Online first articles

Venezuela has a vast and diverse network of rivers and streams that provide essential water resources and ecosystem services, supporting a high biodiversity. This review aims to consolidate knowledge on the abiotic characteristics, hydrology, water chemistry, and sediments of these fluvial ecosystems from 1993 to date, while highlighting key research areas. Over the past three decades, advancements have been made in understanding the physical and chemical properties of these environments. A systematic literature review identified 209 relevant publications, averaging 34 studies every five years. Most studies have focused on the Orinoco River Basin, covering 655 000 km² of Venezuela's land area. Consequently, the distribution of research sites was uneven, with 59% of studies concentrated in the Orinoco basin, followed by 14% in the Caribbean versant, and 11% in the Lake Maracaibo basin. Other basins, such as Paria-San Juan and Casiquiare-Negro, were notably underrepresented. The results revealed that 46% of the studies examined aspects of river hydrochemistry, 30% focused on hydrology, and 24% addressed sediments. The studies emphasized the importance of understanding hydrological dynamics, particularly in forecasting discharge and water levels in watersheds with large hydroelectric dams. While the database of fluvial ecosystems has increased, it is essential to continue these data collections in order to anticipate responses from human activities and climate change. Although the Orinoco, Caribbean, Lake Valencia, and Lake Maracaibo basins have received considerable attention, much of the knowledge is outdated. Additionally, the watersheds of Paria-San Juan, Casiquiare-Negro, and Cuyuní-Essequibo require urgent research due to recent environmental degradation.