Evaluation of Temperature, DO and BOD in Mosul Dam Lake Using Geographical Information System

The aim of this study is to evaluate the seasonal variations of Mosul dam lake by measuring the temperature, dissolved oxygen (DO) and biochemical oxygen demand (BOD) during the period from July 2018 to April 2019. Twenty two sites were selected within the studied lake. The obtained results were integrated with the geographical information system (GIS) using spatial images to create maps utilizing Arc map software. These maps were used to demonstrate the concentrations of the investigated parameters during the study period. The results show that all parameters were within the accepted levels, indicating the good status of the lake.


Introduction
Lakes are key inclusions of the earth's landscape. They are remarkably important environments that provide a range of products and administrations to mankind. However, anthropogenic pressures on lakes have expanded quickly in recent decades [1]. Geographic information systems is a computer-based tool that is utilized to analyse, store, control and visualize geographic data, ordinarily within the frame of an outline. GIS applications allow clients to form and analyse spatial data, adjust information in maps, and display the outcomes of all the operations carried out. Advanced GIS innovations use digital data, for which different digitized information creation methods are utilized [2].

ISSN: 0067-2904
Aljoborey and Abdulhay Iraqi Journal of Science, 2020, Vol. 61, No. 11, pp: 2838-2848 2839 GIS can relate to the information by utilizing area as the key variable. GIS accuracy depends upon source information provided with a high level of positional precision that relies on the GPS-derived positions. Airborne photography and satellite imagery are external sources that enhance the GIS output. Numerous disciplines can benefit from GIS innovation including the development and usage of hydrologic models at different levels [3].
Mosul Dam Lake is located between 36°37′49″N 42°49′23″E at the north of Mosul city. The shape of the lake is almost elongated where the River Tigris enters the upper zone and expands close to the dam site. The length of the lake is approximately 45 km and its width ranges from 2 to 14 km with a water surface area of about 380 km2 at a maximum operation level of 330 m a.s.l [4]. The climate is hot and dry during the summer and cold and rainy during winter with occasional snowfall taking place in the mountainous region. The precipitation season within the Tigris River basin starts in October and lasts until May. The annual precipitation over the Tigris basin ranges between 450 to 1,000 mm [5]. The climate of the study area characterized by hot and dry summers and cold winters with rare snow [6]. The annual mean temperature is 19.5• C and the mean rainfall is 383 mm [7].

Materials and methods
Twenty two stations within Mosul Dam Lake were chosen tocover all the lake's regions. The studied stations names and their coordinates are given in Table-1.

In situ measurement
Samples were taken in the period from July 2018 to April 2019, where July and August represent summer, September and October exemplify autumn, December and January state winter and March and April represent spring. Glass bottles of 1 liter size were washed with distilled water, labeled, and used to collect samples by inundation at 10-20 cm below water surface. The bottles were then kept in icebox and transported to the lab in the University of Mosul/ College of Science/ Department of Biology for the measurement of the below parameters [8]. a) Temperature Water temperature and ambient temperature were measured in the field using electronic thermometer TA-288.

b) Dissolved Oxygen (DO)
Winkler's method was used to estimate the dissolved oxygen concentration. This method was described by the American Public Health Association (APHA) [8].

c) Biochemical Oxygen Demand (BOD)
Similar to the assessment of dissolved oxygen, Winkler's method was used to measure biochemical oxygen demand by calculating the difference between the values of dissolved oxygen for day one and day five, as follows: BOD= DO1-DO5.

Geographical Information System(GIS) Work
All samples were collected during the passage of the satellite across the lake; the times of satellite passage were determined by the official website of landsat8. Remote sensing data used in this study was formulated as Tagged Image File Format (TIFF). These files were scanned by Landsat satellite (Landsat-8 OLI images; path: 168 and row: 37) which has many bands that were used to capture the satellite images, as shown in Table-2, which were downloaded from the website of United States Geological Survey (USGS) (www.glovis.usgs.com). .0 In the present study, ArcGIS 10.6 software was used for creating and using maps, compiling geographic data, analysing mapped information, sharing and discovering geographic information, using maps and geographic information in a range of applications, and managing geographic information in a database depending on Gaussian process method (Kriging). The produced maps represent the mean values of temperature, DO and (BOD during the period of study.

Results and discussion
During the period of study, the elevation of the lake was recorded every month at the time of samples collecting. Also, the area of the lake and the storage capacity were assessed (Table-3). Our results showed that the area of the lake and water capacity were proportional with the elevation of the lake. The largest area and the largest storage capacity were recorded in April/2019, because of being preceded by the rainy season and melting of the snow in Turkey. While the smallest area and the minimal storage capacity were recorded in October/2018 due to being preceded by the dry season where there is no precipitation.
Mean values ± SD of water and air temperatures, DO, and BOD 5 were calculated in the different 22 sites sampled from Al-Mosul Dam Lake during four seasons. Generally, values of water and air temperatures were higher in the hot summer season and lower in the cold winter season.
Also, correlation analysis between these examined variables was carried out using SPSS.

Water temperature
The highest mean value of water temperature (28.93 ± 0.47 ºC) was recorded in site 22 during summer, while the lowest (7.5 ± 0.5 ºC) was measured in both sites 1 and 2 during winter (Figs. 3 and  4). During September 2018, most of the global lands and ocean surfaces were reported to have a very

Aljoborey and Abdulhay
Iraqi Journal of Science, 2020, Vol. 61, No. 11, pp: 2838-2848 2842 warmer climate) than that in the average conditions. The rising temperatures are the most significant aspect in the period of climate variability [9]. The most notable high temperatures were present across southern South America, Alaska, the southwestern and eastern contiguous U.S., most of Europe, the Middle East, as well as western and eastern Russia [10]. Global average temperatures are expected to rise an additional -16.3°C to -13.9°C, depending on future greenhouse gas emissions [11].

Air temperature
The highest mean value of air temperature in the studied stations was 41.0 ± 2.0 ºC, recorded in various sites during summer season, whereas the lowest mean value was 9.0 ± 0.0 ºC, measured again in several sites, but during the winter season (Figures-4, 5). These results correspond to the findings of previous studies. Muslih and Błażejczyk [12] also found more significant changes in summer months compared to winter months, along with more warming in the southern part. The results obtained by Robaa and Al-Barazanji [13] using Sen's slope and MK method at 11 stations over Iraq during the period 1972-2011 are highly similar to the results from this study. Our results also agree with those of Salman et al. [14] which revealed that summer temperature increased at more stations compared to winter temperature.

DO
Our study found that water DO had its highest mean value (12.33 ± 0.40 mg/l) that was recorded in site 22 during spring season. While the lowest mean value was 5.08 ± 1.2 mg/l in site 14 during winter season (Figures-(6 and 8). seasons. Analysis of variance of the obtained data reveals significant differences (P≤0.001) between the studied sites and seasons, while the significant differences (P≤0.05) found by utilizing the least significant difference analysis confirmed such conclusion, with the mean values being 0.7079 mg/l for seasons and 2.08 mg/l for sites.
The biological activity peaks during the spring and summer when photosynthetic activity is driven by high solar radiation. Furthermore, during the summer, most lakes in temperate climates are stratified. The combination of thermal stratification and biological activity causes characteristic patterns in water chemistry [15,16].
Frequent spring storms bring not only water to the lake, but an influx of nutrients from the landscape. This often leads to a series of spring algae and zooplankton blooms that allow nutrients in the lake to be cycled up through the food chain, which leads to a high concentration of dissolved oxygen [17]. The values of dissolved oxygen obtained by the present study show disagreement with those found by Al-Obaidy et al. [18], where oxygen levels of Dokan lake were between 3.55-12.30 mg/l, and with those of Toma [19] for Derbendikhan lake who reported a concentration of 6-9.5 mg/l. Furthermore, consistence with our study finding, Salah et al. [20] found that the DO of Al-Habbniya lake was 6.72-10.57 mg/l. The results of our study are also consistent with those of the study of Iscen [21] on Uluabat lake in Turkey where DO mean was 7.99 mg/l.
The overall DO mean was found to have a highest value in site 22, while the lowest value was recorded in site 9, which were 9.45 mg/l and 7.45 mg/l, respectively (Figure-7).    4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 Overal DO mean Examined Sites 4. BOD 5 The current analysis showed that the lowest BOD 5 mean value (1.32 ± 0.09 mg/l) was found in site 19 in the autumn season, while the highest was 7.375 ± 2.03 mg/l that was measured in site 13 during summer season Figures-(9 and 11 ).
Generally, the recorded BOD 5 values were within the permissible levels of Iraqi standards (Tables-2.4), with the exception of the values in sites 13 and 8(5.23 and 5.3mg/l, respectively). This could be due to the slight increase of levels of organic matters in these two sites. The biochemical reactions are temperature dependent and the activity of the microorganism increases with the increase in temperature up to a certain value, whereas it drops with the decrease in temperature [22].
The estimated BOD values never reached critical values in most times of the study period, indicating good to moderate water quality conditions. The study results are in accordance with the known values of Iraqi inland waters [23,24]. Statistical analysis of the BOD 5 results showed significant differences (P≤0.001) between both seasons and sites. Also, the results of the least significant analysis obviously illustrated such differences (P≤0.05), with the values being 1.494 mg/l and 0.977 mg/l for seasons and sites measurements, respectively.
On the other hand, the highest overall BOD 5 mean was detected in site 8 (5.3 mg/l), but the lowest mean value was found in site 9, which was 2.88 mg/l ( Figure-

Conclusions
The usage of GIS provided an efficient tool to illustrate the distribution of the investigated parameters. The field measurements showed that temperature, DO and BOD values of the Mosul Dam Lake were within the accepted ranges, which reflects the good state of the lake during the study period.