Abstract

MADEREY RASCON, Laura Elena  and  JIMENEZ ROMAN, Arturo. Hydrological cycle disturbances at the lower portion of the Lerma River upper basin derived from water transfer to Mexico City. Invest. Geog [online]. 2001, n.45, pp.24-38. ISSN 2448-7279.

The low portions of the Lerma River upper basin have been seriously affected by the irrational use of the water resource for Its conveyance to Mexico Basin for supplementing Mexico City's water demand, This affectation has led to a remarkable physical transformation of the basin. The environmental Impact caused to the hydro-climatic features at the lower portions of the Lerma River upper basin is studied by analyzing meteorological and hydrometric data, which are either part of the hydrological cycle or indirectly affect it. The analysis was made by comparing the trends in meteorological elements with records between 1920 and 1985 covering information since prior to approximately 30 years after the transformation, and Including hydrometric data examined for two periods: 1945 - 1950 and 1951 - 1980. The available water volume in the Lerma River upper basin was also estimated through mean annual precipitation, evaporation and Köppen's aridity index registered in the basin, to determine whether water extraction has been conducted in excess of the amount available in the basin without altering its natural environment. The results reveal that, although not too obvious, the meteorological elements studied have been altered, namely mean, maximum and minimum temperatures; maximum, minimum and mean annual precipitations and potential evaporation. A clear change in the amount of water in lagoons that give origin to the Lerma River was also observed, as well as water extraction exceeding the available volume from the Lerma River upper basin.

Keywords : Hidrological cycle; Lerma River upper basin; water availability; hydroclimatology.