Hydrological dynamics of a Mediterranean water drain network: Implications for Aedes albopictus surveillance and...

Water drains act as cryptic but prolific mosquito larval habitats and are often the most productive breeding sites in urban landscapes. Understanding how climate and water infrastructures interact to shape these breeding habitats is essential for controlling vectors like Aedes albopictus. Across two mosquito seasons (2023-2024), we monitored drains in a managed (with vector control) botanical garden and an unmanaged residential area to quantify water dynamics and larval presence. We identified discharge outlet height as the critical structural determinant of water retention: drains with outlets near the basin floor rarely retained water, preventing mosquito breeding. Median water residence time was a strong predictor of larval presence, even under active vector control treatments; treated drains with residence times exceeding 7 days exhibited larval positivity rates 7.7 times greater than those with shorter residence times. To associate weather with drain-scale hydrological dynamics, we developed a mass-balance approach to compute a Water Storage Index (WSI), capturing the proportion of stagnant water across a drain network. Our analysis revealed a prolonged system's response, where rainfall adds water rapidly, whereas evaporation removes it slowly, both being equally relevant drivers of water dynamics. The WSI effectively scaled these climatic variables into a metric of network-wide breeding capacity. We propose lowering discharge outlet as a primary prevention strategy. Where water retention persists, median water residence time and the WSI serve as complementary ecological indicators to identify high-risk drains and periods of elevated larval carrying capacity, providing a scalable framework for anticipating mosquito-borne disease risk under intensifying climate variability.