Riverine Ecology Volume 1

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.

Water, a chemical compound, exists in nature in three physical states: liquid, gas, and solids, and all these forms are useful to human beings. Water has become a widespread life-sustaining substance, comprising 50–90% of living materials and covering nearly three-fourths of the Earth’s surface. All living organisms are composed mainly of water, the prime medium of life on earth and those of rivers are partly or wholly immersed in water. Life evolved in water, with water, and with the physical and chemical characters of natural water, and this balance is necessary. The global distribution of water is irregular. Some regions have plenty and others have shortages. The availability of liquid water depends on a reserve of inland waters, characterized by waters in lakes, rivers, reservoirs, wetlands, and groundwater. Water like other substances, expands when frozen, and help ice to float on the surfaces of the freshwater bodies. Cohesion of internal molecular constituents gives rise to another physical property of water, surface tension, which allows water organisms to traverse on the surface of the water. Water being the most essential and integral part of the lives and livelihoods of human beings for food, health, energy, and environment needs proper management in order to achieve sustainable eco-development. The water being a renewable natural resource will never “run out” the availability and variability of water impose the greatest impact on all-round development of a nation. Almost all rivers from a large country like India along with several other regions of the world have been identified as water-stressed rivers because of cumulative impacts of water abstractions, and environmental perturbations out of deforestation, global climatic changes, etc. Although life originated in water, it is really challenging for the aquatic organisms to adjust and survive in the ever-changing aquatic realm which appears to be not only unstable but hostile too as this aquatic environment is governed by unfamiliar rules of cold, wave-swept seacoasts, torrential mountain streams, and rivers, also by the very turbulent waters at the confluence of rivers with the sea. The living organisms of aquatic environments and their bioecological activities are very dependent on the prevailing ecological factors, both living and nonliving in the temporal and spatial scales. The unique physical and chemical characteristics of water and their interaction define the different aquatic environments and constrain the evolution of organisms that inhabit them.

In view of the above, this chapter mostly highlights different properties of water which have made water as the most unique chemical entity of the world. Besides, the mutual interactions among varied properties of water with the physical processes of river ecosystem and vice versa have been taken care of. In view of the problems of nonavailability of water, comments have been put forward to point out basic guidelines for water management.

Application of the knowledge derived from the scientific discipline, ecology and the relevant ecological principles, hypothesis, theories, and methods relating to this subject, is not only to address the intricate relationships among different structural components of mother earth with all its ecosystems but also to scrutinize the cause and effect of human-mediated ecological threats to environment and finally to develop solutions to all those environmental perturbations.

Achieving this target is thought to be possible only by adhering to the basic ecological thoughts and principles on a harmonized interaction between people and nature by making a balance in between resource harvesting and also sustainability of the ecosystem. Several research studies have unearthed pertinent information of the human actions on the environment and biological responses, to chalk out systematic and strategic eco-management strategies for eco-remediation followed by ecorestoration of eco-degraded environmental sectors and also to attach importance on decision-making processes that regulate human activities.

Awareness, especially towards riverine ecology and ecological perturbations, have been developed and proper actions are being taken where habitats are becoming fragmented, ecologically altered, eco-degraded, and reduced worldwide, at steady rates and scales. The diversity and populations of biotic components within this landscape of this world have been declining in numbers and becoming genetically eroded.

Integration of several interdisciplinary research outcomes for undertaking systemic and strategic conservation planning and efforts still requires additional thoughts to make the venture more effective in the present era. Sustainable eco-management of the resilient ecosystems is in need of maintaining the balance in the eco-dynamics of the ecosystems over time adhering more on to the operating principles of the ecology in order to meet the expectation of the human society in achieving ecologically healthy environment.

In such context, this chapter has been written to acquaint the readers on basics of subject ecology and their applicability towards eco-management of river’s ecosystem at global, national, and regional scales.

All the essential and major biochemical elements (carbon (C), nitrogen (N), oxygen, phosphorus (P), sulfur (S), etc.) of life tend to circulate among different structural components of ecosphere obeying the rules and principles of ecology following characteristic pathways of to-and-fro movements in between environment and organisms. Origins, behaviors, association, and movement of all those elements maintain the stability of any ecosystem functioning.

Two such ecological processes dispensing with exchange, transfer, and cycling of materials are: (i) Trophic interactions among different biological components and (ii) Biogeochemical cycle facilitating the cyclical movements of major nonbiological elements of nature from the environment to biological organisms and back to environment following characteristic pathways, on which functioning of ecosystems entirely depend. Similar cyclical movement of these inorganic elements and compounds through the biological components and processes is designated as nutrient cycling. All those interactions are concerned to maintain the biogeochemistry of the earth and living world putting more emphasis on the exchange of elements among different components of Earth’s crust, its atmosphere, oceans, rivers, and other water bodies along with their living organisms.

This chapter has dealt with these ecological processes in respect of riverine and its adjoining ecosystems as the ecological health of rivers are entirely dependent on them. Growth and reproduction being the most important among the obvious characteristics of life require the basic chemicals ingradients from which new and diversified cellular materials are build up, which in turn provide energy in order to drive the life processes so that harnessing and distributing this energy is taken place. Baseline information and knowledge pertaining to the underlying ecological principles of these ecological processes have appeared to be instrumental of harvesting more ecological services, chalking out proper conservation measures and ensuring sustainability.

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.

In order to address the water–sediment interactions in the fluvial system, different subjects have emerged as hydrogeology, hydrology, eco-hydrology, etc., during the different phases of last century mostly utilizing the knowledge of earth science supplemented by mathematical ones. However, focus on interdisciplinary and multidisciplinary research and application has been in practice to address multidimensional problems pertaining to the ecology/geomorphology/hydrogeology of any fluvial landscape, especially rivers and streams during the last couple of decades which has brought so-called distant subjects closer to one another. Conceptualizing the functioning of a river or a stream has been attempted in different angles and perspectives by an engineer, or a geomorphologist or an ecologist giving due emphasis on their own fields of expertise.

Although the definitions of ecology and hydrology sound very similar, they differ on both conceptual and application perspectives as the subject ecology deals with the interrelationships among organisms in respect of their environments while the hydrology refers to the study of the interactions of several structural components of water environment emphasizing more on the hydrological cycle. In general, ecology represents a more descriptive and experimental science whereas hydrology is more predictive and analytical. Hydrogeology is also an interdisciplinary approach for studying the documentation of water resources, pollution studies, and environmental management. In view of ever-increasing demand of integrated river basin management, combining of hydrogeology with the issues such as river basin and watershed management, climate change, water-soil interactions, etc., has been increased which are now being addressed adhering to the scientific principles pertaining to hydrogeology giving more emphasis on the importance of sources, volume, mode of recharging, and protection of groundwater as a finite and vulnerable resource.

Considering the ecological goods and services rendered by the rivers, environmental researchers and planners are very much concerned in generating baseline information in the fields of the geohydrology and fluid mechanics through holistic ecomanagement of rivers. Besides, the impacts of water and its water balance pathways, water conservation and pollution abatement have become parts and parcels in today’s life of human beings in terms of ecology and economy. For this reason, environmental hydrologists or hydrogeologists should be familiar with the science of hydrology which can be defined as the ecological study of the water and associated components and processes. Three districts of South West Bengal, India, viz., Midnapore (West), Bankura, and Purulia, topographically possess the high lands of lateritic uplands (100–300 m) and hillocks (300–500 m) which occupy a large portion of geomorphic surfaces of these districts. The land resources of these areas are activated by riverine networks comprising of five major rivers, viz., Subarnarekha, Kansai, Shilabati Dwarakeswar, and Rupnarayan, and also some tributaries like Kaleghai, and many minor streams like Dulung, Kumari, Parang, etc. In this drought-prone part of India, most of the rainwaters (>1500 mm) are discharged into the Hooghly estuary and the Bay of Bengal through the riverine runoff, and very little amount of surface water is recharged into groundwater storage.

Moreover, continuation of drought and declining of annual rainfall over the years, especially in view of the global warming, have resulted in decrease of subsurface water flows that supported traditional land-use practices along the riverine tracts. This chapter deals with the pros and cons of sustainable water budgeting in such tropical environmental setups integrating meteorology, geomorphology, resource availability (living/nonliving), land-use patterns, and people’s dependence on the existing ecological goods and services and hypotheses of the consequences on implementation of recommendations based on ground truth verification survey.

Relationship between surface, subsurface, and groundwater flows has been highlighted taking into consideration the coefficient of permeability, porosity, grain size distribution, water storage coefficient, and recharge dynamics based on extensive drilling operations in the selected zones on riverbed and analysis of satellite imageries. Artificial recharging of the groundwater as well as the surface water storage through check dams and excavation of tanks; construction of horizontal wells and surface dykes, rainwater harvesting; the microcatchment-wise water assessment; and introduction of dry crop practices in place of traditional wet crops are being recommended based on the baseline information

Several inland water bodies such as lakes, streams, and rivers have visible structures based on their morphometry, drainage basins, geomorphology, and physicochemical parameters (pH, temperature, dissolved oxygen, alkalinity, etc.). All those ecological variables are regulated by several other macroclimatic processes such as precipitation, intensity of sunlight, wind flow, waves, and currents resulting in diurnal and seasonal variations. This chapter has dealt with characteristics and significance of major ecological parameters of riverine system citing case studies of the riverine networks from South West Bengal, India, alongside highlighting the water qualities of a couple of other major rivers in India, and their roles and influence in determining ecosystem health of freshwater systems in general and physicochemical parameters of rivers in particular.

Large rivers being the lifeline of human beings have been serving for millennia as sources of food, water, and energy, easy means of transportation, as sinks for an array of pollutants, as a place for religious activities, and as objects for the artistic and aesthetic interest. Despite the importance of large rivers, research studies on the eco-functionality of large rivers in view of the ongoing ecological perturbations mostly caused by the direct or indirect intervention of human beings is limited. An integrative and holistic approach has been made in writing up this book in order to arrive at an understanding of the mutual interactive relationships between aquatic and terrestrial landscapes through the exchange of both biotic and abiotic components. Besides, geohydrological assessment of the riverine ecosystems mostly emphasized on the geomorphological and hydro-biological problems along the ecological gradients (geological processes coupled with climatic variability, flow patterns, depth and volume of water, channel slope, stream discharge, sediment input, sediment transport, sediment caliber, characteristics of banks and valley slope, and the resultant biological organization) in the temporal and spatial scales by combining relevant inputs of the different disciplines of geomorphology, hydrology, and ecology at different levels of organization and associated scales have been dealt with. The diversity and heterogeneity of the habitats considerably influence the oxygen balance of river systems, both by enhancing exchange with the air and through biological activity (riffles, levees, floodplains, etc.) which promote aeration of the water through turbulent and diffusion processes, whereas profuse growth of macrophytes produce oxygen through photosynthesis.

Several concepts, theories, hypothesis, and models have been discussed in order to unravel the mysteries of the intricate relationships among different structural components of the riverine ecosystem which appear to be the driving force behind the sustenance and function of the riverine ecosystem. Among all, the river-continuum concept, after its origin from the studies on stable and unperturbed streams of north-temperate regions surrounded by forested watersheds, advocates that the changing gradient of physical forces across the length of the river enables the development of longitudinal structure of forested river systems enjoying a continuum of morphological and hydrological features from the headwaters to the mouth. The benchmark to assess and measure the longitudinal axis of the river-continuum concept, another striking issue in the realm of river studies has emerged in order to ecologically characterize different forms of rivers, streams and tributaries. In addition, Flood-Pulse Concept (FPC) enabled to understand the eco-dynamics of majority of large floodplain rivers which experience and enjoy the benefits of transportation of nutrients and organic matter in the floodplain during the time of flood and thereby supporting the higher abundance and diversity of river life.

Besides, several other theories and models proposed for explaining the biocomplexity across spatiotemporal scales in river networks emphasize and address upstream-downstream changes in respect of the sources and allocation of energy, nutrient spiraling, river network and landscape interactions, and serial discontinuity. Besides, eco-geo-physical processes involving hierarchical habitat templates and tending to operate at mid to fine scales in order to shape and structure flow regime, environmental perturbations, inshore retention, patch dynamics, river discontinua, and hydraulics within streams and rivers. In addition, physical hydrogeomorphic patches, serving as a template for ecological “Functional Process Zones” (FPZs), often are used to depict the mode of functioning of ecosystem in variable ecological conditions. The book has also attempted to protect the ecological significance of river-floodplain wetlands, groundwater-surface water interactions, ecomonitoring of water and soil quality parameters, quantification of ecosystem flows, anthropogenic intervention in the temporal and spatial scales, etc. which all have appeared to be prerequisites for the sustainable management of river ecosystem.