Polska Akademia Nauk. Stowarzyszenie Infrastruktura i Ekologia Teren贸w Wiejskich PAN
Doi
Abstract
In Polish hydrology and water management the term characteristic
flow exists denoting a specific value of flow at the given cross-section of
a river calculated as the long-term minimum, mean, median or maximum
calculated using the annual minimum, mean, median or maximum flow
taken for each year from a series of (usually) daily flows. Some of these
characteristic flows are used to define the low-flow (o drought) periods
while the another criterion: a percentage flow Qp taken from the long-term
flow duration curve is also widely used.
In the paper the study on the frequency structure the empirical exceedance
probability of a given characteristic flow made for some low
and average characteristic flows (SNQ, WNQ, NSQ and SSQ) is presented.
The results show that the exceedance probability of a given characteristic
flow is variable, and the amount of this variability may be large, as is the
case of WNQ and NSQ. So assigning a characteristic flow to a single FDC
quantile value Qp (as can be find in the literature) cannot be justified.
Correlation analysis made for the pairs (P. , characteristic flow),
( P., catchment area) and (P. , gauging station elevation) revealed
some significant correlations. Only for SNQ is not correlated at
all; correlation for other characteristic flows is statistically significant
for at least one of the cases. The highest correlations (greater
than 0.4 in absolute values) were found for the pairs ( P, gauging
station elevation) for NSQ and, for SSQ, ( P, SSQ) and ( P, catchment area)