Assessment of Water Quality in Tigris River-Iraq by Using GIS Mapping ()
1. Introduction
Water is the most precious gift of nature, the most crucial for sustaining life and is required in almost all the activities of man—for drinking and municipal use, irrigation to meet the needs of growing food, industries, power generation, navigation, and recreation [1]. However, water quality in many large rivers has deteriorated significantly worldwide due to anthropogenic activities in the past 2 - 3 decades [2,3].
It is also widely accepted that discharges from sewage treatment plants provide the major rivers sources of Phosphorus (P) and Nitrogen (N), predominantly in populated urban areas [2,4,5]. A continuous monitoring of water quality is very essential to determine the state of pollution in River [6]. Over large parts of the world, Rivers and Lakes show increasing trends of water pollution. This holds especially for developing countries under economic expansion and increasing population sizes. Evaluation of the physical, chemical, and biological water pollution is essential for the abatement of freshwater pollution.
The Tigris River is one of the largest rivers in Iraq, and is considered the main source of drinking water for Baghdad, which is the largest city in the country and the second largest city in the Arab world with a population estimated by 7.5 million [7,8].
In this study, a geographical information system (GIS) was used, in order to compare water quality data and related information collected for water quality in Tigris River, and display the distribution of contamination in the river in easily viewed maps that can be used by the public and decision makers.
2. Materials and Methods
2.1. Study Area
The Tigris River is one of the largest rivers in the Middle East, stretching for over 1900 km, of which 1415 km are within Iraq, the catchment area reach to 235,000 km². Tigris River sharing with Euphrates River the main source for man uses, especially for drinking water since they pass the major cities in the country [6]. The River enters Baghdad city at coordinates 44˚24' E, 33˚36' N and divides the city into two parts (Karkh & Risafa). The length of the river along Baghdad city is about 110 km.
2.2. Chemical Analysis
Eight locations were selected for this study. The locations included east Tigris (site 1), Al wathbah (site 2), Al karamah (site 3), Al Qadisiya (site 4), AD Dawrah (site 5), AR Rashid (site 6), Al Wahdah (site 7) and Diyala Bridge (Site 8). The locations of sampling points are shown in Figure 1. These locations were chosen to cover all the distance of Tigris River within Baghdad city.
Figure 1. The sampling sites at Tigris River, Baghdad.
The water samples were collected in good quality polyethylene bottles during Jun-Dec 2008. Physical parameters such as pH and EC were determined at the site by using digital portable water (PH, EC meter), while other examinations were done according to standard specifications presented by the American public health association [9]. For Determination of major cations, anions and heavy metals were made in the laboratory using the analytical methods shown in Table 1.
2.3. Geographic Information System (GIS) Analysis
Geographical Information system (GIS) is a computerbased technology for handling geographical data in digital form. It is designed to capture, store, manipulate, analyze, and display diverse sets of spatial or geo-referenced data [10,11]. Coordinates of sampling points were recorded by mobile GPS (Etrax). The results of the chemicals analysis (mean value per sampling point) were then used as input data in ArcGIS 9.2. The sampling locations were integrated with the water data for the generation of spatial distribution maps. The present study used the Inverse Distance Weighted (IDW) method for spatial interpolation of water parameters. IDW determines cell values using a liner-weighted combination set of sample points. The weight assigned is a function of the distance of an input point from the output cell location. The greater the distance, the less influence the cell has on the output value [12].
3. Result and Discussion
Table 2 illustrates the mean value of 17 water quality parameters which compared with three standard WHO [13], CCME [14], Iraqi standard [15].