Extended Data Fig. 5: Distribution of surface water–groundwater interaction classes for north America as simulated using the physically based global-scale GSGM.

The figure distinguishes four classes: gaining streams, losing streams, intermittently disconnected streams and continuously disconnected streams. Results are shown for the month of July (generally the driest month of the year, on the basis of monthly discharge) and represent five-year moving averages of river drainage and groundwater levels. A stream is classified as a continuously disconnected stream if the stream is disconnected for at least two years in a row over the moving average window of five years. a, Spatial maps of surface water–groundwater interaction for July 1964 and 2004 under natural conditions and including human water withdrawal. b, Temporal variation of the total area covered by each surface water–groundwater interaction class. The thinner continuous lines are yearly values, thicker dashed and dotted lines are the five-year averages.