Characterizing and Classifying Rainfall‐Runoff Response, Storage Variability and Water Quality Dynamics in a Small, Forested Catchment

ABSTRACT

Numerous rainfall‐runoff event studies exist and focus on collecting different catchment response variables, from streamflow to catchment storage and solute concentrations. However, few to no studies provide multi‐faceted classifications and typologies of events using multiple types of response metrics. The goal of this study was to use rainfall event data, antecedent condition proxies and response metrics related to streamflow, groundwater and water quality dynamics to classify rainfall‐runoff events. A small, forested catchment was monitored and 30 rainfall‐runoff events were delineated. Individual storm hydrographs were used to calculate streamflow response metrics, water table data were used to estimate the magnitude and timing of groundwater responses and water quality statistics were analyzed for the rising and falling limbs of individual event hydrographs. Spatial variability in groundwater dynamics was observed, with the water table responding differently in different parts of the catchment. Nutrients typically displayed higher concentrations on storm hydrograph rising limbs, which is consistent with the flushing of shallow organic soils. Runoff generation for most events was primarily through shallow subsurface flow, with larger magnitude events also involving overland flow contributions. Classifications of rainfall‐runoff events, using a clustering algorithm, revealed very different clusters depending on the catchment response metrics considered. Classifications incorporating groundwater data notably led to more homogeneous classifications (with two clusters) compared to classifications using other catchment response metrics (i.e., rainfall event and antecedent conditions, streamflow, water quality) that yielded four clusters. Multi‐faceted classifications are therefore recommended whenever possible, as they can help infer the dominant drivers of variability of catchment response to rainfall.