Nicole Kretschmer

Statistical downscaling of precipitation and temperature in north-central Chile: an assessment of possible climate change impacts in an arid Andean watershed.

Abstract Downscaling of atmosphere–ocean general circulation models (AOGCMs) is necessary to transfer predictions of potential climate change scenarios to local levels. This is of special interest in dry mountainous areas, which are particularly vulnerable to climate change due to risks of reduced freshwater availability. These areas play a key role in hydrology, since they usually receive the highest local precipitation amounts, which are then stored in the form of snow and glaciers. The performance and ability to simulate extreme events of a statistical downscaling model (SDSM) were tested in the arid Upper-Elqui watershed, Chile. Thereafter, future temperature and precipitation seasonal trends along with agro-hydrological indices were analysed for the HadCM3 A2a and B2a scenarios. Maximum and minimum temperatures for both linear trends and extreme events were simulated accurately. However, the results show that SDSM was not a very robust method for the simulation of precipitation. Nevertheless, future trends and indices indicate possible strong inter-seasonal perturbations. Citation Souvignet, M., Gaese, H., Ribbe, L., Kretschmer, N. & Oyarzún, R. (2010) Statistical downscaling of precipitation and temperature in north-central Chile: an assessment of possible climate change impacts in an arid Andean watershed. Hydrol. Sci. J. 55(1), 41–57.

Application of water quality indices and analysis of the surface water quality monitoring network in semiarid North-Central Chile

Surface water quality has increasing importance worldwide and is particularly relevant in the semiarid North-Central Chile, where agriculture and mining activities are imposing heavy pressure on limited water resources. The current study presents the application of a water quality index in four watersheds of the 29°–33°S realm for the period 1999–2008, based on the Canadian Council of Ministers for the Environment approach and the Chilean regulation for irrigation water quality. In addition, two modifications to the index are tested and a comprehensive characterization of the existing monitoring network is performed through cluster analysis. The basins studied show fairly good water quality in the overall, specially the Limarí basin. On the other hand, the lower index values were obtained for the headwaters of Elqui, associated with the El Indio mining district. The first modification of the indicator (i.e., to consider parameters differentially according to their effect on human health or the environment) did not produce major differences with respect to the original index, given the generally good water quality. The second modification (i.e., to consider as threshold values the more restrictive figures derived from a set of regulations) yielded important differences in the indicator values. Finally, an adequate characterization of the monitoring network was obtained. The results presented spatial coherence and the information can be used as a basis for the optimization of the monitoring network if required.

Natural factors and mining activity bearings on the water quality of the Choapa basin, North Central Chile: insights on the role of mafic volcanic rocks in the buffering of the acid drainage process.

This contribution analyzes water chemical data for the Choapa basin, North Central Chile, for the period 1980–2004. The parameters considered are As, Cu Fe, pH, EC, SO

Evaluating piezometric trends using the Mann-Kendall test on the alluvial aquifers of the Elqui River basin, Chile

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A hydrogeochemistry and isotopic approach for the assessment of surface water–groundwater dynamics in an arid basin: the Limarí watershed, North-Central Chile

, Cl − 1, and HCO

Chemical and isotopic assessment of surface water–shallow groundwater interaction in the arid Grande river basin, North-Central Chile

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Using synoptic tracer surveys to assess runoff sources in an Andean headwater catchment in central Chile

, from samples taken in nine monitoring stations throughout the basin. Results show rather moderate contents of As, Cu, and Fe, with the exception of the Cuncumén River and the Aucó creek, explained by the influence of the huge porphyry copper deposit of Los Pelambres and by the presence of mining operations, respectively. When compared against results obtained in previous researches at the neighboring Elqui river basin, which host the El Indio Au–Cu–As district, a much reduced grade of pollution is recognized for the Choapa basin. Considering the effect of acid rock drainage (ARD)-related Cu contents on the fine fraction of the sediments of both river basins, the differences recorded are even more striking. Although the Los Pelambres porphyry copper deposit, on the headwaters of the Choapa river basin, is between one and two orders of magnitude bigger than El Indio, stream water and sediments of the former exhibit significantly lower copper contents than those of the latter. A main factor which may explain these results is the smaller degree of H + -metasomatism on the host rocks of the Los Pelambres deposit, where mafic andesitic volcanic rocks presenting propylitic hydrothermal alteration are dominant. This fact contrast with the highly altered host rocks of El Indio district, where most of them have lost their potential to neutralize ARD.Ces pages resument les resultats d’une decennie de recherches geochimiques dans les trois bassins-versants de la region de Coquimbo (centre-nord du Chili). L’extraction miniere et l’agriculture en sont les principales activites economiques. Les etudes concernent la geochimie des eaux et des sediments fluviaux et les mesures de mercure atmospherique. Les principaux resultats indiquent les concentrations elevees des ions cuivre, arsenic et zinc dans la fraction fine des sediments fluviaux du bassin-versant du rio Elqui (le plus au nord), concentrations qui atteignent des moyennes de l’ordre de 0,1 a 0,2 % dans le cas du cuivre. Ces chiffres sont en mettre en relation avec le drainage acide du secteur minier de El Indio (or, cuivre, arsenic), situe tout a fait a l’amont du bassin et entoure par une zone d’alteration hydrothermale et argilique avancee. Y contribue egalement l’erosion des deblais miniers laisses sur les flancs des vallees par une activite miniere cuprifere a petite et moyenne echelle. La plus grande exploitation miniere de la region de Coquimbo, Los Pelambres, qui exploite un gisement porphyrique de cuivre-(molybdene) de classe mondiale, est situee a l’amont du bassin-versant du rio Choapa, le plus meridional. Un resultat inattendu fut que les eaux et les sediments fins du Choapa ne presentent aucune anomalie concernant les ions cuivre et les ions molybdene. Ceci peut etre explique par le fait que les roches de ce secteur sont de caractere magmatique basique et n’ont ete que faiblement affectees que par une alteration hydrothermale, ce qui a permis la neutralisation d’un drainage acide.

Decision support system for catchment management with focus on mining impacts and arid zones – Elqui Valley, Chile.

Abstract Today, more than ever, there is a need to implement robust statistical methods to ensure the proper evaluation of water resources data to support decision makers in water resources planning and management. Graphing or mapping data for visualization is the easiest way to communicate trends, especially to a non-technical audience. This paper describes the use of an approach that combines the Mann-Kendall test, Sen slope test and principal component analysis to detect and map the monthly trends of piezometric time series and their magnitude in the period 1979–2008. The data were obtained in 23 shallow wells in the alluvial aquifers of the Elqui River basin in central Chile, an area characterized by scarce water resources and intense agricultural and mining activities. The results show significant downward trends at the majority of the wells. Because groundwater in these shallow wells is highly dependent on the water in the river and its tributaries, the reasons for these downward trends are mainly related to a decrease of streamflow observed in the Elqui River. The streamflow is derived from mountain snowmelt rather than from rainfall, which showed no flow trend during the same period.

Multi-method assessment of connectivity between surface water and shallow groundwater: the case of Limarí River basin, north-central Chile

This paper describes the results of a hydrochemistry and isotopic study of surface water and groundwater dynamics at the Limarí River basin, arid North-Central Chile. The study involved two sampling campaigns, performed in April (Fall, at the end of the irrigation season) and December 2010 (late Spring, at the peak of the irrigation season). The main results show the effect of La Paloma and Hurtado dams on the chemical and isotopic compositions of the Grande and Hurtado rivers (main tributaries of the Limarí River), the influence of return flows to the Limarí River from surface water irrigation in agricultural areas, the local effects of metallurgical operations in the El Ingenio Creek, the effect of water–rock interaction processes, and the nearby coastal belt influence on the Punitaqui Creek area and the lower part of the Limarí River. In addition, this study shows an active interaction between surface water and shallow groundwater, and a minor importance of local precipitation events, on the hydrological behavior in the study area. An exception is the Rinconada de Punitaqui zone where the results are consistent with the origin of the water being associated with local precipitation. Also, sources of sulfate, which is present in high levels especially in surface waters, have been assessed. The results of this study, based on an integrated use of chemical and isotopic tracers, provide sound and useful information to establish the level of interaction between surface water and groundwater, allowing the development of a hydrological conceptual model for the area.

Abandoned tailings deposits, acid drainage and alluvial sediments geochemistry, in the arid Elqui River Basin, North-Central Chile

ABSTRACT This paper analyses the composition of surface water and shallow groundwater in the Grande River basin, North-Central Chile, using this information to characterize water interactions. Chemical and isotopic data for surface water and groundwater (7 and 6 sampling locations, respectively) were obtained from three sampling campaigns performed in March–April (autumn), August–September (late winter) and December (early summer) 2012. Precipitation samples were also collected. Data was processed using spatial distribution charts, Piper and Stiff diagrams, and multivariate analysis. In general, the results for each method converge on a high degree of connectivity between surface water and shallow groundwater in the study area. Furthermore, approximately a 10% of groundwater contribution to the surface flow discharge was estimated for a particular reach. This multi-method approach was useful for the characterization of surface water–groundwater interactions in the Grande River basin, and may become a suitable and replicable scheme for studies in arid and semi-arid basins facing similar water management challenges. Editor D. Koutsoyiannis; Associate editor B. Dewals