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Relationships of Florida Sandhill Lake Soil Parameters with the Capillary Fringe, Oxidation-reduction Potential, and Air Entry Values

出版	University of Florida, 2006
URL	http://books.google.com.hk/books?id=uHt6AQAACAAJ&hl=&source=gbs_api

註釋ABSTRACT: Sandhill lakes typically lack reliable hydrologic indicators so Minimum Flows and Levels (MFLs) have proven difficult to determine. The MFLs define the minimum hydrologic regime needed to protect the water resources and associated ecological systems of an area from unacceptable harm resulting from consumptive use of water. Lake stage indicators (LSIs) were developed at sandhill lakes to support the determination of minimum levels. The LSIs are unique soil morphologies that have been linked to specific long-term lake stage statistics. Existing changes and structural alterations must be considered in determining MFLs therefore; LSIs cannot be directly applied as the elevation component of minimum levels. Thresholds that allow for an offset from the LSIs, were recommended by St. Johns River Water Management District to support the determination of minimum levels. The thresholds are intended to allow for a hydrologic shift from the LSIs equivalent to the capillary fringe height (CFH) or the height of anaerobic conditions (HAC) above a water table in soils associated with LSIs. The CFH and HAC were measured in soil cores collected where LSIs were identified at three sandhill lakes in northeast Florida, USA and ranged from 3.3 to 11.8 cm and 5.4 to 16.5 cm, respectively. The CFH and HAC are time consuming to measure and thus multiple regressions were developed to estimate these parameters from easily determined physical soil characteristics. The CFH was best predicted by the soil characteristics clay (cl), very coarse (vc), coarse (c), fine (fi), and very fine (vf) sand fractions (Eq. AB-1, adj. R2 = 0.6279). CFH = 2.60(%cl) + 9.22(%vc) 1.90(%c) 0.37(%fi) 0.60(%vf) + 28.15 (AB-1) The physical soil characteristics that provided the best relationship with HAC were the same as in Eq. 1, however the strength of the relationship was diminished (Eq. AB-2, adj. R2 = 0.4601).