Case Studies - Coastal Lagoons: Ecosystem Processes and Modeling for Sustainable Use and Development - page 457

of a decision support system for the entire Koycegiz-Dalyan Lagoon system.
According to the data analyses one-dimensional (longitudinal) stream water quality
models were found to be appropriate for both streams.
Modeling of the streams was done in two stages. First, a preliminary modeling
study, using QUAL2E and QUAL2E-UNCAS, was done in order to better under-
stand the system behavior and the impact of different nutrient loads on the water
quality of the streams. Uncertainty analyses were done with the Monte Carlo
Simulation option in QUAL2E-UNCAS. To obtain the uncertainty parameters
(type of distribution of parameters, mean value, and input variable variances), a
simple spreadsheet-based database management system was developed using
Microsoft® Excel. The details of the preliminary modeling study for rivers are
given in Ertürk et al. 31 The results obtained from QUAL2E and QUAL2E-UNCAS
applications were used as initial values for the dynamic simulation of rivers. These
simulations have already begun. WASP 6.1, 32 developed by the U.S. EPA, was
selected as the most appropriate model for modeling of both streams. The EUTRO
module of WASP 6.1 was chosen as the water quality model for dissolved oxygen,
BOD, and nutrient calculations of streams.
A parallel study for calculating the run-off flow rates and nonpoint source
loadings into the streams and the lagoon is still ongoing. Despite its large data
requirement, the Hydrological Simulation Program FORTRAN (HSPF) is preferred
over various other hydrological models due to the wide range of output parameters
it is capable of producing. This is a commonly cited U.S. EPA model that has been
successfully applied to rural/agricultural zones for more than two decades.
The model requires various time series and input parameters, which differ
according to the selection of modules to be run. To simplify the modular structure
of the model the first step is to eliminate the impervious land (IMPLND) module,
which simulates the run-off from impervious catchments because almost the entire
basin is unpaved, i.e., pervious. The results of the meteorological analysis show that
the dominant type of precipitation within the watershed is rainfall. Thus, rainfall
was assumed to be the major source of run-off. Processes to melt snow packs at the
highest zones of the watershed area would be utilized only if a justifiable water
budget could not be attained.
As HSPF uses a standard time series format called watershed data management
(WDM), datasets obtained from the State Meteorological Service of the Turkish
Republic were converted to WDM format by a sequence of programming opera-
tions.
Subsequent to a successful run on a fictitious basin with input parameters
gathered according to a literary study to set compliant values for the real basin, the
watershed was then divided into model segments. The segmentation is based on
discrete hydrological patterns and basin topography. Thus, the subwatershed bound-
aries determined by the watershed modeling system (WMS) 3D topographical model
were further segmented regarding changes into soil structure, crop types, and agri-
cultural practices.
Hydrological modeling studies to adjust a water budget for the basin are ongoing
and the ultimate goal is to attain a reliable understanding of the significance of
nonpoint loads on the aquatic environment of the entire watershed.