Geoscience Reference
In-Depth Information
Concentrations of fuels and hydrocarbons were significantly higher in the petrol
station and on the roads than in residential areas. Concentrations of pesticides were
higher in industrial areas, but in residential areas as well concentrations close to the
standard for methylene and simazine. In the 2008-2009 sampling year, an abnormal
quantity of simazine was found in the residential area, higher than the standard in
one isolated instance.
In a sampling done in 2007 on runoff water for volatile organic compounds
(VOC), all the compounds measured by the Water Authority laboratory were
found to be under the discovery threshold. The exception was Methyl Tertiary
Butyl Ether (MTBE), a fuel additive found in concentrations of 2.11 and
11.33 ppb in two samples in the Herzliya industrial area. MTBE was not found
in the other land uses.
5.6 Summary and Conclusions
Storm runoff rain ratios in urban basins of Ra'anana and Herzliya were examined in
the years 2007-2009. On the basis of the incorporation of the results of this study
with previous studies carried out on this topic, it was found that the regressive
coefficient of these connections (runoff coefficients) to residential areas on the
coastal plain is 0.26-0.46. In most of the basins, the runoff coefficient varies within
narrower boundaries, and at the present stage, an average runoff coefficient of
approximately 0.30 may be used. For the first time, an estimate of the urban runoff
coefficient in a modern industrial area has been established and found to be
approximately 0.70. These average values represent the total urban area. The sites
chosen well represent various urban land uses: residential, industrial, roads.
Land uses were characterized and established by use of tools and work methods
of ground and aerial remote sensors and use of information layers of the GIS. Use
was made of active remote sensing methods. The use of color aerial photography
was found to be useful and very inexpensive for mapping and characterizing land
uses for estimating water resources from urban areas.
For the purpose of making a rough estimate of water resources in coastal plain
basins with a large urban area component, a model was developed which makes it
possible to establish urban runoff thickness at various probabilities on the basis of
information on multi-annual average rain thickness. It was found that a square
kilometer of urban area creates a 50% probability (close to the multi-annual
average) of 157,000 m
3
runoff water per year.
The separation between industrial areas and residential areas made it possible to
better estimate runoff which may be used due to problems of water quality
characterizing urban runoff, from industrial areas in particular.
The quality of runoff water is affected by land use. The best quality of runoff was
found in residential areas, which represent most of the urban area. The quality of
water from industrial areas, roads and areas of petrol stations is lower. An analysis
