1. INTRODUCTION
Owing to the continuous growth of the human population, social
productivity demands associated with development are rapidly increasing
in many countries (Liu and Diamond, 2005). However, demands for the
protection of water resources and ecological environments restrict
development (Bian et al., 2022; Jiang et al., 2022). Water conservancy
projects are essential for flood control, water storage, sediment
retention, and enhancement of agricultural production. The interference
of human activities on the ecological environments have been gradually
amplified (Zeng et al., 2022; Zhu et al., 2017). Such projects enhance
production and the standard of living in many regions. However, they
also impact hydrological processes and damage nature in associated
basins (Xu et al., 2022). For example, regardless of its benefits, flood
control, directly or indirectly affects the natural water cycle and
causes ecological changes in basins (Ding et al., 2020; Du et al.,
2019).
Previous studies on water conservancy projects focused on the
hydrological response to changes in runoff and impacts on the water
ecological environment (Sun et al., 2019; Wu et al., 2019). For example,
Assani et al. (2011) showed that changes associated with a water
conservancy project on runoff in a basin differed from those caused by
climate change. These obvious differences indicate that a water
conservancy project represents an in–dependent factor that controls
runoff changes in a basin. Based on several models, Callow and Smettem
(2009) indicated that the construction of small water diversion
embankments and collection infrastructures significantly impacted runoff
changes in areas of major agricultural activities in Italy. Schreider et
al. (2009) investigated 12 basins, including that of the Jamieson River
in Mexico, and noted that the construction of dams in farming areas
significantly affected runoff and its changes in basins. Flood
forecasting and sediment transport in basins following water conservancy
projects have been reported in many studies. Analyses of changes in
water and sediment flow in response to varying driving factors have
improved our understanding of the evolution of hydrological regimes
associated with floods in basins and impacts on water and soil loss
prevention (Roberta et al., 2022; Yuan et al., 2014). Considering the
evolution of hydraulic engineering facilities and the paucity of
records, a detailed characterization of the impacts of such facilities
on runoff is challenging (Sarah et al., 2022). Therefore, hydraulic
engineering modules have been incorporated into many simulators, and
this has been exploited in many studies on hydrological modeling (Wu et
al., 2020). Cao et al. (2019) incorporated water conservancy projects to
explore trends in flooding based on basin hydrological models, and this
significantly improved the accuracy of flood forecasting. Xiong et al.
(2020) used a hydrological model and field data to explore changes in
flooding and the ecological environment of a basin. GIS technology has
been increasingly employed in the construction of distributed
hydrological models for the characterization of ecological changes in
basins (Lyu et al., 2019). Therefore, based on a distributed
hydrological model, Guo et al. (2022) explored the impacts of the
construction of check dams on ecological changes in the Loess Plateau.
The increasing water conservancy projects are exacerbating the changes
to the ecology in the plateau region; these changes elevate
uncertainties in results from different studies (Wu et al., 2017).
Comprehensive evaluation of the impact of water conservancy projects on
the regional ecological environment is an important research topic.
The Loess Plateau is in the hinterland of Eurasia and is an important
area of agricultural production in China. The ecology of the region is
fragile because of the limited natural endowment of water resources and
severe soil erosion. Therefore, as a prominent area in China that
requires ecological protection, several water and soil conservation
measures, including forest and grass measures and engineering measures,
have been implemented in the region since the 1970s (Wu et al., 2017).
Forest and grass measures can fundamentally prevent water and soil loss
(Wang et al., 2016). However, the effects of the implementation of
forest and grass measures on water and soil loss control cannot be
immediately observed. Surveys indicate that afforestation to sediment
reduction measures require 3–5 years to be effective. The benefits of
engineering measures such as reservoirs in flood detention and sediment
reduction are more obvious than those of forest and grass measures (Wu
et al., 2018). Thus, construction of reservoirs can provide certain
ecological benefits for the regional environment (Nilsson et al., 2005).
These measures were intended to prevent deterioration of the regional
environment, increase its ecological bearing capacity, and ensure a
balance between development by humans and the conservation of nature.
However, interference from human activities complicates the ecological
environment and hydrological cycle in the region (Yang et al., 2004; Li
et al., 2018; Guo et al., 2022). Therefore, evaluation of the extent and
impacts of human activities on hydrological processes and the ecological
environment, as well as shaping and preserving ecological stability in
the basins under new water and sediment conditions associated with water
conservancy projects, are gaining increasing attention in basin ecology
and hydrology studies (Wen et al., 2022;Kang et al., 2021).
The Qinhe River Basin is part of the Shanxi Plate in the Loess Plateau.
The upper and middle reaches of the basin are valley landforms, where
flood disasters frequently aggravate water and soil loss. (Wang et al.,
2006). The lower reaches are important areas for agricultural
activities. According to Lyu (2006), cultivated land occupies
approximately 26% of the drainage area but is under increasing pressure
because of the increasing population and urbanization. Considering the
safety of agricultural production and human life, many reservoirs have
been constructed that have been implemented in the basin since the
1950s. The primary objectives of these measures were to mitigate
ecological deterioration and water and soil loss (Wang et al., 2016).
However, because of its complexity, the relationships between human
activities and the ecology in the basin remain uncertain. The
construction of reservoirs creates challenges in the assessment of
trends in ecological and driving factors of changes in the basin (Zhang
et al., 2011; Lv et al., 2018). Therefore, the achievement of
coordinated sustainable development of the ecological environment and
social component of the basin involving impacts of the construction of
reservoirs is a major problem that requires urgent attention because of
its significance for the development of semi–arid regions in the Loess
Plateau (Wang et al., 2016). The findings of the present study are vital
for assessing changes in the ecological environment in the region during
the last 30 years of the 20th century (Lv et al., 2018). The findings
also provide a reference for environmental governance and the prevention
of soil erosion in the Qinhe River Basin (Montanari et al., 2013;
Jerome, 2000).