Simulation and Characterization of Streamflow Time Series

Abstract

Streamflow can be partitioned into distinct time scales to better understand the underlying governing processes: fast flow, representing surface runoff controlled mainly by meteorological processes that operate over relatively shorter time scales and slow flow, representing the baseflow through groundwater flow and subsurface flow that occur at a slower rate. Because of the significant differences between fast and slow process controls, each may be used to explain streamflow variability independently. The thesis considers this concept by including seasonal (timing) streamflow variability in a regional context. In order to isolate the effects of these drivers on the observed Flow Duration Curves (FDCs), a modeling framework is developed that comprises of partitioning streamflow in multiple ways: seasons/months in the time domain, east-west/north-south directions in the space domain, fast/slow flows in the process domain, and small to large catchments to account for the size of the catchment in a basin. This modeling framework is demonstrated through the Peninsular Indian river system, in which the hydrology is primarily governed by the monsoon rains. The framework of stratifying streamflow variability consists of three independent elements: (i) process partitioning: partitioning of the total streamflow into the fast flow and slow flow, each of which is impacted differently by climate and landscape properties, (ii) time scale partitioning: stratifying the temporal streamflow variability into distinct seasons namely-South-West monsoon, North-East monsoon, and Non-monsoon, and (iii) investigating the directional aspects of west-east and north-south gradients in the space domain. Findings of the study showed that South-West monsoon and fast flows are the major contributors to mean annual flow and total flow respectively, in these river systems. The spatially increasing mean rainfall towards the northern part and favourable geology compounded by seasonal rainfall pattern in the southern parts of the Peninsular regio...