Global empirical analysis of the role of forest in water surface availability on large basins

Abstract

ABSTRACT: Water availability is a fundamental element for any society and ecosystem. This availability depends mainly on climate. However, there are other factors that could affect the surface water availability such as soil properties, topography, drainage area and land cover. These factors are approximately invariant except for land cover, which is very sensitive to continuous changes along time. Among the different types of existing land covers, the forest is one of the most important. There is scientific evidence suggesting that forests play an important role in mass, energy and momentum exchanges between atmosphere and surface, which altogether affect surface water availability. Nevertheless, there is also a current debate about the actual importance of forests on water availability. Most of the studies analyzing these effects of forest cover on water yield are developed in a local spatial scale and/or in a short-term period. Accordingly, a research to test the linkage between surface water availability and multiple physical and ecological factors, especially forests, in global large basins was conducted. The main finding of these research is that forests are efficient descriptors of global water balance partitioning. Additionally, after evaluating multiple attributes of the basins and accounting possible bias in the analysis (e.g human intervention by dam construction), forests have a strong relation with water partitioning in tropical and temperate basins, while the snow-melt processes are controlling the partitioning in boreal basins. Finally, after analyzing the effects of climate and land cover changes over streamflow changes using a Budyko-based method in large basins of the world, it is concluded that more studies are required in order to develop a proper approach capable of accounting for all processes in the surface-atmosphere exchanges between vegetation and water balance.