黄土土壤结皮对产流临界雨强的影响分析

依据野外资料,从影响产流的各项因子出发,分析黄土高原典型区土壤结皮对产流临界雨强条件的影响,得出:在该区特殊的超渗产流方式下,土壤结皮降低入渗,使得产流时的临界雨强条件降低,因而大大提高了产流的可能性。但是,在实际情况下,雨强变异很大,应考虑不同雨强情况下土壤结皮对产流量的影响。而在室内条件下,各项因子均是可控的,一般情况下,雨强恒定,产流时的临界雨强条件降低,意味着产流提早,必然带来产流量的增加。     

基于集中度与集中期的径流年内分配研究

借鉴年降水量年内分配的向量法,描述径流年内分配的径流集中度和集中期,尝试提出一种计算河川径流年内分配不均匀性的定量新方法。实例研究表明,用月径流量计算的集中度比径流年内不均匀系数有更高的分辨能力和敏感性,用月径流量计算的集中期对应的月份与月径流最大值出现的实际月份完全一致,径流集中度、集中期能够充分定量地表征径流在年内分配的非均匀性。     

塔里木河流域径流变化趋势及其对气候变化的响应

This paper has studied the change of streamflow and the impact of climatic variability conditions on regional hydrological cycle in the headwater of the Tarim River Basin. This study investigates possible causes of observed trends in streamflow in an environment which is highly variable in terms of atmospheric conditions, and where snow and ice melt play an important role in the natural hydrological regime. The discharge trends of three head streams have a significant increase trend from 1957 to 2002 with the Mann-Kendall test. Complex time-frequency distributions in the streamflow regime are demonstrated especially by Morlet wavelet analysis over 40 years. The purpose is to ascertain the nature of climatic factors spatial and temporal distribution, involved the use of EOF （Empirical Orthogonal Function） to compare the dominant temperature, precipitation and evaporation patterns from normally climatic records over the Tarim＇s headwater basin. It shows that the first principal component was dominated since the 1990s for temperature and precipitation, which identifies the significant ascending trend of spatial and temporal pattern characteristics under the condition of the global warming. An exponential correlation is highlighted between surface air temperature and mean river discharge monthly, so the regional runoff increases by 10%-16% when surface air temperature rises by 1 ℃. Results suggest that headwater basins are the most vulnerable environments from the point of view of climate change, because their watershed properties promote runoff feeding by glacier and snow melt water and their fundamental vulnerability to temperature changes affects rainfall, snowfall, and glacier and ice melt.     

Dominant climate factors influencing the Arctic runoff and association between the Arctic runoff and sea ice

By using the Arctic runoff data from R-ArcticNET V4.0 and ArcticRIMS, trends of four major rivers flowing into the Arctic Ocean, whose climate factor plays an important role in determining the variability of the Arctic runoff, are investigated. The results show that for the past 30 years, the trend of the Arctic runoff is seasonally dependent. There is a significant trend in spring and winter and a significant decreasing trend in summer, leading to the reduced seasonal cycle. In spring, surface air temperature is the dominant factor influencing the four rivers. In summer, precipitation is the most important factor for Lena and Mackenzie, while snow cover is the most important factor for Yenisei and Ob. For Mackenzie, atmospheric circulation does play an important role for all the seasons, which is not the case for the Eurasian rivers. The authors further discuss the relationships between the Arctic runoff and sea ice. Significant negative correlation is found at the mouth of the rivers into the Arctic Ocean in spring, while significant positive correlation is observed just at the north of the mouths of the rivers into the Arctic in summer. In addition, each river has different relationship with sea ice in the eastern Greenland Sea.     

夏季澜沧江跨境径流量变化与夏季风的关系

以澜沧江跨境径流量观测数据、NCEP/NCAR的U场、V场和NOAA的OLR场资料为基础,应用统计分析方法,研究了纵向岭谷作用下的夏季澜沧江跨境径流量变化与夏季风的关系。结果表明:澜沧江夏季跨境径流量变化在20世纪60年代中期至80年代末期为显著减少时段,而从90年代初期以来则表现出了一种显著增多的演变趋势;夏季澜沧江跨境径流量变化与较低层东西风分量变化的相关性不显著,与较高层东西风分量变化的相关性显著;夏季澜沧江跨境径流量变化与中低层和较高层南北风分量变化的相关性都是显著的,与OLR场变化的负相关性也是显著的;根据这些相关性特征建立的影响澜沧江夏季跨境径流量变化的夏季风环流指数能够较好地反映出澜沧江夏季跨境径流量变化的基本特征和规律。     

基于径流还现的洮河流域径流变化特征研究

河川径流还现计算是准确反映区域水资源状况的基础,同时也是水资源规划和决策的重要依据.选取甘肃省洮河流域李家村、红旗2个代表水文站长系列径流资料作为基础数据,在还原计算的础上,对洮河流域径流进行还现计算,同时对径流变化特征进行研究.结果 表明:1956—2016年洮河流域李家村、红旗多年平均实测径流量分别为39.52×1...     

Precipitation‐runoff processes in Shimen hillslope micro‐catchment of Taihang Mountain,north China

Precipitation runoff is a critical hillslope hydrological process for downslope streamflow and piedmont/floodplain recharge. Shimen hillslope micro‐catchment is strategically located in the central foothill region of Taihang Mountains, where runoff is crucial for water availability in the piedmont corridors and floodplains of north China. This study analyzes precipitation‐runoff processes in the Shimen hillslope micro‐catchment for 2006–2008 using locally designed runoff collection systems. The study shows that slope length is a critical factor, next only to precipitation, in terms of runoff yield. Regression analysis also shows that runoff is related positively to precipitation, and negatively to slope length. Soil mantle in the study area is generally thin and is therefore not as critical a runoff factor as slope length. The study shows a significant difference between overland and subsurface runoff. However, that between the 0–10 and 10–20 cm subsurfaces is insignificant. Runoff hardly occurs under light rains (<10 mm), but is clearly noticeable under moderate‐to‐rainstorm events. In the hillslope catchment, vertical infiltration (accounting for 42–84% of the precipitation) dominates runoff processes in subsurface soils and weathered granite gneiss bedrock. A weak lateral flow (at even the soil/bedrock interface) and the generally small runoff suggest strong infiltration loss via deep percolation. This is critical for groundwater recharge in the downslope piedmont corridors and floodplains. This may enhance water availability, ease water shortage, avert further environmental degradation, and reduce the risk of drought/flood in the event of extreme weather conditions in the catchment and the wider north China Plain. Copyright © 2011 John Wiley & Sons, Ltd.     

Hydrological responses to climatic variability in a cold agricultural region

Extended severe dry and wet periods are frequently observed in the northern continental climate of the Canadian Prairies. Prairie streamflow is mainly driven by spring snowmelt of the winter snowpack, whilst summer rainfall is an important control on evapotranspiration and thus seasonality affects the hydrological response to drought and wet periods in complex ways. A field‐tested physically based model was used to investigate the influences of climatic variability on hydrological processes in this region. The model was set up to resolve agricultural fields and to include key cold regions processes. It was parameterized from local and regional measurements without calibration and run for the South Tobacco Creek basin in southern Manitoba, Canada. The model was tested against snow depth and streamflow observations at multiple scales and performed well enough to explore the impacts of wet and dry periods on hydrological processes governing the basin scale hydrological response. Four hydro‐climatic patterns with distinctive climatic seasonality and runoff responses were identified from differing combinations of wet/dry winter and summer seasons. Water balance analyses of these patterns identified substantive multiyear subsurface soil moisture storage depletion during drought (2001–2005) and recharge during a subsequent wet period (2009–2011). The fractional percentage of heavy rainfall days was a useful metric to explain the contrasting runoff volumes between dry and wet summers. Finally, a comparison of modeling approaches highlights the importance of antecedent fall soil moisture, ice lens formation during the snowmelt period, and peak snow water equivalent in simulating snowmelt runoff.     

Analysis of Manning coefficient for small‐depth flows on vegetated beds

The limitations of Manning's formula are analysed when it is in extreme conditions, and more specifically with small‐depth flows on natural‐vegetation beds. A thorough analysis is made of research carried out on macro‐rough beds, placing particular emphasis on vegetated beds. Research carried out to date on the roughness of vegetated beds and macro‐roughness is commented on, including that carried out at the Laboratory of Hydraulics and Hydrology of the Forestry Engineering Faculty (Polytechnic University of Madrid). The work was done in two phases, the first in a laboratory channel with artificial vegetation and the second in natural beds. The results of the experimental research allow the development of a new approximate method of determining Manning coefficient according to the Froude number. This method may be applied in extreme conditions, both in small depths and steep slopes. It was proved that the Manning coefficient depends not only on roughness height, but also on depth and slope values; thus, it is advisable to choose the appropriate method for its calculation. Copyright © 2005 John Wiley & Sons, Ltd.