Abstract
To study the hyporheic exchange driven by a single peak flood-induced
water level fluctuation (i.e. flood wave), a method combining numerical
simulation with theoretical derivation was proposed based on the Inbuk
Stream, Korea, where flooding occurs frequently. The hyporheic exchanges
induced by different flood waves were investigated by varying amplitude
(A), duration (T), wave type parameter (r), and rising duration (tp),
which were adopted from the real-time stream stage fluctuations.
Additionally, the idea of constant upstream flood volume (CUFV)
condition for flood waves was put forward, and the effects of “Botan”
(T/A) and peak number (N) on hyporheic exchange were studied. The
results showed that the hyporheic exchange flux (q) was controlled by
the water level h (sine-type) and its change rate v (cosine-type), and
was proportional to the polynomial of them q“∝” (ω∙h+v), where ω is
the angular frequency of the flood wave. Based on this mechanism, the
influence principles on hyporheic exchanges of the typical flood wave
parameters (A, T, r and tp) as well as T/A and N under CUFV condition
were clarified. The main characteristic variables of hyporheic exchange,
which were maximum aquifer storage and residence time, were positively
correlated. They also had positive relations to the integral of the
flood wave over time, which increased when the wave became higher,
wider, rounder and less skewed. However, when CUFV condition was
imposed, the residence time was positively correlated with T/A, whereas
the maximum aquifer storage was negatively correlated with T/A. With the
increase in N, water exchanged more frequently and some water returned
to the stream early, leading to the slight decrease in maximum aquifer
storage and residence time. These findings enriched the theory of
hyporheic exchange driven by surface water fluctuation and be of great
significance to enhance pollutant degradation in the hyporheic zone
downstream of reservoirs.