Evaluation of three rainfall-runoff formulas in Achibueno Basin, Chile

Pizarro-Tapia, R. Univ Talca, Fac Ciencias Forestales, Departamento de Gestion Forestal & Ambiental, Casilla 721, Talca, Chile

The effects of changes in vegetative cover on river flows in the Purapel river basin of central Chile

Pizarro, R.;Araya, S.; Jordan, C.; Farias, C. Flores, J. Department of Forestry and Environmental Management, Faculty of Forest Sciences, Universidad de Talca, Talca, Chile. Bro, P.B. Department of Engineering Science, Faculty of Engineering, Universidad de Talca, Curico, ChileThe distribution of peak river flows was studied over the period 1960–2000 in the watershed of Purapel River (Maule Region, Chile) in order to evaluate the relationship of these flows to vegetation cover. Maximum annual and summer flows, between decades and between periods, monthly and yearly were compared with multi-temporal analysis for 1955, 1978 and 1997. The evolution of peak flows over the period was irregular, and did not show significant differences in the majority of comparisons. The variation in vegetation cover during the study period was caused by migration from native forests to commercial plantation of Pinus radiata (D. Don). The data from this watershed does not permit the conclusion that variation in peak flows is due to variation in vegetative cover. The peak flows are more highly dependant on precipitation values. For the watershed and period of study the native forest and plantations of P. radiata (D. Don) have a similar hydrological behavior

Temporal variations of rainfall and flows in the Maipo River Basin, central Chile, and the influence of glacier melting on water yield (1963-2006)

Pizarro-Tapia, R (reprint author), Univ Talca, Fac Ciencias Forestales, Dept Gest Forestal & Ambiental, Ave Licray sin Numero,Casilla 721, Talca, Chile.In this paper, precipitation and runoff trends over the past 40 years are inferred for two sub-basins of the Maipti River: El Colorado (1 710 km(2)) and the Alto del Maipo (3521.52 km(2)). The two sub-basins are located in the metropolitan region of Chile and have markedly snowy regimes. Five rain gauge stations with monthly and annual records (mm) were analyzed for the period 1963-2006. After completing the missing information for each station, mean areal precipitation was calculated using the Thiessen Polygons Method. Monthly and annual mean flow data were extracted from two flow gauging stations. The analysis of temporal behavior for rainfall and runoff variables was performed by adjusting the Type-1 Gumbel distribution function and calculating moving averages and the rainfall/runoff coefficient (existing ratio of rainfall to surface runoff; PP/E, abbreviation in Spanish). Thus, it was possible to determine that, over the last 40 years, the Maipo River basin showed increased winter rainfall, decreased summer and autumn rainfall and increased runoff during summer periods. Therefore, it can be inferred that the increase in this runoff is influenced by glacier melting

Influence of wooded masses in the water production of a sub-humid river basin, central zone of Chile

Pizarro-Tapia,R. (reprint author). Univ Talca, Fac Ciencias Forestales, Departamento de Gestion Forestal & Ambiental, Casilla 721, Talca, ChileThis article analyzes the influence of wooded masses in the water production of the Purapel River watershed, located in the central zone of Chile, This watershed has an area of 264 km(2) and has been affected by processes of vegetation replacement, going from native forests to massive forestation, mainly of Pinus radiata (D.Don). The multitemporary analysis made showed that the vegetal cover varied from 0 per cent of forest plantations in 1957 to 51.7 per cent for the year 1997. The methodology studied land use in 1957, 1978, and 1997, precipitations were analyzed and flow and hydrographs were studied on an hour by hour basis; the variation of water reserves was analyzed monthly and annually, monthly and annual runoff coefficients were analyzed, the maximum flow was studied, and finally, their relationship with the vegetal cover and the water production between the years 1960 and 2000 was studied. The results allow to conclude that for the Purapel River watershed there are no differences in the observed hydrology behavior in the 40 years studied. The oscillations observed in the hydrologic variables are due to precipitation amounts and intensities and to the high intermonthly variability. Only the monthly reserves show a different behavior, since they tend to increase in the 1979-2000 period. This had to do with important precipitations in the 80's, and not directly with a change of the type of vegetal cover

A genetic model based on evapoconcentration for sediment-hosted exotic-Cu mineralization in arid environments: the case of the El Tesoro Central copper deposit, Atacama Desert, Chile

lthough the formation of exotic-Cu deposits is controlled by multiple factors, the role of the sedimentary environment has not been well defined. We present a case study of the El Tesoro Central exotic-Cu deposit located in the Atacama Desert of northern Chile. This deposit consists of two mineralized bodies hosted within Late Cenozoic gravels deposited in an arid continental environment dominated by alluvial fans with sub-surficial ponded water bodies formed at the foot of these fans or within the interfan areas. Both exotic-Cu orebodies mostly consist of chrysocolla, copper wad, atacamite, paratacamite, quartz, opal, and calcite. The most commonly observed paragenesis comprises chrysocolla, silica minerals, and calcite and records a progressive increase in pH, which is notably influenced by evaporation. The results of stable isotope analyses (δ13C and δ18O) and hydrogeochemical simulations confirm that evapoconcentration is the main controlling factor in the exotic-Cu mineralization at El Tesoro Central. This conclusion complements the traditional genetic model based on the gradual neutralization of highly oversaturated Cu-bearing solutions that progressively cement the gravels and underlying bedrock regardless of the depositional environment. This study concludes that in exotic-Cu deposits formed relatively far from the source, a favorable sedimentary environment and particular hydrologic and climatic conditions are essential to trap, accumulate, evapoconcentrate, neutralize and saturate Cu-bearing solutions to trigger mineralization. Thus, detailed sedimentological studies should be incorporated when devising exploration strategies in order to discover new exotic-Cu resources, particularly if they are expected to have formed relatively far from the metal sources

Presente y futuro de la responsabilidad civil

Il libro, editato dal comitato scientifico del congresso (Barria, Ferrante, San Martin), riunisce in maniera ampliata e con aggiunte di citazioni e note a piè di pagina, gli interventi del Congresso Internazionale celebrato il 3-4 novembre 2016