## 3 Data and Methods of Analysis  
### Data Collection  
A GSSI Profiler EMP-400 multi-frequency EM conductivity meter integrated with a GPS receiver was deployed in an unmanned, flat-bottomed plastic kayak towed 6 m behind a motorized skiff (Figure 2A). The instrument was initially calibrated at the GSSI factory by suspending it well above the ground and zeroing the field values. Immediately before data acquisition, field calibrations were performed on-site. The field calibration procedure removes any electromagnetic effects of the operator and other equipment in the surrounding area. However, since the kayak contained no conducting materials and was towed 6 m behind the skiff, little if any external effects affected the data. The EM data were recorded in a vertical dipole moment (VDM) at 1, 4, and 16 KHz frequencies. Six electromagnetic surveys were conducted in West Lake and Seven Palm from January 2016 to February 2017 (Table 1, Figure 2A) to assess the seasonal variability in conductivity between wet and dry seasons.  
During the EM survey, at different localities and different intervals of time, the surface water conductivity, temperature, pH, and salinity were measured using a YSI water quality data sonde. Water depths were measured continuously using a sonar transducer and at spot locations using a calibrated rod.  
VES surveys were conducted at spot locations in the Seven Palm and West Lake systems in July 2019 using a floating 14-electrode cable with a 1 m electrode spacing (Figure 1). The cable was suspended at the water surface using foam floats (noodles) attached in between the electrodes (Figure 2B). Each survey consisted of a set of 48 dipole-dipole measurements recorded with both 1 m and 2 m dipole lengths. The dipoles were spaced at distances ranging from 1 to 11 m (n, Figure 2B). Reciprocal measurements where the current and potential electrode pairs are exchanged were included in each survey. These reciprocal measurements provide redundancy and the ability to estimate measurement uncertainty. The measurements from the evenly spaced electrodes were repeated multiple  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Year** & & \multicolumn{2}{c}{**2016**} & \multicolumn{2}{c}{**2017**} \\ \hline
**Month** & **Jan** & **Feb** & **Mar** & **Apr** & **Jan** & **Feb** \\ \hline West Lake & ✓ & & & & & & ✓ \\ \hline Seven Palm & & ✓ & ✓ & ✓ & ✓ & \\ \hline \hline \end{tabular}
\end{table}
Table 1: EM survey times (✓).  
times. The dipole measurements were averaged from either 2 or 4 measurements. The average value of the measurements and the reciprocal measurements were used. This resulted in a set of 11 dipole-dipole VES measurements at each spot location.  
Continuous measurements of water level, temperature, and conductivity were recorded using Aqua troll 200 data sondes in four shallow monitoring wells and at four adjacent locations within the lakes [35] (Figure 1). Coincident conductivity measurements recorded from the wells and resistivity measurements produced using the floating dipole-dipole electrical resistivity array in July 2019 were used to estimate the formation factor. Similar to the EM survey, at different localities and different intervals of time, the surface water conductivity, temperature, pH, and salinity were measured using a YSI water quality data sonde at the electrical resistivity measurement sites. Water depths were measured using a calibrated rod during the electrical resistivity surveys.