61
most part, overly stressed by the water demands posed by a growing population and
by the various economic sectors such as agriculture and industry (Scanlon et al.
2012). In addition to a WL drop produced after heavy groundwater withdrawals, the
water quality of depleted aquifers deteriorates in many cases posing a threat to the
health of communities that use this water (López et al. 2012; Alarcón-Herrera et al.
2013; Reyes Gómez et al. 2015). Since a substantial drop in WL indicates that the
sustainability of a vital resource is at risk, the rate of the WL drop has commonly
been used as an indicator of water availability and sustainability of aquifers. Efforts
towards reducing the negative effects of aquifer depletion require knowing the natural baseline of the hydrogeological behavior for that particular aquifer according to
urban, agricultural, and industrial uses and its water quality evolution. Hydrological
models can then use these data to characterize the response of an aquifer to impact
sources and to identify any potential threats to the quantity and quality of groundwater (El Alfy 2014). Investigators may go a step further and recommend actions
that will help achieving sustainability, such as direct artificial recharge, implementation of water-saving irrigation systems, and integral planning of best management
practices (Gale 2005). The WL continues to drop due to recurring intensive and
long-lasting droughts as well as poor groundwater management practices. Examples
include the Comarca Lagunera aquifer, which experienced an average WL drop of
over 30 m between 1975 and 1999 (1.25 m year
−1
), with a 65 m drop in some parts
and the Meoqui-Delicias aquifer, where the average WL drop was 30 m. In both
cases, the WL dropped as a result of water being used to irrigate crops (Esteller
et al. 2012).
In Mexico, the water policy states that the water is to be distributed among users
based on its availability, but its implementation has been lacking for the past 30 years
or so, as evidenced by water reports showing that the withdrawal volumes are almost
always larger than the approved volumes (Scott 2003). One method to correct this
deficiency is to take into account WL drop rates operating in the region prior to
water allocation, which would become more effective if this information was available for all water uses on a permanent and continuous basis. WL drop rates can also
be used to help identify threats and also to identify if these variations are cyclical in
nature (Scanlon et al. 2005).
Artificial recharge of aquifers has been considered as an action to counteract the
WL drop in systems already undergoing a certain degree of depletion, by means of
retention of surface water, injection to aquifer, or by reusing treated or pluvial water
to irrigate crops. These measures have successfully improved water sustainability in
some other regions where water is scarce (UNESCO 2007).
Although studies about aquifer recharge are common in Mexico, actions towards
achieving this goal at a pilot or at large scale are rare and those few studies have
operated for only a short interval of time (Esteller et al. 2012). One of these projects
aimed at recharging the aquifer of the Comarca Lagunera, a depleted aquifer with
high content of arsenic (As), by diverting water from a reservoir into the Nazas and
Aguanaval dry riverbeds. The attempt produced mixed results after recharged water
flow caused an obstruction in the deeper zones of the aquifer (Rosas et al. 1999).
Ongoing pilot tests to recharge aquifers in Mexico with treated water have been
reported as promising.
4 Changes in the Vegetation Cover and Quality of Aquifers in the Drylands of Mexico…
most part, overly stressed by the water demands posed by a growing population and
by the various economic sectors such as agriculture and industry (Scanlon et al.
2012). In addition to a WL drop produced after heavy groundwater withdrawals, the
water quality of depleted aquifers deteriorates in many cases posing a threat to the
health of communities that use this water (López et al. 2012; Alarcón-Herrera et al.
2013; Reyes Gómez et al. 2015). Since a substantial drop in WL indicates that the
sustainability of a vital resource is at risk, the rate of the WL drop has commonly
been used as an indicator of water availability and sustainability of aquifers. Efforts
towards reducing the negative effects of aquifer depletion require knowing the natural baseline of the hydrogeological behavior for that particular aquifer according to
urban, agricultural, and industrial uses and its water quality evolution. Hydrological
models can then use these data to characterize the response of an aquifer to impact
sources and to identify any potential threats to the quantity and quality of groundwater (El Alfy 2014). Investigators may go a step further and recommend actions
that will help achieving sustainability, such as direct artificial recharge, implementation of water-saving irrigation systems, and integral planning of best management
practices (Gale 2005). The WL continues to drop due to recurring intensive and
long-lasting droughts as well as poor groundwater management practices. Examples
include the Comarca Lagunera aquifer, which experienced an average WL drop of
over 30 m between 1975 and 1999 (1.25 m year
−1
), with a 65 m drop in some parts
and the Meoqui-Delicias aquifer, where the average WL drop was 30 m. In both
cases, the WL dropped as a result of water being used to irrigate crops (Esteller
et al. 2012).
In Mexico, the water policy states that the water is to be distributed among users
based on its availability, but its implementation has been lacking for the past 30 years
or so, as evidenced by water reports showing that the withdrawal volumes are almost
always larger than the approved volumes (Scott 2003). One method to correct this
deficiency is to take into account WL drop rates operating in the region prior to
water allocation, which would become more effective if this information was available for all water uses on a permanent and continuous basis. WL drop rates can also
be used to help identify threats and also to identify if these variations are cyclical in
nature (Scanlon et al. 2005).
Artificial recharge of aquifers has been considered as an action to counteract the
WL drop in systems already undergoing a certain degree of depletion, by means of
retention of surface water, injection to aquifer, or by reusing treated or pluvial water
to irrigate crops. These measures have successfully improved water sustainability in
some other regions where water is scarce (UNESCO 2007).
Although studies about aquifer recharge are common in Mexico, actions towards
achieving this goal at a pilot or at large scale are rare and those few studies have
operated for only a short interval of time (Esteller et al. 2012). One of these projects
aimed at recharging the aquifer of the Comarca Lagunera, a depleted aquifer with
high content of arsenic (As), by diverting water from a reservoir into the Nazas and
Aguanaval dry riverbeds. The attempt produced mixed results after recharged water
flow caused an obstruction in the deeper zones of the aquifer (Rosas et al. 1999).
Ongoing pilot tests to recharge aquifers in Mexico with treated water have been
reported as promising.
4 Changes in the Vegetation Cover and Quality of Aquifers in the Drylands of Mexico…