Our new paper in Journal of Hydrology (link here) examines the groundwater flowing to Silver Springs. To those who have followed our work these past few years, this is our famous saltwater interface paper. We show that the dynamics of the saltwater interface 500 m below ground can explain the lag of about 15 years between the periodicity in recharge and spring discharge. This helps answer the long-standing question of why did Silver Springs discharge decline for decades when rainfall was constant? A quite reasonable hypothesis would be groundwater pumping. But we show that the lag from natural phenomena explains the non-intuitive relationship between recharge and discharge at this spring.
Fig. 1. Time series of 30-year averages of flow (blue) and rain (green) used for fitting sinusoidal long-term trends (red), which reveal a time lag of approximately 15 years.
Fig. 2. Data compared to model scenarios with pumping and saltwater interaction (continuous), without pumping but with saltwater interaction (dashed), and with pumping and without saltwater interaction (dotted). This shows that saltwater interaction is needed to explain the observed lag between recharge and discharge.