Aerial and surface rivers: downwind impacts on water availability from land use changes in Amazonia

Abstract

Abstract. The abundant evapotranspiration provided by the Amazon forests is an important component of the hydrological cycle, both regionally and globally. Since the last century, deforestation and expanding agricultural activities have been changing the ecosystem and its provision of moisture to the atmosphere. However, it remains uncertain how the ongoing land use change will influence rainfall, runoff, and water availability as findings from previous studies differ. Using moisture tracking experiments based on observational data, we provide a spatially detailed analysis recognizing potential teleconnection between source and sink regions of atmospheric moisture. We apply land use scenarios in upwind moisture sources and quantify the corresponding rainfall and runoff changes in downwind moisture sinks. We find spatially varying responses of water regimes to land use changes, which may explain the diverse results from previous studies. Parts of the Peruvian Amazon and western Bolivia are identified as the sink areas most sensitive to land use change in the Amazon and we highlight the current water stress by Amazonian land use change on these areas in terms of the water availability. Furthermore, we also identify the influential source areas where land use change may considerably reduce a given target sink's water reception (from our example of the Ucayali River basin outlet, rainfall by 5-12 % and runoff by 19-50 % according to scenarios). Sensitive sinks and influential sources are therefore suggested as hotspots for achieving sustainable land-water management.

Forest‐Induced Exponential Growth of Precipitation Along Climatological Wind Streamlines Over the Amazon

“…as a large source for terrestrial precipitation (Gimeno et al, 2012;Schlesinger & Jasechko, 2014) through intense moisture recycling (Eltahir & Bras, 1994), which can lead to cascading effects affecting the distribution of continental precipitation (Staal et al, 2018;Weng et al, 2018;Zemp et al, 2017). Collectively, these mechanisms imply that forests have a strong potential to influence precipitation, consistent with converging research results that extensive forest loss can change precipitation patterns over extensive continental regions (including the Amazon; Lawrence & Vandecar, 2015;Mahmood et al, 2013;Spracklen & Garcia-Carreras, 2015).…”

“…There is increasing scientific evidence about forest‐induced mechanisms, which affect land‐atmosphere exchanges of water and precipitation production processes including accumulation and redistribution of soil moisture by root systems (Nadezhdina et al, ), long‐term regulation of extreme river flows (Salazar et al, ), strong capacity for stomatal regulation due to the large cumulative surface area of leaves (Berry et al, ), triggering of shallow convection (Wright et al, ), production of biogenic cloud condensation nuclei (Poschl et al, ), and the surface drag that is caused by the large height of trees affecting the flow of air over the forests (Khanna et al, ). Further, transpiration from the Amazon forests has been identified as a large source for terrestrial precipitation (Gimeno et al, ; Schlesinger & Jasechko, ) through intense moisture recycling (Eltahir & Bras, ), which can lead to cascading effects affecting the distribution of continental precipitation (Staal et al, ; Weng et al, ; Zemp et al, ). Collectively, these mechanisms imply that forests have a strong potential to influence precipitation, consistent with converging research results that extensive forest loss can change precipitation patterns over extensive continental regions (including the Amazon; Lawrence & Vandecar, ; Mahmood et al, ; Spracklen & Garcia‐Carreras, ).…”

“…Fundamental questions are whether and how the extensive forests of the world (including the Amazon) affect these precipitation patterns. Uncertainties and concerns about this issue are highlighted by these ecosystems being highly threatened worldwide (Hansen et al, ; Malhi et al, ; Potapov et al, ) and a growing body of evidence indicating how terrestrial precipitation regimes are related to the presence of forests, especially in the Amazon and neighboring continental areas (Boers et al, ; Davidson et al, ; Hirota et al, ; Khanna et al, ; Lawrence & Vandecar, ; Makarieva et al, ; Spracklen & Garcia‐Carreras, ; Staal et al, ; Stickler et al, ; Weng et al, ; Zemp et al, ).…”

“…Depending on its seasonal variability, the moisture flows toward either northwestern or southern South America (Arraut et al, ; Berbery & Barros, ; Drumond et al, ; Marengo et al, ; Martinez & Dominguez, ; Nieto et al, ). Thus, the Amazon basin connects the Atlantic ocean with other major basins and, therefore, it is an important source of moisture for precipitation in, for example, the La Plata (Martinez & Dominguez, ; Weng et al, ) and Orinoco (Drumond et al, ; Nieto et al, ; Weng et al, ) basins.…”

Atmospheric Basins: Identification of Quasi‐Independent Spatial Patterns in the Global Atmospheric Hydrological Cycle Via a Complex Network Approach

“…Atmospheric moisture transport processes act as "rivers" in the atmosphere (Arraut et al, 2011), transporting moisture from its terrestrial source location where it enters the atmosphere through evaporation, to the terrestrial sink location where it precipitates and leaves the atmosphere. Therefore, atmospheric moisture transport processes build links between evaporation and precipitation locations and serve as linkages between terrestrial river basins (Sorí et al, 2018;Wang-Erlandsson et al, 2018;Weng et al, 2018), closing the hydrological cycle from a land-atmosphere perspective. A deep understanding of atmospheric moisture transport processes and the built links will improve our understanding of the global hydrological cycle from the viewpoint of land-atmosphere coupling.…”