Climate variability and climate change, and their impacts on the freshwater resources in the border region -: A case study for Sonora, Mexico

Climate change scenarios and recent studies on climate variability refer to important low-frequency variations of precipitation regimes for the northern regions of Mexico. Data on precipitation, streamflow, and water levels in storage reservoirs are used to analyze tendencies and changes in water availability during the last 30 years. El Nino/Southern Oscillation (ENSO) events become of particular interest since El Nino boreal winters generally result in more precipitation and increased water availability in northwestern Mexico. However, summer precipitation in the region does not show a clear El Nino signal. Furthermore, the interannual variability of precipitation associated with the Mexican monsoon does not appear to be modulated by sea surface temperature (SST) variations. Historically, the economic development of the state of Sonora has been constrained by inequitable distribution of transboundary freshwater resources, a condition that may seriously worsen in the future. This issue will be particularly important in the design of strategies to adapt to or ameliorate the negative impacts of climate change. The predicted decline in water availability may exacerbate the trend toward increasing competition for water resources, namely, between productive activities, such as agriculture and industry (particularly maquiladoras), and domestic consumption by the increasing population in urban areas. These conditions make northern Mexico one of the most vulnerable regions in the country to climate changes.