The Büyük Menderes River is located in the western Anatolia, southwest Turkey, between 37˚6' - 38˚55' North and 27˚36' - 30˚36' East. Borders of the basin which constitutes 3.2% of Turkey’s land surface includes parts of Aydın, Uşak, Denizli, Muğla, Afyon, Isparta, Burdur and İzmir provinces. With 584 km, it is the longest river in the Aegean Region. Many lateral streams feed the river, with the main tributaries being the Çine, Banaz, Çürüksu and Akçay rivers. The majority of small tributaries dry out in summer. As an important river system, the Büyük Menderes includes wetlands such as

Işıklı Lake, Bafa Lake, and the Büyük Menderes River Delta. It is also a very important river basin in terms of biodiversity, being subject to the effects of both the Mediterranean and continental climates. The locations of the eight stations selected for this study are shown in Figure 1. The stations were chosen deliberately to identify the degradation of the quality of the water as a result of the urban pollution observed in the area. Station 1 is the Adıgüzel Dam. In this dam, there is a certain problem detected in the form of mutations in the genetic structure of the fish and this problem results from the industrial residues which contain leather and textile as well as waste materials coming from Uşak. Station 2 is constituted by the Yenice Regulator. It is 32 km away from the Adıgüzel Dam where pollution stems from domestic waste and pesticides. Station 3 is the Sarayköy Bridge which is influenced by the wastes coming from the Denizli-Sarayköy sewage system, the geothermal plant nearby, and a textile factory. Station 4 is the Feslek Regulator. The Büyük Menderes River is polluted by domestic wastes and pesticide packages coming from the nearby residential and industrial areas. Station 5 is the Yenipazar Bridge which is polluted by the water coming from the Akçay tributary in the Yenipazar Bridge. Station 6 is the Aydın Bridge which is affected mainly by untreated wastewater coming from the industrial zones and municipal sewage treatment plants nearby. Station 7 is the Koçarlı Bridge which merges with the Menderes following the

Cine and İkizdere streams. Station 8 is the Söke Regulator, stations of which are polluted by the domestic wastes and pesticide packages coming from the nearby areas.

The quality of the water was measured in 8 stations which are the Adıgüzel Dam, the Yenice Regulator, the Sarayköy Bridge, the Feslek Regulator, the Yenipazar Bridge, the Aydın Bridge, the Koçarlı Bridge, the Söke Regulator. The temperature, pH and conductivity values were measured in the stations. The samples to be used for the measurements were brought to the laboratories as soon as possible to start the analyses. A Mercury Thermometer with 0.1˚C sensitivity was used in the measurements. The Orion pH Meter (Model SA 720) was used to measure the pH. The Jenway conductometer was used to measure the electrical conductivity. The argentometric method was used to measure the chloride; flame photometry was used to measure the sodium and potassium; the Perkin Elmer automatic absorption Spectrophotometer equipment was used to measure the calcium and magnesium; the calorimetric method was used to measure the sulfate; Total dissolved solid (TDS) was measured by TDS meter (Model: HM Digital); Total water hardness (TH) as CaCO₃; Suspended Solids (SS) dried at 103˚C - 105˚C. In order to analyze the results, the international algorithmic processes were implemented [6] . Analysis of the water samples was conducted at government facilities of SHW Quality Control Laboratory. The measurements were made between the years 2000 and 2013, in the months of February, April, and then June, August, October as well as December. All of the water samples were analyzed for temperature, pH, EC, Cl⁻, Na, Ca²⁺, Mg²⁺, K⁺, , TDS, TH and SS. The SPSS 21 Statistical Analysis Program was used for the data analyses. The One-Way Anova and the Tukey Multiple Comparison tests were applied to the data. The difference between the groups was p < 0.05. The distribution of the data was shown by using the Box-Plot Graphs.

The temperature value was the lowest in the Yenice Regulator (18.44 ± 4.70^a mg/l) and the highest in the Aydın Bridge (20.14 ± 5.52^a mg/l), which is given in Table 2. No significant differences were observed in the annual temperature values of the 8 stations (p > 0.05). The temperature was the lowest (16.62 ± 4.48^f mg/l) in 2012 and the highest (22.07 ± 4.79^a mg/l) in 2007. The difference between the years for which the study was conducted was found to be statistically significant (p < 0.05) (Figure 2). In terms of water temperature, The Büyük Menderes water can be classified as “class I” according to the TWPCR.

The pH value was measured as the lowest in the Adıgüzel Dam (7.79 ± 0.18^d) and as the highest in the Söke Regulator (7.99 ± 0.26^a), which is given in Table 2. In all of the 8 stations, significant differences were determined in the annual pH levels (p < 0.05). The pH was measured as the lowest (7.73 ± 0.24^e) in 2003, and measured as the highest (8.11 ± 0.33^a) in 2008. There were differences between all the years, and these differences were found to be statistically significant (p < 0.05) (see Figure 3). In terms of pH, the water of Büyük Menderes river can be classified as “class I” according to the TWPCR. Therefore, pH value in all the years is compatible with the values proposed by TS 266 and WHO guidelines.

The EC value was measured as the lowest in the Adıgüzel Dam (785.80 ± 135.23^d μs/cm) and measured as the highest in the Feslek Regulator (1997.39 ± 676.72^a μs/cm), which is given in Table 2. In all of the 8 stations, significant differences were determined in the annual Electrical Conductivity (EC) levels (p < 0.05). The Electrical Conductivity (EC) level was measured as the lowest (1249.14 ± 508.22^c μs/cm) in 2004, and it was measured as the highest (1718.66 ± 772.67^a μs/cm) in 2007. The differences between all the years were statistically significant level (p < 0.05) (Figure 4). The electrical conductivity (EC) is usually used for indicating the total concentration of charged ionic species in water [7] . EC value in all the years is compatible with the value proposed by TS 266 and WHO guidelines.

The Chloride was measured as the lowest in the Adıgüzel Dam (50.81 ± 16.45^d mg/l) and it was measured as the highest in the Sarayköy Bridge (160.14 ± 60.24^a mg/l), which is given in Table 2. The differences were observed to be significant in all of the 8 stations (p < 0.05). The Chloride was measured as the lowest (72.85 ± 44.10^e mg/l) in 2013 and it was measured as the highest (130.20 ± 66.44^a mg/l) in 2007. The annual differences were found to be statistically significant (p < 0.05) (Figure 5). Water quality at Adıgüzel Dam was I. class in terms of COD values while Sarayköy Bridge was II. Class. Chloride value in all the years is compatible with the value proposed by TS 266 and WHO guidelines. For freshwater fish, however, the concentration of chloride should not exceed 860 mg/L [8] . All Cl⁻ values recorded in sampling stations in Büyük Menderes River were below the maximum permissible level for protection of aquatic life.

The Sodium was measured as the lowest in the Yenice regulator (75.26 ± 36.50^b mg/l) and it was measured as the highest in the Feslek Regulator (153.30 ± 73.76^a mg/l), which is given in Table 3. In all of the 8 stations, significant differences were determined in the annual pH levels (p < 0.05). The Sodium was measured as the lowest (83.08 ± 36.44^d mg/l) in 2001 and it was measured as the highest (139.85 ± 87.51^a mg/l) in 2007. The annual differences were found to be statistically significant (p < 0.05) (Figure 6). In terms of sodium, the water of Büyük Menderes river can be classified as “class I” according to the TWPCR. Sodium value in all the years is compatible with the value proposed by TS 266 and WHO guidelines. The natural range of sodium ions in water and soil is so low, their existence can show river pollution caused by human activities [9] .

In total hardness Ca and Mg are the most important two elements. They are important for skeleton structure of both aquatic and terrestrial organisms. Also, Mg has an important function in the blood of the human and animals. Water hardness is very important quality criteria for fisheries and drinking [10] .

The Calcium levels were measured as the lowest at Adıgüzel Dam (75.90 ± 25.24^e mg/l) and they were measured as the highest at Sarayköy Bridge (149.02 ± 51.90^a mg/l), which is given in Table 3. In all of the 8 stations, significant differences were determined in the annual pH levels (p < 0.05). The Calcium was measured as the lowest (96.81 ± 37.68^a mg/l) in 2012 and it was measured as the highest (119.42 ± 49.50^a mg/l) in 2007. The differences between the values for the study years were not statistically significant (p > 0.05) (Figure 7).

In fisheries, 400 mg/L calcium values are accepted as suitable [11] . Calcium value in all the years is compatible with the value proposed by TS 266 and WHO guidelines. The higher value of calcium registered during the study period may be due to the influx of industrial waste and sewage to the river water.

The Magnesium was measured as the lowest at Adıguzel dam (38.65 ± 9.59^f mg/l) and it was measured as the highest in the Feslek regulator (109.87 ± 45.58^a mg/l), which is given in Table 3. In all of the 8 stations, significant differences were determined in the annual pH levels (p < 0.05). The Magnesium was measured as the lowest (65.58 ± 27.38^d mg/l) in 2012 and it was measured as the highest (92.74 ± 41.32^a mg/l) in the year 2007. The difference per annum was found to be statistically significant (p < 0.05) (Figure 8). Furthermore, it was highlighted that the amount of magnesium which is found in 95% of water with 14 mg/l magnesium. In addition, it is probable that 100 mg/l - 400 mg/l of poisoned magnesium was found in fresh water. In retrospect, fresh water fish which are found in 1000 mg/l magnesium can also be found salty water which includes sodium and calcium [12] .

Büyük Menderes River is poor in potassium and plankton growth is so low. The Potassium levels were measured as the lowest in the Adıguzel Dam (6.20 ± 1.27^c mg/l) and they were measured as the highest in the Feslek Regulator (10.85 ± 3.77^a mg/l), which is given in Table 3. In all of the 8 stations, significant differences were determined in the annual pH levels (p < 0.05). The Potassium was measured as the lowest (6.31 ± 1.51^e mg/l) in 2001 and it was measured as the highest (11.48 ± 4.09^a mg/l) in 2007. The annual differences were found to be statistically significant (p < 0.05) (Figure 9). In terms of potassium, the water of Buyuk Menderes river can be categorized as “class I” as per the regulations in TWPCR.

The Sulphate () values (Table 4) were measured as the lowest in the Yenice Regulator (108.38 ± 100.47^e mg/l) and they were measured as the highest in the Feslek Regulator (520.81 ± 245.04^a mg/l). In all of the 8 stations, significant differences were determined

in the annual Sulphate () levels (p < 0.05). The Sulphate () values were measured as the lowest (166.07 ± 143.77^d mg/l) in 2003 and they were measured as the highest (378.21 ± 265.45^a mg/l) in 2007. The differences for all the study years were found to be statistically significant (p < 0.05) (Figure 10). Sulphur is present in natural

waters as sulphate. Water quality at Yenice Regulator was I. class in terms of sulphate values while Feslek Regulator was IV. Class. In this region, increase in sulphate originates from land with gypsum.

TDS was measured as the lowest in the Adıgüzel Dam (493.25 ± 105.07^e mg/l) and it was measured as the highest in the Feslek Regulator (1379.86 ± 502.267^a mg/l), which is given in Table 4. In all of the 8 stations, significant differences were determined in the annual pH levels (p < 0.05). TDS was measured as the lowest (797.50 ± 323.745^d mg/l) in 2004 and it was measured as the highest (1239.58 ± 584.13^a mg/l) in 2007. The annual differences were found to be statistically significant (p < 0.05) (Figure 11). Water quality at Adıgüzel Dam was I. class in terms of TDS values while Feslek Regulator was II. class. Klein (1992) has reported that the excess amount of TDS in water disturbed ecological balance and cause suffocation of aquatic life.

TH was measured as the lowest in the Adıgüzel Dam (337.56 ± 74.15^d mg/l) and it was measured as the highest in the Feslek Regulator (797.90 ± 274.25^a mg/l), which is given in Table 4. In all of the 8 stations, significant differences were determined in the annual pH levels (p < 0.05). TH was measured as the lowest (490.69 ± 234.90^e mg/l) in 2013 and it was measured as the highest (655.52 ± 280.59^a mg/l) in 2008. The yearly difference was found to be statistically significant (p < 0.05) (Figure 12). Water quality was found to be Class I grade at the Adıgüzel Dam for the case of TDS values while Feslek

Regulator was found to be Class II grade.

Sophisticated concentrations of suspended solids can assist as carriers of toxics, which readily cling to suspended elements [13] . SS was measured as the lowest in the Yenice Regulator (1.14 ± 0.56^d mg/l) and it was measured as the highest in the Feslek Regulator (2.51 ± 1.42^a mg/l), which is given in Table 4. In all of the 8 stations, significant differences were determined in the annual pH levels (p < 0.05). SS was measured as the lowest (1.17 ± 0.89^e mg/l) in 2009 and it was measured as the highest (2.62 ± 1.10^a mg/l) in 2000. The annual differences were found to be statistically significant (p < 0.05) (Figure 13). Therefore, SS value in all the years is compatible with the values proposed by TS 266 and WHO guidelines.

Inland waters can be categorized in 4 classes as per the TWPCR. Class I is defined as the high quality grade water which is usable with quality of drinking water which can be used after disinfection, and also as water for activities that are recreational in nature (such as swimming which requires body to be in contact with water), as well as breeding of trout and other relevant farming activities. Class II is water which is partially polluted and it can be utilized as a drinking water as long as it is treated with advanced methods, and which can also be used for recreational purposes, fish breeding (excluding trout). It is also possible to use Class II water as an irrigation water as long as it can be maintained so that it has the required quality. Class III is actually polluted which can be used for industrial purposes after extensive treatment. However, industries such as food industry or textile related industries are not good candidates due to their need for very high quality water. Class IV is extremely polluted water with far more poor water

quality as compared to class III and thus it shouldn’t be utilized in any circumstance. The studied parameters are also compared with TS 266 and WHO guidelines [14] [15] .

Knipowitschiacaucasica, Hemigrammocapoetakemali, Pseudophoxinusmaeandri, Gobiomaeandricus, Esoxlucius, Gambusiaholbrooki, Tincatinca, Oxynoemacheilusgermencicus, Oxynoemacheilus cf. Cinicus, Cobitiscfsimplicispina, Chondrostomameandrense, Luciobarbuskottelati, Capoetacapoetabergamae, Ladigesocyprismermere and Alburnoides cf. Smyrnaeare endemic species and have little tolerance to pollution in water. The Buyuk Menderes River does not have many of these species. Carassiusgibelio, Pseudorasboraparva and Lepomisgibbosus, which are endangered species, may tolerate pollution more than the abovementioned species. In this context, Carassiusgibelio is found plenty in this particular river (Table 1).