【作者】 张涛；

【导师】 李怀恩；

【作者基本信息】 西安理工大学 ， 环境工程， 2008， 硕士

【摘要】 沙棘“柔性坝”作为一种新的水土保持生物措施,在治理砒砂岩地区水土流失过程中显现出了良好的效果,它实现了对沟道内泥沙的有效拦截、改善了土壤水分的再分布、提高了土壤肥力,不仅可以从源头上减少向黄河的输沙量,而且能够改善局部的生态环境,起到了标本兼治的作用。沙棘“柔性坝”这些水土保持功能的实现归根到底是由于它通对水流的“消能”实现了对流速场的调节,从而有利于泥沙的沉降和沟道内洪峰的平坦化。本文以野外实验和室内实验相结合的形式进行研究,分别在内蒙古鄂尔多斯市西召沟小流域和陕西华县沙棘“柔性坝”实验基地内开展了实地监测调研,取得了如下成果:(1)有机质的垂向分布与土壤的发育过程、土层结构和土壤中的水分运移过程密不可分;不同坝龄的沙棘“柔性坝”对土壤有机质含量有着不同程度的提高;随着研究范围的扩大,沙棘“柔性坝”引起土壤的空间异质性逐渐显著。(2)坝内淤积的泥沙整体上呈细化趋势,上游断面处此变化最为明显;单个坝体内泥沙淤积无明显规律;沟道内泥沙粒径从上游到下游呈递减趋势,且沙棘对粒径大于0.25mm的粗颗粒泥沙具有较好的分选效果。(3)沙棘的生长形态对水流的流态有着决定性的影响,进而影响着微地形的变化;在一定范围内适当提高沙棘排的种植密度可以减少水流对排后地表的冲刷;每排沙棘后冲坑平均深度的最大值往往出现在第一排后;排数越多越易形成稳定床面,进而使得冲刷强度保持在较低水平。(4)初步分析了沙棘不宜在特别湿润土壤中种植的特点、根系萌蘖的特点,提出了沙棘种植密度对群落稳定及发展的重要性,用Logistic模型和三次多项式拟合了沙棘树高、地径和冠幅的生长。(5)沙棘“柔性坝”若多处出现缺苗、少苗现象,其“消能”的作用就大大降低;水流从进入床面到流出床面经历了先增后减又缓慢增加的一个过程,并由此可将实验床分为进口段、坝前壅水段和坝内段来进行研究;沙棘“柔性坝”对进口段影响较小,而对坝前壅水段影响最大;在实验的准确性、可操作性和效果等方面进行对比分析后发现,PIV法要比染色剂示踪法更具有实用性。(6)小流域内沙棘“柔性坝”的布设要从降雨、下垫面条件和流域面积等水文特征出发,掌握流域内的产汇流规律,然后由设计暴雨推求出设计洪水,由设计洪水和沟道形状共同确定沙棘“柔性坝”的种植参数,提出了这样一个概化的布设思路,并从理论上进行了分析。更多还原

【Abstract】 As new soil and water conservation biological measures, sea-buckthorn plant flexible dams have shown good performance in controlling water and soil erosion in soft rock area. Sea-buckthorn plant flexible dams can effectively intercept sediment within ditches, improve soil water redistributing, and enhance soil fertility. Therefore, the measures can not only radically reduce sediment discharge to Yellow river, but also greatly improve the local ecological environment. The capabilities of sea-buckthorn plant flexible dams in soil and water conservancy all attribute to the function of regulating velocity field through weakening water flow energy, which is in favor of depositing sediment and smoothing flood peak in gullies. Field investigations and laboratorial experiments are combined in this study. Field investigations are carried out both in Xi’zhao watershed in Ordos of Inner Mongolia and in experimental base of sea-buckthorn plant flexible dams in Hua County of Shaan’xi province. The main achievements are summarized as follows:(1) It is revealed that the vertical distribution of organic matter is closely related to soil water transmission process as well as soil’s development process and layered construction; The sea-buckthorn plant flexible dams with different ages can improve soil organic matter contents in different extent; with the extension of research scope, the soil spatial heterogeneity is increasing obviously.(2) The sediment becomes finer in the sea-buckthorn valley especially in the upper cross section; there is no obvious regularity of sediment deposition along a single sea-buckthorn dam; it is observed that the sea-buckthorn plant flexible dam can diminish the sediment particle size from the upper reach to the lower reach along the valley, and also can effectively filtrate the sediment grain with particle size bigger than 0.25mm. (3) The sea-buckthorn intensity imposes an determinative impact on water flow pattern, and further influence the variation of micro-terrain; Increasing the number of sea-buckthorn planting rows appropriately can weaken the erosion of land surface by water flow behind the rows; The maximal sunk depth scoured out by flow often comes behind the first row; It’s easier to form smooth river bed as the number of sea-buckthorn rows becomes more, and then lower level of erosion is achieved.(4) It is preliminarily discussed that sea-buckthorn is not suitable to grow in relative wet soil because of its root feature, and sea-buckthorn intensity is very important for colony’s stability and development. The height of trunk, basal-stem and canopy of sea-buckthorn are simulated using Logistic model and cubic polynomial function.(5) If sea-buckthorn plants are too discrete to keep dam body’s continuity, its capability of weakening water flow energy will be impaired greatly; In virtue of stream experiencing a process of firstly increasing, later lessening, and subsequently gradually increasing from the inlet to the outlet of the flow bed, the experimental flow bed is divided into inlet segment, backwater segment in front of the dam and dam inner segment; Sea-buckthorn plant flexible dam plays less role in inlet segment, while having great effect on backwater segment in front of the dam; Through contrastive analysis in aspect of accuracy, feasibility and efficiency, it is validated that PIV method is more practical than Stain Tracer Method.(6) In small watershed, the method of layout designing of sea-buckthorn plant flexible dams is presented. Such hydrological characteristics as rainfall、underlaying surface features and the area of basin as well as the laws of runoff generating and converging processes should be considered. Firstly, design flood is ascertained according to the design storm, and then planting parameters of sea-buckthorn plant flexible dams are defined according to design flood combined with gully figures. Moreover, a theoretical analysis is performed in this paper.更多还原