Pablo Garcia-Chevesich

Latitudinal Analysis of Rainfall Intensity and Mean Annual Precipitation in Chile

El estudio y analisis de las precipitaciones se ha convertido en una herramienta vital para conocer el comportamiento temporal y espacial del recurso hidrico, tanto en terminos de disponibilidad, asi como de los posibles impactos asociados a los eventos extremos. El objetivo de esta investigacion fue evaluar las intensidades maximas (duracion D = 1 h y periodos de retorno T = 5 y 100 anos) y los montos anuales de precipitacion para diferentes latitudes y zonas climaticas de Chile, analizando la informacion de miles de bandas pluviograficas y la pluviometria anual de 49 estaciones de medicion. Ello, porque aun no es claro que las intensidades de precipitacion difieren latitudinalmente en el pais, asi como lo hacen los montos anuales de las lluvias. Asimismo, no hay evidencia cientifica de los rangos y montos de ambas variables. Asi, se utilizo la funcion de Gumbel y formulas matematicas para desarrollar las curvas intensidad-duracion-frecuencia (IDF) de cada estacion. Los valores minimos y maximos de intensidad de precipitacion registrados para T = 100 anos, fueron 8,79 (zona hiperarida) y 40,17 mm h-1 (zona subhumeda-humeda). Respecto al monto anual de precipitaciones, los valores minimos y maximos fueron 43,9 (zona hiperarida) y 3891,0 mm ano-1 (zona humeda) respectivamente. Adicionalmente, la intensidad maxima real registrada en cada estacion fue analizada para determinar su probabilidad de excedencia. Asimismo, se realizaron comparaciones multiples para detectar diferencias significativas entre las estaciones de medicion y las diferentes zonas climaticas, mediante el test no parametrico Kruskal Wallis (alfa = 0,05). Las diferencias entre los valores maximos y minimos registrados en la totalidad de las estaciones analizadas pueden superar las 80 veces, para el caso de los montos anuales de las lluvias, y pueden llegar hasta 4,5 veces para el caso de las intensidades de precipitacion (T = 100 anos). Sin embargo, se encontraron valores maximos similares de intensidad de precipitacion en diferentes latitudes y altitudes del territorio nacional. Por tanto, se concluye que un mayor monto anual de lluvia no necesariamente involucra una mayor intensidad de precipitacion

Spatio-temporal trends of precipitation, its aggressiveness and concentration, along the Pacific coast of South America (36–49°S)

ABSTRACT Precipitation is the most critical climatic element that directly affects the availability of water resources. The objective of this study was to describe and discuss spatio-temporal patterns of annual precipitation, its aggressiveness, and its concentration along the southwest coast of South America (36°–49°S) from 1930 to 2006. An annual and multi-decadal analysis was applied to 107 sampling stations distributed throughout this region, using the Mann-Kendall test (MK), and the Sampling Uncertainty Analysis (SUA) coupled with Gumbel probability density function (SUA-Gumbel). The analysis revealed positive but not significant trends in annual precipitation and aggressiveness for the region between 36° and 44°S, at least during the last 50 years of the analysed period. However, a significant decrease in annual precipitation and aggressiveness was observed between 44° and 49°S during the same period. The annual concentration of precipitation became slightly more seasonal in the last 50 years within the entire study area.

FORMATION OF POST-FIRE WATER-REPELLENT LAYERS IN MONTERREY PINE (Pinus radiata D. DON) PLANTATIONS IN SOUTH-CENTRAL CHILE

A wildfire burned about 15,000 ha of Monterrey Pine (Pinus radiata D. Don) plantations near Yungay, Chile, in January of 2007. Post-fire water repellency (hydrophobicity) was measured using the water-drop-penetration-time (WDPT) method at depths of 0, 5, and 10 mm from the soil surface. These measurements were collected on burned sites of both young (4-years old) and old (11-years old) plantations having both sand- and clay-rich soils. For purpose of comparison, water repellency was also measured one year after the wildfire on four unburned sites representing the same soil types and plantation ages as those occurring on the burned sites. The statistical analyses indicated that water repellency was present only on old stands, being located on the soil surface (clay soils) or as a layer 10 mm deeper or below (sandy soils). However, a water repellent layer was found on young stands growing on sandy soils, five millimeters below the surface, assumed to be formed when a wildfire burned the area before the new plantation was established.

Dempster-Shafer theory of evidence: A new approach to spatially model wildfire risk potential in central Chile

A spatial modeling was applied to Chilean wildfire occurrence, through the Dempster-Shafers evidence theory and considering the 2006-2010 period for the Valparaiso Region (central Chile), a representative area for this experiment. Results indicate strong spatial correlation between documented wildfires and cumulative evidence maps, resulting in a powerful tool for future wildfire risk prevention programs.