Hydrological thresholds in depression storage and contributing area for low-relief landscapes

这项研究是我在数字地形分析方面早期工作的延伸，旨在提高我们对地表洼地对水流影响的理解和建模能力。加拿大落基山脉以西的低起伏地貌的一个显著特征是冰川和冰缘作用产生的广泛分布的浅层地表洼地。在加拿大大草原，这些洼地通常被称为草原坑或沼泽。它们提供了重要的环境湿地，并对河流和地下水状况进行了重要的控制。地表凹陷的大小和频率在整个地形上有很大的不同。它们通常由排水河道连接，只有当洼地的蓄水能力被填满时，水才会沿着这些河道流动。从填满的洼地溢出的水代表了水文阈值的变化，集水区和流量经常发生巨大变化。南萨斯喀彻温河流域表明了地表洼地蓄水对区域水文和气候过程的潜在意义，科学家估计，由于沼泽和坑洼中断了排水过程，超过50%的景观很少向主要河流系统贡献径流。本研究的目标是：(1)描述在加拿大普雷雷省大部分地区发现的复杂的坳陷间流模式的主要特征；(2)修改数字地形分析中使用的标准算法，以便在局部尺度水文模型中适当地表示这种模式；(3)开发扩大尺度的技术，使我们对该系统的更好理解能够有效地用于区域尺度水文模型。虽然这项研究将特别关注草原景观中地表洼地的水文影响，但其结果也将应用于加拿大地盾和北部冻土带等地区，在这些地区，地表洼地也是景观的重要组成部分。

This research is an extension of my earlier work in digital terrain analysis and aims to improve our understanding and ability to model the impact of surface depressions on streamflow. One of the distinctive features of the low-relief landscapes of Canada west of the Rocky Mountains is the wide-spread occurence of shallow, surface depressions produced by glacial and periglacial processes. In the Canadian Prairies, these depressions are often called Prairie potholes or sloughs. They provide environmentally-important wetland sites and exert a significant control on streamflow and groundwater regimes. The size and frequency of surface depressions can vary greatly across the landscape. They are often linked by drainage courses along which water flows only when the storage capacity of the depressions is filled. Water spilling from filled depressions represents a hydrological threshold shift with catchment areas and streamflow volumes often changing dramatically. The potential significance of surface depression storage to regional hydrologic and climatic processes is illustrated by the South Saskatchewan River Basin where scientists estimate that over 50% of the landscape rarely contributes runoff to the major river system because of the interuption of drainage courses by sloughs and potholes. The objectives of this research are to (1) characterize the major features of the complex, inter-depressional flow patterns found in much of the Canadian Praires, (2) modify the standard algorithms used in digital terrain analysis to appropriately represent this pattern in local-scale hydrological models and (3) develop up-scaling techniques to allow our improved understanding of this system to be used effectively in regional scale hydrological models. While this research will focus particularly on the hydrological impact of surface depressions in Prairie landscapes, its outcomes will also have application in areas like the Canadian Shield and northern tundra where surface depressions are also an important element of the landscape.