1. Introduction

The moving freshwater bodies, ecologically designated as lotic aquatic ecosystem, are represented by rivers, streams, springs, tributaries, etc. and exhibit variability across the world in different periods of an annual cycle mainly because of variable geo-eco-physico-chemical attributes such as their sizes, shapes, carrying capacity, depth and volume of water, discharge potential, and abilities to connect with the water cycle in the watersheds. However, these freshwater ecosystems are in the brink of eco-degradation mainly due to non-judicious handling of this fascinating landscape of the world.

This volume (I) of the book in its six (6) capacious chapters along with an elaborate introduction and conclusion has attempted to highlight multidimensional facets of the physical environment (geomorphology, geohydrology, physicochemical factors and processes) of the riverine ecosystem in the backdrop of an analytical discussion of the properties and distribution of the wonder molecule of this planet, the water, basic ecological concepts and principles with special reference to energy flows, trophic relationships, biogeochemical cycling and interactions among different components within biotic community in an integrated and holistic manners citing original research outcomes of the long-term research studies undertaken in the riverine networks of South West Bengal, India. These detailed and in-depth analyses are expected to unravel the avenues not only for sustainable utilization of fresh water along with its resource bases from the riverine ecosystem but also to identify the causes of eco-degradation so that appropriate mitigation strategies can be chalked out. Besides, types and classificatory schemes for the rivers in the global perspectives have been dealt with in order to understand the mode of ecological processes linking up the biotic and abiotic structural components of the riverine ecosystem with the help of a considerable number of concepts, models, theories, and hypothesis [River continuum concept (RCC), Nutrient spiraling concept (NSC), Serial discontinuity concept (SDC), The flood pulse concept (FPC), Network dynamics hypothesis (NDH), Hyporheic corridor concept (HCC), Patch dynamics concept (PDC), Process domain concept (PrDC), Hydrosystems concept (FHC), Riverine ecosystem synthesis concept (RESC), Hydro-geomorphic patches, Functional Process Zones (FPZs), Environmental Flows, Equilibrium versus disequilibrium theories, Hierarchical patch dynamics model (HPD)], all of which have been put forward by different research scientists from the different corners of the globe.