Limnological study of Sauce Grande Shallow Lake (Argentina) during a dry period

FORNERÓN, C.F.; BOHN, V.Y.; PICCOLO, M.C.

Torres, Brasil

Workshop; GLEON 10; 2010

GLEON

The shallow lakes of the “Pampean” region of the Buenos Aires Province (Argentina) exhibit a strong areal variation under the presence of flooding or drought periods. The aim of this work is to analyze the effect of the drought occurred during 2008‐2009 period on the Sauce Grande shallow lake basin, as well as to describe the physical and chemical parameters distribution during such event. The precipitation data (2003‐2009) was obtained from the Meteorological Service database. The Standard Precipitation Index (SPI) was applied in order to analyze the normal, dry and wet years. A multitemporal study of the shallow lake area was completed by means of MODIS satellite image processing. In situ measurements of physical and chemical parameters were gathered and water samples for chlorophyll‐a analysis were collected from September 2008 to December 2009. For the period 2003‐2005, the SPI indicated normal years with a mean precipitation value of ~690 mm whereas the 2006 year showed a decrease in the precipitation (annual precipitation of ~440 mm). The mean area of the Sauce Grande shallow lake was of ~20 km2 during the normal period decreasing in approximately 5% during 2006. During 2008‐2009 SPI index indicated an extremely dry period (mean annual precipitation of ~390 mm). As a result, the lake area at the ending of the dry period was ~17 km2 (10% decrease). The depth of the lake on normal precipitation periods is 2 m. During the draught the depth decreased almost 40 %. As a consequence, the electrical conductivity increased 5 mS cm‐1 and the trophic state changed from a mesotrophic to eutrophic state.