Abstract
Javah Dam is located on the Sirvan River after the two main tributaries of Qeshlaq and Gavehrud, which predicts the trophic conditions of the Javah Dam reservoir in the existing conditions, is one of the most important research priorities before exploitation. Sampling operations were carried out in 5 selected stations, during the fall of 2020 to the summer of 2021, in the two branches of Qeshlaq and Gaveh River and in the water intake of Javah Dam. The comparison of the data of this research with different domestic and foreign standards showed that only the nitrate parameter was less than the permissible limit, but other parameters from one to several times (especially organic nitrogen) exceeded the permissible limit, which indicates that the water is polluted and of bad quality in different stations. According to Iran's water quality index (IRWQI), the highest quality was recorded in station 4 and the lowest quality was recorded in stations 2 and 3. Based on the TOC% of the sediments, the region was considered slightly polluted to very polluted, especially in stations 2 and 3, but the condition of station 4, which is related to the Gavehrud branch, was better. The mean and standard deviation of heterotrophic bacteria or the total count of bacteria in autumn, winter, spring and summer seasons in 5 stations are 7.30±0.22, 6.54±0.63, 7.08±0.67, respectively. 7.58±0.32 number per 100 ml, total number of forms 11.4+1.07, 3.61±1.27, 4.48±0.55 and 5.23±1.22 respectively The number per 100 ml and the total count of fecal forms were 2.84±1.07, 3.042±0.79, 2.86±1.18 and 3.44±1.98 respectively. The results of stepwise multiple regression indicated a significant difference between the total number of bacteria with parameters of pH, dissolved oxygen and temperature, and total forms with pH, turbidity and temperature (p≤0.05). Also, a significant difference was observed between turbidity and dissolved oxygen with the overall count of fecal forms (p≤0.05). The increase in other environmental parameters also caused changes in the investigated microbial indicators, but despite this, the resulting changes were not significant. According to the results, 157 species of microalgae were identified in 7 kingdom of Bacillariophyta, Myzozoa, Cyanobacteria Chlorophyta, Euglenozoa, Xantophyta and Cryptophyta in water and periphyton samples. Saprobi index showed changes from 1.5 to 2.5 units during the study period. This range of saprobic index changes indicates water quality with "moderate pollution". In algal periphyton, the average saprobic number of the dominant species was mainly classified in the "moderate pollution" group. Calculation of diatom trophic index (TDI) in water and periphyton samples showed that (except station 2 in spring) it was from 3.7 to 4.9 (dam reservoir, summer). This amount of TDI indicates the condition (hypertrophy) with loading (too much) of nutrients. In this study, 8 families of Macro benthic invertebrates including Chironomidae, Lumbriculidae, Simulidae, Baetidae, Hydropsychidae, Erpobdelidae, Potamidae, Glosiphonidae, Gamphidae, Unionidae and Potamidae were identified. The results showed that the highest density belonged to the Baetidae family with 464 ± 152.3 numbers per square meter and the lowest density belonged to the Gamphidae family with 11 numbers per square meter. Examining the water quality status using the Helsinhof index showed that the value of this index in different stations varied from 5.98 (relatively poor quality class) in station 1 to 8.00 (very poor quality class) in station 2. Based on the obtained results, a total of 2003 fish were caught which belonged to 13 species, the identified fish belonged to 3 families of Cyprinidae, Mastacembelidae and Nemachielidae. The results of the present study showed that the majority of fish species identified with a relative abundance of 96.6% were from the Cyprinidae family. The investigation of Shannon's species diversity index in the studied stations showed that it had an increasing trend from upstream to downstream of the headwaters (stations 1, 3, 4 and 5), so that its minimum was 1.2 in station 1 and its maximum in The amount of 2.05 was estimated at station 5. Examining the ecological integrity of KARR in stations 1, 3, 4 and 5 showed that it had a sinusoidal trend, so that its changes decreased from station 1 to station 3, then increased in station 4 and again in station 5. decreased Also, the results of this study showed that the trend of changes in the biological index of ecological integrity of KARR in the stations in each season is similar to the mentioned changes. The water quality classification based on the ecological integrity of KARR showed that stations 1 and 4 were in the good quality class with a numerical value of 40 and 42, respectively, and stations 3 and 5 were in the good quality class with a numerical value of 9 and 34, respectively. In addition, it is mentioned that the quality of water was 5 km lower than station 3 (at the confluence of two Qeshlaq and Gavehrud tributaries) with a numerical value of 32 in the middle class during a sampling session in the Atumn season. The results of this classification in different seasons of the year showed that the numerical values of this index had changes to some extent (except for station 4 which did not have changes in water quality in different seasons of the year) and the trends of its changes are similar in the stations and in different sampling periods. Overall, in terms of water quality, the lowest water quality class belonged to the summer season, and the winter and spring seasons had the highest water quality class. The components of the reservoir ecosystem of the dam and the type of fish species, the composition and the amount of their reserves can be affected in case of dewatering as a result of the possible occurrence of trophicism. Thus, in such a situation, considering the high pollution of water entering the dam, it is suggested that all the environmental and health considerations that are mentioned in the conclusion part of the plan (in case of possible exploitation of the Javeh dam) be carried out.
Keywords: Water quality classification, Algae, Benthic macroinvertebrates, Fish, Biological indicators, Nutritionism, Javah Dam