Author(s): Dussaillant Alejandro; Galdames Pablo; Sun Chi-Le
Linked Author(s):
Keywords: Coastal lagoon; Groundwater; Hydraulic conductivity; Eutrophication; Fourier
Abstract: The El Yali coastal reserve is the most important wetland complex in central Chile, specially due to its relation with both native and foreign bird fauna which arrives here periodically, being habitat to more than 25% of the bird biodiversity in Chile. This study identifies and quantifies the effect of forcing variables in the lagoon’s water level along one year of data gathering. Transects of piezometers with level sensors were installed between the coastal lagoon and the sea. Monthly water quality data was collected. The soil is sandy with porosity of 0. 43 and hydraulic conductivities circa 10 -4 m s -1. During the rainy season the lagoon connects with the sea via surface water, producing noticeable daily variations in the water level, up to 80 cm depending on the tides. In contrast, during the seadisconnected season the lagoon level is very stable, only dropping very slowly due to evaporation. Rainfall does not affect the lagoon level considerably, although piezometers responded quickly as expected for a sandy material. During the connection phase, analysis of the sea vs. lagoon level signals using general pattern, spectral and Fourier analysis, show that two temporal scale hierarchies are relevant: monthly (moon cycles every 16. 4 days on average) and daily (tidal cycles every 12. 5 and 24. 2 hrs). A simple diffusion numerical model simulated the water table trends well for the sand bar between lagoon and sea, which is hoped to be used soon in connection to riparian vegetation spatial data being gathered.
Year: 2007