Closer Look at the Baseflow Correlation Method

In 2003, Reilly and Kroll examined the baseflow correlation method at river sites throughout the United States. The current study reexamines Reilly and Kroll’s baseflow correlation experiment by investigating the use of different performance metrics, experimental parameters, and model assumptions that were not investigated by Reilly and Kroll. The goal of this study is to provide additional guidance on how to implement the baseflow correlation method in practice. The results confirm that baseflow measurements should be obtained during low flow seasons and as far as possible from runoff events. When one has only five baseflow measurements at the low-flow partial-record site, the correlation coefficient between baseflows at gauged and low-flow partial-record sites should be at least 0.9; when the number of baseflow measurements is 10 or more, the method performs adequately if the correlation coefficient is greater than 0.6. The performance of the baseflow correlation method improves as the number of baseflow measurements increases, but levels off dramatically when one has more than 10 measurements.