Uncertainty in climate change impacts on water resources in the Rio Grande Basin, Brazil

Abstract

Abstract. We quantify uncertainty in the impacts of climate change on the discharge of Rio Grande, a major tributary of the Paraná River in South America and one of the most important basins in Brazil for water supply and hydroelectric power generation. We consider uncertainty in climate projections associated with the greenhouse-gas emission scenarios (A1b, A2, B1, B2) and increases in global mean air temperature of 1 to 6 • C for the HadCM3 GCM (Global Circulation Model) as well as uncertainties related to GCM structure. For the latter, multimodel runs using 6 GCMs (CCCMA CGCM31, CSIRO Mk30, IPSL CM4, MPI ECHAM5, NCAR CCSM30, UKMO HadGEM1) and HadCM3 as baseline, for a +2 • C increase in global mean temperature. Pattern-scaled GCM-outputs are applied to a large-scale hydrological model (MGB-IPH) of Rio Grande Basin. Based on simulations using HadCM3, mean annual river discharge increases, relative to the baseline or control run period , by +5% to +10% under the SRES emissions scenarios and from +8% to +51% with prescribed increases in global mean air temperature of between 1 and 6 • C. Substantial uncertainty in projected changes to mean river discharge (−28% to +13%) under the 2 • C warming scenario is, however, associated with the choice of GCM. We conclude that, in the case of Rio Grande Basin, the most important source of uncertainty derives from the GCM rather than the emission scenario or the magnitude of rise in mean global temperature.

Effect of modelling scale on the assessment of climate change impact on river runoff

“…This partly corresponds to the observation pointed out by several authors , Hughes et al 2011, Nóbrega et al 2011) that the mean annual runoff can mask considerably greater seasonal variations which are of high importance to water management.…”

Hydrologic impact of climate change on Murray–Hotham catchment of Western Australia: a projection of rainfall–runoff for future water resources planning

“…Frederiksen et al (2011c related reduction in rainfall in SWWA since the mid-1970s, to changes in growth rate and structures of leading storm track and blocking modes. During winter, considerable reductions in growth rates of the leading storm track modes were observed across the southern part of Australia between 1949-1968and 1975-1994which continued into 1997-2007(Frederiksen et al, 2011c. Frederiksen et al noted that in recent times storm activity moved from latitudes of subtropical jet to latitudes of polar jet, and reductions in rainfall of SWWA since the mid-1970s are consistent with these changes in storm activity.…”

The global-scale impacts of climate change: the QUEST-GSI project

“…One way to resolve this is to construct coherent spatially-variable, multi-sectoral stories from individual climate model scenarios (as in Arnell et al ( this issue a)), but in order to represent uncertainty it is necessary to build many stories. One major lesson learnt in the QUEST-GSI project from Water Arnell et al (2011), Gosling et al (2010Haddeland et al (2011);Arnell and Gosling (2013), Arnell and Gosling (this issue), Gosling and Arnell (this issue) Catchment-scale ), Arnell (2011), Hughes et al (2011, Kingston and Taylor (2010); Kingston et al (2011);Nobrega et al (2011);Singh et al (2010); Thorne (2011), Xu et al (2011 Agriculture and food Fraser et al (2008;; Osborne et al (2012); Simelton et al (2009;; Dawson et al (2014) Coastal zone Nicholls et al (2011);Brown et al (this issue) Terrestrial ecosystems Gottschalk et al (2012) Human health Lloyd et al (2011);Lloyd et al (2015) presentations to different audiences is that different audiences have different requirements so results need to be presented in a wide variety of ways. Some audiences are more concerned with the ranges of potential impacts and are not concerned with whether the extremes can occur at the same time; others are more concerned with synchronous impacts in different places or sectors.…”