Most of the water used for the development of the main socio-economic activities in Central-Western Argentina (CWA), an arid to semi-arid region, home to most of the Argentinean wine production, relies on surface streamflow from several snow-fed rivers. During the last decade (2010-2020), reduced snow accumulation over the higher elevations of the Andes mountains triggered the occurrence of hydrological drought over CWA, affecting winter tourism, restricting water use for irrigation and domestic use, and leading to socio-political disputes. This study provides a detailed description of the recent hydrological drought conditions through the use of streamflow records from 15 river basins, which were complemented by precipitation, snowpack, and water equivalent thickness measurements to provide a comprehensive picture of the water losses over the last decade. Hydrological drought indices derived from the threshold level method and the standardized streamflow index allowed characterizing the unusualness of this dry period in the context of the last 49 years. The hydrological deficit over the last decade highlighted the challenges faced by the water managers to provide water for irrigation in the main agricultural oases, with a likely overexploitation of the groundwater resources to supplement the limited surface runoff. The hydrological drought severity increased since 2017, with record-breaking levels in several basins, particularly during the period between July 2019 and June 2020 for the rivers located between 35° and 36°S. We identified the main hydrological drought impacts in CWA, as well as the need for improved mitigation strategies to cope with current and future drought conditions. We also analyzed the current limitations in terms of snow and groundwater observations, highlighting the necessity for an effective hydrological drought monitoring system, together with an improved forecast of snow accumulation in the headwaters, which can contribute to better regional water management plans.

El estudio de la variabilidad hidroclimática de una región contribuye a mejorar la seguridad hídrica de las comunidades ya que brinda información para la gestión de los recursos hídricos. El objetivo es identificar los principales modos de variabilidad y la relación entre series temporales de precipitación, temperatura y caudales medios anuales para los últimos 60años de algunas cuencas de la región de Cuyo. Se realizaron pruebas de tendencias, saltos y periodicidades. Los resultados, en líneas generales, muestran que las precipitaciones y los caudales tienden a disminuir y presentan ciclos significativos de alta y baja frecuencia. Por el contrario, la temperatura muestra una tendencia creciente asociada a incrementos en la década del 80, los períodos con mayor intensidad son los que se presentan en escala interanual. Estos resultados brindan información para la comprensión de lasrelaciones entre los patrones de variabilidad hidroclimática y los intercambios entre los diversos componentes del ciclo hidrológico en el centro oeste argentino, lo que permite mejorar la toma de decisiones.

Esta investigación realiza una cuantificación del déficit en los caudales superficiales de los principales ríos de la región de Cuyo, asociado a la extraordinaria sequía hidrológica registrada desde el año 2010. Estos déficits presentan valores récord en el contextode los últimos 50 años, en particular durante el año hidrológico 2019/20. Las diferencias regionales en los valores de déficit acumulado permiten establecer que la mayor severidad se observó en las cuencas de los ríos Atuel y Colorado, las cuales enpromedio registraron caudales por debajo del percentil de excedencia del 80% (Q80) durante el período 2010/11-2019/20. A partir de la estandarización del déficit acumulado por el volumen de los embalses de la región, se obtuvo una medida de fácil interpretación y aplicación para el monitoreo y la toma de decisiones en relación al impacto de la sequía hidrológica en la disponibilidad de agua dulce regional.

The prediction of the maximum annual flow is necessary for flood management. Large amounts of hydrological information are required to make meaningful estimates. The Colorado River System basins have a topography that makes it difficult to maintain hydrometric stations, so there is a lack of continuity in records and in several cases there are ungauged basins. Regionalization methods consist of transferring information from gauged to ungauged sites in order to make predictions. The objective is to find regional regression models that relate the climate and morphometric characteristics of the basins with the maximum annual flow. For this purpose simple linear regression models were used. From this relationship and the regional frequency curve it will be possible to predict the maximum annual flows for different return periods in ungauged basins of the Colorado River System, Argentina. Regionalization models show that the best estimates occur when the predictor variable is the area and perimeter of the basin. Errors in the regionalization models of various sites in the system resulted between 6% and 67%. The models found are a tool for flood management in central-western Argentina.