This special issue will feature the latest advances and developments in hydrologic data assimilation (DA) for operational hydrologic forecasting and water resources management as an outcome of the 2.5-day international workshop in Delft, the Netherlands, on November 1–3 2010. Focusing on data assimilation for operational hydrologic forecasting and water resources management, this special issue will include high-quality papers on various related topics:

• theoretical and mathematical aspects of hydrologic DA applications;
• objective utilization of new and existing sources of data (in situ or remotely sensed, quantitative or qualitative), for hydrologic DA applications;
• modeling and quantification of structural, parametric, observational, and anthropogenic uncertainties in DA applications;
• open-source and community-based tools for hydrologic DA in support of single-valued or ensemble analysis and prediction.