Abstract
The objective of this work is to assess the impacts of IPCC AR5 climate change scenarios on water resources and hydrological processes across the entire Brazilian territory. Hydrological simulations are carried out in total drainage area of about 11,535,645 km2 and average stream flow of about 272,460 m3/s. The study area consists of different climates and land covers such as the Amazon Forest, Northeast Semiarid, Brazilian Savannah, Pantanal wetlands and temperate climate in the South. The atmospheric forcing to drive the large-scale hydrological model MGB-IPH is derived from the downscaling of two global climate models, HadGEM2-ES and MIROC5, by the Eta Regional Climate Model, at 20 km resolution. The Eta model provided the downscaling of the baseline (1961-1990) and three time-slices (2011-2040, 2041-2070 and 2071-2099). These projections adopted two emission scenarios, the RCP 4.5 and RCP 8.5. The change in the average and extremes of precipitation, evapotranspiration, rates of river discharge and soil moisture were assessed. The simulations showed the response of the hydrographic regions due to change of precipitation and potential evapotranspiration in the scenarios. Water availability decreases in almost the entire study area (exception for the South) and the major basins for hydroelectric power generation are affected. The Northwest, Amazon and a small area along the Northeast Atlantic coast exhibited intensification of the extremes discharges, where the anomaly is positive for high-flow (Q10) and negative for low-flow (Q95). The results highlight the most climatic sensitive regions in Brazil in terms of hydrological variables and water resources.
Highlights
In the natural system of a watershed, a number of hydrological processes take place in different space-time frequencies and scales, influenced by physical characteristics related to soil, vegetation, geology, relief, and the drainage network, as well as by prevailing meteorological conditions and mostly the characteristics of the rainfall event
In view of the observed runoff trends in South America and Brazil, and of the projected trends derived from global and regional models, the objective of this study is to assess the impacts of climate change on the water budget and seasonal stream flow in Brazilian hydrographic regions using the new regional climate change projections from the global HadGEM2-ES (Hadley Global Environment Model 2—Earth System) and
The hydrological model was simulated for the present-day climate (1961-1990) using variables calculated by climate models
Summary
In the natural system of a watershed, a number of hydrological processes take place in different space-time frequencies and scales, influenced by physical characteristics related to soil, vegetation, geology, relief, and the drainage network, as well as by prevailing meteorological conditions and mostly the characteristics of the rainfall event. The Intergovernmental Panel on Climate Change-IPCC Fourth (AR4) and Fifth (AR5) Assessment Reports (available from: www.ipcc.ch) highlight the regions on earth that are more vulnerable to climate change, changes such as the increase or decrease of the total annual precipitation and by dryness or wetness that on the long-term affect the basin-scale water budget. The current strategy for estimating impacts of climate scenarios on river flow regimes is to use the Global Circulation Models (GCM) outputs as input for hydrological models. These studies may focus on hydrographic basin scale [2] [3] [4] or global scales [5] [6] [7] [8]. The simulations projected annual runoff reduction in seven river basins and an increase in runoff in seventeen river basins
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