Study on rain-runoff process in the peripheral mountainous area of the Sichuan Basin

Studies on rain-runoff process in the peripheral mountainous area of the Sichuan Basin, which is regarded as a key ecological shelter, will contribute to flood control and environmental protection for the Upper Yangtze River Basin. In two typical catchments--the Fujiang River Catchment and the Wujiang River Catchment, rainfall simulations have been conducted to study the rain-runoff processes of yellow soil and limestone soil in three types of land use--forestland, farmland and grassland. Results showed that （1） within the same rainfall process, overland flow occurs first on farmland, then on grassland, and finally on forestland; （2） soil surface coverage has a great impact on the occurrence and amount of overland flow. The runoff amount can increase 2-4 times after the coverage is removed; （3） the infiltration before the occurrence of overland flow will decrease because of higher gravel contents of soil, but it takes no effect on infiltration once overland flow becomes stable; （4） the runoff coefficient of the limestone soil forestland is greater than that of the yellow soil forest land, but less than that of the farmland; （5） three empirical infiltration models, including Horton＇ model, Kostiakov＇ model, and modified Kostiakov＇ model, were compared by using the observed results under rainfall simulation. The results showed that the Kostiakov＇ model performed better than both the Horton＇ model and modified Kostiakov model. According to the results of this research, the Kostiakov＇s model can be used to simulate rainfall infiltration when water erosion is modeled in the peripheral mountainous area of the Sichuan Basin.     

四川盆地紫色土丘陵区水土流失及防治对策

四川盆地丘陵区是该省水土流失最严重的地区。也是该地区生态环境恶化、自然灾害频繁、农村经济落后、人民生活贫穷的重要原因。文章根据四川盆地丘陵区水土流失面积大、强度高的特征及其致害因素，探讨了水土流失原因。水土流失破坏生态环境及耕地资源，淤积江河湖库，加剧水旱洪涝灾害，造成土壤肥力下降，土壤蓄水抗旱能力降低。由此提出了一些相应的防治措施——加强生态环境建设，整治坡面水系，搞好农田基本建设，强化人口／管理等，从而使水土流失得到控制，生态环境得到改善。加强对紫色砂页岩丘陵区的治理，合理开发利用土地，提高土地利用率和生产率，不仅利于四川盆地丘陵区的经济发展，而且对改善长江上游乃至整个长江流域的生态环境也具有重大的现实意义。     

上方来水对坡面降雨入渗及土壤水分再分布的影响

在防止土壤侵蚀和雨后抑制蒸发的条件下,利用室内模拟降雨试验,研究了上方来水对坡面降雨入渗、湿润锋运移以及土壤水分再分布的影响。结果表明:对于初始含水量很低的土壤,与上方无来水相比,上方来水时降雨入渗过程中入渗率有一个上升的阶段,但平均入渗率反而降低;在降雨入渗初期,由于上方来水的沿程入渗,上方来水对坡面湿润锋运移的影响较大,但随后几乎没有影响,湿润锋的运移主要与基质势梯度有关;土壤水分沿坡面呈"波浪形"分布是坡面径流的波动性、上方来水(径流)的沿程入渗以及侧向沿坡向下流等综合作用的结果。     

Assessment of LULC and climate change on the hydrology of Ashti Catchment,India using VIC model

The assessment of land use land cover (LULC) and climate change over the hydrology of a catchment has become inevitable and is an essential aspect to understand the water resources-related problems within the catchment. For large catchments, mesoscale models such as variable infiltration capacity (VIC) model are required for appropriate hydrological assessment. In this study, Ashti Catchment (sub-catchment of Godavari Basin in India) is considered as a case study to evaluate the impacts of LULC changes and rainfall trends on the hydrological variables using VIC model. The land cover data and rainfall trends for 40 years (1971–2010) were used as driving input parameters to simulate the hydrological changes over the Ashti Catchment and the results are compared with observed runoff. The good agreement between observed and simulated streamflows emphasises that the VIC model is able to evaluate the hydrological changes within the major catchment, satisfactorily. Further, the study shows that evapotranspiration is predominantly governed by the vegetation classes. Evapotranspiration is higher for the forest cover as compared to the evapotranspiration for shrubland/grassland, as the trees with deeper roots draws the soil moisture from the deeper soil layers. The results show that the spatial extent of change in rainfall trends is small as compared to the total catchment. The hydrological response of the catchment shows that small changes in monsoon rainfall predominantly contribute to runoff, which results in higher changes in runoff as the potential evapotranspiration within the catchments is achieved. The study also emphasises that the hydrological implications of climate change are not very significant on the Ashti Catchment, during the last 40 years (1971–2010).     

坡地氮磷流失过程模拟

根据农田坡面氮、磷流失的主要过程,建立了基于次降雨事件的坡面氮、磷迁移模型。模型采用改进的Green-Ampt方程和运动波方程计算下渗与坡面流,土壤侵蚀采用修改的欧洲土壤侵蚀模型计算,用考虑了侵蚀影响与扩散作用的迁移模型计算坡面氮、磷迁移过程,采用一维对流扩散方程计算氮、磷在土壤中的迁移过程。利用室内人工降雨资料对模型进行了率定及验证。结果表明,模型可以较好地模拟地表径流中氮、磷浓度,率定期与验证期模型效率系数均在0.89以上。根据坡地氮、磷流失机理,分析了降雨强度与地表坡度对坡面径流中氮、磷浓度的影响。     

河西内陆河流域土地利用对地表水资源影响研究

土地利用对水资源的影响,直接导致水资源空间和时间分布格局发生变化,从而对流域生态、环境以及经济发展等多方面产生深刻影响.采用多期TM等卫星影像解译土地利用/覆被变化要素,应用斑块破碎度和分段比重百分比指标等方法,研究河西内陆河流域土地利用/覆被变化;应用河川径流的溯源性和零地表水资源尺度等理论,研究土地利用对地表水资源格局的影响.结果表明:土地利用驱使地表水资源格局产生剧烈变异,地表水资源整体向河源溯进;疏勒河水资源受耕地面积扩张等影响中下游径流变化产生紊乱;黑河耕地面积10万hm2成为水资源格局变化的极值,地表水资源损耗量出现逐步减少的趋势;石羊河耕地面积的扩张对地表水资源的影响力不断减小,转化为对地下水影响的加剧.     

人工降雨条件下冲沟型泥石流起动试验研究

下垫面以位于贡嘎山东坡的熊家沟为模型,开展了不同降雨强度条件下冲沟型泥石流起动的模拟试验,初步研究了冲沟型泥石流的形成机理和演化特征.试验研究表明:(1)在强降雨条件下,水体入渗速度、不同深度土体含水量变化与降雨强度呈反比例关系,降雨强度越大,越不利于水体入渗,而有利于坡面汇流、冲沟径流和下切侵蚀; (2)在强降雨和径流条件下,土体破坏方式、破坏程度以及泥石流形成机理表现出差异性.相对较小雨强降雨条件下,土体破坏方式以滑坡为主,泥石流形成模式表现为滑坡液化与转化起动,雨强较大降雨条件下,土体破坏方式以侵蚀垮塌为主,泥石流形成模式为洪流席卷垮塌体和沟床揭底; (3)起动试验中泥石流阵性特征明显.在强降雨条件下,雨强与泥石流的规模、黏度之间没有正相关性,雨强越大,泥石流黏度越小,试验中多出现的是高含砂洪流,而相对较小雨强作用下由土体液化转化形成的泥石流黏度较大.试验现象和结果与熊家沟泥石流起动、发生过程具有较高的一致性.     

不同林草系统对集水区水量平衡的影响研究

应用SWAT99.2模型(Soil and Water Assessment Tool),系统地研究了红壤丘岗集水区4种林草系统(自然草被、阔叶林、混交林和针叶林)的地表径流、根层渗漏、蒸发蒸腾、土壤蓄水量的时空特点,并用实测的地表径流对模型进行校正和验证,月地表径流的Nash-Sutcliffe模拟效率系数达到0.74,模拟值和观测值的决定系数达0.90。结果表明,降水的年内分配不均造成了径流、渗漏、土壤蓄水量月份之间的差异,年际间气象条件(特别是降水)的差异性导致了水量平衡支出项的年际差异,其中径流量和渗漏量受降水的影响最大,蒸发蒸腾量次之,土壤蓄水量的年变化量受降水的影响最小;林地能有效地减少区域的地表径流量,其中以阔叶林和混交林的效果最好;林地入渗性能大于草地;蒸发蒸腾量是林地水量平衡支出中最大的一项,且3种林地的蒸发蒸腾量均大于草地。水量平衡的预测结果显示,土地利用方式是区域短期水量平衡的主要影响因子。     

流域产沙模型的研究

由坡面泥沙颗粒的动力平衡条件,推导出坡面上细颗粒泥沙的起动切应力,由坡面径流的剩余输沙能力,导得坡面径流的侵蚀量计算公式,与文献[4]的雨滴溅蚀量计算公式一起,构成了概念清楚、过程明确、结构完整的流域产沙模型。产沙量取决于水流挟沙能力与可供沙量的对比关系,若水流挟沙能力小于供沙量,则产沙量等于水流挟沙能力;反之,水流将进一步冲刷表土,形成径流侵蚀,产沙量就等于供沙量与径流侵蚀量之和。据此,可计算出坡面和流域产沙量。模型在岔巴沟流域上应用,结果令人满意。     

基于统计理论的产流模型

提出了一个基于统计理论的产流模型,该模型考虑了降雨、土壤下渗能力及土壤蓄水容量的空间变异性。假定每个时段的降雨量在空间上可以用概率密度函数或分布函数描述,根据实测降雨资料通过统计拟合优度途径估计各时段降雨的空间概率分布;采用抛物线型函数分别描述土壤下渗能力和土壤蓄水容量的空间分布。按照超渗产流机制计算地表产流量,通过降雨量和土壤下渗能力的联合分布推导得到地表径流量的统计分布,进而得到平均产流量的解析表达式。下渗水量补充土壤含水量,假定满足田间持水量后形成地下径流,其产流量根据下渗量和土壤蓄水容量的空间分配曲线进行计算。以半湿润的黄河支流伊河东湾流域为例,对模型进行了验证和应用,并与新安江模型的结果进行了对比。结果表明,模型对所研究的半湿润区的洪水模拟预报有较好的模拟效果。     

陆面水文过程与大气模式的耦合及其在黑河流域的应用

陆面过程模式对陆面水文过程有比较详尽的描述,然而,目前的陆面水文过程只考虑了垂直方向的水分运移,比较适合平坦地区的模拟,而在地形坡度较大的山区只考虑垂直方向的水分移动是不够的,尤其是目前随着计算机条件提高,分辨率越来越高,地表水以及土壤水的侧向流动成为山区水文过程必须考虑的部分。同时,目前的陆面过程模式中的径流量是作为诊断量处理,不参与运算。针对以上问题,对Noah陆面过程模式进行了改进,增加了地表积水和积水蒸发、坡面汇流方案、次表面流方案,并且将Routing模块通过次网格过程与大气中尺度模式MM5耦合,发展了高分辨率大气—水文耦合模式。运用发展的高分辨率大气—水文耦合模式,对黑河流域中上游2003年6月23~25日降水过程进行了模拟,研究了陆面水循环过程对大气场的影响。结果表明陆面水循环过程对近地层大气影响很大,首先影响了土壤的湿度与蒸发,进而对边界层稳定性,云结构、云水、雨水含量产生影响,对区域降水也有一定影响。     

Regional modelling of rainfall-induced runoff using hydrological model by incorporating plant cover effects: case study in Kelantan,Malaysia

The objective of this paper is to develop a spatial temporal runoff modelling of local rainfall patterns effect on the plant cover hilly lands in Kelantan River Basin. Rainfall interception loss based on leaf area index, loss/infiltration on the ground surface, and runoff calculation were considered as the main plant cover effects on the runoff volume. In this regard, a hydrological and geotechnical grid-based regional model (integrated model) was performed using Microsoft Excel^® and GIS framework system for deterministic modelling of rainfall-induced runoff by incorporating plant cover effects. The infiltration process of the current model was integrated with the precipitation distribution method and rainfall interception approach while the runoff analysis of integrated model was employed based on loss/infiltration water on the ground surface with consideration of water interception loss by canopy and the remaining surface water. In the following, the spatial temporal analysis of rainfall-induced runoff was performed using 10 days of hourly rainfall events at the end of December 2014 in Kelantan River Basin. The corresponding changes in pressure head and consequent rate of infiltration were calculated during rainfall events. Subsequently, flood volume is computed using local rainfall patterns, along with water interception loss and the remaining surface water in the study area. The results showed the land cover changes caused significant differences in hydrological response to surface water. The increase in runoff volume of the Kelantan River Basin is as a function of deforestation and urbanization, especially converting the forest area to agricultural land (i.e. rubber and mixed agriculture).     

流域坡面汇流研究现状述评

对当前坡面汇流计算方法的研究进展进行了较为系统的总结与分析,并对坡面汇流的非线性效应以及城市低影响开发中的雨水入渗与蓄集对坡面汇流的控制作用进行了简要分析。从模型简单实用的角度出发,认为以流域时间-面积关系与线性水库相串联的ModClark法等为代表的概念性分布式坡面汇流模型具有良好的发展前景;考虑到基于等流时单元的变动等流时线法在反映雨强非线性影响中存在的问题,认为根据水文响应单元在不同雨强条件下汇流时间的变化,调整其汇流参数以反映坡面汇流的非线性效应,对于流域坡面汇流的分布式模拟更具有实际意义;针对目前低影响开发设施长时间序列大空间尺度的室外降雨径流监测资料普遍较为缺乏的现状,给出了后期应积极选择合适的技术以加强低影响开发性能监测工作的建议。     

Wildfire impacts on the processes that generate debris flows in burned watersheds

Every year, and in many countries worldwide, wildfires cause significant damage and economic losses due to both the direct effects of the fires and the subsequent accelerated runoff, erosion, and debris flow. Wildfires can have profound effects on the hydrologic response of watersheds by changing the infiltration characteristics and erodibility of the soil, which leads to decreased rainfall infiltration, significantly increased overland flow and runoff in channels, and movement of soil. Debris-flow activity is among the most destructive consequences of these changes, often causing extensive damage to human infrastructure. Data from the Mediterranean area and Western United States of America help identify the primary processes that result in debris flows in recently burned areas. Two primary processes for the initiation of fire-related debris flows have been so far identified: (1) runoff-dominated erosion by surface overland flow; and (2) infiltration-triggered failure and mobilization of a discrete landslide mass. The first process is frequently documented immediately post-fire and leads to the generation of debris flows through progressive bulking of storm runoff with sediment eroded from the hillslopes and channels. As sediment is incorporated into water, runoff can convert to debris flow. The conversion to debris flow may be observed at a position within a drainage network that appears to be controlled by threshold values of upslope contributing area and its gradient. At these locations, sufficient eroded material has been incorporated, relative to the volume of contributing surface runoff, to generate debris flows. Debris flows have also been generated from burned basins in response to increased runoff by water cascading over a steep, bedrock cliff, and incorporating material from readily erodible colluvium or channel bed. Post-fire debris flows have also been generated by infiltration-triggered landslide failures which then mobilize into debris flows. However, only 12% of documented cases exhibited this process. When they do occur, the landslide failures range in thickness from a few tens of centimeters to more than 6 m, and generally involve the soil and colluvium-mantled hillslopes. Surficial landslide failures in burned areas most frequently occur in response to prolonged periods of storm rainfall, or prolonged rainfall in combination with rapid snowmelt or rain-on-snow events.     

坡地径流入渗机制对水文模拟的影响分析

建立了适用于栅格单元系统的基于运动波理论的降尺度新安江模型(KWXAJ)。在栅格单元中采用新安江模型计算产流,运动波模型进行坡面汇流演算。模型中,为考虑上游坡地单元入流的径流入渗(run-on)效应,在进行坡地产流计算时,降雨及上游坡面流及壤中出流被同时作为来水输入新安江模型。在运动波模型中,糙率系数依据土地利用方式及洪水量级确定。选取淮河史灌河流域黄泥庄以上集水区域,作为研究区域。用流域历史上的13次洪水过程来率定和验证此模型。研究表明,run-on机制对流域产汇流预测有重要影响,其显著影响流域内土壤蓄水量时空分布,进而改变产汇流机制。数据分析还显示,不考虑run-on机制将导致模拟洪峰滞后。     

一个网格型松散结构分布式水文模型的构建

根据流域降雨径流的基本过程,以蓄满产流理论为基础,建立了一个网格型松散结构的分布式流域水文模型。模型将流域离散为包含河道与不包含河道两种类型的单元格,以协克里金方法插值得到空间离散的降雨输入,考虑的产汇流物理过程包括降雨、植被截留及蒸散发、单元格产流、单元格汇流及河网汇流。模型结构简单,参数较少,在充分利用植被覆盖类型图及土地利用类型图的基础上,能够获得大部分参数的选用值。通过在长江三峡区间沿渡河流域的实际应用,模型计算成果令人满意。     

黑河流域山区植被生态水文功能的研究

依据土壤-植被-大气系统的结构特性,从林冠层、苔藓-枯枝落叶层、土壤层剖面结构分析了黑河流域山区水源涵养林在水文过程中的作用.观测试验表明,林冠截留大气降水的32.7%,使到达林地的水分相对减少而养分增加,而林冠遮荫使林内土壤蒸发仅为林外草地的34.2%.苔藓-枯枝落叶层疏松多孔,最大持水量可达12.5mm水层深,加上表层较高的体积含水量和较小的水分变差系数,使其在涵蓄一部分大气降水的同时具有良好的保水性能.林地土壤具有良好的渗透性和涵蓄大气降水的能力,从而减少了地表径流量.森林的蒸散发使林区空气湿度高于周边地区17%,形成山区独特的森林小气候,从而进一步影响着山区的水文过程.     

陇东黄土塬区不同下垫面条件下侵蚀产沙的降雨阈值

根据陇东黄土高塬沟壑区典型小流域——南小河沟流域1954—2014年实测降雨产沙资料,应用降雨侵蚀力偏差系数法研究不同土地利用类型及空间尺度下侵蚀产沙的雨量阈值、雨强阈值及复合阈值标准,并通过对比分析确定了最优降雨阈值标准。结果表明:① 对于林地和草地坡面小区,其雨量阈值标准平均值（21.0 mm）较裸地（8.7 mm）和农地（9.7 mm）坡面小区分别提高了141%和116%,植被措施能够显著提高降雨阈值标准。② 杨家沟林地小流域的雨量阈值标准为16.5 mm,低于布设在该流域的林地坡面小区,同时对比董庄沟草地小流域及其坡面和全坡面小区的雨量阈值标准,其大小亦为:草地坡面尺度 > 草地全坡面尺度 > 草地小流域尺度,由此可见,降雨阈值标准会随着空间尺度增大而减小。③ 降雨阈值标准综合评价结果表明,各样点最优降雨阈值标准均为P≥a或I₃₀≥b这一复合因子标准,而在降雨单因子阈值标准中,对于农耕地和裸地坡面小区,宜采用最大30 min雨强（I₃₀）标准;对于经过水土流失治理的下垫面,宜采用雨量（P）标准。该研究可为区域土壤侵蚀预报提供参考。     

The runoff characteristics under simulated rainfall on purple soil sloping cropland

Rainfall runoff is a critical hydrological process related to soil erosion and agricultural non-point pollu-tion. In this study, 25 simulation experiments on rainfall were carried out in five runoff plots. Rape (Brassica campestris) was planted on the downslope of the plots. Experiments were conducted when the vegetation coverage reached 80%. Each plot was subjected to five rainfall events differing in intensity. The results showed: (1) the runoff coefficients of overland flow and subsurface flow were less than 0.6 and 0.005, respectively; (2) the discharge of overland flow was the quadratic function of time; (3) runoff coefficient was the function of slope gradient and rain-fall intensity. When the slope gradient increased from 8.7% to 46.6%, the runoff coefficient of overland flow first increased and then decreased. The runoff coefficient reached the maximum when the slope gradient was within the range of 17.6%-36.4%; and (4) the process of subsurface flow generation included the increasing phase and reces-sion phase. Discharge was a logarithm function of time in the increasing phase, and an exponential function in the recession phase. Runoff coefficient of subsurface flow decreased first and then increased when the slope gradient varied from 8.7% to 46.6% and was not correlated with rainfall intensity.     

三峡库区不同厚度紫色土坡耕地产流机制分析

土层厚度是影响坡面水文过程的决定性因素之一.通过野外模拟降雨试验(设计雨强60 mm/h),在小区尺度上研究了一个完整坡面上典型土层厚度紫色土坡耕地坡面产流机制.结果表明:对于地表径流,土层厚度为23 cm小区表现为饱和产流,而土层厚度为45 em和76 cm小区均表现为超渗产流;对于壤中流,土层厚度为76 em小区以...