Snow dominated basins in the subtropics are susceptible to climate change, since evaporation and streamflows are affected, impacting key water sectors and increasing the risk of water shortages. This paper shows an integrated assessment of the impacts of climate change on the major water users in the Maipo Basin of Chile, allowing a direct comparison between competing sectors, describing their sensitivity to future climate changes instead of focusing on individual scenarios, and assessing the effect of likely responses, such as pumping, that impact groundwater levels. We developed a statistical downscaling mechanism to correct biases in global circulation model projections and ran a hydrological model to determine the impacts of climate change on the ability of the system to meet water demands. Mean coverage and minimum coverage of urban and agricultural sectors are sensitive to climate change, particularly to larger changes in precipitation. The urban sector is less sensitive because of higher reliability standards and holds a greater fraction of water-use rights in comparison to actual withdrawals. In addition, groundwater pumping represents an additional source of water to meet population demands. However, this favorable condition could no longer be present if climate change also affects aquifer recharge dynamics.

Motivated by recent extreme flow events in the Mataquito River located in the Mediterranean region of Chile, we performed a detailed trend analysis of critical hydroclimatic variables based on observed daily flow, precipitation and temperature within the basin. For the period 1976-2008, positive trends in temperature were observed, especially during spring and summer months. At the same time, we found negative trends in the frequency and intensity of precipitation, especially during spring months. We observed an increasing difference between average streamflow in the rainy season as compared to the snowmelt season. Part of this trend is caused by larger flows during autumn months, although no positive precipitation trends are observed for these months. Finally, significant reductions in minimum flow during spring/summer and a disproportionate concentration of high-flow events occurring in the last 10 years were also identified. These high-flow events tend to happen during autumn months, and are associated with high precipitation and high minimum temperatures. Based on a simple assessment of changes in irrigated agriculture and land use, we concluded that other non-climatic factors seem not to be as relevant to the detected flow trends. All these results are in accord with future climate change scenarios that show an increase in temperature, a reduction in average precipitation and a reduction in snow accumulation. Such future scenarios could seriously hamper the development of economic activities in this basin, exemplifying also a fate that may be shared by other similar basins in Chile and in other regions of the world.Key words climate change; detection and attribution; extreme events; hydroclimatology; trend analysis; land use; Andes Exploration des liens possibles entre événements hydrologiques extrêmes et changement climatique dans le centre méridional du Chili Résumé Motivés par les récents événements extrêmes de débit dans la rivière Mataquito située dans la région méditerranéenne du Chili, nous avons effectué une analyse détaillée des tendances des variables hydroclimatiques critiques, à partir du débit journalier observé, des précipitations et de la température sur le bassin. Pour la période 1976-2008, une tendance à l'accroissement de température a été observée, en particulier pendant les mois du printemps et de l'été. Dans le même temps, nous avons constaté des tendances à la décroissance pour la fréquence et l'intensité des précipitations, surtout pendant les mois de printemps. Nous avons observé une différence croissante entre les débits moyens pendant la saison des pluies et ceux de la saison de fonte des neiges. Une partie de cette tendance est due à des débits plus importants pendant les mois d'automne, bien qu'aucune tendance croissante des précipitations ne soit observée pour ces mois. Enfin, des réductions significatives du débit minimum au printemps et en été, et une concentration disproportionnée d'événements de haut débit survenus au cours des dix dernières années ont également été...

This paper is among the first to report on the full integration of basin-scale models that include projections of the demand and supply of water and energy for residential, commercial, industrial, and agricultural sector users. We link two widely used regional planning models that allow one to study the impact of rising climate variability on water and electricity use in Sacramento, California. Historic data combined with the current energy and water system configuration was used to assess the implications of changes in temperature and precipitation. Climate simulations suggest that electricity imports to the region would increase during hot dry spells, when regional power production is most constrained. In particular, regional imports of electricity would increase over 35 % in hot dry years, assuming a 4°C increase in average temperature and a 25 % decrease in average precipitation.Climatic Change

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14Central Chile is facing dramatic projections of climate change, with a consensus for declining 15 precipitation, negatively affecting hydropower generation and irrigated agriculture. Rising from 16 sea level to 6,000 meters within a distance of 200 kilometers, precipitation characterization is 17 difficult due to a lack of long-term observations, especially at higher elevations. For 18 understanding current mean and extreme conditions and recent hydroclimatological change, as 19 well as to provide a baseline for downscaling climate model projections, a temporally and 20 spatially complete data set of daily meteorology is essential. We use a gridded global daily 21 meteorological data set at 0.25 degree resolution for the period 1948-2008, and adjust it using 22 monthly precipitation observations interpolated to the same grid using a cokriging method with 23 elevation as a covariate. For validation, we compare daily statistics of the adjusted gridded 24 precipitation to station observations. For further validation we drive a hydrology model with the 25 gridded 0.25-degree meteorology and compare stream flow statistics with observed flow. We 26 validate the high elevation precipitation by comparing the simulated snow extent to MODIS 27 images. Results show that the daily meteorology with the adjusted precipitation can accurately 28 capture the statistical properties of extreme events as well as the sequence of wet and dry events, 29 with hydrological model results displaying reasonable agreement with observed streamflow and 30 snow extent. This demonstrates the successful use of a global gridded data product in a relatively 31 data-sparse region to capture hydroclimatological characteristics and extremes. 32 33 34 35 3