Introducing of Ce-Qual-W2 Model and Its Application - Water Quality Management: Assessment and Interpretation - page 91

There are many water quality parameters, but TDS is an important water quality
parameter especially in reservoirs. In fact, TDS can be considered a pollutant for
this reason, it is vital to have information about the existing situation, seasonal
variations and expectations of the future situation of the parameter.
The Department of Environment (DOE) and Institute of Standards and Industrial
Research of Iran (ISIRI) ( 2007 ) have speci ed that the permitted amount of TDS in

drinking water should be less than 500 mg/l (milligrams per liter) and water for
irrigation should be 1,000 mg/l.
If the amount of TDS increases above the standard level, it may cause some
problems which are as follows (Tebbutt 1997 ):

1. Providing an undesirable taste in water.
2. If there is magnesium or calcium carbonate in the water, they may cause a core
problem in the equipment of a dam such as erosion.
3. Increasing cost of water treatment to reduce the amount of TDS.
4. The increasing amount of TDS in water causes a reduction in dissolved oxygen.

flow standards are usually based on some
combination of the following: historic discharge, channel morphology, water
quality, the ecology of aquatic species, empirical evidence, modeling, and ulti-
mately arbitrated between user groups. For a particular area,

In practice, a minimum in stream

ow
requirements will depend on local and downstream conditions and can vary con-
siderably within areas of similar climate and hydrology (Beecher 1990 ).
To predict the damage caused by these problems, modeling of the water
resources is essential. The need for predictive water quality modeling has arisen
largely as a result of increased eutrophication of lakes throughout

in stream

the world

(Can eld and Bachmann 1981 ).

Numerical models have demonstrated an impressive capacity to support
important water resource decisions. Models are typically used to support devel-
opment and public policy decisions in a variety of areas: simulation of discharges,
outfalls, and intakes; changes to wastewater treatment systems; approval of changes
in industrial processes; operation of dams and reservoirs; and water resource
allocations, among other uses. The value of modeling is important in economic and

financial terms with regard to determining particular project options and phased
investment programs (Cox 2003 ).

6.2 Historical Background

There are many studies for modeling river and reservoir water quality which were
used Ce-Qual-W2 model.
Previous studies used the Dyresm model for Mymeh dam in Iran, using salinity
and temperature data from 1970 to 1979. The result indicated, there were very weak
strati

cation (TDS) during winter and strati cation started in spring and during the

summer there was strong strati cation. Comparison between salinity before and