Patterns of total suspended solids concentration and the influence of antecedent conditions on hydrograph response to precipitation events on Beaver Creek, Ontario

This study explored relationships between suspended solids concentration and discharge, the influence of antecedent conditions on event hydrograhs and the state of dynamic equilibrium in a second-order stream (Beaver Creek), draining an agricultural basin in southern Ontario, near the City of Waterloo. Beaver creek was monitored for nineteen weeks from July to November of 2005. Thirteen precipitation events of various magnitude and duration were examined within the study period. Discharge and total suspended soils were sampled throughout the events. Cross sectional profiles of six transects were measured prior to and after each event. Base flow, antecedent conditions and event response were quantified. A strong (R2=0.79) positive relationship was found between antecedent conditions and basin response to precipitation events, whereby, wetter conditions in the basin prior to a storm resulted in greater changes in discharge compared to changes in discharge seen with dryer antecedent conditions. Suspended solids/discharge patterns during storm flow were best described using a hysteretic clockwise loop indicating a change in supply source throughout a given event. Rapid changes in suspended soils concentrations were related to decreased detachment by rainfall splash rather than source exhaustion or dilution. Average suspended solids flux showed only a 34% difference between input and output from the study area. Also, cross sectional bed profiles showed that over the duration of this study the creek was in a state of low morphological activity. For design of monitoring programs as well as planning development within a basin, knowledge of storm sediment patterns, the influence of antecedent conditions on basin response to a precipitation event and resulting sediment flux in agricultural creeks is significant. These patterns should be taken as benchmarks for continued assessment of the impacts of human activities around water ways