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Dryland river systems are becoming saltier, severely degrading the quality of water used for agriculture and limiting its domestic use. In this context, it is becoming important to understand how the sources and abundances of salts in these river systems will respond to increasingly arid climates. Using the Rio Grande in the Southwest U.S. as an example dryland river system, we show that changes in climate over the last century are closely linked to variations in salt chemistry and therefore salt sources. Starting 25 years ago there has been a shift toward more Cl-rich surface waters in the Rio Grande. This shift may reflect a tipping point in the relative influence of anthropogenic activities on the overall surface water budget. Climate change is accelerating this transition through the loss of rain and snow in the headwaters region, resulting in a loss of connectivity of surface flow in the upper and lower sections of the river. The implication of this relationship for dryland rivers is that salt chemistry and sources are likely to become more heterogeneous in the future, reflecting more localized natural (inflow of groundwater) and anthropogenic (waste and industrial effluents, irrigation returns) influences. (C) 2014 Elsevier Ltd. All rights reserved.