This dataset comprises the simultaneous monitoring of about 50 high mountain lakes in the Spanish’s Sierra Nevada carried out in collaboration with government agencies and local communities as part of a citizen science campaign. Standard monitoring protocols were used to collect data on various physical (temperature, pH, dissolved oxygen, water clarity), chemical (nutrients, major cations and anions, chlorophyll a, alkalinity), and biological parameters (bacteria, zooplankton) in two successive years. High mountain lakes are ideal sites to study and understand global change processes. The utilisation of these systems as sentinels of global change can be attributed to various characteristics, such as: modest catchment areas, oligotrophic waters with limited nutrients, remote accessibility, relatively good ecological health, elevated altitudes and harsh environmental conditions, or the presence of relatively uncomplicated biological communities with rapid renewal rates, among others. The involvement of the community in Sierra Nevada Long-Term Monitoring Programs serves as an invaluable complement to scientific endeavours aimed at monitoring environmental changes, as it contributes to alleviate personnel and resource shortcomings (Villar-Argaiz et al. 2022).