Limnological Study in Upstream and Downstream Degala Basin Water Body within Erbil City-Iraq

1.Introduction:

In various essential activities, water plays a key role and is inevitable for all living things because it has a great social and economic significance that eventually affects human life. Water is widely used for irrigation, industrial production, generation of hydroelectric power, fisheries, the protection of human life and domesticated animals. Physicochemical researches are therefore of primary importance in determining water quality for its best use and also in recognizing the pollution load on receipt [1].

Dams, built to change natural flow regimes, are one of the most significant human interventions in the hydrological cycle and they can result in post-impoundment phenomena that are specific to reservoirs and not natural lakes. The size of the dam, its location in the river system, its geographical location with respect to altitude and latitude, the detention time of the water and the source(s) of the water all influence the water quality [2].

In all major rivers and lakes, water contamination is an acute issue, and water is known to contain a large number of chemical elements, the interactions of both the physical and chemical properties of water play a significant role in composition, distribution, and abundance of aquatic organisms [3].

The Degala Basin is about 35 km to the northeast of Erbil city. The main stream that drained to it is composed of two branches which are intermittent. The watershed has a kidney shape. At the outlet there are several springs which are the sources of the base flow during dry seasons. The inhabitants at the upstream are engaged in raising animals and dry farming. Irrigation farming is practiced to a very low extent. The whole area has an undulating topography. The vegetative cover includes oak trees and some accompanying species such as hawthorn, wild cherry and wild pistachio. The soil of the watershed has a fine textured soil with patches of unconsolidated materials belonging to Kolosh formation. The main aims of this investigation were to assess physico-chemical and phycological parameters among upper stream, Degala basin and lower stream with correlation among them at each station.

2.Material and methods:

2.1 Description of the study area:

Generally, the hydrology, geology, climate and vegetation cover of and of Iraqi Kurdistan region area described by [4]. Rocks of these area are in part igneous rocks which are originated from magma, sedimentary rocks that is mainly composed of limestone, mud and sandstone and metamorphic rocks [5]. The present study area covered a distance about 50km east of Erbil City, The Degala basin constitutes of a small water reservoir located in the center of Degala sub- district, the valley drains its water from rain and snow melting water additionally springs located few kilometers to the north will be another important source for accumulating water. The dam is earthy with an elevation of about 30m above ground surface within latitude 36.171586 and longitude 44.38215, and the capacity of the lake reservoir capacity is about 1.06 million cubic meters. (Figure 1; A, B, C).

2.2 Physical and Chemical parameters:

Samples were collected monthly from different sites of Degala Basin from October 2020 to August 2021 for physicochemical and biological analysis using sterile plastic bottles then the samples delivered to the laboratory and preserved for further analysis.

2.2.1 pH, Electrical Conductivity (EC), (μS.cm ^-1) and Total Dissolved Solid(TDS),(mg .l^-1 were measured by a portable multimeter pH, EC, TDS meter model (HANNA, instruments, HI9811, 200), the results were expressed as μS.cm‾ ¹for EC and (mg. l¯¹) for measured TDS [6].

2.2.2 Chloride was determined by argentometric titration using standard silver nitrate titrant (0.014 N) and potassium chromate indicator solution as described by [6].

2.2.3 Sodium, Calcium and potassium (Na, Ca, K) mg.l^-1 were measured by flame Emission photometric method (Sherwood-410).For obtaining the standard curve the instrument calibrated by standard solution as described by[6].

 2.2.4 Magnesium (mg CaCO3. l‾¹):

Determined by EDTA (Ethylene-di amine-tetra acetic acid disodium salts) in which 100ml of water was taken .2ml of buffer solution with pH of ammonia 25%was added, and 6 drop of Erich Rome Black T as indicator [6].

2.2.5 Total Alkalinity was determined in the lab by titration methods using standard sulfuric acid titrant (0.1N) as described by [6],the results were expressed in mg CaCO₃ l^-1.

2.2.6 Nitrogen – Nitrate (N-NO3) (mg. l):

Nitrate was determined by Ultraviolet Spectrophotometric Screening Method. After filtration of water sample 50 ml of water sample acidified by adding 1ml of hydrochloric acid solution 1N and Ultraviolet Spectrophotometer (model Gen way 1400), with a 1cm quartz cuvette cell at a wavelength of 220 nm for nitrate reading and a wavelength of 275 nm to determine interference due to the dissolved organic matter.  Results were expressed in mg l¯¹ [6].

2.2.7 Sulphate (SO4¯²) (mg SO4¯².l¯¹):

Sulphate was determined by Turbid metric method described by [6](APHA,2012) acetic acid medium with barium Chloride , so as to form barium sulphate. Sulfate values were determined from the calibration curve was measured by  spectrophotometre at wavelength 490nm and the results were expressed as mg SO4¯².l¯¹.

2.2.8 Dissolved Oxygen (D.O) (mg .l¯¹):

Directly in the field the dissolved oxygen was measured by using special oxygen –sensitive membrane electrode (HANNA instrument, HI 9142 German company) Results were expressed by mg.l‾¹ [6].

2.2.9 Total Hardness (mg CaCO₃. l ^-1

Total hardness was determined by EDTA (0.01 M) titrimetric method as described by [6], using buffer solution of pH 10 and Eriochrome Black T as indicator.

2.3 Phycological study:

Total number count of algae was performed by using sedimentation method [7]. One liter of each sample taken was put in graduated cylinder (1000 ml), samples were preserved by adding drops of Lugol's solution and left in stand place, after ten days, 900 ml were sucked by siphon technique. The rest was transported to another cylinder (100 ml) and left at the same method to seven days, after that 90 ml drawn and the rest (10 ml) put in covered glass vials, adding2-3drops of Lugol's solution.

Algae were identified using compound microscope based for  morphological characterization such as Filament or Unicellular,  Akinet, Heterocyst, Hormogonia, Clour, Chloroplast and cell shape depending on the following references [8,9,10].

2.4 Statistical analysis

Experimental data in this study was obtained from three replicates, and values were shown as mean ± standard deviation. Statistical significance of correlations between variables was based on correlation test. It is performed by correlation coefficient and significant effects (P < 0.05), which were analyzed based on data obtained under various culture conditions by SPSS statistics vision 27.

3. Result and Discussion:

This study involves determining the physical and chemical parameters of surface water, pH is one of the most important parameters. The pH value of aquatic system is an important indicator of the water quality and the extent pollution in the water shed areas [11] due to determine of the alkalinity and acidity of water condition [12](EPA, 2005) because it  effects biological life, and all biochemical reactions since they are sensitive to the alternation of pH [13]. At downstream, basin, and upstream of reservoir, the pH ranged between minimum 8.1 to maximum 8.9 that were recorded during  January, February, May, and October 2020 respectively in three stations (Table 1, 2, and 3) with ±SD (0.178, 0.242 and 0.14) were recorded from downstream, basin, and upstream respectively (figure 2).

Although, From the results it seems that the pH value shifted toward the alkaline side of neutrality [14] the accumulation of the calcareous soils and consumption of CO2 through photosynthesis [15]. Mostly,  Iraqi inland water was regarded to be on the alkaline side of neutrality (Table 5), reflecting geological formations of the area, specially the geology of Kurdistan composed mainly of CaCO3[16,17]. Similar results were observed in Dukan lake by [18].

Electrical conductivity can be used as an indicator for testing the quality of water thus,  an indicator of salinity and osmotic pressure of water, due to its significant correlation with parameters such as temperature, pH value, alkaliniy , total hardness [19].

Water conductivity and dissolved solids values measured for the basin were higher than for the other streams due to increased surface area and altered dissolved minerals due to excessive water evaporation from the dam, which may have subsequently increased the concentration of dissolved salts by accumulating them as reflected in the TDS values [20]. The high value of conductivity may be related to high concentration of sodium, chloride and TDS[21]. Usually TDS level is directly correlated to the electrical conductivity, primarily when it is in high concentrations [22].  Similar conclusion was reported by[14,23].    

In current observations, the EC varies between (717 - 995) μs/cm were recorded during October and April 2020 individually in three stations (Table 1, 2, and 3) with ±SD (55.79, 44.74, and 75.8) were recorded from downstream, basin, and upstream respectively. While the TDS varied between (394 - 547 ) mg/l^-1   at the same time  (figure 2). The results showed that downstream, basin, and upstream ±SD (30.4, 25.9, and 41). According to standard methods due to the close relationship between EC and TDS  a significant positive correlation obviously found at sites (Table 5). The range of total dissolved solid & electrical conductivity of the water were varied due to natural sources, and Depended on the solubility of mineral in different geological region, and water containing (Table 4).

Nearly in all natural waters, chlorides are present. This is the most natural anion that is inorganic and found in water. Large amounts of chloride are removed by humans and animals, so contamination of water is suggested. The variance observed is often associated with basin hydrology [24].  In the current study. Although chloride concentration was recorded between (17-48) during October and January 2020 in upstream, and basin (Table 1, 2, and 3) with ±SD (4.89, 5.31, and 4.1) (figure 2). The statistical relation among sample stations during study period for Chloride revealed that a significant positively correlated with total hardness and EC while negatively with pH at level 0.05 and 0.01 as shown in (Table 5). Chloride is characterized as innocuous particle, it can change to the inoffensive structure very quickly [25]. The salts of sodium, potassium and calcium contribute to the concentration of chloride inside the water. The large contents of chloride in freshwater are an indicator of pollution, hence the high chloride concentration level in water contributes to deteriorate the domestic plumbing, water heaters and municipal water words equipment[26]. The rocks of high ground and mountain have normally a very low concentration in chloride, therefore running water and ground water often do not have a lot of chloride [27] which is obviously recognized  in the area (Table 4). 

Clearly sodium and potassium are two elements eluted during the rainy season followed by rapidly absorbed via dry soil. [28]. The dominance of Na⁺ over K⁺, can be explained by the solubility of sodium since it is more soluble than potassium, and K⁺ is generally more easily fixed in the rock matrix within clay minerals. Hence K⁺ is the least abundant among cations [29]. 

However sodium and potassium concentrations comes in accordance to the general known levels of these elements in other parts of the world. The concentration recorded was between (22-97) for sodium while potassium recorded (2.2-7.8) during January and May 2020 in upstream, and basin (Table 1, 2, and 3) with ±SD (5.097, 0.82, and 6.01) for sodium, and ±SD (0.9, 0.82, and 0.32) for potassium  (Figure2 ).The statistical analysis revealed that there were  a significant positively correlated with pH and  negatively with EC, TDS, chloride  at level 0.05 and 0.01  as shown in  (Table 5). The values of sodium were found to be always higher than potassium and much less than that of calcium, similar conclusion made by Shekha 1994. The differences between sodium and potassium values in this survey may possibly are related to soil formation [28] The amount of sodium recorded in all water samples was below the maximum permissible limit of WHO and EPA for drinking water, 200 mg/l^-1 [30,31].

The variation of total hardness may be due to source, type and origin of water source, geological and soil properties of the catchments area, various human activities and effect various pollutant as well as the climate conditions have been shown to influence on the hardness value in any water system [32].  Generaly the sites recorded between (418-538) during August and February 2020 in basin and downstream, (Table 1, 2, and 3) with ±SD (40.48, 29.89, and 21.2). Total hardness is primarily imparted by calcium and magnesium ions in most of the fresh water, which apart from sulphate, chloride and nitrates, are present in combination with river carbonates and bicarbonates, resulting in greater erosion of the coastal river level [33. Our study value is slightly higher than WHO 1996 [ 34] recommend value which is 100-300 mg CaCO₃. l^-1. Hardness depends on the amount of calcium or magnesium salts or both [35]). In general, the hardness caused by the presence of  calcium and magnesium originated from the sedimentary rocks, the most common being limestone and chalk [36]. In the present study, the values of total hardness exceeded those of total alkalinity which indicates that hardness in studied area is caused by other ions rather than Ca⁺² and Mg⁺² ions that participate in formation of non-carbonic hardness [37]. Although hard water has no known health effects, it is not suitable for domestic use[ 38].

 In an aquatic environment, calcium is an essential micronutrient and this environment is affected by the metallic oxide adsorption of calcium ions. In addition, microorganisms that play an important role in the calcium exchange between sediments and overlapping water have an impact. Magnesium is an essential for chlorophyll and acts as a limiting factor for phytoplankton growth. Thus, magnesium loss decreases the phytoplankton, Calcium and Magnesium are essential for all the organisms. They are required as micronutrient for algae and important nutrient for the metabolism of plants [39].

Ca and Mg reported values ranging from minimum concentrations of  (285 mg CaCO3/l) at  upstream water in August and (98 mg CaCO3/l) in basin water in August to maximum concentrations (384 mg CaCO3/l) at basin water in April and (179 mg CaCO3/l) in downstream river in May, respectively with ±SD (28.7, 10.1 and 16) and (19.31, 25.83 and 12.8) were recorded at upstream, basin and downstream respectively.

In all sampling sites and dates the level of Ca concentration were higher than Mg concentration and the results shown that a significant positive correlation between sites was found with total hardness at level 0.05 and 0.01 as shown in (Table 5). Calcium and magnesium are considered to be the main constitute of hardness property [40]. The presence of calcium in water supplies results from passage over deposits of limestone and dolomite. While the average abundance of magnesium ion Mg+2 in the earth’s crust is 2.1%; in soils it is 0.03 to 0.84% and in surface waters it is 4 mg. l-1  [6]APHA, 2012) Since these minerals contribute mostly to the dissolved cations in the natural system, an increased rate of weathering does not alter the relative abundance of calcium and magnesium, but increases their concentrations [41]. In the present study, the concentration of calcium was less than that of magnesium. Similar, results have been reported by[42]. This may be attributed to the geological formation of the area which can be related to the nature of soil and rock [43].

The total alkalinity value were ranged between (151 - 262mg/l^-1  ), the highest value was recorded in upstream in August and the lowest value was recorded in basin dam during January with ± SD (17.1, 9.48 and 20.87) from upstream, basin water body and downstream separately (Figure 2) with significant correlation among   sites during studied period a significant positive correlation between sites was found with pH, sodium and negatively with EC, TDS, chloride, and total hardness  at level 0.05 as shown in  (Table 5). Alkalinity in general, was in the range of of Kurdistan and Iraqi standards(Table 5 ) beside its depending on the rock and soil properties caused by the existence of calcium and magnesium carbonate, bicarbonates and possibly hydroxide ions [44]. Although, alkalinity of water has increased in the rainy months. When rainfall passes through the soil layers, it reacts with carbon dioxide to form carbonic acid, the later react with limestone to produce dissolved calcium and bicarbonate (HCO₃) [45].  High alkalinity value in the hot months may be due to the phytoplankton activity, photosynthesis and respiration processes while the low value which recorded at cold month as shown Figure (2) thus may be due to the dilution phenomena by rain or snow which cause the reduction in alkalinity value[46]. Increasing in alkalinity values may be due to decreases in the water level. Bicarbonate increases with the decrease of water levels, accumulation of carbonate during summer results the liberation of free CO₃ during decomposition of bottom deposits, which possibly converts insoluble CaCO3in to soluble Ca (H CO3)₂ have also been reported by [47](Al- Naqishbandy 2020). According to WHO standards (Table 4) the high desirable level of alkalinity concentration is 125mgCaCO3/L and the high permissible level is 200 mgCaCO3/l^-1  [48].

Nitrates are very important nutrient factor in aquatic ecosystems, generally, water bodies polluted by organic matter exhibit higher values of nitrates [49].  The nitrate concentration in surface water is normally low (8-10mg/L), but can reach high level as a result of agriculture run-off, contamination with human and animal wastes. The concentrations often fluctuate with the season and may increase when the river is fed by nitrate-rich aquifers. The sites recorded between (20-36) during April and November 2020 in basin and downstream, (Table 1, 2, and 3) with ±SD (3.16, 2.93, and 4.1) were recorded from upstream, basin and downstream respectively (Figure2). The statistical shown that there is no correlation between sites as shown in (Table 5). The sources of nitrate in water is flowing from agricultural regions which contain chemical fertilizer or from the effluents of factories and sewage wastewater which were discharged without any treatment [50]. This may be due to the nitrate importance in the final phase in oxidation of ammonia and other nitrogen compounds [51].  Also the highest value of nitrate reflects the direct effect of the agriculture runoff [11]. The results of the Nitrate present revealed that the higher values recorded during rainy season. This may be attributed to the oxidation of ammonia by nitrifying bacteria, and the presence of nitrate concentration in indicated level due to presence of many villages and crop farms on upstream river that most of them use fertilizers and it erosion to nearby water during rainy or windy days. The lower values recorded during semi rainy month April may be related to the denitrifying bacteria in basin water body [52]. and mixing of waste water bodies with downstream river due to close contact between Degala sub-district and downstream basin and drain Degala Sewer system through downstream. Commonly, sulfate concentration is an abundant ion in the earth crust and its concentrations of water range from few milligrams to several thousand milligrams per liter, according to water quality criteria in 1989, a guideline value of APHA, 400mg/l^-1 for sulfate was established.

The Sulphate the values ranging from  Minimum value of (204mg/l^-1  were recorded in downstream river in October to maximum concentration(284mg/l^-1 ) during February in basin water body  due to weathering and runoff surface water from the study area [53.54](Fattah,2010 and Kurunc et al.,2005) and ±SD (15.99,23.34 ,and 13.2) were recorded from upstream ,basin and downstream individually (Figure 2). According to statistical relations there were a significant negative correlation with total alkalinity at level 0.05 and 0.01  as shown in  (Table 5). Sulfate is one of the primary particles present in the water in different obsessions going from a couple to a few thousand milligrams for each liter [6](APHA., 2012). In general, Iraqi Kurdistan Region inland water usually contain significant amount of sulfate [55] as shown in table 5.

Dissolve oxygen DO is an important limnological parameter indicating the level of water quality in the water body and the level of organic contamination. When assessing the water quality requirements of an aquatic environment, the determine of DO is remarkably important. The DO values typically remain lower than those of the system where the rate of respiration and organic decomposition is high, and the rate of photosynthesis is high[56]. So dissolved oxygen, may be influenced by water temperature, composition, treatment and any chemical or biological processes taking place in the distribution system [57].

Dissolved oxygen concentration in this study was highly depended on air and water temperature. The maximum value of DO was recorded as 9 mg/l^-1 in April at downstream. This is due to the inverse relationship between oxygen concentration and temperature [58].  and minimum recorded as 4.3 in Degala basin at October and ± SD (1, 0.9 and 1) were recorded from upstream, basin water body and downstream correspondingly. The low oxygen-retaining capacity of water due to the increase in organism respiratory demand at high temperature may also be the reason for low values of dissolved oxygen[59,60]. A significant negatively correlation with total hardness at level 0.05 and 0.01 as shown in (Table 5). During the study period, the maximum DO value was recorded in downstream due to low water temperature and higher atmospheric influences due to its position and heavy water flow and lower temperature at this station and also in the running season compared to other sampling sites [1]. The primary environmental factors directly affect some of the chemical reactions in aquatic ecosystems throughout different seasons of the year [61]. In addition to the biological activities, the solubility of gases also has an effect[62] Meanwhile it can be considered as the dominant factor because of its effect on the rate constant that predict the reaction rate that lead to incomplete insight by ignoring the changes in solute changes and reaction zone areas[63].

Figure 1. A. Map of Iraq showing studied area, B. Map of Erbil province, C. Studied area (Degala)

Table 1: The  physical and chemical properties of studied downstream site during the study period.

Table 2: The  physical and chemical properties of studied basin site during the study period.

Table 3: The  physical and chemical properties of studied upstream site during the study period.

Table 4: The  water resource characteristics standards of Kurdistan, Iraq , and WHO

Table 5: The correlation of physical and chemical properties of studied sites during the study period.

Figure 2.Physicochemical characters of upstream and downstream Degala Basin water (A: PH, B: EC, C: TDS, D: Chloride, E: Potassium, F: Sodium, G: Ca hardness, H: Mg hardness, I: Total alkalinity, J: Nitrate, K: Sulphate, L: Dissolved Oxygen, M: Total Hardness.

passes through the soil layers, it reacts with carbon dioxide to form carbonic acid, the later react with limestone to produce dissolved calcium and bicarbonate (HCO₃) [45].

3. Phycological study:

The total of results of the present study showed that a total of 126 algal genera were recorded. The greatest bulk of identified algal species (65) was belong to Chlorophyta followed by Cyanophyta (35) , Euglenophyta (15) and diatom (11) as shown in table(6).

A total of 126  of algae were identified from the site on the base of their morphological study and the Chlorophyte were dominated over all taxa then Cyanophyta and Diatoms, the isolated strains of algae ranged from unicellular to filamentous in form figure (3). Isolates included Cyanophyta, Chlorophyta and Bacillariophyta (Diatom). The color of the cultures ranged from blue-green to green and yellow-brown for Myxosarcina table (6). Toma and Bahram  [63]  listed and recorded 244 blue-green algae species in the province of Arbil. Aziz and Muhammed [64] recorded a total of 151 algal species in some springs around the Safeen Mountain Area. The majority of the species obtained by Aziz and Muhammed were Chlorophyta with 68 species, followed by Cyanophyta with 46 species, Euglenophyta with 18 species, Chrysophyta with 12 species, Charophyta with 3 species, Rhodophyta with 2 species and Cryptophyta and Pyrrophyta with one species. [65] in five artificial ponds in the main parks within Erbil city, recorded a total of 163 species belong to 69 genera. Furthermore, [66]Aziz and Yasin in 2019 recorded a total of 116 species belonging to 58 genera, 31 families, 19 orders, 9 class, and 8 divisions in eight artificial fish ponds in Erbil.

4. Conclusion: -

The statistical analysis of the data revealed that there were significant differences in physico-chemical parameters between the two sites, with high significant relationships for (EC, TDS, chloride, Na, K, Ca hardness, total alkalinity, nitrate, and DO) and low significant relationships for (pH, total hardness, Mg hardness, and Sulfate) at the (p0.05 level) for all parameters studied. Due to open areas and the drainage of many waste disposals through stream branches that drain their water to an upstream river, as well as the drainage of municipal waste water from Degala town through basins and downstream water bodies, all water samples from all sampling sites revealed the presence of a variety of algal species thus it is recommended to study the  use of algae as an indicator in water pollution and study their role  to remove of polluted substances in present water . There is small change in the pH value during the observation period among upstream, basin and downstream. Different genera of algae found in Degala basin.

                            Table 6: Algal genera isolated from Degala basin

Figure 3: Different algal species from Degala Basin water, a: Chlorella 90X, b: Euglena 200, c: Scenedesmus 58X, d:Chara 25X, e: Spirogyra 90 X, f: Spirulina 200X,  g:Stigeoclonium 58X, h:  Selenastrum 66X, i:Chlamydomonas 300X,  j:Chroococcus 140X, k:Oscillatoria 2000X, :m: Phormidium 2500X, n: Lyngbya 500X, o: Anabaena 2000X, p: Nostoc 500X, q:Myxosarcina 500X, r: Navicula 700X.

Declarations:

Funding: None.

Conflict of interest: The authors declare that they have no conflict of interest.

Data Availability Statement: All of the data supporting the findings of the presented study are available from corre­sponding author on request.