Chongqing Eco Environment Monitoring Station of Soil and Water Conservation

Chongqing, China

Chongqing Eco Environment Monitoring Station of Soil and Water Conservation

Chongqing, China
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Shi D.,Southwest University | Jiang G.,Chongqing Eco Environment Monitoring Station of Soil and Water Conservation | Peng X.,Southwest University | Wang S.,Jiangsu Surveying and Design Institute of Water Resources Co. | And 2 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2015

Engineering accumulation, a kind of loose soil-sock mixture consisted of soil, parent rock and stone caused by various artificial engineering during producing and constructing process, is the most serious erosion-landform in production and construction areas because it can greatly change the terrain, soil and vegetation conditions of original landform in a very short term, thereby causing great soil and water loss under a certain rainfall-runoff condition, and making more difficult for ecological restoration in these project areas. In order to revel the runoff erosion mechanism and its process for engineering accumulations with different slopes and soil-rock ratios, we carried out field scouring experiments from August to November 2012 at the Soil Erosion Experiment Site for production and construction projects in Southwestern University, Chongqing (29° 48'50.2"N, 106° 24'48.8"E). The field scouring experiments were conducted under the simulated runoff conditions according to the regional rainstorm occurrence frequency with the 5, 10, 15, 20, 25 L/min for purple soil deposits and 5, 7.5, 10, 12.5, 15 L/min for yellow sand deposits, respectively. In the experiment, some physical properties, hydraulic properties and runoff erosion process on underlying surfaces of engineering accumulations with different producing sources and soil-rock ratios were all comparatively studied. The results indicated that material composition and infiltration capacity of the two loose engineering accumulations were remarkably different from original landform. The yellow sand deposit was dominated by ≤0.25 mm particles with particles variation coefficient as high as 1.2-2.0 times than its original landform and its stable infiltration rate was 1.70-4.07 times than original landforms, respectively; while purple soil deposit was well-distributed, its' variation coefficient of particles was 2.2 times than original landform and the stable infiltration rate was 7.02-11.59 times than original landforms. The experiments also showed that soil-rock ratio change could influence the slope infiltration performance for the two engineering accumulations and the effects of engineering construction on the purple soil deposits were more powerful than that of the yellow sand deposits. Some dynamic parameters on underlying surfaces of engineering accumulations increased with increasing flow discharge, in which flow velocity of yellow sand deposits ranged from 0.155 to 0.318 m/s, flow shear stress varied between 27.632 and 57.154 N/m2, and soil detachment rate changed from 0.337 to 77.071 g/(m2·s); while the flow velocity, flow shear stress and soil detachment rate of purple soil deposits were 0.184-0.281 m/s, 35.525-53.600 N/m2 and 1.445-61.910 g/(m2·s), respectively. For rocky underlying surfaces, runoff yield rate had continuously waving variations within 9 min after runoff yielded. When flow discharge increased gradually from 5 to 25 L/min, the average runoff yield rate of rock underlying surface from yellow sand deposit increased by 510.38%, 531.96 % and that of purple soil deposit increased by 73.20% and 57.61%, respectively; for same conditions, the cumulative runoff of underlying surfaces showed the similar trend of partial soil deposits larger than rocky deposits, and that of yellow sand deposit higher than purple soil deposit. For rocky underlying surfaces, sediment yield rate presented continuously multi-peak multi-valleys. When flow discharge increased from 5 to 25 L/min gradually, the average sediment production rate of rock underlying surface from yellow sand deposit were 0.001, 0.03, 0.542 kg/(m2·min), respectively, while that of purple soil deposit were 0.0003, 0.012, 0.034 kg/(m2·min), respectively. The collapse on gully wall caused by gravity from underlying surfaces was an important cause for the fluctuating variations of the sediment yield rate. These results provide essential parameters and technical supports for predicting soil water loss caused by production and construction projects and for selecting vegetation measures for soil and water conservation in similar areas. ©, 2015, Chinese Society of Agricultural Engineering. All right reserved.


Shi D.,Southwest University | Wang W.,CAS Institute of Soil and Water Conservation | Jiang G.,Chongqing Eco environment Monitoring Station of Soil and Water Conservation | Peng X.,Southwest University | And 3 more authors.
Catena | Year: 2016

Decreases in the water retention function of various artificial disturbed landform units (DLUs) caused by urbanization activities, compared to original landform units (OLUs), are the main factor that causes urban water and soil loss and the aggravation of urban floods under certain rainfall conditions and specially designed drainage network capabilities. Field investigations, laboratorial analyses of soil physical properties and analytic hierarchy process (AHP) composite methods were performed to comprehensively analyse the effects of various DLUs on the water retention function of OLUs. The results indicated as the following: (iі) The >5 mm particle content (>54%) for various DLUs was higher than that for OLUs (lower than 3%); the natural repose angles of soil-rock mixtures (32-37°) and soil bulk density (1.41-1.74 g/cm3) in the DLUs were all higher than those in the OLUs (30-31°, 1.18-1.14 g/cm3); and the uniformity coefficients and curvature coefficients were 10.00-80.00 and 3.24-5.70 in the DLUs and 6.00-75.00 and 0.17-2.50 in the OLUs, respectively. (ii) The soil steady state infiltration rate in the DLUs decreased from disturbed soil accumulation with 2 months (DSA2m, 15.00 mm/min) to disturbed soil accumulation with 2 years (DSA2a, 5.63 mm/min), disturbed soil accumulation with 4 years (DSA4a, 3.82 mm/min), the slope greening belt (SGB, 1.24 mm/min), and construction roads (CR, 0.51 mm/min). The conversion from forests to DSA2m had the greatest impact on the soil infiltration capacity and soil storage capacity, while the conversion to CR had the lowest impact. (iii) The total reservoir storage in the DLUs' soil was ordered as follows: DSA4a > SGB > DSA2a > DSA2m > CR. The conversion process from grass to CR exerted the greatest impact on storing water and regulating the overland flow. (iv) The water retention functions in the DLUs were all weaker than those in the OLUs: DSA2m was the weakest (0.287), while paddy fields were the strongest (0.668). Thus, the occupied areas of urban water surfaces (e.g., lakes, rivers and ponds), forests and grassland and their spatial distribution during urbanization must be carefully considered. These results could help to understand the ecological service functions of urban soil and water conservation, provide relevant knowledge to landscape rehabilitation, alleviate urban floods during urban development and recover the functions of soil and water conservation ecological services in project areas during the urbanization construction process. © 2016 Elsevier B.V.


Li Y.,Southwest University | Guo H.,Chongqing Eco environment Monitoring Station of Soil and Water Conservation | Shi D.,Southwest University | Huang J.,Chongqing Eco environment Monitoring Station of Soil and Water Conservation | And 3 more authors.
Huanjing Kexue Xuebao/Acta Scientiae Circumstantiae | Year: 2014

Infiltration characteristics of underlying surfaces from disturbed soils with different contents of rock fragments were studied by using ring sampler method in purple hilly area. These results indicated that: (1) All underlying surfaces were significantly different in infiltration capability with increasing rock fragment content. The initial infiltration rate, stable infiltration rate and mean infiltration rate of the underlying surface with 40% rock fragment content were 1.30, 1.13 and 1.54 times greater than that of terrene underlying surface, respectively. (2) The initial infiltration rate and stable infiltration rate of all underlying surfaces had significantly negative correlation with initial water content and bulk gravity, and had significantly positive correlation with total porosity and non-capillary porosity. The correlation coefficients between initial infiltration rate and initial water content varied from -0.689 to -0.912 and from -0.745 to -0.999 between stable infiltration rate and bulk gravity. Furthermore, the stable infiltration rate increased significantly with increasing non-capillary porosity. (3) Determination coefficients for fitting infiltration rate and infiltration time by Horton model were over 0.899, and its relative error between calculated infiltration rate by Horton and measured infiltration rate ranged between 0.07% and 6.60%. Hence, Horton model was suitable for analyzing the infiltration process of underlying surfaces in purple hilly area. These study results could provide some important parameters for predicting and evaluating soil and water loss from disturbed soils in purple hilly area.


Peng X.,Southwest University | Shi D.,Southwest University | Jiang D.,Chongqing Eco environment Monitoring Station of Soil and Water Conservation | Wang S.,Southwest University | Li Y.,Southwest University
Catena | Year: 2014

Disturbed soil accumulation caused by all man-made activities during the producing and constructing process of large-scale projects is the main landform occurred artificial water and soil loss. Because of its different producing sources and soil-rock ratios, the underlying surfaces from disturbed soil accumulation often characterize a unique soil erosion process under same runoff scouring condition. Taking the ubiquitous purple soil deposits and yellow sand deposits associated with different soil-rock ratio as examples, the study aimed to explore the difference in both hydraulic properties and sediment yield characteristics on disturbed soils. Some field scouring experiments were conducted in Chongqing, China. These results indicate that: (i) Runoff regime on all underlying surfaces from disturbed soils often manifest as turbulent and subcritical flow during runoff scouring process. (ii) For rocky disturbed soils from purple soil, sediment production rate shows continuously waving variations, and the average sediment production rates are 0.28, 11.65, 33.69, 73.00, and 177.37g/(m2·min), respectively, when flow discharge increase from 5 to 25L/min gradually; the collapse on gully wall caused by its gravity from underlying surfaces is the important cause for the fluctuating variations of the sediment production rate. (iii) The influencing degree of hydrodynamic parameters on sediment yield is in such order as γQ>γP>γv>γτ>γf{hook}. These study results could be used to control artificial erosion caused by production and construction projects and to provide some important parameters for soil and water loss predicting in the Three Gorges Reservoir Area of Chongqing. © 2014 Elsevier B.V.


Peng X.,Southwest University | Shi D.,Southwest University | Guo H.,Chongqing Eco environment Monitoring Station of Soil and Water Conservation | Jiang D.,Chongqing Eco environment Monitoring Station of Soil and Water Conservation | And 3 more authors.
Catena | Year: 2015

Urbanisation activities can greatly alter original landform unit shapes and reduce their water retention function, which is the major reason for serious artificial water and soil losses and widespread urban waterlogging. Taking original landform units (OLU) as a control, this work aimed to reveal the extent to which disturbed landform units (DLU) reduce the water retention function in a special building construction area. Field investigations and physical and chemical laboratory analyses were performed to analyse soil physical characteristics including the soil porosity, soil usable storage and soil stable infiltration rate. The coordinate composite method was used to evaluate the effects of urbanisation on the water retention function of the original landform during the urbanisation construction process. The soil bulk densities in the various DLU were greater than in the OLU, showing the following order: construction road (CR)>1a slope greening belt (SGB)>1a disturbed soil accumulation (DSA1)>2a disturbed soil accumulation (DSA2)>3a disturbed soil accumulation (DSA3). The soil total reservoir storage and usable storage in the different DLU were lower than in the OLU, with usable storage showing the order DSA3>DSA2>DSA1>SGB>CR, which presented decreases of 12.3%, 16.8%, 22.7%, 28.2% and 33.3%, respectively, compared with sloping land. The soil stable infiltration rate presented the order DSA3 (2.89mm/min)>SGB (2.65mm/min)>DSA2 (1.89mm/min)>DSA1 (1.64mm/min)>CR (0.45mm/min), while the soil initial infiltration showed the order DSA1>DSA3>SGB>DSA2>CR. The overall water retention function of the different landform units varied in the following order: native forest land>fruit forest land>Abandoned land>sloping land>DSA3>SGB>DSA2>CR>DSA1, with DSA1 causing the greatest harm to the water retention function of the OLU. In order to avoid causing serious soil and water losses and urban waterlogging, building construction projects should attempt to avoid strongly disturbing, occupying and destroying natural rainfall-flood regulation systems, especially for native forest land. Since soil characteristics are crucial for vegetation, these results could provide relevant knowledge to landscape rehabilitation and recovering the function of soil and water conservation ecological services in project areas during the urbanisation construction process. © 2015 Elsevier B.V.


Ding W.,Southwest University | Shi D.,Southwest University | He W.,Chongqing Eco environment Monitoring Station of Soil and Water Conservation | Jiang G.,Chongqing Eco environment Monitoring Station of Soil and Water Conservation | And 2 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2016

Various engineering accumulations, caused by all man-made activities during mining process, have resulted in serious artificial soil and water loss in the coal mine area because of great difference in material composition, slope structure and runoff and sediment characteristics from original landforms, which would make great potential risk for the mining safety production and the surrounding areas. Recently, researches begin to focus on artificial soil and water loss in project areas, however, mechanism of runoff erosion on engineering accumulation slopes is still unclear, especially hydrodynamic characteristics in the process of runoff erosion needs further study. Taking typical coal mine engineering accumulation as example, soil test method and field scouring experiment were conducted to study the runoff erosion characteristics and critical hydrodynamic conditions of engineering accumulation slopes in the coal mine area. In this paper, some physical properties, hydraulic properties and runoff erosion process on slopes of engineering accumulations with different producing sources were all comparatively studied. Field scouring experiments were carried out from July to August 2013 at the Soil Erosion Experiment Site for production and construction projects in Southwest University, Chongqing. The field scouring experiments contained 5 flow discharges (i.e. 10, 15, 20, 25 and 30 L/min) and 4 slope gradients (i.e. 25°, 30°, 35° and 40°). The paper mainly studied the hydrodynamic characteristics of engineering accumulation slopes in order to reveal the characteristics of runoff and sediment yield and soil erosion rate, and to analyze the relationship between soil erosion and critical hydrodynamic conditions and the critical slope gradient under different flow discharges. The results indicated that: 1) During runoff erosion process, both flow velocity, flow shear stress and runoff power of engineering accumulation slopes exhibited different degrees of fluctuation, showing a range of 0.187-0.526 m/s, 24.336-126.542 Pa and 2.763-46.861 N/(m·s), respectively, however, resistance coefficient existed a fluctuation from weak to strong in the range of 2.236-19.337. 2) Both runoff yield rate and sediment production rate of engineering accumulation slopes exhibited a trend of first increase and then stability during runoff erosion process except for the 10 L/min flow discharge. The runoff yield rate tended to 0.5, 3.0, 3.8, 6.3 and 9.0 L/min, respectively, under different flow discharges (10 to 30 L/min), however the sediment yiled rate varied between 0 and 27.51 kg/min and the soil detachment rate changed between 9.570 and 4616.064 g/(m2·min). 3) There were great difference in critical flow shear stress and critical runoff power among engineering accumulation slopes with different slope gradients. At sheet erosion stage, both the critical flow shear stress and critical runoff power of 30° engineering accumulation were the minimum, whose values were 23.95 Pa and 1.76 N/(m·s), respectively; at rill erosion stage, however, the critical flow shear stress of 25° engineering accumulation was the minimum and the critical runoff power of 40° engineering accumulation was the least; and the soil erosion rate had a significant linear relationship with the flow shear stress and runoff power. 4) When flow discharge was 10-30 L/min, the critical slope gradients of engineering accumulations were 34.8°, 35°, 33.7°, 34° and 35.2°, respectively. These results not only could provide essential technical-parameters for predicting soil and water loss caused by mining production, but also would help to arrange some vegetation measures for soil and water ecological restoration of these engineering accumulations. © 2016, Editorial Department of the Transactions of the Chinese Society of Agricultural Engineering. All right reserved.

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