I'm just wondering if there is any tool in ArcGIS that can be used to analyse stream flow measurements. For example, estimating runoff, baseflow and baseflow index based on stream flow measurements.
Flow Accumulation (Spatial Analyst) Creates a raster of accumulated flow into each cell. A weight factor can optionally be applied.
If it comes to baseflow you will probably need a more advanced surface runoff - soil programm. look also at CAESAR