Linking landscape structure and rainfall runoff behaviour in a thermodynamic optimality context

在热力学最优性背景下将景观结构和降雨径流行为联系起来

• 批准号: 268244115
• 负责人: Professor Dr.-Ing. Erwin Zehe
• 金额: --
• 依托单位: Max-Planck-Institut für Biogeochemie (MPI-BGC)
• 依托单位国家: 德国
• 项目类别: Research Units
• 财政年份: 2014
• 资助国家: 德国
• 起止时间: 2013-12-31 至 2018-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/268244115?language=en
• 关键词: Linking; landscape; structure; rainfall; runoff

Our main objective is to explore an alternative thermodynamic perspective on rainfall runoff generation on the hillslope and headwater scale. From a thermodynamic perspective any water mass flux is equal to a ¿potential gradient¿ divided by a ¿resistance¿, and fluxes deplete due to the second law of thermodynamics their driving gradients. Relevant potentials controlling rainfall runoff are soil water potentials, piezometric heads and surface water levels and their gradients are associated with spatial differences in associated forms of free1 energy. Rainfall runoff processes thus are associated with conversions of capillary binding energy, potential energy and kinetic energy. These conversions reflect energy conservation and irreversibility as they imply small amounts of dissipation of free energy into heat and thus production of entropy. Energy conversions during rainfall runoff transformation are, though being small, nevertheless of key importance, because they are related to the partitioning of incoming rainfall mass into runoff components and storage dynamics. This splitting and the subsequent subsurface dynamics is strongly controlled by preferential flow paths as they reduce subsurface flow resistances along their main extent, resulting in accelerated fluxes against the driving gradient. This implies an enlarged power in the subsurface flux and with it either enlarged free energy export or increased depletion of internal driving gradients, and thus a faster relaxation back towards local thermodynamic equilibrium. Thermodynamic optimality principles allow for a priory optimization of the resistance field at a given gradient, not in the sense how they exactly look like but in the sense how they function with respect to export and dissipation of free energy. We will thus explore the possibility of independent predictions of rainfall runoff in this project, in the sense that the a-priory optimum model structures should match independent observations at the hillslope and headwater scale. We also explore whether an apparent disequilibrium in landscape structure (reflected in topography, vegetation pattern, soil catena and apparent preferential pathways) implies temporally persistent patterns of soil moisture states in the sense that they coincide with local thermodynamic equilibria. This might offer the opportunity for useful backward predictions of distributed state dynamics by using observed dynamics of stream and ground water levels as boundary conditions characterizing the levels of relevant minima in geo-potential and zero matric potential in the subsurface. Last not least we test the feasibility to define hydrological similarity with respect to free energy stocks and conversions related to rainfall runoff (instead of focusing directly on the mass balance) with respect to classify catchments and hillslopes with respect to similar behavior.

我们的主要目标是探索另一种热力学观点来研究降雨径流在山坡和水源尺度上的产生。从热力学的角度来看，任何水质量通量都等于势能梯度除以阻力，并且通量由于热力学第二定律而耗尽其驱动梯度。控制降雨径流的相关位势是土壤水势、测压水头和地表水位，它们的梯度与相关形式的自由能的空间差异有关。因此，降雨径流过程与毛细管结合能、势能和动能的转换有关。这些转换反映了能量守恒和不可逆性，因为它们意味着少量的自由能耗散成热，从而产生熵。降雨径流转化过程中的能量转换虽然很小，但却很重要，因为它们与进入径流的雨量到径流成分的分配和储存动力学有关。这种分裂和随后的地下动力强烈地受到优先流动路径的控制，因为它们减少了沿其主要范围的地下流动阻力，导致针对驱动梯度的加速通量。这意味着次表面通量的功率增大，随之而来的要么是自由能输出的增大，要么是内部驱动梯度的消耗增加，从而更快地向局部热力学平衡松弛。热力学最优化原理允许在给定的梯度下优先优化阻力场，不是从它们看起来到底是什么样子的意义上，而是从它们在输出和耗散自由能方面的作用的意义上说。因此，我们将探讨在这个项目中对降雨径流进行独立预报的可能性，即优先优化的模型结构应该与山坡和源头尺度的独立观测相匹配。我们还探讨了景观结构的明显不平衡(反映在地形、植被格局、土壤链和明显的优先路径上)是否意味着土壤水分状态在时间上的持续格局，即它们与当地的热力学平衡相一致。这可能提供有用的向后预测分布式状态动力学的机会，方法是将观测到的水流和地下水水位动态作为边界条件，以表征地下地势和零矩阵势中相关极小值的水平。最后，我们测试了定义与降雨径流相关的自由能储量和转换的水文相似性(而不是直接关注物质平衡)的可行性，以及根据相似行为对集水区和山坡进行分类的可行性。