6 Conclusions
In this paper, the impact of Chaersen Reservoir (Northeast China) on
downstream runoff and baseflow recession characteristics is studied
using a preāpost comparison method, and the influence of climate change
is excluded using two upstream sub-watersheds as control basins. In
addition, the impact mechanism of the reservoir is further explored. The
main conclusions are as follows:
1) After the construction of Chaersen Reservoir, the regulation of
runoff directly leads to the reduction of peak flow
(Qmax decreased by 35%) and the increase of
baseflow (7Qmin increased by 235%) of downstream
Zhenxi station, and the increased direct and indirect consumption of
reservoir storage leads to the reduction of average or total streamflow
by about 14%.
2) After the construction of the reservoir, a relatively constant flow
(about 1m3/s) is added to the baseflow recession
process of downstream Zhenxi station, which causes the log
(|dQ /dt |) vs. log (Q ) scatter
points to shift to the right in the late recession stage, and finally
causes the recession coefficient a to decrease by about 60% andb to increase by about 24%. This change also means the upward
shift of the MRC, the slowing down of the recession rate, and the
increase of the active water storage in the basin.
3) After adding a constant flow, the log
(|dQ /dt |) vs. log (Q ) scatter
points no longer satisfies a strict linear relationship. The MRC
obtained by the traditional linear parameterization method is only an
average approximation, which will overestimate the streamflow in the
middle recession stage and underestimate the streamflow in the later
stage, but the deviation is not obvious as a whole.