Assessing the water balance in the Sahel : Impact of small scale rainfall variability on runoff. Part 2: Idealized modeling of runoff sensitivity
Assessing the water balance in the Sahel : Impact of small scale rainfall variability on runoff. Part 2: Idealized modeling of runoff sensitivity
复制标题
评估萨赫勒地区的水平衡：小规模降雨变化对径流的影响。
DOI：
10.1016/j.jhydrol.2006.09.007
复制
发表时间：
2007
影响因子：
6.4
通讯作者：
T. Lebel
中科院分区：
文献类型：
--
作者：
T. Vischel;T. Lebel
与世界上许多其他半干旱地区一样，萨赫勒地区水文环境的特点是由小型内陆集水区镶嵌而成，土壤表面干燥，主要产生霍顿径流。利用SCS型事件模型建立了一个理想化的萨赫勒地区径流模型，研究了径流对小尺度降雨变率的敏感性。一组548个观测到的降雨事件被用来迫使水文模型研究径流对降雨输入的时间和空间变异性的敏感性。降雨时间变异性的敏感性分析表明，保留事件雨深，而不代表雨型强度的主要变量可以转化为径流误差的65%，在最坏的情况下。在覆盖10，000 km 2的1-km 2流域的虚拟镶嵌图上，模拟的径流对事件雨场的空间分辨率从1× 1 km 2降低到100× 100 km 2表现出很高的敏感性。对于对降雨变化最为敏感的低径流系数流域，在100× 100 km 2的粗空间分辨率下，548个事件模拟的全球径流量相对于1× 1 km 2分辨率雨场模拟的径流量低估了50%。20 km的阈值分辨率被确定为特征空间尺度，超过该尺度，模式的性能迅速下降。从可用雨量站数量的影响来看，空间聚集的效果取决于雨量站网络的密度，对于稀疏的网络，空间聚集的效果较低。
As in many other semi-arid regions in the world, the Sahelian hydrological environment is characterized by a mosaic of small endoreic catchments with dry soil surface conditions producing mostly Hortonian runoff. Using an SCS-type event based rainfall–runoff model, an idealized modeling experiment of a Sahelian environment is set up to study the sensitivity of runoff to small scale rainfall variability. A set of 548 observed rain events is used to force the hydrological model to study the sensitivity of runoff to the time and space variability of rainfall input. The rainfall time variability sensitivity analysis shows that preserving the event rain depth without representing the main variabilities of the hyetograph intensities can translate into a runoff error of 65% in the worst case. On a virtual mosaic of 1-km2catchments covering 10,000km2, the simulated runoff shows a high sensitivity to a decrease of the spatial resolution of event rain fields from 1×1km2to 100×100km2. For the catchments characterized by low runoff coefficients, which are the most sensitive to rainfall variability, at the coarsest spatial resolution of 100×100km2, the global runoff computed from the 548 events is underestimated by 50% with respect to the runoff simulated from the 1×1km2resolution rain fields. The threshold resolution of 20km was identified as a characteristic spatial scale, over which the performance of the model rapidly decreases. Looking at the influence of the number of available rain gauges, the effect of spatial aggregation depends on the density of the rain gauge network with lower effect for sparser networks.