Water, agriculture, and climate dynamics in central Chile's Aconcagua River Basin

Agriculture in the Aconcagua Basin is both vital to Chile's economy and critically dependent on water resources from snow and glaciers. Expanding croplands, a growing population, and a changing climate are all expected to exacerbate water scarcity in this arid region where agriculture requires 7.1 x 10(8) m(3)of water for irrigation annually. We investigate agricultural water resources in the Aconcagua Basin by examining the drivers of and trends in river discharge, calculating approximate crop water demand, and assessing the potential for future water scarcity given discharge rates and agricultural demand. We find that growing-season (October to March) discharge is significantly correlated with austral winter precipitation and the El Nino-Southern Oscillation. Austral winter precipitation provides snow that melts during the growing season, supplying water for agricultural irrigation. Time series analysis shows that temperature increased by 0.23 degrees C per decade between 1965 and 2017, and snow cover frequency decreased (2.7% per decade) over the relatively short time period of 2000 to 2017. Based on historical discharge data and our assessment of current agricultural water demand, we show that the Aconcagua Basin is already water-scarce, experiencing demand exceeding supply approximately three out of every 10 years.