Hydrologic Inference A Complex Systems Approach

Abstract

The aim of this thesis is to understand linkages between hydrologic processes and patterns from the perspective of a complex system. In hydrologic systems, there exist interactions of hydrologic components among themselves and with the surrounding environment at a wide range of space and time scales. These interactions impart distinct properties to the spatial and temporal behaviour of variables in the catchment. One of the important aspects of a catchment system is complexity, which describes the inherent structural dynamics of a variable that arises due to multiscale interactions and co-evolution between catchment and environment. The two important aspects of complexity considered in this thesis are hydrologic persistence and the uniformity in rainfall distribution. Both hydrologic as well hydro-meteorologic systems are considered as complex systems and the investigation is performed at catchment and regional scales respectively. Hydrologic persistence plays an important role in natural mechanisms governing hydrologic processes and their interdependence. The space-time evolution of persistence in rainfall and streamflow and their joint behaviour is examined here through the estimation of Hurst Coefficient using Detrended Fluctuation Analysis (DFA) and Detrended Cross-Correlation Analysis (DCCA). The MOPEX (Model Parameter Estimation Project) watersheds in USA and the Cauvery River Basin in India are used as case studies. The analyses show that the temporal dynamics of persistence of rainfall and streamflow and their joint behaviour are non-uniform across different time scales. It is found that the contribution of catchment processes influencing the persistence of the streamflow is a function of the catchment area. The state of persistence of joint behaviour is neither dependent on the rainfall amount nor affected by the changing patterns of dry and wet spells while the persistence of rainfall alone is affected by the latter...