Large‐scale river flow archives: importance, current status and future needs

Time-series for river gauging stations are core blue-skies and applied research resources for understanding impacts of climate and anthropogenic change on basin hydrology. River flow archives hold vital information for evidence-based assessment of past hydrological variability, and support hydrological modelling of future changes. River discharge is an integration of basin input, storage and transfer processes to the gauging point. It is important to set basin outlet data in regional to global and long-term contexts: to better understand nested scales of variability; to pinpoint locations and time periods most sensitive to climate and human impacts; to make predictions for ungauged basins; and to inform decision makers on water security issues, and where and when to take measures to mitigate water hazards and stress, including floods and droughts (Dai et al., 2009; Bonnell et al., 2006; Feyen & Dankers, 2009; Haddeland et al., 2006; Hannah et al., 2005). Thus, there is clear rationale for supporting large-scale (i.e. regional to continental to global) river flow archives. Notable examples of such databases include that held by the WMO Global Runoff Data Centre (GRDC) and the UNESCO Flow Regimes from International Experimental and Network Data (FRIEND) European Water Archive (EWA). For large-scale river flow archives to be valuable research resources, they must be fit for purpose. However, these databases are at risk due to a possible decline in network coverage, associated time-series truncation, growing human impact on (near-) natural flows, and increasingly restricted access to national-scale data. This commentary aims: (1) to demonstrate largescale river flow datasets are crucial to advance hydrological science and solve operational issues; (2) to assess the current status of large-scale river flow datasets; and (3) to propose ways forward to consolidate historical data and secure future river flow data.