TITLE:
Climate Change Effects on Evapotranspiration in Mexico
AUTHORS:
Martín Mundo-Molina
KEYWORDS:
Climatic Change, Reference Evapotranspiration, Irrigation Agriculture
JOURNAL NAME:
American Journal of Climate Change,
Vol.4 No.2,
May
11,
2015
ABSTRACT: In Mexico’s case, the scarcity of water in
the north of the country is worrying, even more from the agricultural point of
view because according to the results of general circulation models, a major
impact due to global warming is expected in this region, and it will have
important repercussions on the rural sector in the north of Mexico. According
to [1] the results of the sensitivity analysis made in this study indicate that
the most vulnerable zone is the north of Mexico, wherein the increase of
evapotraspiration (ET) is greater in comparison to the rest of the country; up
to 8% annual average for a +3°;C growth in mean annual temperature. Due to some
limitations in this preliminary investigation (e.g., global temperature data
was used without regionalizing it), it was decided to make more detailed
studies to estimate the climate change effects on ET on a regional scale, using
the downscaling method to adjust temperature data. In this study a new
methodology to estimate the ET before climate change scenarios is introduced,
which includes the selection of the Hargreaves-Samani method (HS), calibrated
and compared against the Penman-Monteith ASCE method in various irrigation
districts in the northern part of the country, obtaining ET estimations with a
93% precision. This procedure was applied to nine states in north Mexico: Baja
California, Baja California Sur, Chihuahua, Sinaloa, Sonora, Tamaulipas, Nuevo
León, Coahuila y Durango. The principal results are enunciated as follows: the
ET variations between the contemporary scenario and the 2030 scenario are quite
significant, according to the data of 160 meteorological stations; for
temperature variations between 0.1°;C to 0.45°;C the corresponding ET fluctuation
goes from 2% in the current scenario to 7% in the 2030 scenario. These obtained
percentages are greater than the ones expected to happen for the precision of
the method. It is important to note that a 7% rise of ET (related to a regional
temperature increase of approximately one degree) would represent in practice
having more millions of m3 of water in dams to satisfy the water demand of
crops.