Abstract
Rivers and streams representing interfaces between varied forms of aquatic habitats and terrestrial landscape are being recognized as lifeline and inculcated to the core of human life. These lotic water bodies carry and transport all kind of materials of earth from land to sea via a network of aquatic systems (wetlands, flood plains, estuaries, etc.) maintaining interlinkages among different components (soil, water, air, and biodiversity) of the environment. A comprehensive knowledge on the physiography, bio-geo-chemistry, and hydrology of riverine networks along with their associated streams, rivulets, floodplains, and wetlands in order to understand the roles of rivers as formidable driver in global biogeochemistry has become a prerequisite to identify and utilize the services of rivers in respect of freshwater supply, biodiversity development, and control of flood and erosion load.
The term physiography of rivers encompasses the origin, types, extent of regional and local distribution, climatic conditions, and relevant nomenclatures such as streams, riffles, pools, springs, and falls of rivers in an area. This chapter discusses on the characteristics and classification of freshwater rivers (permanent or intermittent), stream orders, basins, catchment, and watersheds, highlighting their relationships among the large and small rivers in the changing agroclimatic conditions.
Moreover, a holistic ecological assessment of rivers along with the streams cannot be completed unless the interactions with adjoining ecosystems and landscapes such as forests, wetlands, agriculture fields, and rural /semi-urban /urban settings are taken into consideration. Besides, several terminologies having some overlapping components are in the use to depict particular geomorphologic setups of riverine system. Explanation and justification of those terminologies have been taken care of. Different stream orders which focus on automated information of such orderings in riverine eco-region with regard to their flow patterns, erosion, and depositional characters have been highlighted.
This chapter also has stressed upon the inclusion of several theories, hypothesis, models, and scientific explanation put forward by different researchers on rivers, its ecology, functional roles, etc. Case studies pertaining to the physiography and interrelationships among different structural components of the two major riverine systems of South West Bengal, viz., Subarnarekha and Kansai, are presented so that a holistic assessment of the potential, prospect and problems of these rivers and river basins could be made. A brief but some salient points pertaining to the Indian rivers giving due emphasis on the mighty river, the Ganges, have also been included.