Assessment of Surface Runoff Vulnerability to Climate Change in the Lerma-Chapala Basin, Mexico

Abstract

The Intergovernmental Panel on Climate Change (IPCC) suggests that vulnerability to climate change depends on three main factors: exposure, sensitivity, and adaptive capacity. Each factor was evaluated in a hydrologic context; for instance, exposure was interpreted as a change in surface runoff. Factors were combined using a geographic information system (GIS), and an overall methodology was proposed to map hydrologic vulnerability. The Lerma-Chapala basin was selected as a case study since the largest water body in Mexico is located at its outlet. The long-term rate of change in surface runoff was estimated considering the variation in future precipitation from 23 atmosphere–ocean general circulation models (AOGCMs) and by using the reliability ensemble averaging (REA) method. Two climate change scenarios from an IPCC special report on emissions scenarios and three time horizons (2030, 2050, and 2100) were chosen. Results showed a decrease in surface runoff of up to 29% (A1B-2100) in the northern part of the basin, and consequently this area is likely to have more frequent droughts. However, it would be challenging to compensate for the lack of surface runoff since groundwater resources are already depleted, and thus adaptive measures need to be taken.