RAINFALL PRECIPITATION AND RECONSTRUCTED EXPENSE OF THE NAZAS RIVER LOWER BASIN

Abstract

The Comarca Lagunera region has an extreme hydroclimatic variability and the lack of extended and reliable instrumental climatic data. To extend back in time precipitation, streamflow, and other climatic information and to analyze their long-term high and low frequency variability a ring width chronology of Taxodium mucronatum was developed from trees located in a riparian area of the lower watershed in the Nazas River. The ring width chronology was longer than 500 years (1500 -2003) and when compared against a seasonal summer regional precipitation (July-September) produced a significant correlation (r = 0.83, p<0.0001). The chronology showed a similar significant response (r = 0.94, p<0.0001) when compared to a regional seasonal fall-winter (August-February) streamflow. The reconstructed precipitation was highly variable at high (annual) and low frequencies (inter-annual). Drought episodes took place in the periods 1509-1520, 1548-1559, 1621-1622, 1684-1691, 1758-1763, 1784-1789, 1809-181, 1846-1849, 1860-1865, 1922-1923, 1949-1956, 1962-1963, 1981-1985, and 1995-2000. Wet episodes surpassing a precipitation over 100% of the reconstructed mean were present in years 1526, 1649, 1791, 1830 y 1991. High streamflow volumes were associated with the warm ENSO phase which has been reported for years 1717, 1725, 1752, 1805, 1855, 1870, 1880, 1888, 1894, 1904, 1925, 1947, 1958 1968, 1974, and 1991. This information could be used by water managers and decision makers to determine the frequency of droughts and extraordinary streamflow events important for the proper management of water resources in the Comarca Lagunera.