1 Introduction
There are about 16.7 million reservoirs larger than 0.01 ha in the
world, and this number will continue to increase (Lehner et al., 2011).
Currently, about half of the stream and river flow is regulated by
reservoirs and dams, and by 2030 this number will climb up to 90%
(Grill et al., 2015). Reservoir’s interception and regulation of river
flow will obviously weaken peak flow and increase low flow (Vorosmarty
et al., 1997). This will have a significant effect on the hydrological
process many hundred kilometers downstream of the dam (Grill et al.,
2015), as well as on the matter and energy cycle with streamflow as the
medium (Pringle, 2003). Qualitative or quantitative research on the
impact of reservoir construction on global or regional hydrological
process and ecological environment is of profound significance.
There are many researches about the impact of reservoir on the
hydrologic alteration and matter cycle: Grill et al. (2015) assessed the
patterns and trends in river fragmentation and flow regulation by global
dams at multiple scales; Hecht, Lacombe, Arias, Dang, and Piman (2019)
reviewed the hydrological impacts of the hydropower dams of Mekong River
basin; Taylor Maavara, Dürr, and Van Cappellen (2014) studied the
worldwide retention of nutrient silicon by river damming; T. Maavara et
al. (2015) studied the global phosphorus retention by river damming; Van
Cappellen and Maavara (2016) studied the global scale modifications of
riverine nutrient fluxes by damming; Meanwhile, many researchers have
also studied the impact of reservoirs on downstream hydrological drought
(Rangecroft, Van Loon, Maureira, Verbist, & Hannah, 2019; Tijdeman,
Hannaford, & Stahl, 2018; Anne F. Van Loon et al., 2019; Wanders &
Wada, 2015). In addition, reservoir’s regulation of streamflow can also
influence the downstream baseflow recession characteristics. However, we
have not found some quantitative global or case studies, this study may
be the first attempt.
The shape of baseflow recession curve is an important feature of a
basin. Baseflow recession analysis can be understood as a statistical
analysis and description of the recession curve for a specific basin
(Stoelzle, Stahl, & Weiler, 2013; Thomas, Vogel, & Famiglietti, 2015).
The detailed baseflow recession analysis method will be described in
Section 3. Baseflow recession analysis is widely used in hydrological
research, water resources planning and management, and watershed
hydrogeological research (Sujono, Shikasho, & Hiramatsu, 2004; Zhang,
Chen, Hickel, & Shao, 2008). The main application objectives include:
estimating long-term groundwater storage trends (Brutsaert, 2008),
estimating watershed groundwater balance (H. Wittenberg & Sivapalan,
1999), baseflow separation (Huyck, Pauwels, & Verhoest, 2005; Hartmut
Wittenberg, 1999), baseflow regionalization (Beck et al., 2013), and
determining basin-wide hydrogeological parameters (Mendoza, Steenhuis,
Walter, & Parlange, 2003; Oyarzún et al., 2014). The influence of
reservoir on the baseflow recession characteristics will obviously
affect the above application results, so we should first make clear the
influence mechanism of reservoir on the baseflow recession
characteristics.
At present, the main methods used to study the effects of human
activities on hydrological processes include scenario modelling method
(Veldkamp et al., 2015; Wada et al., 2017), paired catchments method
(Best, Zhang, McMahon, Western, & Vertessy, 2003; Brown, Zhang,
McMahon, Western, & Vertessy, 2005), pre‑post comparison method (Liu et
al., 2016), upstream‑downstream comparison method (Rangecroft et al.,
2019), and observation‑modelling comparison method (A. F. Van Loon &
Van Lanen, 2013). Anne F. Van Loon et al. (2019) has made a more
detailed summary. Among them, the simpler and more widely used method is
the pre‑post comparison method, which selects two series before and
after human activities to compare. Peñas, Barquín, and Álvarez (2016)
pointed out that this method is hard to separate human activities from
climate change, and it is usually necessary to select a control basin to
eliminate the impact of climate change. However, we must also be wary of
the spatial differences in climatic characteristics between the control
basin and the impact basin. These spatial differences may lead to
incorrect estimates of the impact of climate change.
The main purpose of this paper is to study the impact of Chaersen
reservoir (Northeast China) on the downstream runoff and baseflow
recession characteristics using the pre‑post comparison method with two
upstream sub‑watersheds as control basins. The main contents include: 1)
Before and after the construction of the reservoir, two streamflow
series with similar rainfall‑runoff characteristics are selected to
compare the differences of runoff and baseflow recession
characteristics. 2) The impacts of climate change are estimated based on
two sub‑basins in the upper reaches of the reservoir. 3) The influence
mechanism of the reservoir is further explored.