FACT
A software package called Fast Automatic Calibration Tool (FACT) was
developed for SWAT to increase the calibration performance (Özdemir and
Leloglu 2018). The optimization method applied to the FACT is the
Sequential Uncertainty Conformity Algorithm (SUFI-2) since a large
number of parameters in conjunction with uncertainty analysis can be
performed by this algorithm. The
FACT was developed to reduce some drawbacks of SUFI2 in SWAT-CUP which
are the time consumption, user interaction requirement, and update
problems of SWAT model files (Özdemir and Leloglu 2018). The FACT was
applied by using 16 important parameters that reflect relevant processes
of the system such as surface runoff, baseflow, lateral flow (Table 1).
The stream gauge station on the Namazgah river was used to compare
observed and measured flow rates. Since the observed flow rate values at
the station were between 1991 and 2007, the model was performed between
these years. The station has stayed under dam waters since 2007, so no
measurements are available.
Data preparation
The data prepared for the model are divided into two different types,
time series and spatial inputs. The hydrologic cycle of the basin is
simulated in daily and monthly time steps by the model. Meteorological
data sets, minimum and maximum temperatures, rainfall, average relative
humidity, average wind speed, average solar radiation, are used as time
series type inputs whereas land use and soil layers are spatial data
type inputs. Daily time steps were used in this study.
The Digital Elevation
Model
The Digital Elevation Model (DEM) of the Namazgah dam basin was produced
from 1:25 000 scale topographic maps. The resolution of DEM is 30*30
meters. Universal Transverse Mercator (UTM) projection system and
WGS_1984_35 N geographic coordinate were used in DEM. SWAT calculated
minimum, maximum, mean and standard deviation elevation values which
were 40, 350, 165.437 and 53.72, respectively. After preprocessing of
DEM, minimum, maximum, and suggested sub-basin areas were calculated as
52, 10340, and 1000 in hectares, respectively. Based on streams and
animal husbandry locations in the basin, 50 sub-basins outlets were
defined (Fig. 1).
Soil map
SWAT model calculates hydrological processes in the basin using the
physical and chemical properties of the soil. The most important of
these features are; soil water availability capacity, hydraulic
conductivity, organic carbon content, soil texture (sand, clay and
gravel content) and thickness. Unfortunately, the soil map produced by
the former Ministry of Food, Agriculture and Livestock (Oakes 1958) does
not include these properties. It only includes Great Soil Groups and
combination of soil properties, slope-depth, drainage-texture,
drainage-salt-alkali combinations. The legend of the map is presented in
the following: