Mark Stewart Aaron L. Higer Gary M. Russell 1987 <p>Areas of low topographic relief have low water-table gradients and make the direction of movement of contaminants from land fills in the ground water difficult to predict from regional gradients alone. The landfill, nearby free-flowing ditches or canals, variations in hydraulic conductivity, and the influence of nearby pumping wells can all affect the direction of flow. In low-gradient areas the concepts of “upgradient” and “downgradient” are less useful in planning the location of monitoring wells than in areas of higher relief. Low-relief areas also may be affected by the discharge of mineralized water from deeper aquifers, naturally or through irrigation, which can mask geochemical surveys intended to detect landfill leachate.</p><p>Examples of effects of low topographic relief are noted in southeast Florida where water-table gradients are 7×10⁻-⁴<span>&nbsp;</span>to 5×10⁻-⁴<span>&nbsp;</span>feet per foot. Water-table mounding beneath the landfill and the drainage effects of nearby ditches and well have created multiple leachate plumes in Stuart where one plume migrated in a direction opposite to the apparent regional gradient. In Coral Springs analysis suggests a bifurcating plume migrating along two narrow zones. In Fort Pierce it was difficult to detect leachate because of mineralized irrigation water and fertilizer runoff from an adjacent citrus grove.</p><p><span id="_mce_caret" data-mce-bogus="1" data-mce-type="format-caret"></span></p> application/pdf 10.1111/j.1752-1688.1987.tb02963.x en Wiley Examples of landfill-generated plumes in low-relief areas, southeast Florida article