The future of salt lakes the case of Mexico by rraul


									                            The future of salt lakes: the case of Mexico
                                                    JAVIER ALCOCER1
    Limnology Laboratory, Environmental Conservation & Improvement Project, UIICSE. FES Iztacala, UNAM. Av. de los
    Barrios No. 1, Los Reyes Iztacala. 54090 Tlalnepantla. Edo. de Mexico. MEXICO.

     Williams (2002) reviews the extensive damage that          The lakes of Valle de Santiago
salt lakes have undergone worldwide. Mexico, with two-               There are nearly 30 craters in the Valle de Santiago
thirds of its territory arid or semiarid, shows the             area, however, just a few contain water. These include
problems typical of a developing country (e.g.                  Rincón de Parangueo, San Nicolás de Parangueo, La
exacerbated water pollution and misuse, unplanned               Alberca and Cíntora. Vegetation clearance, overgrazing,
population growth, deficient agricultural techniques)           abatement of phreatic waters through groundwater over-
resulting in an accelerated degradation of all lakes. Salt      exploitation for a continuously increasing agriculture and
lakes have been familiar to Mexicans since prehispanic          salinization have induced severe erosion and overall
times (e.g. Aztecs and Purepechas, respectively on Lakes        desertification in the basin for what, it seems, a long time
Texcoco and Cuitzeo). However, from Colonial times,             (i.e. prehispanic times). Two of the four crater lakes have
population development and agriculture have been                already dried and phreatic mantle abatement reaches up
particularly significant in the decline of Mexican lakes        to 2.5 m per year. The other two are close to be waterless
and, thoughinformation is scarce, the salt lakes are            (i.e. few centimeters left). Through unplanned urban,
vanishing.                                                      industrial and agricultural development in the area,
                                                                aquatic resources are being exploited beyond
Aims                                                            sustainability.
    This paper provides a review of both historical and
recent human activities which have led to change in             The lakes of the Oriental basin
some Mexican saline lakes, and thus aims to provide a                The Oriental endorheic basin is located in the south-
limnological perspective on their past, present and future      eastern most portion of the Mexican Plateau. There are
situation that complement Williams’ (2002) paper.               no permanent but only ephemeral streams in the basin;
                                                                nonetheless, this poorly developed surface hydric
Lake Texcoco                                                    network is scant when compared with profuse
    Lake Texcoco covered a large portion of the Mexico          groundwater resources. Groundwater is the principal
basin and sustained a huge population in the ancient            water source of the lakes (two playa and six crater lakes).
world. Natives perfectly coexisted with the lake; they          However, the water level has been declining mostly
obtained food, transportation and raw materials among           because of the over-exploitation of the groundwater for
other benefits. However, since the arrival of Spanish in        irrigation purposes and the destruction of the natural
1519, Lake Texcoco became less a benefit and more a             recharging areas. In addition, the government has
problem thus starting the desiccation process. Of               considered the Oriental basin as a potential water supply
particular note have been drainage basin activities,            for Mexico City and/or the City of Puebla due to its
diversion of inflows, pollution and over-exploitation of        relatively high altitude (i.e. > 2,300 m asl) that may
groundwater and biological resources. These changes are         reduce pumping expenses in transporting water from
particularly important since they significantly affect          Oriental to Mexico and Puebla. The playa lakes became
water supply, drainage and other urban issues in Mexico         firstly temporal and then episodic. Water level in the
City, Mexico’s largest city and capital located within the      crater lakes is declining rapidly, threatening the survival
general boundaries of the lake basin and gradually              of valuable endemic species (e.g. the isopod Caecidotea
sinking (mean annual sinking is 30 cm).                         williamsi, the atherinid fish Poblana alchichica and the
                                                                ambystomatid salamander Ambystoma taylori). These
Lake Cuitzeo                                                    and other Mexican case studies are further discussed to
      Cuitzeo is the second largest lake in Mexico (ca.         foresee the likely condition of inland saline ecosystems
425 km2), and ranks first in size among the saline ones.        in 2025.
Paleolimnological information reveals Cuitzeo as a
shallow, astatic (i.e., fluctuating) lake, that changes         Reference
dramatically in surface area and volume throughout time.        Williams, W.D. (2002). Environmental threats to salt
In spite of the large fisheries of non-traditional products     lakes and the likely status of inland saline ecosystems in
(e.g., clam shrimps, hemipterans, ephydrids) in the             2025. Environmental Conservation 29, 154-167.
western and more saline portion of the lake, diverse
actions (e.g. highway construction, artificial outflows,
and surface inflow diversions) have desiccated it (almost
one third of the total lake area) for agriculture. Important
social, economical and political problems arise in the
dispute for water and land use in this magnificent lake.

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