植被对小流域汇流及侵蚀产沙影响研究

本文从物理概念出发对小流域产汇流及侵蚀产沙过程进行研究,并结合实例分析了流域内森林植被对产汇流和侵蚀产沙的影响。森林植被的调节径流、防治侵蚀的功能体现在各个层面,林冠及下部枯落层可削减雨滴动能;树干及下部枯落层可削减地表径流流速;林地可改善土壤的渗透性,减少地表径流流量;根系可固持土壤,增加抗蚀力。     

黄土丘陵沟壑区森林土壤水文行为及其对河川径流的影响

通过比较瓦窖沟小流域林地、农田、撂荒地3种主要土地利用方式下的降雨入渗、产流特性及林区与非林区流域径流的季节变化,系统地分析了黄土高原林地水文行为及森林对河川径流的调节作用,主要表现为林地土壤高入渗率、低产流率和强烈的蒸腾耗水作用形成的土壤干层以及森林对河川径流季节分配的均化作用。土壤干层的出现使土壤水库对干旱调节功能丧失,影响林木的持续生长;还将削弱入渗降雨转化为地下水的比例,减少地下水资源的数量,使森林对流域枯季径流的补偿效应受到制约。森林均化径流分配的作用通过削减汛期径流和补充非汛期流水来实现。林区河川径流年内季节分配较非林区均匀,汛期削洪效能明显,并有效地补充了9～11月和3～5月的非汛期流水,补枯效果达4～10个百分点。     

黄土高原沟壑区小流域水土流失治理对径流的效应

本文用小流域平行对比观测法,分析了黄土高原沟壑区典型小流域水土保持对流域地表径流量及暴雨产流过程的影响,表明：（１）在黄土高原沟壑区,水土流失综合治理减少小流域产洪次数,降低了流域地表径流模数和径流系数,尤其以少雨年最显著;（２）使小流域地表径流模数的年际变率增大;（３）在洪水产理措施区土壤水分含量降低,根据生物气候、土壤及区域拦蓄水量特征,推测黄土高原沟壑区,以造林为主的水土保持措施拦蓄径流的作用难以使地表径流转化为地下径流或增加地下水。     

黄土区小流域水沙对降雨及土地利用变化响应研究

降雨和土地利用/覆被变化是流域径流、泥沙的两个主要影响因子。本研究采用SWAT模型,用固定其中一个影响因子而改变另一个影响因子的方法,对研究区降雨变化与土地利用/覆被变化对径流泥沙影响进行估算,目的在于从年月不同时间尺度上确定黄土高原小流域水沙对降雨和土地利用变化的响应状况。结果表明,在年尺度上降雨变化对径流影响的贡献率为84.20%,土地利用变化对径流影响的贡献率为28.63%;在月尺度上,降雨对径流贡献率也大于土地利用对径流的贡献率,尤其在雨季降雨对径流的影响程度和土地利用对径流影响程度的比值最大可以达到4.5。因此,不论在年尺度还是月尺度上,降雨对径流的贡献率都远远大于土地利用对径流的贡献率。此外,研究结果也表明流域年降水量和流域森林植被盖度均与流域径流模数或输沙模数呈指数关系。     

诺敏河流域植被覆盖时空演变及其与径流的关系研究

基于GIMMS/NDVI数据对诺敏河流域1982-2006年间植被覆盖的时空演变特征进行了研究,并结合SCS模型模拟地表径流,在流域和像元尺度分析植被NDVI变化与径流的关系。研究表明:诺敏河流域植被NDVI值较高,但25a间整体呈下降趋势,NDVI减少的区域占总面积的82.5%,植被覆盖有所降低;NDVI空间差异明显,NDVI的高值区主要分布在中上游林区,而耕地分布较多的下游地区NDVI值相对较低。流域尺度上植被NDVI与径流不具有明显的相关性。但从像元尺度来看,植被NDVI和径流的正相关和负相关共存,流域不同空间位置的植被变化与径流的关系并不一致。     

黄土丘陵沟壑区典型治理小流域水沙输移的尺度效应

近年来,水土流失的尺度特征及尺度效应一直是土壤侵蚀研究的前沿。文中通过对黄土丘陵沟壑区第一副区不同空间尺度互为嵌套的小流域(5.97km~2的王茂沟小流域和70.1km~2韭园沟小流域)监测数据的分析,比较了流域治理措施实施后不同空间尺度小流域产流产沙过程及其对降雨事件的响应,揭示该流域淤地坝建设等措施对小流域泥沙输移特征的影响及其尺度效应。研究结果表明:两个尺度小流域径流对降雨响应过程均十分迅速,且退水后几乎没有基流,这同南方丘陵区小流域不同;王茂沟和韭园沟小流域径流量迅速增大,达到峰值后逐渐回退,大致在降雨停止6小时后完全消退;源头小流域(王茂沟)地表径流系数相较更大尺度小流域(韭园沟)略低,土壤流失量则相反;治理后的韭园沟小流域高含沙水流现象减少。重力侵蚀仍是源头区域发生高含沙径流的潜在影响因素,小流域尺度水土流失防治应重点治理源头区域。     

人类活动对秦岭月河流域径流变化的影响分析

气候变化和人类活动是河川径流变化的主要驱动力。在相似气候的前提下,人类活动是流域径流变化的主导因素,定量识别人类活动对径流变化的作用机制对深入探究径流的变化特征具有重要意义。本研究以秦岭月河流域为研究对象,基于流域内水量平衡的基本原理,在相似气候的前提下,结合土地利用/覆被变化(LUCC)和归一化植被指数(NDVI)的变化,分析月河流域的径流变化来量化人类活动对径流的影响程度。结果表明:(1)1960—2018年流域内径流量的平均值为8.3×10⁸m³,径流整体呈现出减少的趋势,变化趋势不显著。(2)在相似气候的前提下,本研究共得出6组气候相似年组,其中有3组年径流量增加,2组年径流量减少。(3)以第3组相似年组(2000年和2016年)为例来定量区分气候变化和人类活动对流域径流的影响,2016年与2000年相比,径流减少了4.7×10⁸m³。(4)在第3组相似年组的时段内有25751.4 hm²的耕地转化为林地,林地面积增加了24998.9 hm²。(5...     

晋西黄土区不同土地利用类型降雨-径流关系的研究

本文以北京林业大学山西吉县科研试验场蔡家川流域为研究对象,采用对比分析法,对降雨—径流关系进行了研究。分析得出在蔡家川流域雨强是影响地表径流的主要因素;由于整地等人工措施的影响,人工林水土保持效果好;对于农地、半牧半农等人为活动频繁的小流域,弱雨强时径流系数极小,大雨强时径流系数相对较大,尤其是半农半牧流域,水土流失严重;当雨量>20mm时,无林流域初损历时小于森林流域,小尺度流域的初损历时小于大尺度流域。     

黄土高原次降雨径流产沙变化及其与雨强和植被盖度变化的相关性

获取12条流域16 a的753次降雨数据,运用雨强、植被盖度、径流系数和产沙系数等指标,分析黄土高原次降雨径流产沙变化及其与雨强和植被盖度变化的相关性。结果显示：① 与1980-1989年相比,2006-2011年黄土高原的降雨-径流和径流-产沙关系发生了明显变化,大部分流域的产流产沙能力有所下降,10个流域中有8个流域的径流系数、产沙系数有所减小,分别减小25.93%~66.1%和59.05%~97.71%;② 分析雨强和植被盖度变化与径流产沙变化的相关性,发现径流产沙变化与植被盖度变化的相关性强于其与雨强变化的相关性,表明植被盖度变化对径流产沙变化的影响更明显;③ 分析不同干湿条件下径流产沙变化对植被盖度变化的敏感性,发现气候越湿润,流域的径流产沙变化对植被盖度变化越敏感,植被改善的减水减沙效果越明显。     

小流域水量水质综合模型模拟研究

水箱模型也称Tank模型,是应用较为广泛的流域水文模型,模型将复杂的降水径流过程简单概化为流域的蓄水与出流关系进行模拟。针对皂河小流域的降水、径流和水循环等水文特性,建立了4层串联水箱模型,模拟流域的降水径流过程,计算流域径流量,并结合河流水质模型,综合模拟河流流量及主要水质指标变化。结果表明:各项指标的模拟值与实测值吻合较好,说明水箱模型用于小流域的径流模拟结果较为准确,可与水质模型耦合使用,综合模拟小流域的水文水质变化。     

滦河流域产流特性变化趋势分析

随着滦河流域下垫面的变化,流域产流特性也相应的发生了变化。文中分析了滦河流域存在的产流模式,通过分析径流系数变化和降雨径流相关关系,发现产流模式有从超渗产流向蓄满产流过渡或先超渗后蓄满的趋势。并选取了20世纪80年代后的几场典型较大洪水过程,分别采用所建立蓄满产流模型(新安江模型)和超渗产流模型(陕北模型)对这几场洪水进行模拟分析,通过两者模拟径流量的差值估算了产流特性变化对径流量变化的影响程度。结果表明:随着滦河流域植被覆盖率的不断提高,产流特性的这种变化对产流量有一定的减少作用,会使滦河流域径流量减少26.9%左右。     

新疆呼图壁河径流时间序列分析

基于呼图壁河石门水文站1956—2011年的年径流数据,采用Morlet小波分析和R/S分析方法,对新疆呼图壁河流域径流周期、变化特征和未来趋势进行分析和预测。研究结果表明:(1)通过对呼图壁河1956—2011年径流量的分析发现,径流时间序列存在5 a、10 a、18 a和28 a左右的震荡周期,18 a尺度震荡周期最强,其次是28a尺度。18 a时间尺度上的震荡在56 a研究时段内均较强,且存在4个丰水期和5个枯水期;28 a震荡周期在56 a尺度时段内相对较强,存在3个丰水期和3个枯水期,目前处于偏丰期;(2)利用R/S分析呼图壁河径流量序列,Hurst指数为0.6442,存在明显的赫斯特现象,这就意味着未来一段时间的径流量与过去具有同样的增加趋势。     

新疆主要河流径流量变化的时空特征研究

以新疆主要26条河流为研究对象,依据1956年~2000年径流量资料,揭示主要河流径流量演变趋势,并基于地理信息系统(G IS)技术探讨河流径流量变化的时空特征。结果表明:1956年~1986年为新疆主要河流径流量的衰减期,而自1987年起,河流径流量呈明显的增加趋势;在空间分布上,1956年~1986年间,河流径流量的衰减主要发生在新疆北部,而河流径流量的微增则发生在新疆南部;1987年~2000年间,河流径流量的变化,在空间格局上发生了明显的逆转,河流径流量的增加主要发生在新疆北部,而河流径流量的微减则发生在新疆南部;在与新疆同期气象资料的分析对比后发现,降水量以及温度的明显增加,是导致1987年以后新疆主要河流径流量增加和其空间格局发生变化的主要原因。     

青海省湟水流域河川径流特征分析

采用湟水流域几个主要水文站的实测年径流序列，分析了河川径流在地区上的分布规律以及年内年际间的变化；并对洪水和枯水特征及河川径流的随机性进行了分析。这些分析有助于掌握干旱半干旱河川径流的特征，为合理开发利用水资源提供依据。     

Effects of vegetation near-soil-surface factors on runoff and sediment reduction in typical grasslands on the Loess Plateau,China

Vegetation near-soil-surface factors can protect topsoil from erosion, however, their contributions to the reduction of soil erosion, especially under natural rainfall events, have not been systematically recognized. This study was performed to quantify the effects of near-soil-surface factors on runoff and sediment under natural rainfall events on grasslands dominated by Bothriochloa ischaemum(Linn.)Keng(BI grassland) and Artemisia gmelinii Thunb.(AG grassland) in two typical watersheds on the ...     

半干旱地区霍林河流域径流演变及其影响机制研究

霍林河流经内蒙古东部和吉林西部 ,处于生态环境脆弱带上 ,是半干旱气候条件下具有典型意义的内流河 ,其径流特征及演变规律对区域环境演化和水资源开发利用具有重要影响。本文通过对霍林河近半个世纪以来径流资料的分析 ,采用 Kendall趋势分析及关联度分析定量研究了径流演变的规律 ,分析了径流变化的驱动机制及对生态环境的影响。结果表明在气候干旱化和人类活动的双重影响下 ,霍林河径流演化具有阶段性、突变性和非线性的特点 ,流域水土资源的不合理开发是导致水文情势变化、水域功能消退的主要驱动力。探讨内流河径流演变的规律对区域生态环境的影响以及水资源合理开发利用具有积极现实的意义 ,为区域资源的合理开发和社会经济可持续发展提供科学依据     

Runoff characteristics and its sensitivity to climate factors in the Weihe River Basin from 2006 to 2018

Exploring the current runoff characteristics after the large-scale implementation of the Grain for Green (GFG) project and investigating its sensitivities to potential drivers are crucial for water resource prediction and management. Based on the measured runoff data of 62 hydrological stations in the Weihe River Basin (WRB) from 2006 to 2018, we analyzed the temporal and spatial runoff characteristics in this study. Correlation analysis was used to investigate the relationships between different runoff indicators and climate-related factors. Additionally, an improved Budyko framework was applied to assess the sensitivities of annual runoff to precipitation, potential evaporation, and other factors. The results showed that the daily runoff flow duration curves (FDCs) of all selected hydrological stations fall in three narrow ranges, with the corresponding mean annual runoff spanning approximately 1.50 orders of magnitude, indicating that the runoff of different hydrological stations in the WRB varied greatly. The trend analysis of runoff under different exceedance frequencies showed that the runoff from the south bank of the Weihe River was more affluent and stable than that from the north bank. The runoff was unevenly distributed throughout the year, mainly in the flood season, accounting for more than 50.00% of the annual runoff. However, the trend of annual runoff change was not obvious in most areas. Correlation analysis showed that rare-frequency runoff events were more susceptible to climate factors. In this study, daily runoff under 10%-20% exceeding frequencies, consecutive maximum daily runoff, and low-runoff variability rate had strong correlations with precipitation, aridity index, and average runoff depth on rainy days. In comparison, daily runoff under 50%-99% exceeding frequencies, consecutive minimum daily runoff, and high-runoff variability rate had weak correlations with all selected impact factors. The sensitivity analysis results suggested that the sensitivity of annual runoff to precipitation was always higher than that to potential evaporation. The runoff about 87.10% of the selected hydrological stations were most sensitive to precipitation changes, and 12.90% were most sensitive to other factors. The spatial pattern of the sensitivity analysis indicated that in relatively humid southern areas, runoff was more sensitive to potential evaporation and other factors, and less sensitive to precipitation.     

Synergistic effects of multiple driving factors on the runoff variations in the Yellow River Basin,China

River runoff plays an important role in watershed ecosystems and human survival, and it is controlled by multiple environmental factors. However, the synergistic effects of various large-scale circulation factors and meteorological factors on the runoff on different time-frequency scales have rarely been explored. In light of this, the underlying mechanism of the synergistic effects of the different environmental factors on the runoff variations was investigated in the Yellow River Basin of China during the period 1950-2019 using the bivariate wavelet coherence (WTC) and multiple wavelet coherence (MWC) methods. First, the continuous wavelet transform (CWT) method was used to analyze the multiscale characteristics of the runoff. The results of the CWT indicate that the runoff exhibited significant continuous or discontinuous annual and semiannual oscillations during the study period. Scattered inter-annual time scales were also observed for the runoff in the Yellow River Basin. The meteorological factors better explained the runoff variations on seasonal and annual time scales. The average wavelet coherence (AWC) and the percent area of the significant coherence (PASC) between the runoff and individual meteorological factors were 0.454 and 19.89%, respectively. The circulation factors mainly regulated the runoff on the inter-annual and decadal time scales with more complicated phase relationships due to their indirect effects on the runoff. The AWC and PASC between the runoff and individual circulation factors were 0.359 and 7.31%, respectively. The MWC analysis revealed that the synergistic effects of multiple factors should be taken into consideration to explain the multiscale characteristic variations of the runoff. The AWC or MWC ranges were 0.320-0.560, 0.617-0.755, and 0.819-0.884 for the combinations of one, two, and three circulation and meteorological factors, respectively. The PASC ranges were 3.53%-33.77%, 12.93%-36.90%, and 20.67%-39.34% for the combinations one, two, and three driving factors, respectively. The combinations of precipitation, evapotranspiration (or the number of rainy days), and the Arctic Oscillation performed well in explaining the variability in the runoff on all time scales, and the average MWC and PASC were 0.847 and 28.79%, respectively. These findings are of great significance for improving our understanding of hydro-climate interactions and water resources prediction in the Yellow River Basin.