Variation in the area of the polymictic Pampean shallow lakes and its relationship with precipitation

The purpose of this study is to analyze the temporal dynamics of the free surface area of shallow lakes during the period 1984-2015 in the Pampas region, Argentina, using satellite image processing (Landsat 4 TM, Landsat 5 TM, Landsat 7 ETM+ and Landsat 8 OLI). The evolution of the free surface of five shallow lakes in two distinct basins of the province of Buenos Aires can be explained using generalized linear models (GLM) and taking as explanatory variables the accumulated precipitation and the number of rainfall days over a given period before the acquisition date of the satellite image. Accumulated precipitation and frequency of days with precipitation were calculated for 1, 7, 30, 90, and 180 days, as well as for 1, 2, 3, and 4 years, respectively. The results show that the explanatory variables linked to the memory of the system (3 and 4 years) contribute significantly in all cases to the reconstruction of the areas. In particular, long-term variables reconstruct accurately (R2 between 0.76 and 0.91) the area of the five shallow lakes for the period 2001-2015. The short-term explanatory variables (7 and 30 days) are also significant to the reconstruction of the variations observed in the first period (1984-2000) but only for the two lakes in the Southeastern basin (R2 = 0.70 and 0.94), while in the Center-South upper basin, only one of the lakes exhibits some short-term dependency in the second period (2001-2015) (R2 = 0.83).