Opportunities for the development of seasonal ecosystem services in the context of sustainable river hydrology

Floodplain meadows, renowned for their biodiversity and ecosystem services, represent the only completely natural meadow ecosystems in Latvia. These areas play a dual role: as natural sponges mitigating flooding and as nutrient-rich environments fostering agricultural productivity. However, the installation and operation of hydroelectric power plants (HPPs) pose significant threats to these ecosystems by altering natural water flows, causing sediment accumulation, and impacting biodiversity, particularly in Natura2000-protected areas. This study focuses on the Svete River basin in central Latvia, which exemplifies the challenges posed by HPPs to sustainable river hydrology. Utilizing nine monitoring stations across a key river section, this research employed cutting-edge hydroacoustic and barometric pressure compensation equipment to assess water level fluctuations, flow dynamics, and water quality parameters. Data collection included automated 15-minute water level readings and comprehensive flow measurements at each station. Initial findings reveal that HPPs contribute to river overgrowth, fluctuating water levels, and increased sediment deposition, which lead to morphological and hydrological changes. Oxygen content was observed to range from 5.2 to 5.6 mg/L in August, while nitrate concentrations peaked between 52 and 56 mg/L in February, highlighting significant seasonal variations. The prohibition of new mechanical barriers on the Svete River under Latvian legislation emphasizes the recognition of these risks and the need for sustainable solutions. Addressing these challenges requires balancing the operational needs of HPPs with the ecological integrity of floodplain meadows. Recommendations include regular maintenance of HPP hydraulic structures and adherence to building safety programs to minimize ecological impacts. These measures, combined with sustainable river management practices, are vital for preserving floodplain ecosystems and enhancing their seasonal ecosystem services.