Gauge Record Hydrologic Statistics: Indicators for Lake Classification
ROBERT J. EPTING, C. PRICE ROBISON,
AND RAVI C. REDDI
Environmental Consulting & Technology, Inc., Gainesville, FL
Division of Water Supply Management, St. Johns River Water Management District, Palatka, FL
Beacon Systems, Inc., Coconut Creek, FL
Surface water structures and associated active stage management and water use have altered many lakes. Assessing the degree of alteration requires an indicator of hydrologic regime as a first step. Water level regime is an organizing principal of soil morphology and the structure and function of wetland vegetative communities in lakes, marshes, ponds, and wet prairies. Although lake classifications have included a wide variety of physical and biological indicators for various purposes, none is based on hydrologic statistics of water level regimes beyond frequency parameters and simple stage range. Statistical measures of exceedance and level change were derived from the gauge record for a sample of 135 lakes. These measures were used in a principal component analysis to derive independent indicators for lake classification. The first two principal components accounted for 88% of the variance of six original variables and identified two indicators of hydrologic regimes: stage range (50%) and stage rise/fall symmetry (38%). These indicators of hydrologic regime classified north Florida lakes into eight groups. The generally close correspondence of lake classes, based on hydrologic statistic indicators, to geomorphic and landscape classifications lends strong support to the general utility of this approach. This method will also be useful because the stage record integrates the inputs and outputs in lake water budgets, thereby providing insight into these components when specific data about their magnitudes are otherwise lacking.
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