RECONSTRUCTION OF THE LEVELS OF CHAPALA LAKE BY DENDROCHRONOLOGICAL SERIES OF Taxodium mucronatum Ten.

Abstract

The Lerma-Chapala-Santiago-Santiago basin draining toward the Chapala Lake has been strongly impacted by humans by altering the hydrological cycle and affecting the annual recovery of the lake. To determine historical behavior of the lake levels, a network of cypress (Taxodium mucronatum) chronologies was developed from trees thriving along the main tributaries of the lake. The tree-ring series were analyzed by Principal Component Analysis and a regional ring-width chronology with a length of 547 years (1462-2008) was developed with those series having a common climatic signal. A correlation analysis between the regional chronology and lake levels with a lag of one year was significantly associated and a regression model was developed for reconstruction purposes. The reconstructed levels showed high inter-annual and multiannual variability and were associated with intensive El Niño Southern Oscillation events, although in the last decades aggressive land-use changes may have masked the influence of this phenomena. Low levels of the lake were associated to intensive droughts reconstructed for the periods 1508-1560, 1581-1608, 1685-1725, 1770-1840, 1916-1924, and 1988-2000. On the other hand, wet episodes took place in the periods 1561-1578, 1610-1616, 1760-1769, 1842-1850, 1863-1893, and 1926-1963. From 1960 to date the annual variability of the lake has decreased due to increased human pressure on available water resources. The historical understanding of the historic fluctuations lake levels will promote actions toward a better use of water resources and for conservation of riparian ecosystems depending on the water yielded in the Lerma-Chapala-Santiago basin.