Open AccessPredicting Vertically Nonsequential Wetting Patterns with a Source‐Responsive Model
Author(s) -
Nimmo John R.,
Mitchell Lara
Publication year - 2013
Publication title -
vadose zone journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.036
H-Index - 81
ISSN - 1539-1663
DOI - 10.2136/vzj2013.03.0054
Subject(s) - wetting , richards equation , observable , domain (mathematical analysis) , flow (mathematics) , rendering (computer graphics) , soil science , mechanics , water flow , environmental science , computer science , soil water , mathematics , physics , thermodynamics , mathematical analysis , quantum mechanics , computer graphics (images)
Water infiltrating into soil of natural structure often causes wetting patterns that do not develop in an orderly sequence. Because traditional unsaturated flow models represent a water advance that proceeds sequentially, they fail to predict irregular development of water distribution. In the source‐responsive model, a diffuse domain (D) represents flow within soil matrix material following traditional formulations, and a source‐responsive domain (S), characterized in terms of the capacity for preferential flow and its degree of activation, represents preferential flow as it responds to changing water‐source conditions. In this paper we assume water undergoing rapid source‐responsive transport at any particular time is of negligibly small volume; it becomes sensible at the time and depth where domain transfer occurs. A first‐order transfer term represents abstraction from the S to the D domain which renders the water sensible. In tests with lab and field data, for some cases the model shows good quantitative agreement, and in all cases it captures the characteristic patterns of wetting that proceed nonsequentially in the vertical direction. In these tests we determined the values of the essential characterizing functions by inverse modeling. These functions relate directly to observable soil characteristics, rendering them amenable to evaluation and improvement through hydropedologic development.