Qin River Research Articles

Assessing the Spatiotemporal Variations in the Hydrological Response of the Qin River Basin in Loess Plateau, China

In recent decades, the hydrological processes on the Loess Plateau have undergone significant changes due to the combined effects of climate change and human activities. This study investigates the Qin River basin, the core area of the Loess Plateau. Between 1971 and 2000, the hydrometeorology of the flood season in the Qin basin on the Loess Plateau in China changed abruptly in 1982 and 1992. This study uses distributed hydrologic modeling and statistical analysis to distinguish the spatial and temporal impacts of climate change and human activities. The fastest dynamic changes in land use occurred in grassland and construction land, accounting for 0.36% and −0.1%, respectively, from 1982 to 1991. From 1992 to 2000, it was 0.29% and 0.3%, respectively. The increase in basin area where the Normalized Difference Vegetation Index increased was 95%. However, except for significant changes in runoff from 1981 to 1992, there were no significant changes in precipitation, runoff, and temperature during other flood seasons. During the two studied variation periods, from 1982 to 1991 and from 1992 to 2000, the contribution rate of climate change to flood season runoff (CClimate) decreased from 83.26% to 74.47%, while the contribution rate of human activity disturbance to flood season runoff (Chuman) increased from 16.74% to 25.53%. In terms of spatial distribution, from 1982 to 1991, areas with a Chuman > 50% were primarily concentrated in the upper reaches of the basin, while from 1992–2000, these areas shifted to the lower reaches. This study offers valuable insights for water resource planning and soil conservation measures in the Loess Plateau and similar arid regions worldwide, aiming to ensure water resource safety and sustainability in response to climate change and human interference.

Spatio-Temporal Variations in Nitrate Sources and Transformations in the Midstream of the Yellow River Determined Based on Nitrate Isotopes and Hydrochemical Compositions

Nitrate pollution is a major environmental problem threatening rivers, and nitrogen and oxygen isotopes have proved to be an effective means of analyzing the sources and transformations of nitrate in rivers. However, a low monitoring frequency cannot accurately reflect the changes in nitrate. In this study, the sources and transformations of nitrate in the middle reaches of the Yellow River and its tributaries during the dry season and the wet season were analyzed based on water quality parameters and nitrate isotopes. Stable isotope analysis conducted using the R (SIAR) model was used to estimate the proportions of different nitrate sources. The results showed that the main nitrate sources in the main stream were soil nitrogen (40.95–45.83%) and domestic sewage and manure (30.93–32.60%), respectively, with little variation between the dry season and wet season because of the large flow of the Yellow River. During the dry season, the nitrate sources of the two tributaries were mainly domestic sewage and manure (45.23–47.40%), followed by soil nitrogen (31.35–34.00%). However, the primary nitrate source of T2 (Qin River) became soil nitrogen (40.05%) during the wet season, a phenomenon that was mainly caused by the significant increase in river discharge and in soil erosion in the basin. During the wet season, the concentrations of total nitrogen (TN) and nitrate (NO3−) significantly decreased in the main stream and tributaries, and nitrification and denitrification processes occurred in both the main stream and tributaries of the Yellow River. In addition, the T2 tributary (Qin River) was also significantly affected by mixed dilution. High-frequency sampling can reflect the isotopic information of nitrate in the river more comprehensively, which helps us to understand the conversion process of nitrate more accurately.

Distribution and adsorption-desorption of organophosphate esters from land to sea in the sediments of the Beibu Gulf, South China Sea: Impact of seagoing river input

Organophosphate esters (OPEs) have been a class of emerging environmental contaminants. However, studies on their environmental behavior, specifically their adsorption-desorption behavior between sediment and seawater in estuarine and coastal areas, remain limited. To address this gap, our study focused on investigating the levels and behavior of 11 OPEs in sediment samples collected from the Beibu Gulf, South China Sea, encompassing estuaries and coastal regions. The total concentrations of 11 OPEs (Σ11OPEs) in the sediments exhibit a significant decrease in summer, both in seagoing rivers (4.67 ± 2.74 ng/g dw) and the coastal zone (5.11 ± 3.71 ng/g dw), compared to winter levels in seagoing rivers (8.26 ± 4.70 ng/g dw) and the coastal zone (7.71 ± 3.83 ng/g dw). Chlorinated OPEs dominated the sediments, constituting 63 %–76 % of the total. Particularly, port and mariculture areas showed the highest levels of OPEs. Through load estimation analysis, it was revealed that the sedimentary OPEs in Qinzhou Bay (221 ± 128 kg) had the highest load, with input from the Qin River identified as a significant source. Chlorinated OPEs showed a trend of desorption from sediments to the water column with increasing salinity, emphasizing the crucial role of land-based OPEs input through suspended particulate matter in rivers as a pathway to the ocean. The impact of strong flow in estuarine environments was highlighted, as it can scour sediments, generate suspended sediments, and release OPEs into the water bodies. Additionally, the results of the ecological risk assessment indicated that most of the OPEs posed low-risk levels. However, attention is warranted for the contamination levels of some chlorinated OPEs, emphasizing the need for ongoing monitoring and assessment.

Community characteristics of macroinvertebrates and ecosystem health assessment in Qin River, a main tributary of the Yellow River in China.

To know well the ecosystem health status of Qin River, a main tributary of the Yellow River and the largest river in Jincheng region, macroinvertebrates from 49 sampling sites in the Qin River and its largest tributary, the Dan River, were investigated, and community characteristics were analyzed in the autumn of 2020; a Benthic index of Biotic Integrity (B-IBI) was established based on four metrics by a series of steps. The results showed that a total of 38 species of macroinvertebrates were collected and identified, belonging to 6 orders and 19 families, consisting of 17 Insecta species, 13 Gastropoda species, and 4 Oligochaeta species. Four species in Insecta belonged to EPT (E, Ephemeroptera; P, Plecoptera; T, Trichoptera); 10 species in Insecta belonged to Chironomidae and Tipulidae families. All species in Gastropoda belonged to Basematophora order, and, especially, Bellamya aeruginosa is highly tolerant to nutrients. All species in Oligochaetes belonged to Tubificidae family, which indicates eutrophication and low-dissolved oxygen. The dominant species in the study were Ephemera orientalis, Chironomus riparius Meigen, and Limnodrilus claparedianus. The final B-IBI scores varied from 0.75 to 3.75, with 5 sites in "excellent," 10 sites in "good," 10 sites in "normal" status, 12 sites in "poor" status, 12 sites in "very poor." "Very poor" and "poor" sites were mainly located in the middle reach of the Qin River and upper-middle reach of the Dan River in Jincheng region. B-IBI strongly differentiated the reference sites and impaired sites, suggesting the suitability of the B-IBI in the Qin River basin. Significantly negative correlations between NH4+-N, TN, and B-IBI indicated the B-IBI characterized well the influence of nitrogen pollution.

A time-varying distributed unit hydrograph method considering soil moisture

Abstract. The distributed unit hydrograph (DUH) method has been widely used for flow routing in a watershed because it adequately characterizes the underlying surface characteristics and varying rainfall intensity. Fundamental to the calculation of DUH is flow velocity. However, the currently used velocity formula assumes a global equilibrium of the watershed and ignores the impact of time-varying soil moisture content on flow velocity, which thus leads to a larger flow velocity. The objective of this study was to identify a soil moisture content factor, which, based on the tension water storage capacity curve, was derived to investigate the response of DUH to soil moisture content in unsaturated areas. Thus, an improved distributed unit hydrograph, based on time-varying soil moisture content, was obtained. The proposed DUH considered the impact of both time-varying rainfall intensity and soil moisture content on flow velocity, assuming the watershed to be not in equilibrium but varying with soil moisture. The Qin River basin and Longhu River basin were selected as two case studies, and the synthetic unit hydrograph (SUH), the time-varying distributed unit hydrograph (TDUH) and the current DUH methods were compared with the proposed method. Then, the influence of time-varying soil moisture content on flow velocity and flow routing was evaluated, and results showed that the proposed method performed the best among the four methods. The shape and duration of the unit hydrograph (UH) were mainly related to the soil moisture content at the initial stage of a rainstorm, and when the watershed was approximately saturated, the grid flow velocity was mainly dominated by excess rainfall. The proposed method can be used for the watersheds with sparse gauging stations and limited observed rainfall and runoff data.

Spatiotemporal characteristics of soil erosion in a typical watershed consisting of different landscape: A case study of the Qin River Basin.

Soil erosion has a severe impact on habitat and productivity. It is considered to be a major environmental threat prevalent in ecosystems. However, few researchers have studied the spatial distribution of soil erosion intensity among different geographic environmental factors. The Qin River Basin is a geographical unit consisting of mountains, hills, and plains with significant regional characteristics, and it has a basin area of 14,810.91 km2. This study uses the Geographical Information Systems, Revised Universal Soil Loss Equation model to analyze the spatiotemporal changes in the soil-erosion intensity in the Qin River Basin from 1990 to 2018. Different environmental factors of land use, slope and altitude on erosion intensities of 19 secondary land types were analyzed. It can better reflect the soil erosion under different environmental factors and different land use types. Results show that the soil erosion modulus of Qin River Basin were 10.25 t hm−2 a−1, and it belong to slight erosion from 1990 to 2018. Soil erosion intensity is greater in grassland and woodland than in cropland. The strongest soil erosion occurred in the sparse forestland, and the lowest was in beach land. Soil erosion was the highest for a slope of 15~25° and an altitude of 1200~1500 m. Rainfall and slope are important factors lead to soil erosion, indicating weak water and soil conservation implemented in these areas. Therefore, priority should be given to these geomorphic units to formulate and implement soil-erosion control and ecological restoration policies in the Qin River Basin. This study provides a good reference for preventing and controlling soil erosion in river basins.

Development and validation of the planktonic index of biotic integrity (P-IBI) for Qin River, a main tributary of the Yellow River in China.

To evaluate the ecosystem health of Qin River, a main tributary of the Yellow River, a planktonic index of biotic integrity (P-IBI) that includes phytoplankton and zooplankton was established based on five metrics using a dataset covering 61 sampling sites in Qin River and its largest tributary the Dan River from October to November 2020. First, an index based on land use pattern and water quality was constructed to select reference sites and impaired sites. Then, five of an initial 38 candidate metrics (phytoplankton density, Palmer algal genus pollution index, zooplankton biomass/phytoplankton biomass, zooplankton Margalef richness index, and zooplankton Simpson diversity index) were selected to establish P-IBI based on their ranges, sensitivity, and redundancy. Finally, five statuses (excellent, good, fair, poor, and very poor) were classified by ratio score method on the basis of their final P-IBI scores. Sites with "excellent and good" and "poor and very poor" status accounted for 26.2% and 49.2%, respectively. "Very poor" sites were mainly located in the Dan River, and "poor" sites were mainly located in the middle reach of the Qin River and upper-middle reach of the Dan River in Jincheng region. Significantly negative correlations between Cl-, SO42-, and F- concentrations and P-IBI values indicated that the P-IBI might reflect domestic and industrial wastewater pollution in the Qin and Dan River in Jincheng region. The P-IBI strongly differentiated reference and impaired sites, suggesting the suitability of the index in the study.

The Spatiotemporal Patterns of Human Settlement during the Longshan and Erlitou Periods in Relation to Extreme Floods and Subsistence Strategy in the Upper and Middle Qin River Reaches, Central China

Human settlement numbers have significantly changed before and after ~4000 cal. y BP in the upper and middle Qin River reaches, but the external and internal factors driving this change remain unclear. In this study, we examine changing spatial and temporal patterns of the Longshan and Erlitou settlements in relation to extreme flooding at ~4000 cal. y BP and a variety of subsistence strategies during the Longshan and Erlitou periods. The results indicate that settlement number, settlement distribution, and subsistence strategies exhibited obvious shifts between the Longshan and Erlitou periods, and the episode at ~4000 cal. y BP was an extreme-flood-rich interval within and around the Qin River Basin. During the Longshan and Erlitou periods, millet-based agriculture dominated local subsistence strategy, and ancient people would prefer to reside in the areas suitable for farming, causing the valley plains in the upper and middle Qin River reaches to contain most Longshan and Erlitou settlements. However, the frequent occurrence of extreme floods at ~4000 cal. y BP, in conjunction with intergroup conflicts due to a large amount of population immigration during the late Longshan period, is likely to have jointly decreased the settlement number and shrunk the spatial range of human settlement distribution. Subsequently, with the end of the extreme-flood-rich episode and the increasing proportion of higher-water-requirement foxtail millet in cropping structures of human subsistence strategy, more Erlitou settlements were distributed in the wetter valley plains of the middle Qin River reaches.

Tropical cyclone-induced water and suspended sediment discharge delivered by mountainous rivers into the Beibu Gulf, South China

Small mountainous rivers can deliver considerable freshwater discharge and suspended sediment discharge (SSD) to the ocean during tropical cyclones (TCs), and this has received special attention worldwide. However, little information is available on how TCs impact variations in water discharge and SSD delivered by mountainous rivers into the ocean. Here, based on the daily water discharge and SSD at the gauging stations of the tidal limit in July and August from 1965 to 2017, the Qin River (QR) and Nanliu River (NR), 2 small mountainous rivers located in the north of the Beibu Gulf, South China, were selected to quantify variations in water discharge and SSD into the Beibu Gulf during the TC period. The main results show that the net TC-induced water discharges in the QR and NR during July and August are larger than those of non-TC days, respectively. The net SSD increases in the QR and NR induced by TCs are far larger than those of normal days, respectively. Meanwhile, the water discharge and SSD in the flood season can be dominated by TC-associated rainfall, but the impacts on water discharge and SSD are influenced by the TC characteristics and basin environment. Moreover, it is found that in these 2 mountainous rivers, high water discharge delivers high SSD, but extremely high water discharge caused by TCs fails to produce extremely high SSD. It is expected that TCs will produce great impacts on SSD and water discharge of the mountainous rivers in South China behind global climatic change with increasing TCs events.

Distribution of microplastics in surface water and sediments of Qin river in Beibu Gulf, China

As a series of pollutants, microplastics have recently attracted widespread attention worldwide. In this study, different surface water and sediment samples were collected at 12 sampling sites along the urban section of Qin River in Guangxi Province, China. Water samples were collected using plankton nets with two different pore sizes (75 μm and 300 μm) and Teflon pump system with 25 μm mesh screen. The results showed that there was no significant difference in the abundance, particle size, and type of microplastics (F = 0.302, P = 0.588) between the two plankton nets, but the microplastic abundance in the samples collected by the Teflon pump was significantly higher (F = 9.12, P = 0.001), especially for microplastic fibers (F = 9.525, P = 0.001). Compared with the plankton net sampling method, the Teflon pump sampling had a smaller sample volume, resulting in a higher estimate of microplastic abundance in the water column. The microplastic abundance in the sediments was 0–97 items·kg−1 dry weight. PE and PP were the main types of microplastics in Qin River, accounting for 67.2% and 72.3% in the water column and sediments, respectively. The microplastics in the water column and sediments were dominated by large-sized particles in the range of 1–5 mm. The sources of microplastic pollution in Qin River may be affected by many factors, including population density, industrial structure, and aquaculture activities. However, aquaculture activities were generally the main source of microplastic pollution in Qin River estuary. Wastewater treatment plants (WWTPs) could effectively decrease the microplastic abundance in urban sewage, reducing the impact of urban sewage discharge on microplastic accumulation in Qin River.

Simulation of sudden benzene leakage water pollution events

Sudden water pollution incidents in rivers occur frequently, which has a serious impact on the ecological environment and residents’ lives. After the sudden water pollution incident, determining the scale of the damage caused by the river water pollution event plays an important role in properly handling the accident. In this paper, the 3EWATER “hydrodynamic-water quality” numerical simulation system is used to simulate the concentration change of a certain pollutant in the river section during a certain period of time and realizes the visual expression of the simulation process. By simulating the sudden benzene leakage event in the Qin River, it was found that when the concentration of the leaked pollutant was 7*10-3kg/m3, the concentration of benzene into the section of Yellow River reached a peak of 1.236mg/L after about 14 hours of leakage, and then began to decrease; after 20 hours of leakage, the concentration of pollutants dropped to the safe concentration of water; the pollutants moved from upstream to downstream in the form of “pollutant band” in the corresponding study area; The highest concentration of pollutants is near the center of the “pollutant band”. The results of this case have strong practical value and provide decision-making basis for water environment planning management,water pollution prevention and emergency response to sudden water pollution incidents.

Application of a developed distributed hydrological model based on the mixed runoff generation model and 2D kinematic wave flow routing model for better flood forecasting

AbstractDue to the specific characteristics of semi‐arid regions, this paper aims to establish a Grid‐and‐Mixed‐runoff‐generation‐and‐two‐dimensional‐Kinematic‐wave‐based distributed hydrological model (GMKHM‐2D model) coupling a mixed runoff generation model and 2D overland flow routing model based on kinematic wave theory for flood simulation and forecasting with digital drainage networks. Taking into consideration the complex runoff generation in semi‐arid regions, a mixed runoff generation model combining saturation‐excess mechanism and infiltration‐excess mechanism is developed for grid‐based runoff generation and 2D implicit finite difference kinematic wave flow model is introduced for routing to solve depressions water storing for grid‐based overland flow routing in the GMKHM‐2D model. The GMKHM‐2D model, the GMKHM‐1D model with coupling the mixed runoff generation model and one‐dimension kinematic wave flow model, the Shanbei model and the Xin'anjiang model were employed to the upper Kongjiapo basin in Qin River, a tributary of the Yellow River, with an area of 1454 km2 for flood simulation. Results show that two grid‐based distributed hydrological models and the Shanbei model perform better in flood simulation and can be used for flood forecasting in semi‐arid basins. Comparing with GMKHM‐1D, the flood peak simulation accuracy of the GMKHM‐2D model is higher.

Analysis of formation fracturing for the Maxi-HDD Qin River crossing project in China

A new irrigation pipeline was installed using the Horizontal Directional Drilling (HDD) method in order to alleviate the water shortage situation in Jiaozuo City, Henan Province, China. This pipe installation project included two parallel HDD crossings, with a pipe diameter of 1016mm and a driven length of 1750m for both of them. Based on the preliminary detailed geological survey report of the riverbed, hydro-fracturing control under high slurry pressure would be a big challenge for this project. This paper summarizes the prediction methods for the maximum allowable mud pressure in the borehole based on different mechanisms of formation fracturing. Based on the geological data of this crossing project, the Delft equation and another prediction method based on tensile failure (termed here the Xia method) were used to calculate the maximum allowable annular pressure. The real pumping pressure of this project was recorded by the contractor. By comparing the theoretical predictions of allowable pressure with the actual pressures for the horizontal section of the borehole, it indicated that the Xia method is conservative and the limits of the Delft equation could not be verified in this project. As a solution dealing with potential hydro-fracturing, finite element modeling shown that increasing the ground surface load would rise the borehole allowable pressure at which fracturing would occur. This solution was used to deal with a blow-out in the entry section of one pilot hole on this project. Under the guidance of the theoretical and numerical simulation results, the Qin River crossing project was successfully completed.

河流多年平均基流分割及其变化分析

以1970~2008年广西北部湾经济区入海河流南流江和钦江的实测月径流量资料为分析对象，采用数字滤波法和最小平滑法对两条河流的总径流过程线进行了平均基流分割。结果表明，数字滤波法滤波3次得出的基流分割结果与最小平滑法得出的结果较为接近。南流江和钦江的年际总径流量变化起伏较大，年平均基流量变化稳定，两条河流的总径流和基流都表现出下降的趋势。 Based on the measured monthly runoff data of Nanliu River and Qin River in Beibu Gulf Eco- nomic Zone in 1970-2008, the digital filtering method and smoothed minima method are used to separate the average baseflow. The results show that the baseflow calculated by the digital filtering method filtering 3 times are similar with that calculated by the smoothed minima method. The total runoffs of Nanliu River and Qin River have large temporal variation. The baseflow changes of two rivers are stable. And the total runoff and baseflow of two rivers appear a decline tendency.

Distributions, possible sources and biological risk of DDTs, HCHs and chlordanes in sediments of Beibu Gulf and its tributary rivers, China

Thirty-five surface sediment samples collected from Beibu Gulf and its tributary rivers, China were analyzed for DDTs, HCHs and chlordanes. Total concentrations of DDTs, HCHs and chlordanes in sediments ranged from 0.59 to 126ngg−1, ND to 2.65ngg−1 and 0.27 to 3.41ngg−1 based on dry weight (dw), respectively. Concentrations of DDTs were higher than those reported in the sediments from other regions of the world, while concentrations of HCHs and chlordanes were relatively low. High concentrations of DDTs were observed in the harbor region and aquaculture bases and high concentrations of HCHs were found in the Qin River Estuary. The ratios of (DDE+DDD)/DDTs reflected a mixed input of weathered and fresh DDTs. The predominant β-HCH indicated that HCHs in the study area mainly originated from the historical usage of technical HCH. The residues of DDTs would pose adverse biological effects on the study area.

Metals in water and surface sediments from Henan reaches of the Yellow River, China

The concentrations of Cd, Cr, Cu, Ni, Pb and Zn were determined in the water and surface sediments from the Henan reaches of the Yellow River. Twenty-three sampling sites along the Yellow River and its tributaries were selected. Generally, metal concentrations were found to decrease in sequences of Zn > Cu > Pb > Cr > Ni > Cd in water and Zn > Cr > Pb > Ni > Cu > Cd in sediments. High levels of metal concentration were determined at a few stations of the river and its tributaries, such as Yiluo River, Si River and Qin River. The pollution of the Yellow River by Cd, Cr, Cu, Ni, Pb and Zn can be regarded as much higher compared to the background values, US EPA criteria (1999) and China water quality criteria (2002). For sediments, metal levels except Pb did not significantly exceed the average shale levels and backgrounds in several countries including China. Data analysis manifests that positive correlations were found between Cu, Ni and Zn in water, and Pb, Ni, Zn and Cr in sediments. The Pearson correlation coefficient analysis and Cluster analysis were provided to assess the possible contamination sources. The results indicate a general appearance of serious pollution along the banks of the Yellow River. The wastewaters discharged by the mine plants, smelter plants, power plants, battery plants, tannery plants, etc., and sewage inputs from the cities along the river banks may be the sources of metals.

Ecological and environmental water requirement in the middle Yellow River

As a significant factor for maintaining river ecosystem function, ecological and environmental water requirement of riv- ers is a key issue of hydrological research. Based on real conditions of the middle Yellow River, a few methods (Montana method, minimum monthly mean discharge method, etc.) were adopted to calculate ecological and environmental water requirement of the river. The results show that in the middle Yellow River the environment water requirement is 47.356×108 m3, the water requirement for sediment delivery is 40.666×108 m3, and the water surface evaporation is 10.314×108 m3. Total tributary ecological and envi- ronmental water requirement from Kuye River, Wuding River, Fen River, Jing River, Beiluo River, Wei River, Yiluo River, and Qin River is respectively 2.071×108 m3, 3.393×108 m3, 10.143×108 m3, 8.699×108 m3, 3.575×108 m3, 34.601×108 m3, 6.481×108 m3 and 2.505×108 m3. Due to the non-independence of the middle Yellow River, further ecological and environmental water requirement research is recommended.