Dominant processes concept, model simplification and classification framework in catchment hydrology

Abstract

Technological and methodological advances have facilitated tremendous growth in hydrology during the last century; however, there are also concerns that these advances indirectly contribute to additional problems in our research. An insight into hydrologic literature reveals our tendency to develop more complex models than perhaps needed, and our increasing emphasis on individual mathematical techniques rather than general hydrologic issues. Some recent studies of diverse forms have suggested that simplification in modeling and development of a common framework may help alleviate these problems. The present study is intended to bring such studies together towards a more coherent approach to research in catchment hydrology. This is done by highlighting the need for model simplification and generalization and proposing some potential directions for achieving such. Through a discussion of difficulties in data measurements, the need for moving beyond the notion of ''modeling everything'' to the notion of ''capturing the essential features'' is explained; the concept of dominant processes in model simplification and the utility of integration of concepts for modeling improvement are discussed. Formulation of a catchment classification framework is advocated as a possible means for a common framework in hydrology, and the role of dominant processes in this formulation is presented; the problems due to adoption of different modeling terminologies are highlighted and potential ways to overcome such are also discussed.

Groundwater and Surface Water Interaction at the Regional-scale – A Review with Focus on Regional Integrated Models

“…Kirchner (2006) and McDonnell et al (2007) suggest that the governing equations that apply in small scale physics might not adequately describe large scale hydrological responses in heterogeneous systems. Several authors have tried to further conceptualise and formalise the different significance and relevance at different scales as well as in different environments, landscapes and climates and to compile this into a theory of dominant processes (Grayson and Bloeschl 2000;Sivakumar 2004;Sivakumar 2008;Sivapalan et al 2003). The question of whether or not processes loose or gain relevancy at the large scale was already been raised in the preceding sections.…”

Hydrologic system complexity and nonlinear dynamic concepts for a catchment classification framework

“…The urgency to formulate a generic classification framework in hydrology is increasingly realized now, especially with our current practice of employing more and more sophisticated mathematical techniques and developing more and more complex models for each and every individual hydrologic system/situation, rather than the emphasis needed for addressing broader-scale hydrologic issues (e.g. Sivakumar, 2008).…”

“…In this "objective of the inquiry" context, Sivakumar (2008) suggests that hydrologic systems may be viewed from three different, but related, angles: process, scale, and purpose of interest. Depending upon the angle at which they are viewed, hydrologic systems may be either simple or complex; for example, the rainfall occurrence in a desert may be treated as an extremely simple process since there may be no rainfall at all, while the runoff process in a large river basin may be highly complex due to the basin complexities and heterogeneities, in addition to rainfall variability.…”

“…data), our increasing emphasis in applying specific (and often pre-selected) mathematical techniques independently as opposed to the integration of techniques for modeling hydrologic systems, and our focus mainly on local-scale hydrologic problems rather than global-scale hydrologic issues have also come under severe scrutiny (e.g. Beven, 2002;Sivakumar, 2008). With growing concerns on the occurrence of global climate change and its potential impacts on water resources and the environment (including more frequent and greater magnitudes of extreme events, such as floods and droughts), the limitations of the "confines of traditional hydrology" and the need to go beyond and perform crossdisciplinary research integrating hydrology with atmospheric science, geomorphology, geochemistry, ecology, and other areas have also been increasingly recognized (see, for example, Paola et al, 2006, for some details).…”

Complex networks for streamflow dynamics

“…It is true that recent developments in measurement technology, computational power, and mathematical sophistication have generally played an important role in overcoming these challenges to a certain extent. It can also not be denied, however, that the 4566 B. Sivakumar and F. M. Woldemeskel: Complex networks for streamflow dynamics same developments have, at times, played an indirect role in creating imbalance and hindering true progress, as they have contributed to the perhaps unnecessary complexification in models (rather than simplification), highly specialized conceptual notions that are often suitable only for specific situations (rather than generalization frameworks that suit all conditions), difficult-to-bridge gaps between theory and practice, and lack of communication among researchers as well as between researchers and practitioners; see, for example, Perrin et al (2001), Beven (2002), Kirchner (2006), Sivakumar (2008), and Young and Ratto (2009) for some details.…”