Analysis of hydrological regime evolution and ecological response in the Min River, China

The river's hydrological regime is the key index to ensuring the ecological function of the river. It can maintain the sustainable development and utilization of water resources and is also the basis for the survival, reproduction, and development of many organisms (Zalewski 2000; Sun et al. 2014). In recent years, many factors such as climate change and human activities have led to the degradation of river ecological functions, especially the construction of large water conservancy projects such as reservoirs and dams, which have significantly changed the hydrological regime in the Min River basin and further affected the stability and health of the hydrological regime in the upper reaches (Zhang et al. 2016; Sun et al. 2019; Bo et al. 2020). Therefore, it is important to evaluate the changes in the hydrological system in tributary watersheds and analyze the ecological response.

Currently, scholars at home and abroad have had a lot of discussions on the quantitative analysis of river hydrological regimes; there are more than 170 indicators describing river ecological flow (Girolamo et al. 2017; Zhuo et al. 2021). Richter et al. (1996) proposed the indicator of hydrologic alteration (indicators of hydrologic alteration [IHA]), which is the most widely used. The indicator system contains 33 indicators divided into five groups (flow, event, frequency, duration, and rate of alter) and further simplifies the common 170 hydrological indicators. It uses alterations in the river flow and the degree of external ecological change to determine the overall degree of alteration in the basin. Later, to better measure the level change, Richter et al. (1998) put forward the range of variability approach (RVA) method for a single variable and comprehensive hydrology change evaluation. Lv et al. (2020) made a comprehensive assessment of the changes in sediment transport and runoff caused by reservoir construction in the Min River basin and concluded that the hydrological regime changes in the basin were related to reservoir construction. Although the 33 indicators have been greatly simplified, the correlation between the indicators has not been well solved and cannot reflect the specific changes in ecological flow in the river channel. To solve this problem, Vogel et al. (2007) evaluated the surplus and deficit of river flow based on the dimensionless ecological index analysis (ecological surplus and ecological deficit) of the flow duration curve (FDC) and established targets and thresholds for each index (25th percentile and 75th percentile). Zhang et al. (2015) evaluated the change process of total surplus and deficit ecological water demand targets in the Dongjiang River basin after being affected by the reservoir based on ecological index analysis. In addition, Black et al. (2005) developed D₀ (degree of hydrologic alteration) and DHRAM (Dundee hydrological regime assessment method) to evaluate the degree of overall change of the reservoir to river flow and the risk of causing river ecosystems.

The attribution analysis of river hydrological regime evolution is a key link in the global assessment of river hydrological status. On the basis of Budyko's theory, Choudhury (1999) and Yang et al. (2008a, 2008b) proposed a coupled water–heat balance equation in the basin and divided the impact of climate change into rainfall and potential evaporation to more accurately and easily study the contribution rate of climate change and human activities to watershed runoff change over a long time series. The impact of river hydrological regime changes on biodiversity is an important objective of ecosystem assessment (Vilardy et al. 2011; Bing et al. 2022). Yang et al. (2008b) proposed the biodiversity index (SI) concept, which has been widely applied in river ecology. Pettersson (1998) further proved that SI is a convenient and reliable method to test the change in biodiversity. YongWei et al. (2021) used the Budyko hydrothermal coupling balance equation and biodiversity index (SI) to analyze the attribution and ecological impact of Dongting Lake. It was found that the main reason for the change in the hydrological regime in Dongting Lake was the influence of human activities (50–60%), and rainfall and evaporation were secondary (20–30%).

Different scholars have achieved good results in evaluating the hydrological conditions of different river basins using different hydrological evaluation methods. However, the evaluation of the Min River hydrological situation by many scholars is limited to the analysis of the degree of hydrological change and lacks a quantitative analysis of the attribution and ecological response to the change in the Min River hydrological situation. In this article, based on the quantitative analysis of the degree of hydrological change in the Min River, a suitable hydrological research method is selected to quantitatively evaluate the attribution and ecological response to the change. A comprehensive assessment of the hydrological changes in the Min River is carried out in the logical sequence of ‘abrupt points analysis – hydrological change analysis – attribution analysis – ecological response analysis’. Specifically, the following five aspects were identified: (1) The Mann–Kendall and Pettitt tests were used to find out the abrupt runoff points under the natural flow patterns of the middle Gaochang station in the Min River basin, study the trend of runoff change, and analyze the influence of runoff on ecological indicators in different periods before and after the abrupt runoff points. (2) Ecological index analysis (ecosurplus and ecodeficit) and the hydrological change index (IHA) were adopted to evaluate the hydrological situation in this region. (3) A quantitative evaluation was made on the change degree of the hydrological regime in the Min River by combining DHRAM and D₀. (4) Using the Budyko hydrothermal coupling equilibrium theory, the attribution analysis of hydrological regime changes in the Min River was carried out. (5) Use the biodiversity index (SI) to assess and analyze the ecological response of the Min River.

The Min River is an important tributary in the upper reaches of the Yangtze River originating at the southern foot of Minshan Mountain. The total watershed area is 1.35 × 10⁵ km², while the total length of the mainstream channel is 735 km, and the natural drop is 3,560 m. The annual average total water resources of the whole basin are 9.5 × 10¹⁰ m³ (Wenxian et al. 2022a). The Min River as the most important water resource in Chengdu Plain has provided basic support for the formation of the ‘Land of Abundance’. However, the construction of large water conservancy projects in the upper reaches and frequent human activities have changed the characteristics of water resource distribution in the Min River basin and the natural hydrological regime in the lower reaches of the Min River (Mittal et al. 2016). The most influential ones are Zipingpu Reservoir with its annual regulation capacity and Pubugou Reservoir with its seasonal regulation capacity on the Dadu River (Xu 2007). Gaochang station is located in Gaochang Town, Yibin City, at the junction of the Dadu River and Min River, which is considered to be the largest tributary of the Min River basin, accounting for half of the Min River basin's water content (Xiao et al. 2022; Zhou et al. 2022). Gaochang station is the control station for the outlet reach of the lower Min River. The hydrological regime changes are very representative of the study of the whole Min River basin.

The Mann–Kendall test is widely used to test the trend of long time series of precipitation, runoff, temperature, and other data, with a wide range of tests and simple calculations (Hamed & Rao 1998; Gajbhiye et al. 2016; Hu et al. 2020). The test steps are as follows:

• (1)
  Set the time series {X_t} and the observed value series {x_t, t = 1,2…,n}, construct order column:

  

  (1)
• (2)
  Under the assumption of random independence of time series, the statistic is defined as follows:

  

  (2)

In general, when p ≤ 0.05, it is considered that there are mutation points in the data.

Richter et al. (1996) put forward the hydrological regime change index (IHA) to reflect the river ecohydrological regime, including five indicators from discharge, event, frequency, duration, and rate of change (Table 1), which can quantitatively analyze the degree of influence of climate change and human activities on the hydrological regime of the Min River and provide a basis for estimating the river ecological flow sequence.

Black et al. (2005) proposed another hydrological change index (DHRAM), which aims to assess the degree and scope of hydrological regime change caused by human activities. Each of the 32 hydrological indicators for the IHA produces an absolute percentage change in the mean and an absolute percentage change in the coefficient of deviation. DHRAM has reassigned the weight of the hydrological indicators based on the IHA hydrological indicators. The degree of change was divided into three levels: 1 for low change, 2 for moderate change, and 3 for high change. DHRAM classifies the impact degree into five levels (Table 2). According to the score calculated by DHRAM, higher score values indicate higher levels of hydrological change and a greater likelihood that ecosystems will be at risk. The combination of DHRAM and D₀ is used to assess the degree of change in the hydrological situation (Dyer et al. 2014; Lu et al. 2018; Xiaoming et al. 2021).

The combination of the Mann–Kendall test and the Pettitt test can accurately identify mutation points, solve the absence of mutation points, and improve the drawbacks of a single test method. Based on the two test methods, it was determined that 1993 was the hydrological variation year of the Min River. By analyzing the influence of human activities on runoff in this region before and after the abrupt change point, it can be seen that under the natural flow state (before 1993), the construction of reservoirs was few and slow, and most of them were small- and medium-sized reservoirs, which had a little change to the discharge of the Min River. In 1993, Tongjiezi Reservoir within the control range of the Min River basin was put into use, which significantly changed the hydrological sequence within the control area of the Gaochang station, resulting in abrupt changes in the annual discharge of the Gaochang station in the lower reaches of the Min River. After the sudden change (since 1993), the number of medium and large reservoirs continued to increase. In 2003, Pubugou Reservoir in the upper reaches of the Min River and Zipingpu Reservoir in 2005 was put into use, resulting in an increased average storage capacity far exceeding the sum of previous periods and forming a series of reservoirs. This indicates that the construction of large- and medium-sized reservoirs in the Min River basin has had a significant impact on the variation of its discharge since the 1990s.

At the annual scale, the change range of the annual ecological surplus is small and presents a decreasing trend, while the change range of the annual ecological deficit is large and presents an increasing trend. In the period before and after the abrupt change, the ecological surplus was greater than the ecological deficit in the natural flow state during the period before the abrupt change (1956–1993), while in the period after the abrupt change (1994–2019), the ecological deficit was greater than the ecological surplus due to the influence of multiple factors such as climate change and human activities. The most obvious change was in the period 2005–2012 when the ecological deficit reached its highest (0.24). The main reason was that the runoff decreased due to less precipitation in this period, which led to an increase in the ecological deficit. In this way, it is confirmed that the ecological indicators and runoff changes caused by the precipitation anomaly have a significant synchronized change rule; that is, when the runoff increases, the ecological surplus increases, while when the runoff decreases, the ecological deficit increases.

At the seasonal scale, the FDC ecological indicators correlate differently with their precipitation spacing in different seasons. As shown in Figure 5, the precipitation distance level correlates best with the ecological indicator in any given period in summer and weakest in winter, with spring and autumn in between, because precipitation levels are much greater in summer than in winter, and when precipitation is high enough, precipitation can be a major factor in changing its flow. The results also show a concentration of peak ecological surpluses in 2000, 2006, and 2010, consistent with the annual variability results. These peaks occurred after the year of the abrupt change (1993), suggesting that climate change and human activities are interfering with changes in ecological flows in the basin. Compared to the sudden change period, it can be concluded that the ecological surplus shows an unusually increasing trend, especially in winter (2019 maximum value of 0.37) and spring (2012 maximum value of 0.41), which never occurred before the sudden change. Figure 5(b) also shows that precipitation patterns in summer are consistent with annual scale variability, while Figure 5(a)–5(d) show that precipitation in spring, autumn, and winter is less consistent with precipitation variability over the whole year, which together suggests that the variability of precipitation and ecological indicators in summer is most representative of the whole year.

Two calculation methods, DHRAM and D₀, were used to obtain the results of the hydrologic change degree (Table 5). From the overall score and results of DHRAM, the total DHRAM score of the Gaochang station was three points, and the change level was 2, which belonged to a low change degree; D₀ was 45%, which belonged to a moderate change degree. Considering that the proportion of moderate and low changes among the 32 hydrological change indicators in the IHA was 44%, the degree of hydrological regime change in the Gaochang was determined to be a moderate change by combining the results of the two methods.

The attribution analysis of the change in the hydrological situation of the Min River mainly adopts the Budyko hydrothermal coupling balance theory. We obtain the calculation results of the multiyear average rainfall, multiyear average potential evapotranspiration, multiyear average runoff depth, underlying surface parameters n, rainfall, evaporation, and elastic coefficients of human activities in the Min River basin (Table 6).

Table 6

Hydrometeorological characteristic values of the Min River

Period .	P/mm .	ET0/mm .	R/mm .	n .	R/P .	ET0/P .	εp .	.	εn .
Before dam construction	1,100.82	466.34	643.55	1.31	0.58	0.51	1.56	−0.39	−0.29
After dam construction	1,007.88	459.18	593.70	1.93	0.59	0.52	1.53	−0.40	−0.31

Period .	P/mm .	ET0/mm .	R/mm .	n .	R/P .	ET0/P .	εp .	.	εn .
Before dam construction	1,100.82	466.34	643.55	1.31	0.58	0.51	1.56	−0.39	−0.29
After dam construction	1,007.88	459.18	593.70	1.93	0.59	0.52	1.53	−0.40	−0.31

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According to the calculation results, compared with before the dam construction, P, R, and ET₀ in the Min River basin decreased after the dam construction, with a rate of 8.44, 7.75, and 1.54%, respectively. n is increased, and the growth rate was 47.33%. The dryness index (ET₀/P) and runoff coefficient (R/P) increased slightly compared with the base period. The elastic coefficients of runoff on rainfall, potential evaporation, and underlying surface parameters after dam construction in the Min River basin are 1.53, −0.40, and −0.31, respectively, indicating that when rainfall, potential evaporation, and underlying surface parameters increase by 1%, the runoff depth will increase by 1.53%, decrease by 0.40%, and decrease by 0.31%, respectively. The change in the runoff depth in the Min River basin is positively correlated with P but negatively correlated with ET₀ and n. As the absolute value of the elastic coefficient reflects the sensitivity of runoff to the influencing factors, the results show that runoff depth is most sensitive to the change in P and least sensitive to the change in n.

We further studied and obtained the contribution rate of each influencing factor to runoff change in the Min River basin (Table 7). The results show that the variation in runoff caused by rainfall is −83.83 mm. The potential for evapotranspiration increased to 3.68 mm in runoff depth. The underlying surface parameter resulted in a 103.54 mm decrease in runoff at the Gaochang station. The contribution rate of underlying surface parameter change to runoff change in the Gaochang station is the largest, which is 54.20%. The contribution rate of rainfall to the runoff change at Gaochang station was 43.88%. The contribution rate of potential evapotranspiration to runoff change at the Gaochang station was the lowest, which was 1.92%. Therefore, the change of the underlying surface parameter is the main factor leading to the decrease of runoff at the Gaochang station, followed by precipitation and the least by potential evapotranspiration.

Table 7

Attribution analysis of runoff change in the Min River basin

Hydrographic station .	Base period .	Change period .	ΔRP (mm) .	Δ (mm) .	ΔRn (mm) .	ΔR (mm) .	CP (%) .	(%) .	Cn (%) .
Gaochang station	1956–1993	1994–2019	− 83.83	3.68	− 103.54	− 49.85	43.88	1.92	54.2

Hydrographic station .	Base period .	Change period .	ΔRP (mm) .	Δ (mm) .	ΔRn (mm) .	ΔR (mm) .	CP (%) .	(%) .	Cn (%) .
Gaochang station	1956–1993	1994–2019	− 83.83	3.68	− 103.54	− 49.85	43.88	1.92	54.2

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We can see that under the natural flow regime (1956–1993), the declining trend of the Min River flow biodiversity index is in a stable change phase. In the posttransformation period (1993–2019), the decline in the Min flow biodiversity index accelerated slightly, followed by a slow change from 2010 onward. It can be shown that the construction of reservoirs under the influence of human activities has changed the hydrological situation of the Min River in its natural state, causing a further decrease in its biodiversity, but with the protection of the ecological environment in recent years, the decreasing trend of the biodiversity index has been alleviated, which also indicates that the protection of the Min River's biodiversity has played an important role.

Quantitative analysis of the influence of climate change and human activities on hydrological regime change is not only a hot topic in the field of hydrology but also a difficult one (Wu et al. 2017; Li et al. 2020). As an important tributary of the Yangtze River basin, the Min River has been affected by multiple factors, such as climate change and human activities, for a long time, and its hydrological regime has changed significantly (Shao et al. 2021; Wang et al. 2022). Therefore, the change and attribution of the hydrological regime in the Min River are discussed in depth from five aspects: runoff change, interannual change, ecological index change, hydrological degree change, and Budyko change result.

This article used the MK and Pettitt tests to find that 1993 was the year of hydrological abrupt in the Min River. Before the abrupt change (before 1993), the runoff in the Min River basin was in a stable change stage; after the abrupt change (after 1993), the natural hydrological regime of the Min River changed significantly, and the runoff showed a downward trend. The attribution analysis proves that the construction of tandem reservoirs in human activities is an important factor leading to its change. We studied the relationship between ecological indicators and precipitation anomalies at the annual scale and the seasonal scale, respectively, and found that the annual scale FDC ecological indicators and precipitation anomalies showed a significant correlation, in which the ecological surplus increased with the increase of precipitation and decreased with the decrease of precipitation. At the seasonal scale, the relationship between ecological indices and precipitation anomaly changes in summer is most similar to that between annual changes, which is related to more precipitation in summer. By analyzing the attribution, we know that the change of runoff at the annual scale is mainly influenced by precipitation, and the change of runoff at the seasonal scale is mainly regulated by the reservoir. The combined effects of climate change and human activities lead to a decreasing trend of ecological surplus and an increasing trend of ecological deficit in the Min River basin. The overall change degree of the Min River hydrological regime reached 44%, which was a moderate change, indicating that the Min River ecosystem was facing a moderate risk of destruction. The Budyko results quantitatively analyzed the degree of each influencing factor on the runoff change, in which the change in rainfall caused the runoff decrease of 83.83 mm, and the change in the underlying surface parameter caused the runoff decrease of 103.54 mm. It can be seen that runoff changes are mainly affected by rainfall and underlying surface parameter changes, and with the rapid development of the social economy in recent years, underlying surface parameter changes have become an increasingly important factor affecting runoff changes.

To further discuss the rationality of the paper's conclusions on hydrological regime changes of the Min River and attribution, we further elaborate on the relevant conclusions of existing scholars on the Min River and other river basins. Du et al. (2022) made a systematic analysis of the precipitation of the Min River and observed that the precipitation of the Min River basin decreased year by year from 1956 to 2020 with a slight change rate of 1.028 mm/10a and showed a decreasing spatial distribution pattern from the southeast to the northwest. Zhao et al. (2020) evaluated the hydrological situation of Panzhihua Station based on the FDC ecological index and found that the main reason for the change in the hydrological situation at the seasonal scale was the influence of the reservoir, and for any season, the ecological surplus and ecological deficit showed a parabolic law of ‘low-high-low’. Zhang et al. (2021) used the ecological runoff index system composed of a 12-month ecological surplus and a 12-month ecological deficit on the basis of a new evaluation method for hydrological regime change of the ecological runoff index and confirmed that each month before and after the reservoir construction would have varying degrees of influence on the change of the ecological runoff. Wenxian et al. (2022b) used Budyko to analyze the attribution of hydrological regime changes in the Jialing River and observed that the contributions of precipitation, potential evapotranspiration, and human activities to runoff changes were 61, −16, and 55%, respectively, among which precipitation and climate change were the main influencing factors. Duan et al. (2016) used the IHA-RVA method to study the hydrological regime changes in the middle and lower reaches of the Yangtze River and observed that the degree of hydrological change at Yichang Station was high, while that at Datong Station was moderate change. Guo et al. (2022) conducted a quantitative analysis of the hydrological regime of the Min River and observed that the degree of hydrological change was 45%, which was not much different from the results of the study in this article.

After further discussion of the changes in the hydrological regime of the Min River and its attribution, it is not difficult to find that the research results of this article are more comprehensive than the previous research results on the Min River basin. Previous research results have been limited to the analysis of the hydrological change of the Min River and have not quantitatively evaluated the contribution rate of climate change and human activities to the change in the hydrological regime. In this article, while calculating the contribution rate, the proportions of each impact factor are considered separately, which makes the research results more rigorous and scientific, and indirectly indicates that the research results in this article are more reasonable.

Ecological response analysis is an important form of assessment to cope with the adverse effects of river hydrological regime changes on ecosystems (Döll & Zhang 2010; Alban et al. 2021). In this article, the SI index was used and it was found that the biodiversity index of the Min River was in stable change under the natural flow state. The biodiversity index decreased significantly with the influence of human activities after the mutation, and the more intense the interference of human activities, the faster the declining trend. The conclusion of this study is also confirmed by the research results of many researchers on the water environment, species diversity, and fish in the Min River. Chen et al. (2019b) observed that the ammonia nitrogen content in the Min River basin was low and showed a slowly increasing trend under natural hydrological conditions, and the water quality was good. However, the construction and use of reservoirs and the increase of ammonia nitrogen discharge by many enterprises along the Min River basin destroyed a natural hydrological regime, which led to the deterioration of the Min River's water environment. Chen et al. (2019a, 2019b) used the image element decomposition method to conclude that the overall vegetation cover of the Min River basin shows a fluctuating downward, decreasing trend. In 2008, with the increasing frequency of human activities such as reservoir maintenance and power station reconstruction in Min River basin, the vegetation coverage changed significantly, and the decreased area accounted for 26.4% of the study area, which further led to the deterioration of the vegetation coverage structure in Min River basin. In 1957, Zhang & Liu (1957) conducted a preliminary survey of fish resources in the Min River and found 92 species of fish in 68 genera in the study area. Lv et al. (2018) surveyed the main flow of the Min River in 2015 and found 71 species of fish in the study area. He et al. (2021) conducted field surveys on the Dadu River, the largest tributary of the Min River, from 2017 to 2019, and fish sampling showed that 24 species of fish were collected in the upper reaches of the Dadu River. This indicates that the construction of water conservancy projects has caused certain barriers to the migration and spawning of fish and even changed the community structure and functional groups, bringing adverse effects on the reproduction of fish in the Min River basin.

Although nature has a certain ability to adjust to changes in the external environment, the ecology and water environment have undergone drastic changes in recent years under the long-term influence of human activities, and the original ecological environment of the Min River has been intensified by the continuous invasion of alien species (Buytaert et al. 2011). Especially, the construction of the cascade reservoir has seriously affected the species and quantity of fish in the Min River area. To reduce the negative impact of changes in hydrological conditions on the ecological environment, many researchers have used hydrological distribution models and neural networks to predict changes in runoff. The results of these studies have helped to improve the accuracy and reliability of long-term runoff probability predictions in multisite systems, and have helped to improve the efficiency of integrated water resources development and use, and to reduce uncertainty and risk (Minglei et al. 2020; Ebtehaj et al. 2021; Wang et al. 2022). Therefore, the hydrological distribution model should be applied to the hydrological study of the Min River basin in future research, so that relevant managers can develop and utilize the Min River basin resources scientifically and rationally and thus achieve ecologically sustainable development within the Min River basin.

The land cover change in the Min River basin from 1980 to 2018 shows fluctuating changes: the grassland area coverage increased from 42.15 to 42.58% (105 km²) (Table 8); the construction land area changed more between 1980 and 2018 (0.23%), which indicates that with the continuous industrialization and urbanization, the construction land area increased gradually with time; and the decreasing and then increasing trend in barren land area and the decrease in the forest, cropland, and wetland area indicate that human activities have had an impact on the habitats in the watershed. In recent years, human activities in the Min River basin have increased significantly, leading to a rapid increase in the proportion of land used for construction and a decrease in wetland areas.

The evolution of land types and land use patterns in the Min River basin are analyzed in Table 9. The watershed area decreased by 9 km² from 1980 to 2018, converting mainly to grassland and barren land, indicating the severity of soil erosion. Since the implementation of soil and water conservation measures in 1980, the forested area showed a trend of growth followed by a decrease during this period. With the development of hydropower projects and the dramatic increase in human activities, the total forested area continued to decrease (230 km²). Grassland and construction land increased by 100 km² and 321 km², respectively, with the most dramatic increase in the construction area during 1980–2018.

To determine the degree of influence of climate change and human activities on the hydrological regime of the Min River basin, the hydrological changes are evaluated comprehensively from the characteristics of interannual and annual changes. With the help of Mann–Kendall and Pettitt tests, the abrupt change points of the Min River runoff were found. The ecological indicator (FDC) was used to analyze the causes of runoff change in the Min River at the annual and seasonal scales. With IHA-RVA, DHRAM, and D₀, the degree of hydrological regime change in the Min River was quantified. The effects of climate change and human activities were quantitatively separated based on the Budyko hydrothermal coupling equilibrium theory. The changing trend of biodiversity in the Min River was obtained by SI index changes. The results are summarized as follows:

• (1)

  MK and Pettitt tests comprehensively indicate that 1993 is the abrupt change point of Min River runoff under the natural flow state. At the annual scale, runoff changes in the Min River basin are mainly caused by precipitation; at the seasonal scale, runoff changes are mainly caused by reservoir regulation. Climate change and human activities have led to a decrease in the ecosurplus and an increase in the ecodeficit of the Min River.

• (2)

  According to the comprehensive analysis of the IHA-RVA method, DHRAM, and D0 change degree analysis, the 32 ecohydrological indicators in the Min River basin are mainly moderate and low change, and the overall change degree is 44%, which belongs to the moderate change.

• (3)

  The elastic coefficients of runoff for the influencing factors were calculated according to the Budyko water–heat balance equation. It was found that the contribution rate of human activities was 10.32% higher than that of rainfall, indicating that human activities greatly affected the hydrological regime in the Min River basin.

• (4)

  The change in the hydrological regime of the Min River basin resulted in a decreasing trend in the SI index, with a significance level exceeding the 95% confidence interval. The influence of human activities led to a faster decline in the alteration period (1994–2019) compared to the base period (1956–1993).

The impact of climate change and human activities on hydrological conditions in different river basins is a long-standing and complex issue. The results of this article can be well applied to river management in the Min River basin and provide reasonable guidance for changes in river hydrology in other regions. In future studies, the focus should be on the ecological response of different meteorological scenarios and reservoir operations to hydrological changes, in conjunction with hydrological modeling, to provide a further basis for water resource management and protection of the river ecosystem.

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The authors are giving consent to publish the article in the submitted journal.

H.W.: funding acquisition, project administration, resources, investigation, supervision. B.W.: conceptualization, data curation, formal analysis, investigation, methodology, resources, software, validation, visualization, writing – original draft, and writing – review and editing. H.Y.: investigation, formal analysis, methodology, validation, and visualization. H.Z.: visualization, investigation, and formal analysis. H.C.: formal analysis, investigation, and methodology. W.G.: funding acquisition and project administration.

This study was supported by the National Natural Science Fund of China (51779094); The 2016 Henan University Science and Technology Innovation Talent Support Plan (16HASTIT024); and The Guizhou Provincial Water Resources Department 2020 Water Conservancy Science and Technology Project (KT202008).

Data cannot be made publicly available; readers should contact the corresponding author for details.

The authors declare there is no conflict.