notebook - Southwest Florida Water Management District

Item 38
Operations and Land Management Committee
October 30, 2012
Routine Report
Structure Operations
September historically marks the last month of the four-month wet season and this year’s
September provisional rainfall totals were less than expected, falling into the low-normal to
below-normal range in all regions of the District. Rainfall received during the first three months
of the 2012 wet season significantly improved hydrologic conditions, but the passage of Tropical
Storm Isaac in late August saw a weather pattern shift to somewhat drier conditions. Analysis of
provisional rainfall data for the four-month wet-season shows District-wide totals to be about
5.1 inches above the long-term historic average. As the District enters into the 8-month dry
season (October through May), the 12- and 24-month cumulative rainfall deficits, District-wide,
are approximately 1.4 and 7.3 inches, respectively.
Hydrologic indicators continued to show improvement in most regions of the District during
September, while the Tampa Bay Region saw declines in lake levels and streamflow.
Streamflow conditions in regional index rivers continue to remain at levels that allow their use as
public supply sources.
NOAA climate forecasts continue to predict above-normal rainfall conditions from October
through April due to continuing development of El Niño conditions in the Pacific Ocean. Above
normal rainfall during the dry season would help maintain or improve overall hydrologic
conditions, and would help prevent any resource-related impacts during the coming dry season.
Updated weather forecasts will be available in mid-October. Staff will continue to closely monitor
conditions in accordance with the District's updated Water Shortage Plan, including any
necessary supplemental analysis of pertinent data.
Rainfall
Provisional rainfall totals as of September 30 th were below-normal in the northern and southern
regions of the District, while they were in the low-normal range in the central region. The normal
range is defined as rainfall totals that fall on or between the 25 th to 75 th percentiles derived from
the historical data for each month.
• Northern region rainfall averaged 3.69 inches, equivalent to the 19 th percentile
• Central region rainfall averaged 5.21 inches, equivalent to the 29 th percentile.
• Southern region rainfall averaged 5.10 inches, equivalent to the 21 st percentile.
• District-wide, average rainfall was 4.75 inches, equivalent to the 21 st percentile.
A summary of the operations made in September is as follows:
• Inglis Water Control Structures: Both the Inglis Main Dam and Bypass Spillway were
operated during the month of September in order to maintain water levels in Lake Rousseau
and provide flow to the lower Withlacoochee River. The average monthly water level for Lake
Rousseau was 27.61’ NGVD compared to the recommended maintenance level for the
reservoir of 27.50’ NGVD.
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