Runoff-sediment relationship for various spatial scales in the Daqinghe rocky mountainous area
YUANZaijian1,2,, SUNQian1 1.School of Economics & Management,Hebei University of Science & Technology,Shijiazhuang 050018,China2. Guangdong Institute of Eco-environment and Soil Sciences,Guangzhou 510650,China 收稿日期:2015-10-19 修回日期:2016-02-18 网络出版日期:2016-04-25 版权声明:2016《资源科学》编辑部《资源科学》编辑部 基金资助:国家自然科学基金项目(40901130)河北省自然科学基金项目(10457205)河北省高等学校青年拔尖人才项目(BJ2014078) 作者简介: -->作者简介:袁再健,男,湖南武冈人,博士,教授,主要从事水土保持、生态水文与GIS应用研究。E-mail:selfsurpass@163.com
关键词:大清河土石山区;空间尺度;比例函数;减水减沙 Abstract Soil and water loss in the Daqinghe rocky mountainous area in the Haihe Basin,China is serious. Here,we discuss the runoff-sediment relationship at five spatial scales:micro runoff plot,normal runoff plot,micro watershed,watershed,medium and large basin. The results show that there are strong positive linear correlations between sediment yield modulus (Ms) and surface runoff depth (Rs) at these spatial scales,and the proportional function can be used to fit their linear relationship. There is a good linear correlation between Ms and rainfall,but there are no obvious correlations between Ms and the average rainfall intensity. In the several land-use patterns (i.e. Platycladus orientalis,pine,shrubbery,uncultivated land and bare land),the Ms and runoff coefficient of bare land are significantly higher than those of others. The Ms and runoff coefficient of the arborvitae plot are smaller than those of the pine plot, the reason is the canopy interception of arborvitae is slightly larger than the pine. In addition, forest litter cover can greatly reduce water loss and soil erosion of slopes in this region. At the plot scale, with the deciduous vegetation or litter cover there are similar runoff-sediment relationships. In our opinion, vegetation cover can reduce sediment due to a reduction in runoff for slopes in the Daqinghe rocky Mountainous area. For the lack of grassland and farmland runoff plot data in this study,the results primarily analyzed the relationship between runoff and sediment. This study can help lay a theoretical foundation for predicting soil and water loss in the comprehensive management of the Haihe River basin.
对比分析径流小区的产流产沙情况发现,在降雨条件相同情况下,裸地小区产沙模数(MS,t/km2)、径流系数(α)明显大于其它小区,荒地小区次之,侧柏小区最小,灌草小区介于松树小区与荒地小区之间(见表2)。由此可见,在这几类径流小区中,植被覆盖是引起其产沙模数、径流系数差异的主要原因,侧柏小区的径流系数小于松树小区的原因可能是侧柏的树冠截留能力比松树强,进而使得侧柏小区的产沙模数也小于松树小区; 荒地小区和裸地小区的差别说明在大清河山区枯枝落叶能显著减少地表降雨径流,进而减少土壤侵蚀,当然其减水减沙的效果比树木、灌草差。 Table 2 表2 表2研究区相同降雨条件下各径流小区产沙模数与径流系数比较 Table 2Comparison of the sediment yield modulus and runoff coefficient of each plot under the same rainfall (t/km2)
分析表明,大清河山区这5种不同空间尺度的产沙模数(MS)与降雨径流深(RS,mm)均具有较好的线性正相关关系(见表3),产沙模数与径流深之间的决定系数R2在0.56~0.92之间。 Table 3 表3 表3研究区不同空间尺度产沙模数与地表径流深的线性关系 Table 3Relationship between the sediment yield modulus and surface runoff of the different scales
空间尺度类型
空间尺度
水沙关系式
样本数
决定系数R2
微型径流小区
荒地小区
11
0.69
裸地小区
17
0.70
普通径流小区
侧柏小区
15
0.92
松树小区
22
0.77
灌草小区
22
0.82
微型小流域
万亩林
14
0.86
小流域
崇陵小流域
42
0.56
杨树沟
34
0.80
中大流域
唐河上游
35
0.66
拒马河上游
48
0.69
注:表中MS为产沙模数;RS为地表径流深。 新窗口打开 从表3可以看出,水沙关系拟合结果中的常数项大多较小,而当径流深很小时,用表3中的一元线性方程模拟荒地小区、裸地小区、侧柏小区、松树小区以及唐河上游也能得到较大的产沙模数,这显然不合适(因为正常情况下,径流深很小时产沙量很少或者没有),因此,这里尝试用比例函数来分析研究区的水沙关系,结果发现用比例函数拟合大清河土石山区的径流产沙比较合适,决定系数R2在0.56~0.86之间(见图2),且决定系数和表3中y=ax+b形式几乎相同。在这几种空间尺度水沙关系模型中,荒地与裸地微型小区的系数差异较大,侧柏、松树与灌草小区的系数接近,系数介于0.81~1.56之间,微型小流域与小流域的系数接近,系数介于1.09~1.77之间,且两个中大流域的系数接近,分别为3.45和3.89(见图2),从这些系数的比较可看出,随着尺度的扩大,径流对产沙的影响更强烈。另外,通过与他人研究结果的比较,本研究的水沙关系模型中的决定系数明显低于黄土高原,Zheng等研究的水沙关系决定系数在0.85~0.99之间[7]。这说明,在大清河山区,尽管径流也是影响产沙模数的主要因素,但其影响程度较黄土高原弱,且次降雨径流含沙量及产沙模数也远低于黄土高原。 显示原图|下载原图ZIP|生成PPT 图2各空间尺度产沙模数与次降雨地表径流深的线性相关性 -->Figure 2Linear relationship between Ms and Rs of each spatial scale -->
进一步分析产沙模数与降雨量的关系,发现在唐河上游与拒马河上游的产沙模数与降雨量无明显相关(决定系数R2分别为0.04与0.06),其主要原因可能是中大流域的降雨条件、径流产沙存在较大的空间异质性;而在其他4种空间尺度,产沙模数与次降雨量有较好的线性正相关关系(见图3)。在各尺度降雨产沙关系式中,小区尺度的决定系数高于其它尺度,这说明降雨量对小尺度的产沙影响更强烈。 显示原图|下载原图ZIP|生成PPT 图3各空间尺度产沙模数与次降雨量的线性相关性 -->Figure 3Linear relationship between Ms and rainfall of each spatial scale -->
在小区尺度水沙关系模型中,侧柏、松树、灌草以及有枯枝落叶覆盖的小区系数接近,但与裸地小区差异很大,因此可以近似认为,在大清河山区,有植被覆盖的坡面具有相似的水沙关系,且植被覆盖可以通过减水来减沙,它能有效减小溅蚀与面蚀强度,甚至可以抑制细沟产生[14],植被覆盖改变了裸地的水沙关系。 由于缺少草地、坡耕地等土地利用的径流小区资料,且1m2小区所受的边界条件对分析结果影响较大,本文研究结果存在一定的偏差,也未能分析土地利用能否改变小流域、流域尺度的水沙关系。 另外,气象要素的空间异质性对中大流域水沙关系的影响也是一个值得深入研究的科学问题。 The authors have declared that no competing interests exist.
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