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2009 Weeki Wachee Exploration Report
9 July 2010
In 2009, the Karst Underwater Research (KUR) team had just under 80 days of theoretical access (March 11 - May 28). During this period, the discharge at Weeki Wachee Spring dropped enough to allow the KUR cave exploration team to gain effective entry into the cave system beneath the spring. During this period, over 20 working dive days were conducted in a safe and efficient manner.
Based on KUR's direct experience, our team has determined that the safe cave diving can undertaken when the USGS Weeki Wachee Well (reference 283201082315601) stage level falls below 11.7 feet. As a point of comparison, the range of 11.5 - 11.7 feet of well stage is approximately 97 cubic feet per second (cfs). This equivalence is based on the well regression model for calculating discharge (Knochenmus and Yobbi 2001, SWFWMD 2008). It is important to recognize that a .1 foot fluctuation in the well stage can have a perceptible impact on the force of discharge, particularly at the restricted entrance area from the depth of 150 to 180 Feet Fresh Water (ffw). At 11.7 feet of well stage, the spring is viable to dive, but still far from easy. See further discussion of this topic under the "Diving Operations" section.
The 2009 window of opportunity varied in many ways from our two prior years (refer to Chart 1 below). We gained access earlier in the calendar year then either of the previous years (due presumably to the cumulative effective of the ongoing regional drought and a dry winter). Unfortunately, we also experienced earlier than normal seasonal rainfall which abruptly ended the season sooner than our two previous access intervals.
This year also saw a record minimum discharge on May 13, 2009 with the lowest recorded well stage of 10.67 feet (or 84 cfs per the well regression model). This eclipsed the previous record set in 2007 of 10.96 (or 88 cfs). It should be noted that discharge estimates using the well regression model applied to the USGS Weeki Wachee Well are considerably lower than the reported discharge for the Weeki Wachee River (USGS Site 02310525) and the well regression model appears to underestimate spring discharge, but it is a useful tool for judging diving conditions for Weeki Wachee Spring.
We could not guarantee that flow conditions would be conducive to access in future years. Given this uncertainty, rather than prioritizing further exploration during the 2009 access period, KUR decided to focus on collecting samples and video documentation of the system explored to date. The goal was to round out the body of information surrounding the spring to provide academia as well as the interested public with a richer appreciation of this unique underwater environment.
During 2009, KUR was able to:
Click here to view the entire 2009 Weeki Wachee Exploration. As always, we thank our sponsors and supporters for making the exploration at Week Wachee possible.