Time Series Modeling - Water Quality Management: Assessment and Interpretation - page 60

Table 4.2 Situation and characteristics of stations upstream and downstream of Latian dam
River Station Longitude

(degree/min)

Latitude
(degree/min)

Altitude
(m)

Basin area
(km 2 )

51 o 33 ′ 35 o 51 ′ Jadj Rud Roodak 1,690 416

51 o 41 35 o 48 Lavark Ali

Abad

′ ′ 1,600 103

51 o 40 35 o 50 Afjah Narvan ′ ′ 1,750 30

51 o 38 ′ 35 o 49 ′ Galandovak Najar

Kola

1,700 59

51 o 41 35 o 47 JadjRud Zir-e-

pol

′ ′ 1,560 710

C. The hottest month of
the year is late of July to late of August with a maximum temperature of 34

In the catchment area, annual average temperature is 10 °

C and
the coldest is late of December to late of January with the minimum temperature of
−

°

C. Average rainfall of Latian basin is more than 500 mm a year. Latian Dam is
located at 35

8 °

E. In addition to producing 70,000 MW/hours hydro-
power energy, it supplies drinking water to some parts of Tehran and also agri-
cultural water to some parts of the Southeastern part of Tehran (Varamin Plain).
Some characteristics of the dam are shown in Table 4.2 .
This case study was primarily aimed at developing suitable and con

° 47 ′ N, 51 ° 40 ′

dent time
series models for water quality data in two inlets and an outlet of the dam. The
second objective was to predict variations in water quality from developed models
to be used in water quality management. Third aim is to show application of time
series in water quality (Asadollahfardi et al. 2012 ).

4.17.1.1 The Software

Statistical Analysis System (SAS) version9/1 was applied for calculations and
analyze of the models of this case study. This software needs to be programmed;
however, there are also some menus for simplicity. First, it is necessary to build a
library in the software to save data and calculations of each stage. Figure 4.4 shows
the procedures for building, con

rming and, forecasting models with SAS software.
The aim of this case study was to develop proper models for
Ca þþ ; Mg þþ ; SO 4 ; pH ; HCO 3 ; Na þ ; Cl and TDS parameters. The data used in
building time series model as well as con rming and comparing the models were

monthly collected for 24 years (1981 2005) by local water authorities in Tehran.

For validation of the models, the predicted monthly values from September till
March 2005 were compared to the observed values. Finally, a relation was made for
every parameter (Asadollahfardi et al. 2012 ). The results are presented in
Tables ( 4.4 ), ( 4.5 ) and ( 4.6 ).
As shown in Tables 4.4 and 4.5 most of the models developed for water quality
in Aliabad and Roudak stations were Auto Regressive Integrated Moving Average

-