紫色土区玉米季横垄坡面细沟侵蚀过程研究

发布时间：2018-01-29 05:49

本文关键词： 细沟侵蚀横坡垄作玉米叶面积指数地表糙度水动力学紫色土区　出处：《四川农业大学》2016年硕士论文　论文类型：学位论文

【摘要】：紫色土区细沟侵蚀作为坡耕地最严重的水蚀方式之一,严重阻碍着区域土壤可持续利用与农业的可持续发展。由于细沟形态不断演变,影响径流的水动力学特性,水流的动态变化将引起细沟侵蚀的演化。因此,本文以紫色土丘陵区坡耕地为对象,采用野外人工模拟降雨,开展不同雨强、坡度和生长期条件下,横垄坡面细沟侵蚀特征研究,揭示野外实地细沟形态演变及其主要影响因素,阐明玉米各生长期细沟流水动力学特性,建立细沟产流产沙与水动力学参数的耦合关系,以期为紫色土区坡耕地水土流失的有效防控及区域水蚀测报模型构建提供一定的理论依据。主要研究结果如下：(1)随玉米生长期推进,细沟出现时间总体呈先增加后减少的趋势。横垄坡面细沟侵蚀多发生在跃垄或破垄后,苗期、拔节期跌坎与细沟出现的平均间隔时间分别为10'59"和15'30",其细沟侵蚀发育过程为跌坎、断续细沟(破垄)、细沟发育、细沟调整。2.0 mm min-1降雨条件下,苗期细沟发育长、宽、深分别达77.62cm、6.25 cm和4.04 cm。苗期、拔节期、抽雄期及成熟期细沟形成对应的平均降雨量分别为35.17 mm、48.91 mm、81.63 mm和65.82 mm,抽雄期、成熟期细沟侵蚀发育过程为溅蚀坑、溅蚀坑贯穿(越垄)、细沟发育、细沟调整。(2)玉米各生长期,15°与20°间的细沟产沙量均无显著差异。随雨强的增加,横垄坡面细沟产流量在各生长期均呈增加的趋势。随玉米生长期推进,横垄坡面雨前地表糙度(R1)整体呈衰退趋势。降雨后地表糙度最大变幅均出现在抽雄期,15°坡面,抽雄期的平均糙度变幅较苗期、拔节期和成熟期分别增加了2.63倍、1.74倍和3.21倍；20°坡面,抽雄期的平均糙度变幅较苗期、拔节期和成熟期分别增加了2.85倍、6.54倍和37.74倍。随玉米生长期的推进,叶面积指数、覆盖度均呈先增加后下降的趋势,抽雄期叶面积指数为2.34。各因素与细沟产流的灰关联度表现为雨强叶面积指数植被覆盖度坡度雨前地表糙度株高,与产沙的灰关联度表现为植被覆盖度叶面积指数株高雨前地表糙度雨强坡度。(3)随玉米生长期推进,流速呈先减少后增加的趋势,平均径流整体呈下降趋势,径流剪切力、水流功率均呈先减小后增加的趋势。细沟流流态主要分布于“缓过渡流”区,抽雄期细沟流流态向“缓层流”区延伸,苗期和成熟期局部达到“缓紊流”区。抽雄期曼宁糙率系数n值较小,苗期相对较大。15°坡面,1.0mm min1降雨条件下,各生长期细沟流流曼宁糙率系数n变化范围为0.088～0.16, Darcy-Weisbach阻力系数f变化范围为83.67-140.69。曼宁糙率系数n与Darcy-Weisbach阻力系数f变化趋势基本一致。(4)玉米各生长期,细沟产流率均与单位水流功率耦合度最高。苗期,产流率与单位水流功率呈二次函数关系。拔节期,产流率与单位水流功率呈幂函数关系。抽雄期、成熟期,产流率与单位水流功均呈对数函数正相关。苗期,产沙率与单位水流功率耦合度较高,呈二次函数。拔节期,产沙率与各水动力学参数耦合度均较低。抽雄期、成熟期产沙率与单位能量耦合度较高,且均呈二次函数关系。玉米季横垄坡面细沟产流模型由雨强、流速、叶面积指数构成,产沙模型由流速、傅汝德数、Darcy-Weisbach阻力系数f构成。
[Abstract]:As one of the most serious erosion of slope farmland in purple soil area of rill erosion mode, sustainable development seriously hindered the sustainable utilization of soil and agricultural area. Due to the continuous evolution of rill morphology, the influence of water dynamics of runoff, the dynamic change of water flow will cause the evolution of rill erosion. Therefore, in the hilly area of purple soil slope land in this paper as the object and the field of artificial rainfall simulation in different rainfall intensity, slope and growth conditions, characteristics of rill erosion Cross Ridge, to reveal the factors of field rill evolution and its main influence, clarify the growth period of maize rill flow dynamics, relationship between rill runoff and sediment and hydrodynamic parameters, in order to provide the construction of a theoretical basis for effective prevention and control of soil erosion and water erosion area of purple soil slope land forecasting model. The main results are as follows: (1) With the corn growth stage to promote the emergence time of rill showed a decreasing trend after the first increase. The transverse ridge slope rill erosion occurred in the long jump or broken ridge, seedling stage, jointing stage or average interval ridge were 10'59 and rill appeared "and 15'30", the rill erosion development process is the sill. Intermittent rill (broken ridge), rill rill, adjust the.2.0 mm min-1 under the condition of rainfall, seedling development of rill long, wide, deep were 77.62cm, 6.25 cm and 4.04 cm. at the seedling stage, jointing stage, heading stage and mature stage of rill formation corresponds to the average rainfall were 35.17 mm, 48.91 mm, 81.63 and mm 65.82 mm, tasseling stage, mature stage of rill erosion development process of sputtering pit, sputtering pit through (the ridge), the rill, rill adjustment. (2) the growth period of maize, there was no significant difference in rill sediment between 15 DEG and 20 DEG. With the increase of rainfall intensity, cross the ridge of rill runoff in the The long-term increased. With the corn growth stage to promote cross ridge slope before surface roughness (R1) showed an overall declining trend. After the rainfall surface roughness maximum appeared at tasseling stage, 15 degree slope, tasseling the average roughness amplitude than the seedling stage, jointing stage and mature stage respectively. 2.63 times, 1.74 times and 3.21 times; 20 degree slope, tasseling and average roughness amplitude than the seedling stage, jointing stage and mature stage were increased by 2.85 times, 6.54 times and 37.74 times. With the corn growth period development, leaf area index, coverage showed a downward trend after the first increase. Extraction of leaf area index for 2.34. male factors and grey correlation degree for the performance of the rill runoff rainfall leaf area index of vegetation slope before surface roughness height, and grey correlation degree of sediment yield for the vegetation coverage and leaf area index were high surface roughness before rain rain intensity gradient (3. With the corn growth period) Advance velocity is decreased and then increased trend, the average runoff decreased, runoff shear stress, water power was first decreased and then increased. Rill flow pattern is mainly distributed in the "slow transition flow", tasseling rill flow pattern to "slow laminar" extension, seedling and mature stage the "slow turbulence". Tasseling Manning roughness coefficient n value is smaller, relatively large seedling.15 degree slope, 1.0mm Min1 under the condition of rainfall, the growth period of rill flow Manning's roughness coefficient n ranged from 0.088 to 0.16, the drag coefficient Darcy-Weisbach. The range of F 83.67-140.69. N and the Manning roughness coefficient the drag coefficient Darcy-Weisbach f the trend is basically the same. (4) the growth period of maize, rill runoff rate and unit stream power coupling is the highest. At seedling stage, a quadratic function relationship between runoff rate and unit stream power. At jointing stage, runoff rate and single There is a power function relationship between bit stream power. The tasseling stage, mature stage, the logarithm function is related with unit stream power production flow. At the seedling stage. The sediment yield and unit stream power high coupling degree, a quadratic function. The jointing stage, the sediment yield and the hydrodynamic parameters coupling degree are low. Pump male period, mature period of sediment rate and unit energy high coupling degree, and showed a quadratic function relationship. The maize season Cross Ridge rill runoff model by rainfall intensity, flow rate, leaf area index, sediment model by velocity and Fu Rude number, the drag coefficient Darcy-Weisbach f.

【学位授予单位】：四川农业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：S157.1

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