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Insights into riverscape dynamics with the hydrological, ecological and social
dimensions for water sustenance
T.V. Ramachandra1,2,3,*, S. Vinay1,4,
S.Bharath1, M.D. Subhash Chandran1
and Bharath H.Aithal1,4
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1Energy and Wetlands Research Group, Centre for Ecological Sciences [CES],
3Centre for infrastructure, Sustainable Transportation and Urban Planning [CiSTUP],
Indian Institute of Science, Bangalore – 560012, India.
*Corresponding author: tvr@iisc.ac.in, emram.ces@courses.iisc.ac.in
Study area & Methods
Uttara Kannada district located in the Central Western Ghats
(Fig 1) lies between latitude 13.769o and
15.732o N, and longitude 74.124o and
75.169o E covering approximately an area of
10,291 km2. The district extends N-S to a maximum
of 180 km and W-E to a maximum width of 110 km. Arabian Sea
borders it on the West creating a long, continuous, narrow,
coastline of 120 km. The district has varied geographical
features with thick forests, perennial rivers and abundant
flora and fauna. The district falls in 3 agro-climatic zones
– i) the coastal region, which has a hot humid climate
(rainfall varies between 3000-4500 mm, ii) the Sahyadri
interior region of the Western Ghats (500-1000 m elevation),
which is very humid in the south (rainfall varies between
4000-5500 mm) and iii) the plains which are regions of
transition that are drier (rainfall varies between 1500-2000
mm). The district has four major rivers namely, Kali (with a
catchment of 5085 sq.km.); Gangavali (Bedthi) with a
catchment of 3935 sq.km; Aghanashini (1448 sq.km.) and
Sharavati (3042 sq.km.). A relatively small river
Venkatapura with a catchment of 460 sq.km. and innumerable
creeks is also found33. They all discharge into
the Arabian Sea. These rivers are under various levels of
stress like regulation of water flows for hydro-electric
power generation (Kali and Sharavati Rivers), irrigation for
vast expanse of horticultural and monoculture plantations.
Upper reaches of Kali, Gangavali, Sharavati have large
number of interconnected lake systems (lentic ecosystems),
while the Ghats are dominated by dense drainage network.
Figure 1: Study Area
Gangavali catchment has the highest population (1.01 Million)
followed by Kali (0.54 Million), Sharavati (0.35 Million),
Aghanashini (0.24 Million), and Venkatapura (0.17 Million)
as of 201834. Population growth rate between 2001
and 2011 was highest in Gangavali (15.3%), followed by
Venkatapura (14.5%) and the least in Kali (8.9%).
Venkatapura has the highest population density (377
persons/sq.km), followed by Gangavali (258 persons/sq.km)
and the lowest in Kali (107 persons per sq.km).
Topographically, the coastal zone (in the west) and plain
lands (towards the east) are flat with slopes (ranging up to
5 degrees); the transition zones between the coast and Ghats
and the transition zones between Ghats and plain lands have
slopes up to 15 degrees. The Ghats have slopes > 15
degrees35,36. Interconnected lake systems in the
plains were created (during the Kadamba (525 BCE - 345 BCE)
and Hoysala (1063 AD - 1353 AD) periods) to cater to
domestic and irrigation water requirements. Current research
is based on the field ecological research carried out to
understand the linkages of the landscape dynamics with the
eco-hydrological footprints in the four major west flowing
rivers of Uttara Kannada district.
Data and Method
Figure 2 describes the method adopted for assessing the role
of landscape dynamics with the ecological, hydrological and
social dimensions in lotic ecosystems. This involved (i)
assessment of spatio-temporal patterns of land cover using
multi-resolution remote sensing data, (ii) assessment of
eco-hydrological footprint through the analyses of the
rainfall patterns, hydrologic regime with the demand of
biotic components.
- Data Collection: Optical Satellite data from
Landsat 1 MSS (1973), Landsat 8 OLI (2018) and
Topographic data from SRTM were downloaded from the USGS37.
GPS based field observations, Survey of India
Topographic Maps36,38, French Institute
Maps39, virtual earth data such as Google
Earth40, NRSC Bhuvan41 were used
to geo-rectify (corrections for geometric shifts) and
classify the Remote Sensing data to land use categories.
Long term meteorological data such as temperature,
rainfall, solar radiation were collected from the KSNDMC
Karnataka42, Directorate of Economics and
Statistics Karnataka43, India Meteorological
Department44, Food and Agriculture
Organisation45. Population census for the
year 2011 and 2001 were collected from the Census of
India 34. Livestock data such as Census,
water requirement were collected from Directorate of
Economics and Statistics 43, District at a
Glance 46, and through public interviews.
Agriculture data such as various crops grown, cropping
pattern, water requirement at different growth phases
were collected from District at a Glance46,
public interviews, online portals such as Raitamitra,
iKisan, Tamil Nadu Agriculture University, etc.47–50
and other published literature. Field investigations in
the select stream catchments were carried out for 24
months to understand the intra and inter variability of
hydrologic regime in Central Western Ghats and the
information for ungauged streams were compiled from
published literatures. Steams were chosen based on the
land cover in the catchment as (i) dominated by
vegetation of native species to an extent > 60%, (ii)
dominated by vegetation of monoculture species, (iii)
vegetation cover in the catchment < 35%. This helped
in understanding the natural flow regime of surface
run-off, sub-surface flows and infiltration dynamics to
estimate the minimum flow to sustain aquatic life (also
known as environmental flow or ecological flow)51–55
for the rivers in central Western Ghats. Species
composition and distribution pertaining to flora and
fauna were mapped through quadrat based transects in the
field (representative regions across different forest
types), published
literatures60,61,70,71,62–69, Biodiversity
Portal56–58, Forest department
records59 and species distribution database
was created considering their occurrence26,56–59,80–84,
habitat (villages, transects, GPS coordinates, forest
ranges, etc.), conservation status85,
etc. The spatial overlay of biodiversity
information with the hydrologic regime provided valuable
insights of hydrologic, ecological and biodiversity
linkages with the land use dynamics across the four
river basins with the various levels of anthropogenic
stress.
Figure 2: Method adopted for the analyses of
eco-hydrological footprint with forest transitions
- Land use dynamics: Satellite data for the year
1973 and 2018 were resampled to 30 m resolution in order
to maintain the same spatial resolution72.
Training sites were developed based on field information
(collected using pre -calibrated handheld GPS) and
secondary data sources such as the SOI topographic maps,
Vegetation Map published by French Institute,
Pondicherry and virtual globe datasets. The
pre-processed satellite data was classified using
Supervised Gaussian Maximum Likelihood classification
technique 73. Of the collected data, 60% of
field data (training data) was used for classification,
while 40% for accuracy assessment74.
Additional training sets were used and the process was
repeated when classification accuracy was less than 80%.
Land use of 1973 and 2018 were compared for assessing
spatiotemporal patterns of landscape dynamics.
- Forests: Spatial distribution of forests was
extracted from the land use information of 1973 and
2018. The binary map of forest and non-forest areas were
used for fragmentation analysis75 which also
emphasizes its relationship with
biodiversity76,77, climate
change78, etc. Forest fragmentation
at pixel level was estimated based on earlier proven
protocol79 by computing Pf (the
ratio of pixels that are forested to the total non-water
pixels in the window) and Pff (the proportion
of all adjacent (cardinal directions only) pixel pairs
that include at least one forest pixel, for which both
pixels are forested) indicators. Based on the level of
fragmentation, forests were classified as interior
(intact or contiguous) forests, patch, transition, edge
and perforated forests.
- Species distribution and water quality: Water
quality of the samples collated from the field
experiments at various locations in each of the river
basins and also from published literatures68 were
analysed based on the various physical, chemical and
biological parameters. The surface water standards were
used to define the water quality status as highly
polluted, polluted and non-polluted68.
- Temperature: Spatial patterns of temperature
variations were computed based on mono window
algorithm86,87, using red, NIR and Thermal IR
(Band 10) Landsat 8 data for the year 2018.
- Eco-Hydrological Footprint: Eco-hydrological
footprint of a river basin is computed through
assessment of hydrologic regime for sustaining vital
ecological functions and appropriation of water by
biotic components (including humans).
Biotic demand included societal, terrestrial ecosystem
demand and aquatic ecosystem demand (minimum flow required
to sustain aquatic biotic components also known as
ecological flow). Societal demands include water requirement
for agriculture, horticulture, domestic and livestock
sectors88–90. Transpiration and evaporation from
the forests only, have been accounted for under the
terrestrial water demand. Minimum flows (E-flows) to be
maintained to sustain aquatic life was computed based on
field observations53–55,91,92, which shows about
25% of annual flow needs to be maintained as natural flow
regime during lean seasons to maintain the ecological
integrity.
Natural water catering the societal and environmental needs
depends on rainfall, land use, soil and lithological
characteristics of the catchment (or watershed). Water
supply in the catchments was considered as a function of
over land flows, subsurface (vadose and saturated zones)
flows (pipe flow and base flow). Overland flow was monitored
for 18 months at 12 locations across the river basins.
Overland flows were estimated sub-catchment wise for each
river basin using the rational method93 and the
catchment coefficients for varied land uses were based on
field observations. Ground water recharge was estimated
using Krishna Rao equation which holds good for
Karnataka51. Subsurface flow was estimated based
on the specific yield of rocks and porosity of
soils88. Monthly supply (based on hydrologic
regime assessment), were compared with the biotic demands,
in order to understand the eco-hydrological status in every
sub-catchment; ratio < 1 indicates deficit, while ratio
> 1 indicates surplus or sufficient situation.
- Eco-Hydrology and landscape structure
linkages: Spatial variability of forests,
fragmentation status of forests, temperature, species
distribution and water quality were compared spatially
with the eco-hydrological status to understand the
linkages of these variables with water sustenance.
Citation :Ramachandra T. V., Vinay S., Bharath S., Subash Chandran M. D. and Bharath H. Aithal, 2020. Insights into riverscape dynamics with the hydrological, ecological and social dimensions for water sustenance, Current Science, Vol. 118(9): 1379-1393
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Dr. T.V. Ramachandra
Centre for Sustainable Technologies, Centre for infrastructure,
Sustainable Transportation and Urban Planning (C iSTUP),
Energy & Wetlands Research Group, Centre for Ecological Sciences, Indian
Institute of Science, Bangalore – 560 012, INDIA.
E-mail : tvr@iisc.ac.in emram.ces@courses.iisc.ac.in
Tel: 91-080-22933099/23600985,
Fax: 91-080-23601428/23600085
Web: http://ces.iisc.ernet.in/energy
Citation:Ramachandra, T. V, Jefferey Sellers, Bharath,
H. A, Vinay, S
Ganesh Hegde
Energy & Wetlands Research Group,
Centre for Ecological Sciences, Indian Institute of Science, Bangalore – 560
012, INDIA.
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