3.3 Filtering criteria of the recession flow
To effectively improve the filtered results as low-flow, the filtered
data must meet certain criteria. Cheng, Zhang, and Brutsaert (2016)
evaluated the sensitivity between the recession index and each filtering
criterion. The results indicated that the criteria for the number of
data points before and after the recession events and those affected by
the major streamflow event can be reduced in a relatively smaller basin
due to the faster hydrological response after the rainfall event.
According to the small catchments used here, this study used and revised
the filtering criteria based on Brutsaert (2008) as follow:
- Eliminate the data where the flow variation is equal to or larger than
zero.
- Eliminate the one data point before and two data points after each
data point that meets criterion (1).
- Eliminate three data points after a major streamflow event defined
from the flow duration curve (Kingsford, 2000).
- Eliminate data points with singular values.
3.4 Dynamic
storage properties
To explore the physical-based representative of impact parameter, this
study estimated the change in dynamic storage and storage-discharge
sensitivity as dynamic storage properties derived from recession
analysis.
Based on Kirchner’s (2009) storage-discharge sensitivity function,
substituting equation (2) with environmental change can be expressed as
follows: