Environmental modelling of Omerli catchment
area in Istanbul, Turkey using remote sensing
and GIS techniques
H. Gonca Coskun & Erhan Alparslan
Received: 21 November 2007 /Accepted: 14 April 2008 / Published online: 9 June 2008
# Springer Science + Business Media B.V. 2008
Abstract Omerli Reservoir is one of the major drink-
ing water reservoirs of Greater Metropolis Istanbul,
providing 40% of the overall water demand. Istanbul
where is one of the greatest metropolitan areas of the
world with a population over 10 million and a rate of
population increase about twice that of Turkey. As a
result of population growth and industrial develop-
ment, Omerli watershed is highly affected by the
wastewater discharges from the residential areas and
industrial plants. The main objective of this study is to
investigate the temporal assessment of the land-use/
cover of the Omerli Watershed and the water quality
changes in the Reservoir. It is not possible to ade-
quately control urbanization and other pollution
sources affecting the water quality. Responses of these
detrimental effects are due to rapidly increasing popu-
lation, unplanned and illegal housing, and irrelevant
industries at the protection zones of the watershed,
together with insufficient infrastructure. The study is
focused on the assessment of urbanization in relation to
land use and water quality using Remote Sensing (RS)
and Geographic Information Systems (GIS) techniques
for all the four protection zones of the Reservoir and a
time variant analyzing model is obtained. IRS-1C LISS
and IRS-1C PAN, LANDSAT-5 TM satellite data of
1997, 1998, 2000, 2001 and 2006 are analyzed by con-
firmation through the ground truth data. RS data have
been transferred into UTM coordinate system and image
enhancement and classification techniques were used.
Raster data were converted to vector data that belongs to
study area to analyze in GIS for the purpose of planning
and decision-making on protected watersheds.
Keywords Remote Sensing . Geographic Information
System . Land-use .Water quality . Drinking water .
Satellite image maps .Water resources management
Abbreviations
DIE State Statistics Institute
ERDAS US Image Processing Software
Developer Company
GIS Geographic Information Systems
HIS hue intensity saturation
IRS Indian Remote Sensing Satellite
ISKI Istanbul Water and Sewerage
Administration
Landsat US Remote Sensing Satellite
LISS multispectral sensor of IRS
Map Info US GIS software Developer Company
Netcad a Turkish GIS software developer
company
Environ Monit Assess (2009) 153:323–332
DOI 10.1007/s10661-008-0358-7
H. G. Coskun
Department of Remote Sensing,
Faculty of Civil Engineering,
ITU, Istanbul Technical University,
Maslak, Istanbul, Turkey
E. Alparslan (*)
Scientific and Technological Research Council
of Turkey Marmara Research Center,
Gebze, Turkey
e-mail: Erhan.Alparslan@mam.gov.tr

PAN panchromatic sensor of IRS
RMSE root mean square error
RS remote sensing
SIM Satellite Image Map
TM Thematic Mapper
TWPCR Turkish Water Pollution Control
Federation
UTM Universal Transverse Mercator
Introduction
Istanbul Metropolis has the highest population in
Turkey. Latest Demography World News from the
most comprehensive global news network stated that
Istanbul’s current population is 12,249,536 as of 30
November 2007 (DWN 2007). As a result of popu-
lation explosion in the recent years, residential areas
have extremely expanded beyond the planned urbani-
zation program, and unfortunately, illegal housing
becomes a common concern. It is obvious that urbani-
zation, either legal or illegal, consumes the vast agri-
cultural land and other green areas leading to
deterioration of the environment. Such a huge popula-
tion causes some administrative, social and economical
problems in Istanbul, together with pollution of surface
water bodies. In order to control and monitor the water
quality, routine field studies are necessary. However,
these inventories done with the classical methods are not
sufficient enough compared to remote sensing (RS) and
Geographical Information Systems (GIS) techniques as
they are used to determine and update information on
pollution loads and land use changes in the watersheds
and concerning water quality (Brivio et al. 2001).
The RS technique has a high potential for such a goal
(Hua et al. 2004; Vignolo et al. 2006; Chen et al. 2007).
Passive optical sensors from satellites can measure
the amount of solar radiation at various wavelengths
reflected by surface water, which can be correlated to
water quality parameters (e.g. total suspended solids,
chlorophyll a concentrations; Hellwegera et al. 2004;
Wang et al. 2004). In order to ensure a clean water
supply to the cities, a technique needs to be developed
which can be used to obtain reliable data, permitting an
assessment of water quality in support of the manage-
ment of water resources (Hua et al. 2004).
When solar incident energy on the water surface is
not specularly reflected, it is refracted downwards at the
water surface and is also affected by absorption and
scattering. Reflectance and backscattering are not only
a function of the properties of the present sediments at
water, but also dependent e.g. on biological constituents
such as phytoplankton. Distinct spectral signatures
obtained from satellite observations correspond to water
bodies of different composition. Remotely sensed
satellite data must always be combined with ground
truth (in-situ) measurements to allow for an accurate and
unambiguous interpretation (Coskun et al. 2006).
Istanbul Metropolis has 8 surface water reservoirs
among which 6 are used as the main drinking water
supply reservoirs. The most important reservoir
regarding the water capacity is the Omerli Reservoir
located at the Asian side of the city, supplying 40% of
the overall drinking water demand of the mega city.
Irrigation, urbanization and other natural conditions
have influenced the water quality status in the Omerli
Reservoir. Its annual population increase rate of 4.6%
is twice the average of the country (Tanik et al. 2000).
In this paper, it is described how presently avail-
able satellite technologies can be used to conduct
basic and rapid assessments of coastal and drinking
water dams regions.
The main purpose of this study is to assess the
quality of this water body using RS and GIS tech-
nologies in support of operational management. The
water quality and water supply maintenance is under
control of Istanbul Water and Sewerage Administration
(abbreviated as ISKI in Turkish). RS and GIS tech-
niques are used to obtain rapid and reliable data for
better water quality monitoring. The resulting infor-
mation on temporal changes in urbanization and water
quality are presented in this research for the Ömerli
water catchment area. These results were obtained by
merging and image processing of different spectral
and spatial resolution data which are IRS-1C
LISS-III (1998, 2000), IRS-1C PAN (1998, 2000)
and Landsat-5 TM data for years 1997, 2001 and 2006.
The study area
Istanbul is one of the most populated metropolitan cities
of Europe, spreading over two continents with a
population of about 12 millions. One of the major
drinking water reservoirs of Istanbul is the Ömerli Lake,
located on the Asian side, as shown in Fig. 1. The
Ömerli surface area of the drainage basin is about 220×
106 m2. It provides 40% of the water demand of the
324 Environ Monit Assess (2009) 153:323–332