6. Geo-hydrological Perspectives of Riverine Flows

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