Investigating the linkage between streamflow recession rates and channel network contraction in a mesoscale catchment in New York state

The rate of recession (dQ/dt) in a given time interval has long been plotted in log-log space against the concurrent mean discharge (Q(avg)). Recent interpretations of these dQ/dt-Q(avg) plots have sought to look at curves for individual events instead of the data cloud from all the data points together. These individual recession curves have been observed to have near-constant slope but to have varying intercepts, features hypothesized to possibly be explained by the nature of the contraction of the active channel network during recession. For a steep, 150-ha forested catchment in central New York state with an 8.8-km channel network, changes in the active channel network were mapped between April and November 2013. Streamflow recession occurred in a matter of days, but changes in the active channel network occurred over a matter of weeks. Thus, in this catchment, it does not appear that channel contraction directly controls recession. Additionally, field observations indicate that dry down did not occur in a spatially organized, sequential way such that the upper end of higher-order streams dried first. Instead, the location of groundwater seeps, in part, controlled the active portion of the channel network. Consistent with the presence of different types of flow contributing zones, the paper presents a conceptual model that consists of multiple parallel reservoirs of varying drainage rate and varying degrees of recharge at different times of the year. This conceptual model is able to reproduce a slope of 2 and a seasonal shift in intercept typical of individual recession curves. Copyright (C) 2015 John Wiley & Sons, Ltd.