previously published USGS reports (Pugh, 1998(Pugh, , 2008Schrader, 2001Schrader, , 2005Czarnecki and others, 2014). A comparison of the predevelopment potentiometric surface (Imes, 1990) (Imes, 1990).…”

Potentiometric Surface of the Ozark Aquifer in Northern Arkansas, 2007

“…The lowest measured water level of 118 ft Table 1. Stratigraphic column with descriptions of lithologic and hydrogeologic properties of the Ozark aquifer and adjacent confining units within Arkansas (modified from Lamonds, 1972;Imes, 1990;Imes and Smith, 1990 In most of the study area, the general level and shape of the potentiometric surface has changed little since predevelopment or as mapped in previously published USGS reports in 1995 (Pugh, 1998), 2001(Schrader, 2001, and 2004 (Schrader, 2005). A comparison of the predevelopment potentiometric surface (Imes, 1990) and the 2007 potentiometric surface indicates general agreement between the two surfaces with the exception of parts of Benton, Carroll, and Washington Counties.…”