The water quality in Al Thawra Lake was getting worst recently because of the
increscent of the concentration of nutrients, which reached the lake from point and
nonpoint sources. The Geographic Information System GIS was widely used in the last
d
ecades in evaluating quality of water depending on models operates within GIS one of
these models is The BASIN software (Best Assessment Science Integrating Point and
Nonpoint sources)which used in this research .The Pload model(Pollution load) which is
one of the BASIN models was used to estimate the pollution loads. The Pload was run by
using satellite image, Digital Elevation Model (DEM30), land use map, and export
coefficient values. The result showed that the total annual pollution loads of TP&TN are
TP=11543 kg/yr ,TN=61367 kg/yr that came out of the watershed of the lake, Open maki
and rock out crops are the dominate contributors to TP load in the watershed for about 30
%of total TP load, while Olives and citruses are the dominate contributor to TN load in the
watershed for about 33 %of total TN load, the model results also indicated that the
nonpoint sources are the main contributor to TP&TN loads in the watershed for about
80%of the total TP loads while only 20% from point sources, and for about 75%of the total
TN loads from nonpoint sources while only 25% from point sources.
This study aims to show the land use changes during the period 1970 – 1991.
The study includes the city of Homs and the surrounding areas, with total
surface area of 9686 ha. To carry out this study, aerial photographs were used
where sets of diff
erent periods were taken, one was taken in 1970 with a scale of
1/20000, and the other set for the year 1991 with a scale of 1/15000, the two sets
of aerial photographs were interpreted and analyzed after the delineation of the
targets, and two maps were prepared after unifying the scales and selecting the
proper legend.
The results indicated obvious changes in land use, for example, the area of
cereals crops was in 1970 about 32.9 % of the total area and decreased by 11.8
% in 1991. In the area of gardens a reasonable increase was recorded, while in
the area of vineyards an increase of about 1 % was noticed.
But the big issue is the urban expansion at the expense of arable lands, the
expansion area of housing has been increased from 8% in 1970 to 24% in 1991,
and the area of civil establishments was increased from 2.27 % in 1970 to 5.47
% in 1991, in the new concept of desertification urban expansion at the
agricultural land means a permanent desertification, this matter should be
considered seriously and the necessary measurements must be taken into
account.
