Fig. 1. Hydrological energy budgets for small High Arctic streams.

a Daily stream power records for a small, non-glacial High Arctic stream at the CBAWO (West river; 8 km²; 2003–2017) normalized to the first day of nival runoff and separated into annual hydrological regimes; (1) nival-dominated regime with little-to-no hydrological response to summer/fall rainfall inputs (skewed distribution; black/gray; n = 8); and (2) nival- and pluvial-dominated hydrological regime (multimodal distribution; blue; n = 4). b Cumulative mean daily stream power (% of the total annual stream power) for the same annual hydrological regimes. In all years, 49 ± 15% of the annual available stream power is expended in the first ten days of freshet and 74 ± 13 % is expended during the full nival period (22 ± 5 days). In warmer wetter years with proportionately more pluvial discharge (blue) we observe a transition in the timing and magnitude of fluvial energy to later in the summer thaw season. In these years, pluvial runoff expended 25 ± 12% of the annual stream power budget during the summer and fall shoulder seasons. Baseflow periods had the lowest stream powers expending <5% of the annual stream power budget.