Lakes of varying salinity are ubiquitous in dune environments with semiarid climates. Often these lakes become solute traps due to specific groundwater flow conditions. Over geological time after emergence of such lakes, the groundwater flow and mass transport processes lead to accumulation of solutes. This salinity increase can result in mineral deposition and free convection from lakes. However, high solute concentrations in these lakes are often not observed. We propose a conceptual model that estimates the lake salinity dynamics and yields concentration profiles beneath the lakes over centennial and millennial scales. Unlike previous approaches, a simple mathematical model is proposed based on coupling the lake solute mass balance with the advection-dispersion equation. We discuss limitations of the model and apply it to conditions of the Nebraska Sand Hills, USA. We show that the lake salinity concentration is consistent with the regional paleoclimate data. The proposed model can be used to constrain hydrologic paleoclimate reconstructions, which is a significant challenge for lakes in dune environments.