Introduction to River Science

Applied River Science
Assignment – 01
(January 20, 2017)
“River System and River Science: Indian
Context”
An assignment submitted by
Mohammad Imran Khan
Integrated[B.Sc.(H) Geology]- M.Sc. Geology 6th Sem
Department of Geology
University of Delhi,
New Delhi, Delhi-11007
To
Dr. Vimal Singh
Department of Geology
University of Delhi,
New Delhi, Delhi-11007

‘one goes to rivers only for hints and half-truths … their facts are often crude until you have observed
them in many different ways and then absorbed and translated these’. ……..Burroughs (1886)
1. Introduction
 Rivers are the great shapers of terrestrial landscapes. Geomorphologist Luna Leopold once described rivers
as the gutters down which flow the ruins of continents (Leopold et al., 1964).
 River science is a rapidly developing interdisciplinary field of study focusing on interactions between the
physical, chemical and biological components within riverine landscapes and how they influence and are
influenced by human activities. These interactions are studied at multiple scales within both the riverscape
(river channels, partially isolated backwaters and riparian zones) and adjacent floodscape (isolated oxbows,
floodplain lakes, wetlands and periodically inundated flat lands).
 According to the National Academy of Science, River Science is the study of how hydrological, geological,
chemical, and ecological processes interact to influence the form and dynamics of riverine systems and
how riverine ecosystems in turn influence these processes across multiple spatial and temporal scales (NAS
2007).
 Major drivers and challenges in river science include ecological restoration, removal of dams and relicensing
of hydropower facilities, water allocation, invasive species, climatic variability, urbanization and other land
use changes, and water quality (NAS 2007).
 The modern era of river science is a challenging one because climate, landscapes and societies are changing
at an ever-increasing rate. Thus, our use, perceptions and values related to riverine landscapes are also
changing.
 In India, most river management programmes have been primarily targeted towards water allocation and
water quality and there has been no consolidated effort towards river restoration from an ecological
perspective.
 Even after spending more than Rs. 2,700 crores from 1950 to 1990, the flood problem and flood affected
area have increased considerably in India (Agarwal and Narain 1996).
2. Scale and Hierarchy
 Scale is the most important parameter in river studies, as observations, approach and methodology and
causality in river studies varies with change in scale.
 For example, at basin scale, the basin shape and drainage network are important parameters, which are
governed by basin geology and climatic conditions. A basin may be consisting of various landscapes, which
will be characterized by different set of surface processes. These processes are governed by slope, rainfall,
vegetation and riverine fluxes. In a given landscape, river reaches are characterized by valley, floodplain and
association of different bars in the channel, which are in turn controlled by variation in stream power and
sediment supply. Further, each bar is characterized by variation in grain size in response to site-scale
channel hydraulics and processes. Grain size variations and bar morphology are important input parameters
for river ecology, as they characterize habitats for different biota.
 These various landforms and geomorphic processes operating at different scales can be linked in a
hierarchical model.

 The hierarchical integration is currently leading to the development of new landscape evolution models in
fluvial systems. These landscape evolutionary models have been developed on the basis of knowledge
available from analysis of a single grain dynamics in a river system.
3. Eco-Geomorphology
 Eco-geomorphology represents an integration of river ecology, hydrology and fluvial geomorphology and
builds upon eco-hydrology which aimed to bring hydrologists and ecologists together to analyse and predict
the flow regime and the ecological status of rivers.
 A landform may respond differently for the same forcing mechanism, and this is governed by landform
sensitivity.
 Sensitivity is defined as the ‘propensity for the landscape to undergo a recognizable change in response to
changes in the external variables controlling the geomorphic system’.
4. Connectivity
 Connectivity is defined as the way in which different landscape compartments fit together in the catchment.
 Connectivity, sometimes referred to as coupling, is multi-faceted. It includes hydrologic connectivity, river
connectivity, sediment connectivity, biological connectivity, landscape connectivity, structural connectivity
and functional connectivity.
 Connectivity structure in a river system can be studied in four dimensions namely, longitudinal, lateral,
vertical and temporal connectivity.
 A reach-to-reach connectivity presents an example for longitudinal connectivity. Channel-hillslope or
channel-floodplain connectivity is defined as lateral connectivity while groundwater-surface water
connectivity represents vertical connectivity.
 The nature of the connectivity can show significant spatial and temporal variation.
 A basin may be ‘connected’ in one dimension but may be ‘disconnected’ in other dimensions. Further, in a
given basin, the nature of connectivity in different dimension varies downstream.
 The nature of connectivity will have a significant influence on riverine fluxes, which further governs
morphology, habitats and distribution of biota.
5. Environmental Flow (E-Flow)
 There is an increasing awareness of allocation of water for human use as well as to continue functioning and
maintenance of biodiversity.
 Water which is allocated and made available for maintaining ecological processes in a desirable state is
referred to as the in-stream flow requirement or environmental flows (E-flow).
 Environmental Flows is the provision of water within rivers and ground water systems to maintain
downstream ecosystems and their benefits, where the river and underground system is subject to
competitive uses and flow regulation. ………… 3rd World Water Forum(2003), Kyoto
 The correct perspective of the environmental flow (IUCN 2003) would require the maintenance of a flow
pattern (the annual hydrograph) and sediment supply in the rivers in such a manner that the ecosystem
services would continue to function in a moderated flow even in a partially degraded state.

6. River Management and River Health
 River management strategies all around the world have moved from the engineering dominated command
and control approach to an integrated ecosystem based approach that relies on the synthesis of
hydrological, geomorphological and ecological data.
 The command and control approach is a deterministic approach designed for a single purpose and focused
on, ‘effects’. Such approaches typically address the problems at site or reach specific scales without serious
considerations of upstream and downstream consequences and related connectivity issues. Even though
provisions for ecosystem protection were made, they were minor issues and were never implemented fully.
 The ecosystem based approach is a cross-disciplinary, holistic approach, focused on ‘causes’ and applied at
catchment to reach scale. This is a probabilistic approach that recognizes uncertainty and complexity in the
system.
 The human relationship to any given river system is a key factor for ensuring healthier river futures, and the
importance of place in designing rehabilitation initiatives cannot therefore be underestimated.
7. Impacts of Future Climate Change and Challenges Ahead
 In addition to the increased demand due to growing population, the freshwater supply in future will also be
influenced by climate change impacts such as monsoon variability and retreating glaciers.
 Analysis of the daily rainfall for the last five decades has shown a significant rising trend in frequency and
magnitude of extreme rain events although the monsoon system as a whole has remained stable.
 Gosain et al. (2011) suggest that most large river basins except the Brahmaputra and the Cauvery will have
an increased precipitation at the basin level in a GHG scenario and there will be an associated increase in
water yield in these basins for the next 20 years or so.
 However, the situation changes drastically when the modelling period changes to another 50 years (2080s)
under which ET increases by 40% for a majority of the basins due to increase in temperature and enhanced
precipitation.
 In the Nepal Himalaya, the glaciers are reported to be retreating at rates of 10–60 m per year and many
small glaciers (<0.2 km2) have already disappeared.
 Results from the Normalized Melt Index(NMI) analysis suggest that the glacier melt water is extremely
important in the Indus Basin(NMI = 1.5) whereas it is reasonably important for the Brahmaputra River (NMI =
0.27) but only plays a modest role for the Ganga River (NMI= 0.1).
8. River Science in the Indian Context
 The Indian sub-continent has several large river systems, defined generally on the basis of physical
parameters, namely channel length (>2,500 km) or basin area(800,000 km2).
 A large river system is a hierarchical entity, which is characterized by complex and nonlinear response due to
different stages of threshold, connectivity and equilibrium conditions in its smaller compartments.
 At present, the total annual flow availability from the rivers draining from the Himalaya as well as Peninsular
India is estimated to be about 1,870 km3/year out of which the Himalayan rivers constitute the major share
of about 1,180 km3/year.
 Out of the total available annual flow from rivers, the ‘utilizable’ flow has been assessed as about 690
km3/year and again about 50% of this (about 320 km3/year) comes from the Himalayan Rivers.
 The current estimates of total freshwater demand for the years 2025 and 2050 are 843 km3/year and 1,180
km3/year respectively. Expectedly, the demand for the irrigation sector is the highest (about 70%).

 Comparing this with the presently available resources (1,121 km3/year including 689 km3/year for surface
water and 432 km3/year for groundwater), it is clear that India would be close to stretching its limits to meet
the demands by the year 2050.
 A large programme on Ganga River Basin Management Plan (GRBMP) has been initiated by the Ministry of
Environment and Forests, Government of India which aims to provide a basic framework for developing a
river management plan based on five fundamental premises:
(1) river must continuously flow,
(2) river must have longitudinal and lateral connectivity,
(3) river must have adequate space for its various functions,
(4) river must function as an ecological entity, and
(5) river must be kept free from any kind of wastes.

Introduction to River Science

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