Nature Environment and Pollution Technology

Hongjie Wang ¹, Jianen Gao ¹, Hong Wang ², Li Liu ¹

Affiliations
1 College of Water Resources and Architectural Engineering, Northwest A & F University, 712100, Yangling, CN
2 Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, 712100, Yangling, CN

Abstract

The impact of the soil and water conservation measures in the process of river runoff and sediment discharge has caused wide attention. The Wei River, which has a serious water shortage and a high sediment concentration, was selected as the research watershed. Based on the measured data of rainfall, runoff and sediment, the statistical methods of wavelet analysis, Mann-Kendall test, and double cumulative curve were used to analyse the impact of soil and water conservation on runoff and sediment environment in Wei River Basin. The results showed that the river transported sediment increased during 1930s-1970s, and the average increasing rate was about 0.035×108 t/a. And the river transported sediment decreased after 1970s and the average decreasing rate was about 0.047×108 t/a. The relationship between water and sediment in Wei River Basin can be divided into two phases i.e., from 1940-1970s and after 1970s. From the 1940s to 1970s, there was less human activity, such as soil and water conservation, in the Wei River Basin, so the runoff and sediment yield changes were mainly affected by climate change. When the runoff was larger, the sediment load was larger and when the runoff was smaller, the sediment load was also smaller. After 1970s, large-scale measures of soil and water conservation were developed, which has great impact on soil erosion and sediment yield of basin and resulted in changing of laws between the runoff and sediment load. When the runoff was larger, the sediment load was smaller and when the runoff was smaller, the sediment load was also smaller, especially after 1997. It was concluded that the soil and water conservation play an important role in the reduction of the sediments of river. And when the comprehensive treatment reaches a certain level of governance, it has positive environmental benefits for both sediment and runoff.

Keywords

Soil and Water Conservation, Runoff Sediment, Mann-Kendall Test, Wavelet Analysis.

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Hongjie Wang ¹, Jianen Gao ¹, Jianmei Ji ¹, Xiuquan Xu ², Chunhong Zhao ³

Affiliations
1 College of Water Resources and Architectural Engineering, Northwest A & F University, Yangling, Shaanxi Province, CN
2 Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, Shaanxi Province, CN
3 College of Natural Resources and Environment, Northwest A & F University, Yangling, Shaanxi Province, CN

Abstract

Ecological base flow is a basic requirement of water flow for a healthy river ecosystem. But in Weihe River the ecological flow is not guaranteed because of the water shortage, high sediment concentration and considerable agricultural water use along the river. In this study, Baojixia under-tableland irrigation area was selected as a representative area to which a mathematical model of one-dimensional steady water non-uniform sediment regulation was applied, to analyse the impact of channel desilting on guaranteeing the ecological base flow of Weihe River. The results indicated that scouring and silting of the channel was significantly correlated with the channel water capacity and sediment content in water flows. In addition, channel desilting contributed to 55.9×10⁴m³ and 79.2×10⁴m³ water saving in the irrigation area in January and December which belonged to the dry season. Their contribution rates to basic flow were 3.5% and 4.9%, respectively.

Keywords

Ecological Base Flow, Sediment Dispatching, Sediment-Laden River, Weihe River.

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Yuanxing Zhang ¹, Jianen Gao ¹, Li’na Wu ¹, Huijuan Li ¹, Xianfa Bai ¹, Juan Li ¹, Xinghua Li ¹

Affiliations
1 Northwest A&F University, College of Resources and Environment, Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, CN

Abstract

The terraced field was an important way to develop the high-efficiency agriculture on the loess plateau, however, lots of terraced field were heavily damaged by the extreme rainstorm in 2013. Improving the terraced field design standard had become a difficulty in recent research. Based on the field observation and similarity theory, this paper constructed a 1:10 terraced field scale model. The artificial rainfall together with water releasing experiments were designed to simulate the soil erosion process in the scale model. The experimental results revealed that the erosion process of the prototype in extreme rainstorm could be reappeared under the experimental condition that the rainfall intensity was 0.395 mm/min and the experiment lasting time was 2.68 hours. Both the erosion amount and the erosion gully topography of the scale model could be verified by the measured data of the prototype. It can be inferred that the equivalent erosive precipitation of the extreme rainstorm was 636 mm. And it was an effective method to research the soil and water erosion process and the terraced field design standard utilizing the terraced field scale model.

Keywords

Loess Plateau, Terraced Field, Artificial Rainfall Experiment, Extreme Rainstorm, Erosion.

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Xiuquan Xu ¹, Jianen Gao ²

Affiliations
1 Institute of Soil and Water Conservation, CAS & MWR, University of Chinese Academy of Sciences, Yangling-712100, CN
2 Institute of Soil and Water Conservation, CAS & MWR, College of Natural Resources and Environment, College of Water Resources and Architectural Engineering, Institute of Soil and Water Conservation, Northwest A&F University, Yangling-712100, CN

Abstract

Multivariate statistical techniques, including cluster analysis (CA), principal component analysis (PCA), factor analysis (FA) and discriminant analysis (DA), were applied for the evaluation of temporal and seasonal variations and interpretation of a complex water quality data set at Yangling Section of Weihe River. Hierarchical cluster analysis grouped 12 months into three clusters, i.e., C1 (relatively highly polluted months), C2 (moderate polluted months) and C3 (less polluted months), based on the similarity of water quality characteristics. Factor analysis/principal component analysis, tested to the data sets of the three groups obtained from cluster analysis, identified 9, 6 and 7 latent factors explaining more than 76, 69 and 62% of the total variance in the data sets of C1, C2 and C3, respectively. The varifactors obtained indicate that parameters responsible for variation are mainly related to temperature and DO (natural), COD_Mn, turbidity, NH₄⁺, TN, pH and TOC (point source: domestic wastewater) in C1; temperature, DO and EC (natural), COD_Mn, TN, pH, and TOC in C2; and temperature, DO and EC (natural), COD_Mn, pH and TOC (point source: domestic wastewater and industrial effluents), turbidity and TN (non-point source: agriculture and soil erosion) in C3. However, discriminant analysis showed no significant data reduction, as it used 8 parameters (turbidity, EC, NH₄⁺, DO, TN, pH, temperature and TOC) affording more than 81% correct assignations in temporal analysis, while 8 parameters (COD_Mn, turbidity, EC, DO, TN, pH, temperature, TOC) affording more than 88% correct assignations in seasonal analysis. Thus, this research illustrated the necessity and usefulness of multivariate statistical techniques for analysis and interpretation of large complex water quality data sets, identification of possible pollution sources/factors and information about variation in water quality for effective river water quality management.

Keywords

Water Quality Assessment, Multivariate Statistical Techniques, Weihe River.

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Yuanxing Zhang ¹, Jianen Gao ², Hui Shao ¹, Hongjie Wang ¹, Chunhong Zhao ¹, Hong Wang ¹, Xiuquan Xu ¹

Affiliations
1 Northwest A&F University, College of Resources and Environment, Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, National Engineering Research Center for Water-Saving Irrigation at Yangling, Yangling, CN
2 Northwest A&F University, Institute of Soil and Water Conservation, CAS & MWR, College of Water Resources and Agricultural Engineering, Yangling-712100, CN

Abstract

The terraced field widely distributed in Loess Plateau where serious soil and water loss happens, has a significant influence on watershed hydrological environment. At present, for the deficiency of watershed scale terraced fields hydrological environment impact assessment model and lacking of measured data, the terraced fields environmental impact assessment has attracted many attentions of the researchers. This paper adopts the hydrologic analogy combined with a scale physical model method, to infer the runoff and sediments in data-scarce area. Using the embedded terraced module SWAT model to assessment of terraced fields environmental impact, the results show that was a new way to conjecture the hydrologic data in data-scarce area. And the terraced field module can meet the accuracy requirement, the NS sufficient were both above 0.5 in calibration and verifying period. The soil erosion modulus of terraced fields contained in and removed from the watershed, was respectively 5.3% and 16.2% greater than the real. This indicates that the embedded terraced module SWAT model could be used in terraced fields environmental impact assessment in Loess Plateau small watershed.

Keywords

Terraced Fields, SWAT Model, Loess Plateau, Soil Erosion, Run-Off.

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