Potential Climate Change Impacts
In parts of Mexico climate change is projected to produce a decrease in water flow. Furthermore, an increase on water demand is expected due to increasing temperature and extreme weather conditions such as droughts and floods due to El Niño Southern Oscillation and La Niña are expected to become more frequent.
The IPCC considers various scenarios with increases in temperatures ranging between 1 and 6 degrees Celsius. By 2050, the Mexican Institute of Water Technology expects a 7-12% decrease in precipitation in the southern basins, 3% in the Mexican Golf basin, and 11% in the central basin. Precipitation is estimated to continue to decrease over the next 50 years. An increase in category 5 hurricanes is also expected.
During some El Niño/La Niña years, winter precipitation may be so great that stream flow and water levels in dams may exceed those observed during summer. In contrast, summer droughts during these events can lead to serious deficits in reservoir levels and in rain-fed maize production. In Mexico during 1997, the estimated costs of climate anomalies associated with El Niño were 900 million US dollars, particularly in agricultural activities, when 20,000 km² (5 million acres) were affected by a severe drought.
In 2007, SEMARNAT together with the Instituto Mexicano de Tecnología del Agua published a study “Climate Change Effects on Water Resources in Mexico.” The main findings are summarized below.
Qualitative vulnerability to climate change by hydrologic-administrative region
| Hydrological Region | Change in demand | Change in availability | Scarcity | Hurricane, storms | Droughts | Change in sea level | Observations |
|---|---|---|---|---|---|---|---|
| Baja California | Major | Decrease | Very vulnerable | Not very vulnerable | Vulnerable | Not very vulnerable | The basin depends on water flowing from the US, which is expected to reduce |
| Northeast | Major, agriculture biggest water use | Decrease | Very vulnerable | Not very vulnerable | Vulnerable | Sea intrusion on coastal aquifers | One of the most vulnerable regions in Mexico |
| North Pacific | Major, agriculture biggest water use | Unknown | Vulnerable | Vulnerable | Unknown | Sea intrusion on coastal aquifers | Need further studies |
| Balsas | Major | Probable decrease | Vulnerable | Very vulnerable in the coastal region Guerrero and Michoacan | Vulnerable | Sea intrusion on Rio Balsas | Severe effects on agriculture in Tlaxcala and highlands |
| South Pacific | Major | Unknown. Some models expect increased precipitation | Specially on high mountain | Very vulnerable, coastal region | Not very vulnerable | Not very vulnerable | One of the most vulnerable to storms |
| Rio Bravo | High due to increased population and temperature | Expected decrease on flows and aquifer recharge | Very vulnerable | Not very vulnerable | Very vulnerable | N/A | One of the most important basins and most vulnerable to scarcity and droughts |
| Central north basins | High, due to increased temperature | Expected decrease on flows and aquifer recharge | Very vulnerable | N/A | Very vulnerable | N/A | On of the most vulnerable basins to scarcity and droughts |
| Lerma-Santiago-Pacifico | Medium | Unknown, models predict few changes | Very vulnerable due to high use | Not very vulnerable | Vulnerable, high natural variability | Not very vulnerable | Need further research due to high vulnerability and uncertain models |
| North Gulf | High, due to increased temperature | High probability of increasing, according to most of the models | Not very vulnerable | Vulnerable | Not very vulnerable | High vulnerability on several rivers’ mouths | Probable need to revise design of hydraulic infrastructure, dams, and flooding control. |
| Center Gulf | High, due to increased temperature | High probability of increasing, according to most of the models | Not very vulnerable | Vulnerable | Not very vulnerable | High vulnerability on several rivers’ mouths | Probable need to revise design of hydraulic infrastructure, dams, flooding control, and landslide |
| South frontier | High, due to increased temperature | Few changes due to high availability | Not very vulnerable | Very vulnerable, especially on coastal Chiapas | Not very vulnerable, but need for new regulation works | High vulnerability especially on Grivalda and Campoton estuaries | Probable need to revise design of hydraulic infrastructure, dams, flooding control, and landslide |
| Yucatán | High, due to increased temperature | Vulnerable due to lack of regulation | Vulnerable due to lack of regulation | Very vulnerable, especially on coastal area | Vulnerable due to seasonal droughts | Vulnerable, due to sea intrusion on aquifers | Need of detailed research due to unique geology |
| Valley of Mexico | Low | Low | Very vulnerable | Vulnerable | Not very vulnerable | N/A | Already on water deficit, in need of high coast adaptation measures |
Source: SERMANAT (2007)
Read more about this topic: Water Resources Management In Mexico
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