Roberto Pizarro

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

Respiratory disease and particulate air pollution in Santiago Chile: contribution of erosion particles from fine sediments.

Air pollution in Santiago is a serious problem every winter, causing thousands of cases of breathing problems within the population. With more than 6 million people and almost two million vehicles, this large city receives rainfall only during winters. Depending on the frequency of storms, statistics show that every time it rains, air quality improves for a couple of days, followed by extreme levels of air pollution. Current regulations focus mostly on PM10 and PM2.5, due to its strong influence on respiratory diseases. Though more than 50% of the ambient PM10s in Santiago is represented by soil particles, most of the efforts have been focused on the remaining 50%, i.e. particulate material originating from fossil and wood fuel combustion, among others. This document emphasizes the need for the creation of erosion/sediment control regulations in Chile, to decrease respiratory diseases on Chilean polluted cities.

The need for a hydromorphological approach to Chilean river management

El manuscrito refleja la opinion de los autores acerca de la necesidad de aplicar un enfoque hidromorfologico para la gestion de los rios chilenos. Se presenta una breve resena de los ultimos avances cientificos sobre el enfoque hidromorfologico en la gestion de rios, asi como una vision general de las condiciones de los rios chilenos y sus mayores perturbaciones. Por otra parte, se hace enfasis en la necesidad de incluir en la toma de decisiones los servicios directos como los indirectos proporcionados por los rios. Se afirma que la hidromorfologia es un elemento fundamental a considerar al determinar el estado ecologico de los rios. La comprension de como las variables hidrologicas y morfologicas interactuan de forma dinamica es sin duda clave para evaluar la presencia o ausencia de un equilibrio dinamico, una condicion que, a su vez, fomenta tanto la diversidad de habitat como el desarrollo sostenible de los ecosistemas acuaticos y riberenos. Los autores concluyen que es necesario cambiar el paradigma actual de gestion aplicado en los rios chilenos desarrollando una estrategia que permita evaluar las condiciones hidromorfologicas y ecologicas de los rios. Ademas, sugieren implementar legislacion especifica orientada a promover estandares ecologicos y geomorfologicos en la practica de gestion, con el apoyo de un fortalecimiento y una ampliacion de la ensenanza academica de la geomorfologia y ecologia fluvial.

A RAINFALL SIMULATOR FOR THE IN SITU STUDY OF SUPERFICIAL RUNOFF AND SOIL EROSION

A rainfall simulator is an important tool for the study of runoff generation and soil loss because it can be used either under laboratory conditions, or in disturbed or natural soil. The objective of this study was to describe the design and operation of a rainfall simulator to evaluate soil loss in situ. The rainfall simulator has four full-cone spray nozzles with a Unijet system mounted in a straight line pipe configuration, and easily transported and assembled. Simulated rainfall uniformity was evaluated in the laboratory, whereas the applicability of the simulator in natural soil erosion plot conditions in an experimental field with different slopes was tested by quantifying runoff and evaluating soil erosion. Twenty simulations were carried out in the laboratory and sixteen in the field with slopes of 11, 21, and 39%. Four water-sprinklers in a straight line generated rainfall with uniformity close to 90%. The constructed simulator was easy to use and low cost, facilitating the necessary experimental replicates to achieve a suitable spatial representation of superficial runoff and soil loss on hillsides.

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.

Multi-decadal variations in annual maximum peak flows in semi-arid and temperate regions of Chile

Abstract In determining the possible influence of climate change, it is important to understand the temporal and spatial variability in streamflow response for diverse climate zones. Thus, the aim of this study was to determine the presence of changes in annual maximum peak flow for two climate zones in Chile over the past few decades. A general analysis, a flood frequency analysis and a trend analysis were used to study such changes between 1975 and 2008 for a semi-arid (29°S–32°S) and a temperate (36°S–38°S) climatic zone. The historic annual maxima, minima and mean flows, as well as decadal mean peak flow, were compared over the period of record. The Gumbel distribution was selected to compare the 30-year flood values of two ±15-year intervals, which showed that streamflow decreased by an average of 19.5% in the semi-arid stations and increased by an average of 22.6% in the temperate stations. The Mann-Kendall test was used to investigate the temporal changes in streamflows, with negative trends being observed in 87% of the stations analysed in the semi-arid zone, and positive trends in 57% of those analysed in the temperate zone. These differences in streamflow response between climate zones could be related to recent documented increases in altitude of the zero-degree isotherm in the Andes Mountains of Chile, since most of the significant positive and negative changes were detected in first-order rivers located closer to this mountain range. Editor D. Koutsoyiannis; Associate editor H. Lins Citation Pizarro, R., Vera, M., Valdés, R., Helwig, B., and Olivares, C., 2013. Multi-decadal variations in annual maximum peak flows in semi-arid and temperate regions of Chile. Hydrological Sciences Journal, 59 (2), 300–311.