=Paper=
{{Paper
|id=Vol-1498/HAICTA_2015_paper21
|storemode=property
|title=Using ArcSWAT to Predict Discharge in Ungauge Torrents of Thasos Island
|pdfUrl=https://ceur-ws.org/Vol-1498/HAICTA_2015_paper21.pdf
|volume=Vol-1498
|dblpUrl=https://dblp.org/rec/conf/haicta/KoutalakisZEII15
}}
==Using ArcSWAT to Predict Discharge in Ungauge Torrents of Thasos Island==
https://ceur-ws.org/Vol-1498/HAICTA_2015_paper21.pdf
Using ArcSWAT to Predict Discharge in Ungauge
Torrents of Thasos Island
Paschalis Koutalakis1, George N. Zaimes2, Dimitrios Emmanouloudis3, Konstantinos
Ioannou4 and Valasia Iakovoglou5
1
Labaratory of Management and Control of Mountainous Waters (Lab of MCMW),
Department of Forestry and Natural Environment Management, Eastern Macedonia and
Thrace Institute of Technology (EMaTTECH), 1st km Drama, Mikrohoriou, Drama, Greece
66100, e-mail: koutalakis_p@yahoo.gr
2
Labaratory of Management and Control of Mountainous Waters (Lab of MCMW),
Department of Forestry and Natural Environment Management, Eastern Macedonia and
Thrace Institute of Technology (EMaTTECH), 1st km Drama, Mikrohoriou, Drama, Greece
66100, e-mail: zaimesgeorge@gmail.com
3
Labaratory of Management and Control of Mountainous Waters (Lab of MCMW),
Department of Forestry and Natural Environment Management, Eastern Macedonia and
Thrace Institute of Technology (EMaTTECH), 1st km Drama, Mikrohoriou, Drama, Greece
66100, e-mail: demmano@teikav.edu.gr
4
Labaratory of Management and Control of Mountainous Waters (Lab of MCMW),
Department of Forestry and Natural Environment Management, Eastern Macedonia and
Thrace Institute of Technology (EMaTTECH), 1st km Drama, Mikrohoriou, Drama, Greece
66100, e-mail: ioannou.konstantinos@gmail.com
5
Labaratory of Management and Control of Mountainous Waters (Lab of MCMW),
Department of Forestry and Natural Environment Management, Eastern Macedonia and
Thrace Institute of Technology (EMaTTECH), 1st km Drama, Mikrohoriou, Drama, Greece
66100
Abstract. Water resources management requires the knowledge of the
environmental conditions and hydrologic processes. The development of
Geographic Information Systems (GIS) has allowed the use of spatially and
physically based hydrologic models in order to simulate the hydrology in a
complicated natural system. It is very important to use such tools especially in
regions with limited available data. In this context, the objective of this study
is to model the hydrologic conditions in the island of Thasos by using the Soil
and Water Assessment Tool (SWAT) in a GIS environment. In order to
understand the hydrologic processes, it was required to predict the water
balance of the island and simulate the discharges of its ungauged torrents. The
outputs of the model revealed the simulated values of the hydrologic phases,
the torrent discharges and a map that identifies the watersheds with the highest
discharges. The results could be used by experts and by every interested
authority in order to manage the surface stream water for various purposes,
such as suppression of forest fires.
Keywords: hydrologic modeling, water balance, GIS, water management
154
1 Introduction
Surface water and especially stream and torrent flow is important for environmental
scopes including the sustainability of living organisms and habitats in and adjacent to
the stream and torrent but also for human purposes (Arthurton et al., 2007). The
proper management can combine these two scopes, mitigate any possible negative
influences on the environment but also utilize the stream water that is lost in larger
water bodies. Potential water beneficial uses could include agricultural irrigation,
production of hydro-electric energy, municipality water supply and wildfire
suppression.
It is essential to determine the stream/torrent discharge in order to meet the above
objectives. A quick, widely and frequently used technique, but also efficient
application is to use hydrologic models (Singh and Woolhiser, 2002). This study
describes the implementation of Soil and Water Assessment Tool (SWAT) in order
to predict the torrent discharges and propose the necessary management plans to
utilize the water.
The study area is the island of Thasos, located in northern Greece that belongs to
Kavala Prefecture. It is the northernmost Greek island and the 12th largest by area.
The surface of the island occupies about 378 km² while the shape of the island is
almost rounded and the perimeter is approximately 102 km (Mallios et al., 2009).
The terrain is mountainous; while the highest peak is Ypsarion with an elevation of
1203 m. The climate of the island is characterized as Mediterranean (Vlachopoulou
and Emmanouloudis, 2014). All of the streams are characterized as intermittent or
ephemeral torrents because they do not flow year around and even the major torrents
(intermittent) have no flow during the summer.
2 Materials and Methods
2.1 SWAT Model Description
The SWAT model is a physically based, semi-distributed model Neitsch et al.,
2011). The model predicts the impact of land management practices on water,
sediment and agricultural chemical yields. It can accomplish these takes in large
complex basins with varying soils, land-use and management conditions over long
periods of time (Neitsch et al., 2011). SWAT processes are separated in two main
components. The first one is the land phase where the hydrologic cycle in a basin is
simulated based on the water balance equation (Equation 1):
(1)
155
where t is the simulation period, SWt is the soil water content after the simulation
period, SW0 is the soil water content at the beginning of the simulation period, and
Rday, Qsurf, ETday, wday and Qgw are daily values (in millimeters) for precipitation,
runoff, evapotranspiration, infiltration and return flow, respectively.
In the second phase the channel hydrology is simulated, more specifically the
loadings that are calculated earlier are routed through the stream network of the basin
(Neitsch et al., 2011). The spatial configuration of SWAT is performed by dividing
the watershed into sub-watersheds based on topography. These are further
subdivided into a series of hydrologic response units (HRU) based on unique soil,
land use and slope characteristics.
The major benefits of the model are that it is a free product, it is applicable with
the available data, it is documented well, it has good technical support through many
databases and assistance programs (Gassman et al., 2007) and it has good integration
with the Geographic Information Systems (GIS) through ArcSWAT (Winchell et al.,
2013).
2.1 SWAT Model Set Up
The data used in this study was the topographic map of Thasos that developed
based on the Military Geographic Service that had a scale of 1:50,000. This map was
used to create the Digital Elevation Model (DEM) in ArcGIS 10.1 by digitizing the
contour lines and the stream network (Figure 1.A.). The SWAT model requires the
DEM for the creation and delineation of watersheds. There is the possibility of
burning onto the hydrographic network for better results (Figure 1.B.). The next
process is to fill the sinks of the DEM and calculate the flow direction and flow
accumulation grids (Winchell et al., 2013). According to the properties of the DEM,
SWAT proposes a minimum threshold value which represents the area (in hectares)
for the establishment of the drainage area. In this study, the value of 100 hectares
was selected and the island of Thasos (entire basin) was divided in 145 smaller sub-
basins. Each sub-basin (or watershed) includes a stream (reach), an outlet and the
simulated extension of the stream based on the DEM (longest path).
156
Fig. 1. The study area of Thasos Island: a) The DEM and b) the delineated watersheds.
Most watersheds are typically not homogenous as they consist of different soils
and land-uses. As it was mentioned, SWAT can divide the watershed into smaller
hydrologic response units (HRU) that are unique combinations of soil type, land
cover and slope category (Arnold et al., 2012). SWAT created 2415 HRU considered
all soils, land cover types and slope classes. The slope was produced based on the
statistics of the DEM and it was divided into five slope classes: i) 0-10 %, ii) 10-20
%, iii) 20-30 %, iv) 30-50 % and v) >50 %.
The soil map was downloaded from the European Soil Portal and the Harmonized
World Soil Database Viewer 2012 that had a scale of 1:1,000,000. In addition, the
geological map was digitized and the geological parent material was considered and
combined in order to create the final soil map (Table 1).
Table 1. The geologic substrate categories of Thasos
Soil Category Geological Matter Coverage (%)
1 Transition Zone 42.49
2 Marbles 28.63
3 Gneiss 21.09
4 Sedimentary rocks 7.79
The CORINE 2000 vector files by European Environment Agency were acquired
in order to display the land-cover of the island and had a scale of 1:100,000. The land
cover of CORINE was reclassified to the categories of land cover that already exist
in the SWAT database (Table 2). All of these maps were geo-referenced in the Greek
157
Geodetic System (D_GGRS_1987). Finally, the weather data were obtained by a
meteorological station located in the city of Limenas. The data concerned monthly
precipitation and temperature that covered the period from 1975-1997 (Figure 2).
Table 2. The Corine 2000 land cover and the reclassification in the SWAT database.
Code Corine 2000 Code SWAT Database Coverage (%)
112 Discontinuous urban fabric URML Urban medium low density 0.57
121 Industrial or commercial units UCOM Urban commercial units 0.09
131 Mineral extraction sites UIDU Urban industrial units 0.48
211 Non-irrigated arable land AGRL Agricultural land Generic 0.06
223 Olives OLIV Olives 9.7
243 Land principally occupied by AGRR Agricultural land row crops 6.65
agriculture, with significant areas of
natural vegetation.
311 Broad-leaved forests FRSD Forest deciduous 0.25
312 Coniferous forests FRSE Forest evergreen 22.33
313 Mixed forests FRST Forest mixed 0.16
321 Natural grasslands PAST Pastures 17.45
323 Sclerophyllous vegetation SHRB Shrubland
324 Transitional woodland-shrub SHRB Shrubland 36.73
331 Beaches, dunes, sand BARR Barren areas 0.02
333 Sparsely vegetated areas BSVG Barren-sparsely vegetated areas
334 Burned areas BSVG Barren-sparsely vegetated areas 0.49
332 Barren rocks TUBG Bare ground 5.02
Fig. 2. The ombrothermic diagram of Limenas.
158
3 Results and Discussion
The simulated outputs were printed in a monthly step. The average precipitation
was 844.7 mm. The results showed that most water becomes lateral flow (238.9 mm)
through the soil profile because of the highly permeable soils and parent material
such as marbles that allow the infiltration. The average surface runoff was about 70
mm and the groundwater flow 63 mm. These three phases consist the total water
yield of the area (371.26 mm). The average percolation in aquifers was about 72 mm.
There was also a high percentage of evapotranspiration (449 mm) due to the high
vegetation of the island.
In addition, a map was produced (Figure 3) that identifies the average simulated
stream discharges based on the outputs of SWAT. The depiction is in the view of the
sub-basins/watersheds and shows which watersheds discharge had the highest
amount of water. Five categories were selected based on the statistics of the flows
and specifically they were divided in: i) 0-0.05, ii) 0.05-0.10, iii) 0.10-0.25, iv) 0.25-
0.50 and v) 0.50-1.0 (the discharge values are in m3/sec).
The average monthly water discharge of the major torrent is depicted in figure 4.
The upper part of this torrent is situated in central Thasos while its outlet is in
southeast region of the island. The specific outlet is also depicted in figure 3 as the
left red colored watershed. The simulated results showed that the discharge of the
specific torrent ranged between 0.04 to 1.2 m3/sec. The almost no flow period was
noted in the summer period, specifically in July and August, while the highest during
November and December.
Main challenges of the study included the lack of important data. Specifically,
daily weather inputs were not available, only monthly statistics were used. Observed
field discharge data were not available for the calibration of the model. Also, an
extensive soil map would be very helpful for the parameterization. Finally, the land
cover concerns the 2000 period as Greece has not update the database. Any current
satellite images could be helpful for the classification of land cover because Thasos
has suffered by many fire disaster during the last 15 years.
159
Fig. 3. The average simulated discharges of the watersheds
Fig. 4. The average discharge of the major stream
160
The results could be used for many purposes. The produced map could be a
practical guide for water managers and other scientists for water resources
management plans. Furthermore, future study could include the implementation of
Multi-Criteria Analysis to combine other information such as wildfire maps and road
network to identify best locations for water reservoirs to save water resources. The
properly managed and stored surface stream water could be utilize for agricultural
irrigation, the production hydro-electric power, water supply for municipalities
during the summer where problems arise due to tourism and for fire suppression.
4 Conclusions
This study was an attempt to predict the water balance and the stream discharges
of Thasos Island. For the specific scope, the hydrologic model SWAT was
implemented to simulate the hydrologic conditions. The data used were the
topographic map through the DEM, the soil map, the geological map, the land cover
map and monthly weather data of the meteorological station located in Limenas. The
produced results, maps and hydrographs have some limitation but could be used for
water resources management plans and especially to sustainably utilize the surface
torrent waters.
Acknowledgments. This research has been co-financed by the European Union
(European Social Fund – ESF) and Greek national funds through the Operational
Program "Education and Lifelong Learning" of the National Strategic Reference
Framework (NSRF) – Research Funding Program: ARCHIMEDES III. Investing in
knowledge society through the European Social Fund.
References
1. Arnold JG, Kiniry JR, Srinivasan R, Williams JR, Haney EB and Neitsch SL,
(2012) Soil and Water Assessment Tool, Input/Output File Documentation,
Version 2012. Texas Water Research Institute. Technical Report 439, College
Station, Texas. European Environment Agency.
2. Arthurton R., Barker S., Rast W., Huber M., Alder J., Chilton J., Gaddis E.,
Pietersen K., Zockler C., Al-Droubi A., Dyhr-Nielsen M., Finlayson M., Fortnam
M., Kirk E., Heileman S., Rieu-Clarke A., Schafer M., Snoussi M., Tang Lingzis
D., Tharme Rebecca., Vadas R., Wagner Greg., Ashton P., (Editor); Diop S.,
(Other contribution); M'mayi P., (Other contribution); Akrofi J., (Other
contribution); Gaitho W., (Other contribution). (2007) Water, Global
environment outlook 4: environment for development (GEO-4). United Nations
Environment Programme, 2007. http://www.unep.org/geo/geo4/report/GEO-
4_Report_Full_en.pdf
161
3. Corine Land Cover 2000 seamless vector data http://www.eea.europa.eu/data-
and-maps/data/corine-land-cover-2000-clc2000-seamless-vector-database-4#tab-
gis-data (accessed September 10th, 2014).
4. Gassman P.W., Reyes M.R., Green C. H., and Arnold. J.G. (2007) The soil water
and assessment tool: Historical, development, applications and future research
direction. Transactions of the American Society of Agricultural and Biological
Engineers, 50(4), pp. 1211-1250.
5. Harmonised World Soil Database Viewer (2012)
http://webarchive.iiasa.ac.at/Research/LUC/External-World-soil-
database/HTML/ (accessed May 14th, 2014)
6. Mallios Z., Arapaki S., Frantzis A. and Katsifarakis K.L. (2009). Management of
water resources of Thassos island in the frame of sustainable development.
Proceeding of common conferences 11th of EYE kai 7th of EEDYP pp 27-34
Tomos 1 (In Greek with English abstract).
7. Neitsch, S.L., Arnold J.G., Kiniry J.R., Williams J.R. and King K.W. (2011) Soil
and Water Assessment Tool – Theoretical Documentation – Version
2009.Grassland, Soil and Water Research Laboratory, Agricultural Research
Service and Blackland Research Center, Texas Agricultural Experiment Station,
Temple, Texas.
8. Singh V. P. and Woolhiser D. A. (2002) Mathematical Modeling of Watershed
Hydrology, Journal of Hydrologic Engineering, 7(4), pp. 270-292.
9. Topographic map of Thasos (1979) in scale 1:50,000 developed by the Military
Geographic Service.
10. Vlachopoulou A. and Emmanouloudis D. (2014) The contribution of hydro-
informatics to the refilling capacity evaluation of small reservoirs under semi-arid
conditions. Police Academy “Alexandru Ioan Cuza” – Fire Officers Faculty XVI
Scientific Conference SIGPROT 2013-2014, Bucharest, Romania, pp 80-88.
11. Winchell M., Srinivasan R., Di~Luzio M., and Arnold J. G. (2013) ArcSWAT
Interface for SWAT 2009: User's Guide. Texas Agricultural Experiment Station
(Texas) and USDA Agricultural Research Service (Texas), Temple, Texas.
162