Abstract: Water transport in the unsaturated zone results from nonlinear relationships between soil moisture state, suction gradients, and conductivity, leading to complex flow processes. This study presents an innovative approach for discretizing the pore spectrum and partitioning capillary-dominated flows into an arbitrary number of pore spaces. While preserving Richards’ equation and soil physical Van Genuchten and Mualem relationships, pore spaces are discretized into fine, medium, and macropores to quantify their individual states and flow contributions to total percolation. The approach has been applied to a continuously monitored soil profile with a depth of 1800 mm over a period of two years. The results reveal that the medium pore space, with a pore diameter of 10 µm < d ≤ 63 µm, plays a significant role, accounting for 80–90 % of the total percolation, controlling most of the transport process. The fine pore space (d ≤ 10 µm) remains consistently active throughout the entire period, contributing only 2–10 % to total percolation, being primarily defined by their interactions with larger pores. Macropores (d > 63 µm) emerge as particularly active during winter, enabling rapid vertical water displacement with contributions of up to 13 % through distinct fast flow events. Flow partitioning further illustrates the development of the critical zone during summer.

Abstract: Demonstration des Potentials der Nitrat-Isotopenanalytik für die Strategieentwicklung der Sanierung Nitrat-belasteter Brunnen