Lake Kinneret (the Sea of Galilee) is a key freshwater source in the water-scarce Eastern Mediterranean. However, its relatively high salinity (~260 mg Cl/L) poses challenges for agriculture, groundwater quality, and drinking water supply in Israel and Jordan. Salts enter the lake through onshore and offshore saline springs (point sources) and seepages from surrounding sediments (non-point sources). Fluctuations in lake and groundwater levels alter the hydraulic gradient, affecting Lacustrine Groundwater Discharge (LGD). However, the impact of these changes on brine discharge and shallow groundwater salinity remains poorly understood. To investigate these processes, shallow (~1 m) monitoring wells were hand-dug along the shore near the Kinneret Limnological Laboratory. Groundwater was monitored using sensors (every 15 minutes) and water sampling (biweekly). Sensors recorded electrical conductivity (EC), water level, temperature, dissolved oxygen (DO), and pH, while water samples were analyzed for major ions, trace elements, and water isotopes (δ¹⁸O, δ²H). Results show that as lake levels rose and flooded the monitoring area, groundwater salinity increased. The hydraulic gradient between groundwater and the lake intensified, leading to higher salt influx. Chemical and isotopic analyses revealed two distinct water sources: a fresh end-member (Lake Kinneret water) and a saline end-member, a mixture of non-Ca-chloridic brine (abundant around the lake) and fresh groundwater with a light isotopic signature. Since the saline end-member is located beneath the lake, it contributes to well salinization when the lake level rises and inundates the area. This occurs because the lake, as the lowest hydraulic head in the region, directs brine flow toward it. This study demonstrates that lake level fluctuations influence brine discharge and groundwater mixing. The monitoring approach can be applied to similar lacustrine environments to distinguish water sources and LGD regimes, improving our understanding of saltwater intrusion in freshwater lakes.