Scenarios of climate change effects in water availability within the patos Lagoon’s Basin

ABSTRACT The decision-making processes involving water resources in Brazil and in neighboring countries have been based solely on analyses of the historical behavior of hydroclimatological variables. However, this may lead to inappropriate strategies in regards to the use of natural resources, since the impact of future climate change may significantly affect the availability of water resources. This study proposes an analysis of the variation in water availability of basins within the Patos Lagoon contribution area, which may be a consequence of climatic changes predicted by CMIP5 (Coupled Model Intercomparison Project Phase 5) models, published in the most recent International Panel on Climate Change (IPCC) report. Two 30-year periods were simulated, from 2006 to 2035 and from 2051 to 2080, through the MGB-IPH hydrological model, considering two extreme greenhouse gas scenarios and twenty climate change models. A tendency of increase of the flows was verified in the simulated basin, since over 60% of the simulations indicated some percentage of average flow increase across all discretized modeling units. The analysis of the simulation results indicated that the data from climatic models HadGEM2-ES and GFDL-CM3 used as input in the hydrological model are the ones that respectively provide upper and lower flow thresholds for the ensembled simulations. A joint evaluation of the results generated by these two models, associated with the scenario of high greenhouse gas emissions, is capable of covering extreme flow scenarios making predictions considering climate change in the Patos Lagoon’s basin. Whereas the results provided by bcc-csm1, BNU-ESM and CNRM-CM5 are similar to the median of the ensemble of simulations generated by all models evaluated in this research. In addition, the northernmost region of the study area was identified as having the highest sensitivity to climate change, as projected by global models of CMIP5 published in AR5.

摘要 巴西及周边国家的水资源决策此前仅基于水文气候变量的历史变化特征展开分析。然而，未来气候变化的影响可能显著改变水资源可获得性，进而导致自然资源利用策略失当。本研究针对帕图斯潟湖汇水区内各流域的水资源可利用性变化展开分析，该变化或由最新发布的国际气候变化专门委员会（International Panel on Climate Change，IPCC）报告中所采用的耦合模式比较计划第五阶段（Coupled Model Intercomparison Project Phase 5，CMIP5）模型预测的气候变化所引发。本研究借助MGB-IPH水文模型，对2006-2035年与2051-2080年两个30年时段展开模拟，考量了两种极端温室气体排放情景与20种气候变化模式。模拟结果显示，研究流域的径流量呈现上升趋势：超过60%的模拟结果表明，所有离散化建模单元的平均径流量均出现一定幅度的增长。对模拟结果的分析表明，作为水文模型输入的HadGEM2-ES与GFDL-CM3气候模式数据，分别为集合模拟提供了径流量的上下阈值。将这两种模式的结果与高温室气体排放情景相结合，能够覆盖帕图斯潟湖流域气候变化背景下的极端径流量情景预测。而bcc-csm1、BNU-ESM与CNRM-CM5的模拟结果与本研究评估的所有模式的集合中位数相近。此外，根据第五次评估报告（Fifth Assessment Report，AR5）中发布的CMIP5全球模式预测结果，研究区域的最北部被识别为对气候变化敏感性最高的区域。