Yiluo River Research Articles

Tracking Riverine Nitrate Sources and Transformations in the Yiluo River Basin by Nitrogen and Oxygen Isotopes

The impacts of natural processes and anthropogenic input on riverine nitrate (NO-3) could be identified by NO-3 concentrations and nitrogen and oxygen isotope ratios (δ15N-NO-3 and δ18O-NO-3); however, the effects of variable land use on riverine NO-3 sources and transformations remain unclear. In particular, the human impacts on riverine NO-3 in mountain areas are still unknown. The Yihe River and Luohe River were used to elucidate this question due to their spatially heterogeneous land use. Hydrochemical compositions, water isotope ratios (δD-H2O and δ18O-H2O), and δ15N-NO-3 and δ18O-NO-3 values were utilized to constrain the NO-3 sources and transformations affected by different land use types. The results indicated that ① the mean nitrate concentrations in the Yihe River and Luohe River waters were 6.57 and 9.29 mg·L-1, the mean values of δ15N-NO-3 were 9.6‰ and 10.4‰, and the average δ18O-NO-3 values were -2.2‰ and -2.7‰, respectively. Based on the analysis of δ15N-NO-3 and δ18O-NO-3 values, the NO-3 in the Yihe and Luohe Rivers were derived from multiple sources, and nitrogen removal existed in the Luohe River, but the biological removal in the Yihe River was weak. ② The contributions of different nitrate sources were calculated using a Bayesian isotope mixing model (BIMM) based on δ15N-NO-3 and δ18O-NO-3 values of river water in the mainstream and tributaries with spatial locations. The results revealed that sewage and manure had major impacts on riverine nitrate in the upper reaches of both the Luohe River and Yihe River, where forest vegetation was widely distributed. However, the contributions from soil organic nitrogen and chemical fertilizer were higher in the upper reaches than in downstream ones. The contributions of sewage and manure still increased in the downstream reaches. Our results confirmed the primary impacts of point sources, e.g., sewage and manure, on riverine nitrate in the studied area, and the contributions of nonpoint sources, e.g., chemical fertilizer, had not increased as the agricultural activities elevated the downstream. Therefore, more attention should be paid to point source pollution treatment, and the high-quality development of ecological civilization in the Yellow River Basin should be maintained.

Study on the Contribution of Land Use and Climate Change to Available Water Resources in Basins Based on Vector Autoregression (VAR) Model

Under the influence of global climate change and urbanization processes, the number of available water resources (AWRs) in basins has become significantly more uncertain, which has restricted the sustainable development of basins. Therefore, it is important for us to understand the relationship between land use (LU) patterns and climate change on AWRs in a basin for sustainable development. To this end, the vector autoregressive (VAR) method was adopted to construct a quantitative model for AWRs in the basin in this study. Taking the Yiluo River Basin (YRB) as an example, the dynamic relationship between the five elements of agricultural land (AD), woodland (WD), grassland (GD), construction land (CD), and annual precipitation (PREP) and AWRs in the basin was studied. The results show the following: (1) The constructed VAR model was stable, indicating that the use of the proposed VAR model to characterize the degree of the effect of LU pattern and PREP on AWRs in the YRB was reasonable and effective. (2) AWRs in the YRB showed a downward trend, and their responses to the change in LU and PREP were delayed. The changes in the AWRs in the YRB tended to occur the year after changes to the LU pattern and PREP occurred. (3) In the long run, the degree of the contribution of each influencing factor to changes to AWRs was 23.76% (AD), 6.09% (PREP), 4.56% (CD), 4.40% (WD), and 4.34% (GD), which meant that the impact of the LU pattern was more than 90%. This study provides new ideas for similar research, water resource allocation, and LU planning in other river basins from a macroscopic perspective.

Evaluation of water-land resources regulation potential in the Yiluo River Basin, China

Our study was designed to spatially assess the regulation potential of watershed water-land resources, and determine its regulation objectives for subsequent optimal allocation. We centred around the Yiluo River Basin, being a soil conservation demonstration plot in the middle course of the Yellow River Basin. In accordance with the criteria of the green development, the high efficiency and the safety, the evaluation system of water-land resources regulation potential was established. Then the fuzzy comprehensive evaluation method was applied to assess the watershed water-land resources during 2001–2020 and 2030–2050, and the evaluation results were represented by the eigenvalue T. The research findings pointed out that the assessment grade of watershed water-land resources was mainly moderate and better state, and presented significant spatial agglomeration features in the historical and forecast years. In the context of dual influences of climatic variation and water-land resources exploitation, the assessment eigenvalue T of watershed water-land resources increased by 6% in the historical periods, and decreased by 4.57 ∼ 7.74% in the future periods. Based on the assessment results, it was recommended to restrict the water-land resources exploitation in the upstream, control the soil erosion in the midstream, and coordinate the relationship between the exploitation and protection of water-land resources in the lower reaches. Our study offers scientific evidence for the elaborate regulation of watershed water-land resources.

Assessment of changes in water conservation capacity under land degradation neutrality effects in a typical watershed of Yellow River Basin, China

Large-scale implementation of the Grain for Green Project since 1999, which took the Yellow River Basin (YRB) as the core ecological restoration area, has had an important impact on the hydrological processes and ecological environment. Whether such forest restoration construction is conducive to achieving land degradation neutrality as well as improving water conservation capacity has become a hot research topic. The Yiluo River basin (YLRB), one of the most important water conservation areas in the YRB, was selected as the study area. Firstly, the transfer matrix was used to analyze the changes in the two land use maps in 1990 and 2015 and to determine the transformation relationship between different land use types. Furthermore, land degradation was also investigated for further exploration of the correlation between land degradation neutrality and water conservation. The effects of land use and cover changes (LUCC) on the water conservation capacity across the YLRB were investigated by combining the Soil and Water Assessment Tool (SWAT) model, water conservation assessment method and land use change scenarios method. The results showed that the land degradation area was mainly located in the residential area and agricultural land in the downstream of the YLRB, and the execution of the Grain for Green Project is beneficial in promoting land degradation neutrality and increasing the water conservation capacity. The water conservation capacity across the YLRB approximately increased by 19.30 mm yr−1 as every 10% of agricultural land converted to forest, showing a greater increase in the upstream than that in the downstream. Rainfall, Normalized Difference Vegetation Index (NDVI), and temperature were the primary factors affecting water conservation in the YLRB, while geological lithology also affects the spatial distribution of water conservation. The findings of this study could provide a theoretical basis for water resources and ecological environment protection.

Late Quaternary slip rate of the Fengmenkou-Wuzhiling fault at the southern margin of North China block (S-NCB)

The regional crustal slipping behaviour within the interaction zone of the North China and Qinling blocks reveals the pattern of extensional grabens merging with strike-slip faults and establishes the contribution of these faults to the regional basin generation. In this study, we aimed to assess the active slipping at the Laojing Gou site along the Fengmenkou-Wuzhiling fault (FMK-WZLF), one of the main active faults at the southern margin of North China block (S-NCB), by setting a three-dimensional measurement of the offset in buried paleochannels. Mapping, trenching, and age constraints of the geomorphic and stratigraphy units illustrate three offset paleo-fluvial surfaces since the Late Pleistocene, named S1, S2, and S3, along the fault strike direction. Beneath the surface, the structure of isolated confined paleo-channels C1 and C3 was exposed on the stratigraphy profile, and they were active during 130–75 ka and 2.8–3.0 ka, respectively. We presented a set of adapted scripts for three-dimensional measurements to calculate the lateral and normal tectonic components. The left lateral slip rate for the FMK-WZLF was estimated to be 0.25–0.45 mm/a, and the long-term oblique slipping behaviour generated the scarps in a dip of 70° ± 5° across the fault plane. The oblique slip of the FMK-WZLF, together with the regional E-W and SW-NE striking normal fault system, shapes the northeastward flowing Yiluo river and the southeastward flowing Huai river at S-NCB.

Spatiotemporal variations and driving factors of reference evapotranspiration in the Yiluo river basin

The variations in the reference evapotranspiration (ET0) are closely related to meteorological factors. The purpose of this study is to explore the relationships between the meteorological factors and the ET0. Based on meteorological data from 26 meteorological stations in the Yiluo River Basin (YLRB) and its surrounding areas from 1958 to 2020, in this study, the temporal and spatial variations and driving factors of the ET0 in the YLRB are investigated. The results are as follows. Spatially, the annual ET0 decreases from the northeast to the southwest in the YLRB. Temporally, the annual ET0 exhibits a fluctuating decreasing trend rather than a monotonic decreasing trend during the entire period. The trend of the ET0 contains two mutation points, in 1972 and 1994. Thus, the research period can be divided into three periods. It is concluded that the variations in the ET0 are the most sensitive to the relative humidity, but the driving factor that contributes the most to the variations in the ET0 is the wind speed. The driving factors are closely related to the rates of relative change of the meteorological factors.

Delayed response of net primary productivity with climate change in the Yiluo River basin

Climatic factors are the main drivers that change net primary productivity (NPP). We chose the Yiluo River Basin as the study area to investigate the response of NPP to climatic factors in the Yellow River’s middle reaches. The temporal and spatial distribution of net primary productivity and the trend change of slope in the basin from 2000 to 2020 are analyzed. In addition, we analyzed the correlation between the NPP and climatic factors (precipitation and temperature) and the time-lag effect. The results show that 1) the annual average NPP in the basin is 556.4 gC/m2/a, the maximum value that occurred in 2019. Most of the NPP’s mutation points in the basin’s forest appeared in 2004, while the NPP’s mutation points in arable land mostly appeared in 2008 and 2009. 2) The slope trend analysis result of NPP from 2000 to 2020 shows that the NPP in 67.88% of the basin shows a significant increasing trend, 3.8% of the basin shows a significant decrease, and the other area show no significant change. 3) The correlation analysis between NPP and climatic factors shows a positive correlation between precipitation and NPP in 62.3% of the basin and a positive correlation between air temperature and NPP in 62.5%. The response of NPP to precipitation and temperature in the basin has different degrees of a time-lag effect. The NPP has a time-lag effect on precipitation in 44.8% of the basin, and its mean lag time is 8 days. NPP has a time-lag effect on temperature in 55.7% of the basin, and its mean lag time is 1 day. This study is beneficial to understanding the influence of climatic factor change on vegetation activities in the Yiluo River Basin. Our study illustrates the significance of time lag in analyzing the relationship between NPP and climatic factors. Furthermore, it provides support for scientific vegetation regulation and allocation, as well as adaptation to climate change in areas similar to the Loess Plateau, based on the lag time distribution corresponding to different vegetation types in different regions of the Yiluo River Basin. After that, these areas’ water resources will be fully utilized by vegetation, and ecological restoration could be accelerated.

Comprehensive Evaluation of Surface Water Quality in the Flood Period of the Yellow River by Various Methods and Theories

Field monitoring of water quality during the autumn flood season in the middle and lower reaches of the Yellow River in 2021 was carried out. During this period, a host of methods, including the single-factor evaluation method, index evaluation method, and fuzzy mathematics method, were utilized to evaluate the water quality status. The relevant findings indicate that the water quality of the mainstream and tributaries in the middle and lower reaches of the Yellow River in the autumn flood season is excellent, which meets the water function zoning and water quality goals. In particular, the single-factor evaluation method emphasizes the use of the single index with the most serious pollution to represent the comprehensive water quality category, whereas the fuzzy mathematics method uses the multi-factor contribution rate to calculate the membership degree of water quality. Therefore, it is superior to the single-factor evaluation method in determining the water quality of the water functional zones within the evaluation scope. Meanwhile, the Nemerow index of the water quality of the tributaries of Yiluo River and Qinhe River at the section entering the Yellow River is lower than that of the mainstream, indicating that the water quality of tributaries is better than that of the mainstream during the monitoring period. Overall, the results of this research are conducive to the objective evaluation of the water quality of the Yellow River during the autumn flood season, thus providing more scientific technical support for the ecological conservation and restoration of the Yellow River basin.

Delineation of traditional village boundaries: The case of Haishangqiao village in the Yiluo River Basin, China.

In the conservation and development of traditional villages, it is vital to delineate reasonable village boundaries. At present, China's traditional village boundaries are mainly defined through the boundaries of village construction land in its land policy. This approach ignores the "natural" state of traditional village boundaries and does not truly reflect villagers' use of their villages. Using the constituent line segments of traditional village boundaries as parameters, we delineate a series of traditional village boundaries and constructed an assessment system for traditional village boundaries in terms of the convenience of villagers' activities and their habitual use of village space. We used the delineation of the boundary of Haishangqiao village in the Yiluo River Basin in China as an example to test the effectiveness of the traditional village boundary delineation method and assessment system. The results show the following: (1) The virtual line segments connecting the buildings on the traditional village boundary are the main factors affecting the delineation of the traditional village boundary. (2) The amplitude of vibration and the global deviation of traditional village boundaries are the main influencing factors of complexity. (3) The complexity of traditional village boundaries is negatively correlated with the convenience of villagers' activities. (4) The complexity of traditional village boundaries is negatively correlated with the emptiness of the internal space of traditional villages. The results of this study can provide practical reference values for scholars of rural planning, rural construction, rural conservation, rural management, and rural research.

Watershed-Scale Shallow Groundwater Anthropogenic Nitrate Source, Loading, and Contamination Assessment in a Typical Wheat Production Region: Case Study in Yiluo River Watershed, Middle of China

Nitrate pollution in groundwater has become a global concern for agriculture and regional ecology. However, tracing the spatiotemporal groundwater nitrate pollution sources, calculating the total nitrogen loading, and assessing contamination at the watershed scale have not been well documented. In this study, 20 groundwater samplings from 2020 to 2021 (in dry and wet seasons) on the Yiluo River watershed in middle China were collected. Tracing groundwater nitrate pollution sources, calculating total nitrogen loading, and assessing contamination using dual isotopes (18ONO3 and 15NNO3), conservation of mass, and the nitrate pollution index (NPI), respectively. The results indicated that there were three nitrate sources in groundwater: (1) manure and sewage waste input (MSWI), (2) sediment nitrogen input (SNI), and (3) agriculture chemical fertilizer input (ACFI) in the Yiluo River watershed. ACFI and SNI were the main groundwater nitrogen pollution sources. The average nitrogen loading percentages of ACFI, SNI, and MSWI in the whole watershed were 94.7%, 4.34%, and 0.96%, respectively. The total nitrogen loading in the Yiluo River watershed was 7,256,835.99 kg/year, 4,084,870.09 kg/year in downstream areas, 2,121,938.93 kg/year in midstream areas, and 1,050,026.95 kg/year in upstream areas. Sixty percent of groundwater in the Yiluo River watershed has been polluted by nitrate. Nitrate pollution in midstream areas is more severe. Nitrite pollution was more serious in the wet season than in the dry season. The results of this study can provide useful information for watershed-scale groundwater nitrogen pollution control and treatment.

Evolution and attribution of the water yield coefficient in the Yiluo river basin

Our aim in this research was to detect historical and future water yield coefficient evolution and attribution. Based on the calibrated and validated water yield coefficient model in the Yiluo River Basin, the coefficient for the years 2000–2020 was simulated, along with the future projection for 2030–2050 under four Shared Socioeconomic Pathways (SSP126, SSP245, SSP370, and SSP585). The spatio-temporal evolution of historical and future water yield coefficients was then analyzed. Moreover, the geographical detector model was used to detect the impacts of climate, land use, and terrain factors on the water yield coefficient. The results showed that the water yield coefficient increased by 8.53% from 2000 to 2020, with the coefficient of farmland increasing by 10.47% and that of forestland decreasing by 8.93%. The coefficient was highest under the SSP370 scenario and the lowest under the SSP585 scenario in projections for 2030–2050. Compared to 2000–2020, the coefficients of the two scenarios increased by 12.2% and 2.0%, respectively. Consequently, under the SSP370 and SSP585 scenarios, the coefficient of farmland increased by 13.2% and 2.7%, and that of the forestland decreased by 0.9% and 14.6%, respectively. Driving factors detection indicated that land use types had the strongest explanatory power affecting the water yield coefficient; the explanatory value reached 26.5% in 2000–2020 and will exceed 29.5% in 2030–2050. In addition, the interaction between any two factors was stronger than a single factor. This research provides scientific support for the precise management of watershed and water-land resources.

Quantitative analysis of self-purification capacity of non-point source pollutants in watersheds based on SWAT model

• Based on SWAT model and different self-purifying capacity expression indicators. • Quantitative identification of the self-purifying capacity of the watershed. • Analysis of the causes of change over time and under different land uses. • Quantitative analysis of the self-purifying capacity of the watershed for non-point source pollutants. • The conclusion is of great significance for future ecological protection. It is of great value to reveal the self-purification capacity of surface-sourced nutrients in the watershed and its change pattern, which is important to enrich the study of self-purification capacity of rivers and provide scientific basis for river water environment management. Based on the SWAT model and different self-purification capacity expression indicators, the self-purification capacity of non-point source pollutant nutrients and its change pattern in each river section of the Yiluo River basin from 2018 to 2021 were analyzed, and the physical significance of each indicator, its influence factor and its use range were systematically discussed. The results show that the self-purification of TN and TP in the Yiluo River exceeds 50% of the self-purification of the whole water system, but the self-purification rate is smaller than that of the Yiluo and Luo Rivers; the self-purification of TN and TP is the largest during the abundant water period and the smallest during the dry water period. The self-purification capacity expressed by the indicators of self-purification amount RL and area self-purification amount RA increases with the increase of hydrological variables such as flow (including water depth and velocity), river morphological parameters such as river width and length, and pollutant load; The self-cleaning ability expressed by the self-cleaning coefficient Kx/Kt, self-cleaning length SL, self-cleaning rate Re and load weight self-cleaning rate RLw is opposite; The self-purification rate Vf of the river only increases with the increase of water temperature. From the perspective of differences in application, the two indicators of self-purification speed Vf and area self-purification amount RA should be used for spatial comparison; The other six indicators should be used for the comparison of the same river at different times, of which the self-purification length SL can be used to reflect the influence of hydrological conditions on the self-purification process because of its sensitivity to changes in hydrological conditions.

Temporal and Spatial Variation Characteristics of Actual Evapotranspiration in the Yiluo River Basin Based on the Priestley–Taylor Jet Propulsion Laboratory Model

Evapotranspiration is an important part of the hydrological cycle, affecting the terrestrial hydrological process and the relationship between water resource transformation. Analyzing and mastering the temporal and spatial variations in evapotranspiration are of great significance for the rational development, utilization, and protection of water resources in the basin. Based on MODIS remote sensing data and combined with meteorological and hydrological data, the PT-JPL model was used to estimate the actual evapotranspiration of the Yiluo River Basin, and the applicability of the PT-JPL model for estimating actual evapotranspiration in the basin was analyzed. The spatial and temporal characteristics of actual evapotranspiration in the Yiluo River Basin were analyzed, and the correlation between actual evapotranspiration in the basin and influencing factors such as precipitation, temperature, and vegetation was explored. The main conclusions are as follows: the PT-JPL model has good applicability in the Yiluo River Basin; the total actual evapotranspiration in the basin showed a decreasing trend, which was consistent with the trend of precipitation, indicating that the actual evapotranspiration may be limited by water conditions in the study area. The evapotranspiration of the basin was higher in the upstream and lower in the downstream, which may be related to the better vegetation coverage in the upper basin than in the downstream. As an important indicator of vegetation change, NDVI showed a good correlation with evapotranspiration, which also verified this. In addition, the correlation between evapotranspiration and temperature was also good.

Study on the propagation probability characteristics and prediction model of meteorological drought to hydrological drought in basin based on copula function

Studying the probability characteristics of meteorological drought transmission to hydrological drought can help alleviate drought and optimize the allocation of water resources. This study takes the Yiluo River as the research object, and Standardized Precipitation Index (SPI) and Standardized Streamflow Index (SSI) were used to represent meteorological and hydrological drought, respectively. First, the stability of the precipitation and stream flow sequence is tested by using the heuristic segmentation algorithm. The correlation between meteorological and hydrological watershed was analyzed using cross wavelet transform and lag correlation to study the transmission time of meteorological drought to hydrological drought. Second, the characteristics of drought such as drought duration, drought intensity, and drought intensity are discussed by using the run theory. Finally, the joint distribution of the SPI and SSI sequence is constructed using Copula function. From the perspective of conditional probability, the propagation probability and propagation threshold from different levels of meteorological drought to hydrological drought are calculated. A hydrological drought prediction model based on the SPI—P(SSI|SPI) relation curve is proposed. The model is also validated based on the historical data. The results show that the model is suitable for light and middle hydrological drought prediction.

The Agriculture and Society in the Yiluo River Basin: Archaeobotanical Evidence From the Suyang Site

The Yiluo River Basin is located in the Central plains of China, an area commonly known as the center of origin of ancient Chinese civilization. Agriculture lays the foundation for social and economic development and triggers societal change and archaeobotany can provide important clues on this issue. archaeobotanical study is an important perspective on the relationship between agriculture and society development. However, relatively few archaeobotanical studies have been conducted in the Yiluo River basin, and the paucity of data has hindered our understanding of the relationship between agriculture and society. Therefore, the archaeobotanical analysis at the Suyang site in the middle reach of the Luo River provides an opportunity to understand how and why agriculture and society developed. Our analytical results of carbonized plant remains and phytolith, coupled with radiocarbon dating, showed that millet was the main crop in the late Yangshao culture (5,500–5000 BP), followed by rice. However, rice cultivation in the area expanded during the Longshan culture (5,000–4000 BP), and its importance as a crop possibly exceeded millet at Suyang. From the late Yangshao to Longshan, rice was cultivated in wet fields by utilizing the Luo River floodplain on a large scale. The proportion of rice at Suyang is the highest among contemporary sites in the Central Plains. It may be related to many reasons such as suitable environmental and geomorphological conditions, advanced water management, the influence of the Qujialing culture, and population growth. In the late Yangshao culture, crop processing seemed to have been concentrated in communal areas. However, during the Longshan culture, different steps of crop processing were scattered throughout the site. This change is hypothesized as a change in the family structure and economic production. After the Yangshao period, the nuclear family became the fundamental unit for social, cultural, and economic production in the Central Plains.

The assessment of baseflow separation method and baseflow characteristics in the Yiluo River basin, China

The assessment of baseflow separation method and baseflow characteristics in the Yiluo River basin, China

Integrated geographical environment factors explaining forest landscape changes in Luoning County in the middle reaches of the Yiluo River watershed, China

Analysis of forest landscape changes and its driving factors is vital to forest ecosystem management and sustainable development. However, it is difficult to integrate various environment factors and explain the change of forest landscape. Research on the impact of integrate geographical environment factors on forest landscape changes is still lacking. In this study, we quantified forest area and mapped forest landscape distribution in 1990, 1995, 2000, 2005, 2000, 2010, and 2015 in Luoning County in the middle of the Yiluo River watershed by using multi-temporal land use data, and detected spatio-temporal changes of the forest landscape. Three types of forest landscape changes (unconverted, reforestation, and deforestation) and ten geographical environment factors (elevation, slope, proximity to previous forest edge, distance to rivers, mean annual temperature, mean annual precipitation, distance to roads, distance to residential centers, population density, Gross Domestic Product) were identified. Pearson correlation analysis and line regression analysis were applied to examine the relationships between forest landscape changes and geographical environment factors. Based on the relationships, correlation coefficient and adjusted R2, these environment factors were formed into an integrated geographical environment factors index (IGEF), and an approach for analyzing forest landscape changes along the geographical environment factors gradient was proposed. The results showed that: (1) the total area of forest landscape decreased from 1990 to 2000 and continued to increase from 2000 to 2015; (2) reforestation and deforestation were closely related to individual geographical environment factors and IGEF index; (3) reforestation and deforestation mainly occurred in the areas with low and medium IGEF index values, while forest landscape unconverted was mainly distributed in the areas with high and medium IGEF index values. The observed forest landscape changes could be explained by a set of given geographical environmental factors. Our findings are expected to enhance the understanding of integrated analysis method of geographical environmental factors and contribute to the targeted forest landscape management in mountain areas.

Watershed scale spatiotemporal nitrogen transport and source tracing using dual isotopes among surface water, sediments and groundwater in the Yiluo River Watershed, Middle of China

Nitrogen pollution has been shown to have strong potential threaten to the human drinking water and agriculture. However, identifying the nitrogen and spatial-temporal variation and nitrogen pollution sources among surface water, sediments and groundwater at the watershed scale is still of insufficient understanding. In this study, multi-methods (dual isotopes, hydraulic, hydrogeochemical methods) have been used and 400 samplings (40 sediments, 20 shallow groundwater and 40 surface waters in four periods in dry and wet seasons) were collected from 2018 to 2020. The results showed that the concentration of NO3−-N, NH4+-N, NO2−-N and total nitrogen (TN) had variable spatial and temporal changes in whole watershed. The concentration of TN, NO3−-N, NH4+-N and NO2−-N in downstream was higher than midstream and upstream both in dry and wet seasons. The concentration of TN, NO3−-N, NH4+-N and NO2−-N of the whole watershed in wet season was higher than dry season. The dual isotope values indicate that nitrogen sources were mainly derived from manure and sewage waste input (MSI), agriculture chemical fertilizers (ACFI) and sediments nitrogen input (SNI). Those nitrogen sources have different proportion in downstream, midstream and upstream in dry and wet seasons (the largest proportion: MSI 95.24% in downstream and ACFI 86.26% in upstream both in dry season, SNI 31.75% in midstream in wet season). Water exchange has positive correlation with the nitrogen concentration. High level of nitrogen in river also can be a diver in different location and seasons. Those results can be useful for developing regional management strategies and plans for water pollution control and treatment at watershed-scale.

Baseflow separation and spatiotemporal variation characteristics in the Yiluo River basin

Baseflow separation and spatiotemporal variation characteristics in the Yiluo River basin

Analysis and Prediction of Ecosystem Service Values Based on Land Use/Cover Change in the Yiluo River Basin

Ecosystem service values are closely related to land use/cover change, however, the values affected by land use/cover change in the context of climate variability remain unclear. Based on the land use/cover data of 2000, 2010, and 2020 in the Yiluo River Basin, we quantitatively analyzed the impacts of historical land use/cover change on the ecosystem service values. Then the future land use simulation model was applied to predict the land use/cover distribution in 2030 under three Representative Concentration Pathways scenarios, and the influences on ecosystem service values were analyzed further. We found that the total ecosystem service values in the Yiluo River Basin presented a growth from 9217 million dollars (2000) to 9676 million dollars (2020), which attributed to the increase of forestland and water bodies in recent years. By 2030, the total ecosystem service values continued to present an upward trend, while also showing a difference under three scenarios, this discrepancy was mainly caused by different precipitation conditions. With the introduction of the ecological protection and high-quality development of the Yellow River basin in the new period, climate change may be the main factors affecting the ecological field in the future.