Range Of Variability Approach Research Articles

Quantitative evaluation of runoff drivers based on the MLLR-Budyko framework

ABSTRACT Few evaluation frameworks investigate the mechanisms causing runoff alterations by quantifying the causes of runoff alterations across different time scales (wet/normal/dry seasons and months) and in-depth analysis of each meteorological indicator's contribution to runoff change. This study quantitatively evaluated the hydrological regime of the Jialing River before and after the abrupt change predicated on the indicators of hydrologic alteration and range of variability approach (IHA-RVA) and the Gini coefficient. Through the partial differential equation of runoff characteristics (MLLR-Budyko), and separated in detail the contribution of each meteorological indicator to runoff alterations. Additionally, the ABCD model expanded and validated the results of the partial differential equations on the runoff contribution on a time scale. The findings demonstrate that the overall hydrological regime changed moderately in the river (48.63%). Of the 14 meteorological indicators separated by MLLR-Budyko, the wet season precipitation contributed the most to the runoff alterations, with a contribution rate of −178.12% of the runoff changes driven by all the meteorological indicators, and the coefficient of variation of the annual precipitation contributed the least, with a contribution rate of 2.16%; use ABCD model reconstruction of natural runoff found significant differences in the contribution of drivers at different time scales.

How does the daily regulation hydropower station reduce the hydrological regime impact? A case study in upper Yellow River

ABSTRACT Human activities, particularly the regulation of hydropower stations, have profoundly altered river flow patterns. While studies have extensively assessed the impact of large or multi-year regulated hydropower stations on hydrological regimes using indicators of hydrological alteration (IHA) and range of variability approach (RVA), the impact of daily regulation hydropower stations has received comparatively less attention. This study aims to evaluate the influence of daily regulation hydropower stations on hydrological regime changes, focusing on the upper Yellow River region in China. Using daily runoff data from 1954 to 2020 at the Guide station, the study compares the impacts of multi-year regulated (Longyangxia) and daily regulation (Laxiwa and Nina) hydropower stations. The Mann-Kendall test showed that 27 out of 32 Indicators of Hydrological Alteration (IHAs) had significant trends under Longyangxia operation, which reduced to 18 IHAs with the inclusion of daily regulation stations. The Range of Variability Approach (RVA) revealed that only 46.87% of IHAs exhibited high alteration from the natural regime when daily regulation was considered, down from 75.00% with Longyangxia alone. This suggests that daily regulation can mitigate the negative impacts of multi-year regulation, potentially enhancing the river's eco-hydrological health.

Evaluation of hydrological regime alteration and ecological flow processes in the changing environment of the Jialing River, China

Abstract Ecological flow is a key element in maintaining the biodiversity of a basin's aquatic ecosystem. This study quantifies the degree of hydrological regime alteration in the Jialing River and the contributions of various driving factors using the indicators of hydrologic alteration and range of variability approach (IHA-RVA), the river impact method (RI), and the elasticity coefficient method based on long-term hydro-meteorological data. Cross-wavelet analysis is used to reveal the periodicity and coherence of runoff and driving factors. Additionally, the improved Q90 method presents a more effective annual ecological flow process. The results show that the overall hydrological regime in the Jialing River has undergone a moderate change, with RVA and RI values of 45.02% and 0.66. Human activities contribute 54.68% to the changes in streamflow. Streamflow has an extremely significant correlation with precipitation and aridity index (Φ). Approximately 85% of the wavelet cone of influence (COI) area, tested at a 95% confidence level, falls within the region. The study also found that the ecological flow obtained through the improved Q90 method is more conducive to the healthy development of the river ecosystem in the Jialing River. These findings can provide some assistance for aquatic ecosystem restoration in the Jialing River.

A novel Joint Probability Density Difference Approach for assessing the alteration of hydrologic regime

AbstractThe construction and operation of upstream reservoirs have significantly altered downstream hydrologic regime. Appropriate and quantifiable assessment method for the alteration of hydrologic regime is considerably vital and emergent for ecological protection and restoration. The Range of Variability Approach (RVA) and modified RVA methods have been widely used in practice to assess the hydrological alteration. However, these methods have failed to concurrently describe the distribution of indicator and morphological features in detail, which might inevitably lead to the misjudgment of alteration. This paper proposes a Joint Probability Density Difference Approach (JPDDA) method to address the major drawbacks of these previous methods with the introduction of Gaussian Kernel Density Estimation (KDE) and copula function. The annual average flow is selected as the reference variable to construct a proper joint probability density function between itself and other hydrological alteration indicators. The JPDDA method could describe the marginal distribution in detail through Gaussian KDE and also link the morphological features with copula function. Along with pervious methods, the hydrological alterations at Yichang hydrological station, Yangtze River are estimated based on the measured flow from 1949 to 2022. It is shown that the hydrologic regime has suffered from a moderate or even heavy alteration under the influence of massive upstream cascade reservoirs, and the JPDDA outperforms the other methods in terms of rationality and stability for practical assessments. Thus, the proposed JPDDA method is strongly advised to handle the hydrological alteration and could provide a reasonable reference for ecological operation.

Response of hydrological regimes to land use change: A case study of the Han River Basin

Abstract Comprehensive and systematic research linking land-hydrological correlations is lacking in the study of factors driving watershed runoff variations. It quantitatively analyzes the overall watershed hydrological conditions using the range of variability approach (RVA) and applies the Budyko hypothesis to identify driving factors of annual runoff variations. The study also explores the impact of individual land use types on runoff across various timescales using the SWAT model in conjunction with historical and extreme scenarios in the Han River Basin. Results reveal that following abrupt changes, the Han River Basin experiences negative alterations in its hydrological indices and overall conditions. Among the driving factors, the lower cushion surface has the most significant impact on runoff. At an annual scale, runoff increases by 12.57 and 20.4% for cropland and construction land scenarios, while forest and grassland scenarios lead to decreases of 8.45 and 2.32%, respectively. Runoff sensitivity to land use changes is notably higher in the wet season than in the dry season at the quarterly and monthly scales. This study offers valuable insights into the integrated management of land use and water resources in the Han River Basin.

Evaluating Effects of Terraces on Flow Regimes in a Hilly and Mountainous Basin

Terraces play a crucial role in regulating the water cycle. The management and restoration of, and the conservation strategies and plans for basins rely heavily on the assessment of alterations in hydrological characteristics, whether natural or man-made, within these basin systems. This study centers on evaluating the impact of terraces on temporal variations in the hydrological regime within the Laixi River basin, within the context of climate variability. To achieve this, we employed a hydrological model and applied the Indicators of Hydrologic Alteration and Range of Variability Approach (IHA–RVA). The results show that, under the influence of terraces, the annual flow exhibited an overall decreasing trend. There was a noticeable decrease in streamflow from March to July, while from October to December, there was a clear upward trend, with increases ranging from 4.76% to 8.10% at the Guanshenxindi (GSXD) and Watershed outlet (WO) cross-sections. The indicators related to the minimum flow showed an overall increasing trend, whereas all indicators related to the maximum flow exhibited a clear decreasing trend. Both high and low flow pulse counts decreased, while high and low pulse durations increased overall. The overall trend of flow reversal counts also showed a decrease. All hydrological indicators exhibited low levels of alteration, with hydrologic alteration values lower than 33.33%. However, the influence of terraces on the upstream hydrological conditions was more pronounced than their downstream effect. The terraces in the study area have played a beneficial role in the flood regulation, drought mitigation, and water resource conservation of the Laixi River. They have contributed to stabilizing the daily average flow during high flow periods and have had a positive impact on the ecological base flow during low flow periods, thereby improving the aquatic ecological environment. This study provides theoretical support for river regulation within the framework of soil and water conservation measures.

Evolution of Hydrological Conditions and Driving Factors Analysis of the Yongding River in a Changing Environment: A Case Study of the Xiangshuipu Section

Hydrological conditions are key factors in the evaluation of water resources and ecosystems. The Yongding River Basin has many irrigated areas, and excessive agricultural water consumption has led to serious water shortages and ecosystem damage. To investigate the evolution of ecohydrological conditions and their driving factors in the Yongding River basin in a changing environment, this study combines indicators of hydrologic alteration with the range of variability approach (IHA-RVA) to identify the most ecologically relevant hydrological indicators (ERHIs) and to determine the periods of hydrological variability in the basin, using the Xiangshuipu section on the Yang River as the study area. By calculating the degree of hydrological alteration, the evolutionary pattern of ecohydrological conditions in the basin was analyzed, and the WetSpa model was used to quantitatively identify the contributions of climate change, reservoir storage, and irrigation water withdrawal to the alteration of hydrological conditions. The results showed that the rise and fall rate; maximum and minimum 1 day flows; dates of maximum flow; and July flows were the most ecologically relevant hydrological indicators for the Xiangshuipu section. Variability of this section occurred between 1982 and 1988; except for the annual maximum 1 day flows and fall rate, which underwent moderate changes; all other indicators exhibited small changes and the overall hydrological alteration of the Xiangshuipu section was low. The most influential change in the hydrological conditions was irrigation water withdrawal (from specific irrigation); followed by climate change and reservoir storage. The results of this study provide an important basis for water resources utilization and ecological management in the Yongding River basin.

Projected flow regimes and biodiversity changes under climate change in the planning western route source areas of the South-to-North Water Diversion Project

Scientific evaluation of the eco-hydrological regimes is of great significance for water resource management and aquatic ecosystem protection. The paper took the western route source areas (WRSA) of the South-to-North Water Diversion Project (SNWDP) as the research region. In order to quantify climate-induced eco-hydrological effects, a general framework was proposed to predict changes in flow regimes and fluvial biodiversity under climate change: The coupling of Global Climate Models (GCMs) and the Distributed Time Variant Gain Model (DTVGM) was used to simulate discharge under different climate conditions. Based on Indicators of Hydrologic Alteration (IHA), changes in eco-hydrological regimes were evaluated by using the Range of Variability Approach (RVA), assessment of overall hydrological change degree (D0), and Shannon index (SI). Changes in discharge, flow regimes, and fluvial biodiversity of WRSA were analyzed during the projected period (2041–2100) compared to the base period (1960–2014). According to the projections, under four SSPs-RCPs scenarios, the future discharge of WRSA increases significantly compared to the base period. D0 of WRSA is moderately or severely changed, and hydrological changes are mainly reflected in high flows such as monthly median flows during flood season, maximum flows, and high pulse duration. While flow regimes are disturbed, SI values of WRSA keep rising and the biodiversity is improved. The increase of discharge and SI becomes progressively greater with elevated radiation intensity, and the quantity of severely altered indicators of IHA increases. In conclusion, future hydrological alterations in SNWDP are expected to further intensify with higher levels of climate change, and these changes are generally conducive to the improvement of fish biodiversity.

Rainfall and Discharge Variability in the Senegal River Basin Based on the IHA/RVA

The hydrological regime of a river is a driving force of its ecosystem. The operation of dams and locks has significant impacts on the hydrological situation of rivers. The objective of this study was to study the change and variability of precipitation and hydrological data in the Senegal River basin and to assess the change in the discharge regime of the Senegal River caused by the operation of the Manantali hydroelectric dam. Based on the IHA (Indicators of Hydrologic Alteration), a range of variability of thirty-three hydrological parameters was calculated and the hydrological alteration associated with the functioning of the dam was quantified. Using the RVA (Range of Variability Approach) method, the hydrological alteration at the Bakel site was evaluated and showed the influence of the dam on the hydrological state. The results showed a strong influence of the dam on the hydrological regime. The fluvial eco-hydrological objectives calculated in this study can constitute certain support for the management of water resources and ecosystems of the Senegal River basin.

Quantifying the Potential Vegetation Distribution under Climate Change: The Case of Cryptomeria fortunei in Dongting Lake Watershed, China

Potential vegetation distribution is an important study in environmental sciences. We utilized the Mixed Least Squares–Total Least Squares (MLS-TLS) method and the Signal Mode Decomposition method and the Ecological Niche model to identify the inter-correlations of internal climate change factors and constructed an environmental factor response regression model. We identified the resonance periods and trend relationships among climate factors (temperature, precipitation, and evapotranspiration) and found that the evapotranspiration of the watershed interferes with the correlation between temperature and precipitation on a five-year scale. The specific change degree of extreme climate indicators in the region was quantified by the Range of Variability Approach, among which the precipitation indicators were all below 33% (low change). There were significant differences between the key bioclimatic variables and Aspect of the development of suitable vegetation habitats. The difference between the Aspect and average daily air temperature is the main contributor to the spatial distribution of vegetation, and the mutual contribution is 76.19%. Our regression model can effectively simulate the potential distribution of vegetation (r = 0.854). Compared to the MaxEnt model, our regression model can quantitatively and intuitively provide suitable habitat values for Cryptomeria fortunei at any given location in the basin. Under future scenarios (2021–2040), suitable habitat for Cryptomeria fortunei in the eastern and western regions of the basin is projected to deteriorate further. The research results can provide some help for policymakers to eliminate the potential adverse effects of future climate change on regional ecology.

Quantitative evaluation of the impact of climate change and human activities on Jialing river runoff changes in the past 60 years, China

Abstract Runoff is one of the key driving forces of watershed hydrological cycle processes. Quantifying the relative impacts of climate change and human activities on runoff change is critical to clarify the mechanisms of watershed hydrological responses. This study analyses the characteristics of hydrological changes in the Jialing River Basin based on observational data from 1957 to 2017. The degree of runoff change was then quantified with the aid of Indicators of hydrologic alterations and Range of variability approach (IHA-RVA) method. By establishing the Budyko model and comparing the Slope change ratio of accumulative quantity (SCRAQ), the influencing factors of runoff change are quantified. The result: (1) Except for Qu River Basin, the average annual runoff of other basins showed a significant downward trend. 1985 was chosen as the abrupt change year. (2) The overall flow alteration in the basin is 50.87%, which is close to the height change. (3) The effects of climate change and human activities on runoff have some spatial variation. Human activities are the main influence factors, of which the contribution rates to the Fu River Basin, the mainstream of Jialing River, Bailong River Basin, and Qu River Basin are 64.57, 66.31, and 74.17% respectively.

Trends of hydroclimatic variables and outflow in the Athabasca River basin

Our study focuses on assessing trends of hydroclimatic variables and their impact on the runoff regime in the Athabasca River basin in two periods (from the beginning of monitoring until 2011 and 1971−2011). Applied methods included the Mann-Kendall statistical test, linear regression, multiplicative decomposition of data series, the Indicators of Hydrologic Alteration, and the Range of Variability Approach. Temperature records indicated a strong regional warming trend, which influenced decreased snowfall and a declining trend in spring runoff. Our results indicate that between 1971 and 2011 median discharge values decreased by > 20% on the lower and middle courses of the Athabasca River. Although on the upper course the median long-term minimum discharge increased due to the melting of mountain glaciers, on the middle and lower courses a significant decrease occurred. The discharge variability has also increased. All factors and changes are important because they affect the Athabasca-Peace delta’s ecosystem and socioeconomic activities on the lower course.

Hydroelectric plant effects and climate change/land use impacts on flow regime in the tropical headwater watershed

AbstractThe effects of hydropower plants (HPPs) and climate/land use change pose a threat to the natural river regime. Although some approaches distinguish the climate action from anthropogenic influence on hydrological regimes in large basins, few methods propose to separate the climate effects from the regulation consequences of unique/few dams. This paper presents a new method to quantify effects of HPP and climate change/land use under the main altered river regime components, which is based on flow duration curves. The method was applied in the Grande River (Brazil), which is regulated by a large reservoir (with surface area > 70 km2). The indicators of hydrological alterations and the range of variability approach indicated that all drivers' effects promoted a moderate alteration in five regime components. The Itutinga‐Camargos HPP implications were the major driver, with a contribution higher than 90% in every component, and it was responsible for a 0.28 × 109 m3 year−1 reduction in water superficial availability downstream. The flow regimes in headwater watersheds can be highly sensitive to dam operations, but other factors may aggravate their effects on river dynamics. The quantification of anthropogenic actions has possible applicability in other systems worldwide to assess the ecosystem services of flow regimes.

Study on water regime assessment and prediction of stream flow based on an improved RVA

Abstract Considering that many hydrological analysis methods compare and analyze the runoff before and after the construction of the reservoir, without restoring the measured data of the hydrological station, in this case, when the length of the measured data series is short, the evaluation results will be affected. In this article, based on the runoff reduction of stations affected by water conservancy projects, an improved range of variability approach (RVA) which can be applied to 1-year hydrological change analysis is proposed by coupling the hydrological variation index with the appropriate upper and lower limit theory of RVA. As Jialing river watershed is selected as the research area, the runoff depth of Beibei station is reduced, and then the improved RVA is employed to analyze the degree of change in river water regime. It is concluded that the change degree of overall hydrological index in Beibei station is high, and the prediction of variation of water regime of Beibei station can be made with the aid of simulating the operation of cascade reservoirs, with the inflow of Beibei station in flood season to reduce, and the inflow in dry season to increase. The example verifies the effectiveness of the improved RVA method, and the analysis results can provide a reference for the adjustment of the operation mode of upstream cascade reservoirs.

Hydrological Response and Ecological Flow Optimization in Water Diversion Area of Inter-basin Water Diversion Project

This article investigates the hydrological response and ecological flow in the diversion area from the Hanjiang River to the Weihe River. Quantifies the impact of the inter-basin diversion project on the hydro-ecological environment of the downstream river. MIKE BASIN is initially utilized in this research to create the multi-year reservoir operating model of Sanhekou Reservoir. Then Indicators of Hydrologic Alteration (IHA) and Range of Variability Approach (RVA) are used to evaluate the change degree of hydrological indicators. Secondly, set seven different ecological flow process schemes considering ecological demand and inter-annual wetness and dryness variability. Finally, evaluate the optimization scheme by Analytic Hierarchy Process (AHP). According to the hydrological response results, suggestions are put forward from the perspective of engineering and non-engineering. The results show that the simulation results of the MIKE BASIN have a high degree of fitting with the design results, which verifies the rationality of the model. Under the design scheme, the overall hydrological change of the river is 72.91% and the hydrological response of the river is high changed. Scheme 6 can reduce the overall hydrological change to (56.63%) moderate change under the premise of less impact on economic benefits, and scheme 6 is the optimal scheme. The research results not only guarantee the ecological function of the river but also provide guidance and reference significance for the actual operation of the reservoir.

Multi-scale impact of climate change and cascade reservoirs on hydrothermal regime alteration in regulated rivers

Study regionThe upper reach of the Yangtze River (URYR) basin, China. Study focusThere are few studies on the factors driving the change in hydrothermal regime and its ecological response. This study proposes a framework to quantify the impact of climate change and reservoirs on hydrothermal and fish reproduction. The framework identifies mutation years of water temperature by the TFPW-MK method and characterizes hydrothermal variability on multiple time scales using hydrologically meaningful indicators (Sample Entropy and Range of Variability Approach). The differences in hydrothermal driving forces are then clarified utilizing the Long Short-Term Memory model and contribution calculation method. In addition, we established water temperature scenarios to assess the ecological effects of hydrothermal alteration. New hydrological insights for the regionAfter mutation, URYR hydrothermal tends to be uniform. With the increase in hydrothermal complexity, the relative contribution of reservoirs is 98%. On an annual scale, climate change is the dominant factor in river warming. On the seasonal and monthly scales, reservoirs are used as heat sources in autumn and winter, and as cold sources in other seasons. Moreover, the reservoirs have a significant impact on hydrothermal in the non-flood season, especially in March and December, which are − 0.72 °C (48%) and 1.17 °C (87%), respectively. The reservoirs delayed the spawning time for Coreius guichenoti and Myxocyprinus asiaticus but increased the duration of Myxocyprinus asiaticus (19 days).

The density difference and weighted RVA approaches for assessing hydrologic regime alteration

Assessing the natural or man-made alterations in the hydrological characteristics of watershed systems is a prerequisite to develop watershed management, restoration, and conservation strategies and plans. The Range of Variability Approach (RVA), based on a suite of Indicators of Hydrologic Alteration (IHA), is most widely used to assess hydrologic alterations. However, the traditional RVA and its revised versions and alternatives all suffer from major challenges such as binning the data and using only the target range to compare the probability distributions of the hydrologic variables in the pre- and post-impact periods through applying simplified statistical analyses. This paper proposes the Density Difference Approach (DDA) and the weighted RVA to overcome these challenges. Despite the previous approaches, which divide the time series of the continuous variables into discrete groups, DDA uses the continuous probability density function (pdf) estimated by the Gaussian Kernel Density Estimation (KDE) technique. It considers the magnitude, frequency, and order position of all individual data in the alteration analysis. Furthermore, to account for the variations in the values and frequencies of the variables beyond the target range, which is neglected in the traditional RVA, the weighted RVA approach has been proposed. These suggested approaches, along the other widely used alteration assessment approaches, have been applied to quantify the hydrologic alteration in the Gharnaveh watershed in the northeast of Iran using 50 years of daily discharge data recorded at the Tamar hydrometry station at the outlet of the watershed. The performance of the alteration analysis approaches was further evaluated using the randomly generated time series with the arbitrary changes in the probability distribution parameters. The results indicate a significant difference in the alteration values and ranks calculated by different alteration analysis approaches. Compared to the traditional RVA, the weighted RVA resulted in higher alteration degrees for most of the IHA indicators. DDA outperformed the other alteration analysis approaches for both the observed and randomly generated data. It better accounted for the alteration in the key characteristics of the probability distribution (including the location, dispersion, and skewness parameters) of the randomly generated data series. We recommend DDA as an appropriate hydrologic alteration assessment approach that assists water resource managers and decision-makers through accounting for multi-dimensional attributes of hydrologic alterations.

Analysis of changes in the hydrological regime in Lalin River basin and its impact on the ecological environment

Lalin River is a first-level tributary of the right bank of Songhua River. High-quality corn production bases irrigated by the Lalin River are famous throughout the country. However, in the last few decades, the hydrological regimes changed severely due to expansion of the irrigation area, leading to more water used for irrigation. To investigate the variation of the hydrological situation, we analyzed the daily runoff data at the Caijiagou Hydrological Station from 1954 to 2015 by using the Indicators of Hydrologic Alteration (IHA) and the range of variability approach (RVA). The results showed a severe decreasing trend of the average monthly flow during the water level with regular and high periods, with a negative slope of −2.924 in August and −2.518 in September. The increasing trend of low pulse and fall rate of flow and the decreasing trend of the rising rate of flow demonstrate that water resources are drying up. Regarding the flow rate, the annual maximum value decreased significantly in slopes of −7.9, −7.6, −6.09, −5.28, and −2.98 on the 1-day, 3-day, 7-day, 30-day, and 90-day, respectively. The flow reversals’ average value is 65 to 50 times/year from 1954 to 2015. From RVA analysis, the hydrological alteration of the basin decreased 50% after 1978. To investigate the influencing factors for the hydrological alteration, we analyzed the variation in land cover and land use between 1978 and 2015. The results showed that the area of paddy fields in 2015 was 1.5 times that of 1978, and the water consumption in paddy fields accounts for 80.8% of the total water resources. Consequently, the wetland area of the basin in 2015 was only 53% of 1978, and the wetland area of the two wetland nature reserves at the mouth of the Lalin River in 2015 was about 53% of 1978. Furthermore, the meteorological condition in the LRB shows a warming and drying tendency. The air temperature has shown an intensively increased tendency, and precipitation decreased in the last 50 years. This indicates that the hydrological situation in the Lalin River Basin has changed considerably under the dual influence of human activities and global warming.

Determination of irrigation water quantity and its impact on crop yield and groundwater

The objective of reservoir water allocation based on considering the ecological water demand of the downstream river has an important impact on the water allocation of each water user and the downstream ecology. Agricultural irrigation with large water consumption will directly affect crop yield. Irrigation water, as the recharge of groundwater in irrigation districts, also plays an important role in the restoration of groundwater. This research used the range of variability approach (RVA), a method of flow management considering the water demand of river ecosystems, to provide the recommended outflow range (RVA target) of the Huangbizhuang Reservoir upstream of the Shijin irrigation district. First, we used the RVA target to determine the water allocation of each water user, set 27 irrigation schemes with the water allocation of agriculture as a constraint, and used the validated AquaCrop model (seven years of field experiment data were used to calibrate AquaCrop model parameters) to evaluate the most appropriate irrigation schemes and their impact on groundwater restoration in the irrigation district. The results showed that the amount of water available for agricultural irrigation in the flood season under the RVA target was 84 mm, which was 36 mm less than the current irrigation quota (120 mm). Three irrigation schemes better than the current scheme (scheme 0) were selected, i.e., scheme 1 (irrigate 42 mm at the seedling and jointing stages), scheme 16 (irrigate 42 mm at the seedling stage), and scheme 22 (irrigate 84 mm at the seedling stage). Scheme 22 increased the yield of corn and WP (water productivity), which were 17 kg/ha and 1 kg/ha/mm higher than scheme 0, respectively, which provided the greatest increase in yield. Scheme 22 can restore 0.727 m of the groundwater table. The yield increased in scheme 16 was 4 kg/ha higher than that in scheme 0. Scheme 16 can restore 0.982 m of the groundwater table, which was the most conducive scheme for groundwater recharge. The WP of scheme 16 and scheme 1 was slightly different from that of scheme 0. There was a slight difference in biomass among the four schemes. The yield increased in scheme 1 was 12 kg/ha higher than that in scheme 0, which could restore 0.727 m of the groundwater table simultaneously, which was for a normal year. This research can provide a reference for the formulation of a local irrigation scheme to stabilize and increase summer maize yield on the premise of satisfying the ecological water demand of the river and restoring the groundwater table.

Quantitative evaluation of runoff variation and its driving forces based on multi-scale separation framework

Study regionThe Xiangjiang River (XJR) basin, China. Study focusOn multiple time scales (annual, quarterly, and monthly), there are few comprehensive and comprehensive quantitative evaluation frameworks for the factors that drive changes in watershed runoff. The focus of this study is to use the Range of Variability Approach (RVA) to quantitatively analyze the changes in the overall hydrological regime of the basin. The Budyko model and the deterministic hydrological process model (ABCD model) were then used to quantitatively separate the factors affecting runoff in the monthly window, and to clarify the differences in the runoff driving force at different time scales. New hydrological insights for the regionAfter the mutation, the runoff of the XJR basin increased by 11%, and the changes in the five groups of hydrological and ecological indicators indicated that the ecological response process of the basin was undergoing negative changes. The contributions of the driving forces on different time scales show significant differences: the climatic factor is the dominant factor of the runoff change on the interannual scale. However, on the seasonal scale, human activities have a greater weight in spring, accounting for 82 % of the total. On a monthly scale, it presents a more complicated situation. Human activities contribute significantly in February, May, and October (60 %, 52 %, and 54 %), while climate factors are the main driving factor in the remaining months (51–170 %).