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Weeki Wachee River System Recommended Minimum Flows and ...

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It is possible that the effect of pumpage is countered by an increase in precipitation over the last<br />

30 years. The Panel examined the relationship between discharge <strong>and</strong> precipitation as a possible<br />

indicator (Figure 4). One would expect that under similar conditions, rainfall <strong>and</strong> discharge<br />

would be related. Discharge <strong>and</strong> precipitation are significantly related but not very predictive.<br />

Perhaps a lag term needs to be applied because of the long residence time of the aquifer.<br />

300<br />

250<br />

Annual Discharge (cfs)<br />

200<br />

150<br />

100<br />

50<br />

y = 0.8718x + 125.41<br />

R 2 = 0.1047<br />

P=0.004<br />

0<br />

30 40 50 60 70 80 90<br />

Annual Precipitation (in)<br />

Figure 4. Regression of annual precipitation <strong>and</strong> <strong>Weeki</strong> <strong>Wachee</strong> Spring discharge.<br />

Another way to look at this is by plotting the discharge:precipitation ratio (Figure 5). It is clear<br />

that there has been no great change in the relative amount of discharge. While the ratio has been<br />

declining since the 1960s, it is not any lower than it was prior to then. If pumpage was having a<br />

significant effect on discharge, it should be evident from this graph.<br />

13

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