Figure S1. Photo 1 of ADCP discharge monitoring site (67.0499°N, -49. 0180°W). A SonTek River Surveyor® M9 Acoustic Doppler Current Profiler (ADCP) mounted on a SonTek HydroBoard II is being ferried across the Rio Behar supraglacial river channel cross-section in southwest Greenland. The ADCP and hydroboard are tethered to a specialized bank-operated cableway developed by the field team for deployment on ice surfaces with wireless (radio frequency) data relay. A total of 847 ADCP profiles were collected 5-13 July, 2016.