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Hydrology

May 2019 Hydrology Report

Posted June 17th, 2019

May 2019 Hydrology Report

Precipitation

The Winter Haven area grossed a total of 2.9 inches of rainfall during the Month of May. This total was below May’s long-term average of 4.08 inches, but still within the normal range for this month. Accounting for water loss due to evapotranspiration, the net rainfall total for the City was -2.2 inches. This marks the fourth consecutive month in 2019 where the City totalled below-average gross rainfall and a negative net precipitation value. With increasingly warmer weather, the low precipitation numbers have resulted in increasingly greater rainfall deficits over the course of the year. See Figure 1 for rainfall details.

Figure 1 

Surface Level

Environmental response to rainfall can be observed by the change in local lake levels. The monthly average surface level for the South Chain of Lakes dropped from 131.66 ft above sea level in April, to 131.48 ft in May. Not only is this minor decline in lake levels normal for this time of year, but May typically marks the point where lake levels hit their lowest point annually.  Figure 2 illustrates this change of lake levels in response to rainfall. While surface levels have dropped over the last three months, they still remain well above the long-term average of 130.26 ft; currently still sitting above the upper limit of the normal range.

Figure 2

Groundwater

Measured as the elevation in feet above sea level, the Upper Floridan Aquifer (UFA) level is an important metric used to assess the hydrologic impacts on the City’s municipal water supply. As with lake levels, the UFA elevation fluctuates in accordance with net rainfall values. Below-average rainfall from February to May has resulted in a continuous decrease in the UFA level over the last four months. The average UFA level for May was 115.5 ft which is still above the long-term monthly average of 112.1 ft (Figure 3). Like with lake surface levels, the UFA typically reaches its lowest point annually during the month of May. Despite this decrease, the current level of the UFA remains unseasonably high; likely the result of significant winter rainfall on the tail-end of 2018.

Figure 3