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 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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