1 Introduction

The quantity and quality of water is the basis of sound water resources use and achieving sustainable development goals (SolaimaniSardo et al., 2013). River and streams are considered as vital arteries of living environment that affect any human activity directly or indirectly (Ebrahimi-Dastgerdi et al., 2017; Poff et al., 2007). Recognition of water in terms of quantity and quality and is an essential step in optimizing consumption of water resources (Candido et al., 2022). The main aim of water resources management through infrastructures is to provide water for agricultural and drinking, environment, and industrial purposes, which need different water quality considerations (Dadebo et al., 2023). Rivers have undergone many changes, apart from their natural variability of flow regimes. There are various elements in the water that are effect the chemical and physical characteristics. The analysis of anions and cations and selected chemical parameters can reveal many of water characteristics. In terms of water quality, physicochemical parameters include fluorine, chlorine, sodium, sulfate, iron, TH, and EC. The Na+, Ca2+ and K+ parameters are of most important elements in water quality analysis and practical applications (Balboul et al., 2019; Benjeddou et al., 2023; Gaur et al., 2022). Maintaining the quality of fresh water and tackling the problem of water caused by point and non-point pollution as well as pollutants released from agricultural lands requires serious action (Khiavi et al., 2013; Nasiri et al., 2023). Considering the water scarcity and degraded water resources, population growth, and ongoing growth of industry and agriculture in Iran, the optimal management of available water resources will be the most important policies in water sector (Mobarhan et al., 2024; Barahooei et al., 2024). Therefore, water quality monitoring is one of the important tasks in the field of the environment due to recent droughts and urban and rural development (Jafarzadeh et al., 2011; Mohammad Taghi Samadi et al., 2009a, 2009b).

Increased contaminants caused by population growth, urban runoff drainage, industrial and agricultural sewage disposal, and waste disposal sites have contributed to the spread of pollution and water resources degradation (Elsayed et al., 2020; Samadi et al., 2009a, 2009b; Sánchez et al. 2007).

The average precipitation of Iran as an arid/semi-arid area is about one-third of the Earth's average, also the spatial and temporal pattern of precipitation is not uniform throughout the country. Therefore, controlling surface water and construction of small and large dams is one of the priorities of surface water management in different climatic regions. Therefore, determining water quality and its monitoring is necessary to implement appropriate measures to preserve water quality (Gad et al., 2022). Healthy water bodies are an essential prerequisite for maintaining the environmental, and economic development (Yousef-Zadeh, 2013). Dams are built for satisfying variety of purposes, including hydroelectric generation, flood control and provide a store of water for drinking and agricultural purposes. As the population grows and as a result of increasing demand for water for various sectors, the necessity of water-based investments, and hydraulic structures is inevitable. Water scarcity is the main issue of almost all countries over the world. The construction of dam results in the displacement of local communities, causing social and economic disruptions (Bomzon et al., 2023). Dams can disturb natural habitats, leading to biodiversity loss and impacting ecosystems and species dependent on the natural river flow. These structures have the potential to modify water flow and quality, affecting downstream ecosystems, water availability, and the overall water quality for both human and natural systems (Soltani et al., 2021; Winton et al., 2019). While dams offer benefits such as water storage and flood control, they also pose challenges, introducing vulnerabilities in water supply systems and elevating the risk of conflicts among various users and stakeholders (Ehsani et al., 2017; Karamouz et al., 2010). Dam construction may affect the water quality at downstream, which depends on the source of water and rate of regulated outflow. In hypolymion water (under reservoir lake water), organic matter decomposition consumes oxygen and results in anaerobic conditions due to the lack of sunlight penetration. In these reduced conditions, hydrogen sulfide gas is produced along with CO2 and the pH of the water is reduced and Fe and Mg2+ are dissolved in the sediments. The release of this water leads to the deposition of Fe and Mg2+ on the bed of the river (Samani et al., 2009).

Salehi & Zeinivand, 2016) in the Kuhdasht region of Lorestan province examined the groundwater quality for drinking and irrigation using AqQA software, and determined the suitability of water. (Priya, 2013) examined the quality of water in India using AqQA software, which confirmed the appropriateness of the water quality of the study area. (Sappa et al., 2014) examined the quality of water for irrigation and drinking using the AqQA software in Italy, which showed that water quality is good for drinking and irrigation. (Ding et al., 2015) examined the effects of land degradation on water quality of Dongjiang River in China using RS and GIS. They found that the water quality parameters had significant changes in urban and forest land uses, especially in in dry periods. According to the literature review, the assessment of water quality may alter due to diverse driving forces, which the impacts of damming has received less attention. Alterations in water quality and flow patterns induced by dams have the potential to influence the well-being of downstream ecosystems, encompassing fisheries, wetlands, and riparian habitats (Nilsson & Berggren, 2000; Palmer & Ruhi, 2019). Dams can disturb the natural flow dynamics, causing shifts in water temperature, oxygen levels, and nutrient concentrations, thereby affecting the vitality of aquatic ecosystems and water quality (Soomro et al., 2023). The prolonged operation of dams can result in cumulative effects on water quality over time, as reservoirs accumulate sediment and pollutants, and the original river flow undergoes modifications, impacting the overall health and quality of the water (Li et al., 2022).

The Balikhlouchai River is one of the main upland tributaries of the Gharehsou River, which supplies the drinking water of Ardabil city, Yamchi irrigation network, and ecological flow requirement of lake Shorabil. Also, the Sabalan Dam constructed on Gharehsou River for agricultural use and possibly drinking in a near future. It should be noted that these rivers are regulated by construction of dams and are severely affected by pollutants while passing through population centers and agricultural lands.

While existing studies emphasize water quantity and quality assessment, there is a lack of comprehensive research on specific alterations in downstream water quality due to damming activities. Despite acknowledging dams' benefits, addressing potential negative consequences like disruptions to downstream ecosystems and water use for various purposes remains inadequately explored, underscoring the vital role of healthy water bodies in environmental and economic development. It should be noted that the impact of dam construction on water quality parameters has received less attention, which is a significant highlight of the current study. Therefore, the primary goals of this study were to assess the physicochemical parameters of water and examine their variations at river gauge stations both upstream and downstream of the Yamchi and Sablan dams in Ardabil province, Iran. The analysis of water quality changes in these regions was conducted using Schoeller, Piper, Durov, and Stiff charts.

2 Materials and methods

2.1 Study area

Ardabil province located at the northwest of Iran in Azerbaijan region. Gharehsou River drains an extensive area of surrounding Ardabil region with a length of 285 km. The average annual flow of the Gharehsou is about 554 million cubic meters is, the longest and most important river in terms of water yield in the Ardabil province. The site of Sabalan Reservoir Dam is located 40 km from Meshginshahr city and at a height of 77 m from the stream bed of Gharehsou River. The average height of the project area is about 1000 m amsl and it has been under operation since 2005. The purpose of the Sabalan dam construction was to store 105 million cubic meters, regulation of 115 million cubic meters of runoff from the Gharehsou River, irrigate 15,000 hectares of Meshginshar orchards, drinking water supply, flood control, and immigration reduction (Asgharpour et al., 2014; Jafarzadeh et al., 2011). Also, the Balikhlouchai River is one of the permanent rivers in Ardabil province, which provides the required water of Yamchi irrigation network and agricultural lands of Ardabil plain (Ghorbani et al. 2014).

The Balikhlouchai and Gharehsou Rivers play a vital role as water sources in Ardabil province, serving drinking water needs and supporting irrigated agriculture in the region. The Balkhlochai River serves as a permanent habitat for aquatic mammals and a transitional habitat for various migratory birds, facing increased environmental threats as it passes through Ardabil city. Despite being considered a permanent river, the Gharehsou River experiences significant dry periods in the summer due to water extraction for irrigation. The Pole-Almas and Dostbeiglu stations are located in downstream of Yamchi and Sabalan dams, respectively. The location and characteristics of the dams and hydrometric stations are presented in Fig. 1. Nir serves as the upstream hydrometric station for the Yamchi dam, while Poleh-Almas station recorded the water quality data as the downstream station. Additionally, Arbabkandi and Dostbeiglu stations are situated upstream and downstream, respectively, of the Sabalan dam.

Fig. 1
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Location of the stations and dams studied in Ardabil province

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2.2 Methodology

In the present study, water quality parameters of Nir, Pol-e-Almas, Arbabkandi and Dostbeiglu river gauge stations have been used to study the possible effects of Yamchi and Sabalan dams on the Balikhlouchai and Gharehsou rivers. The water quality parameters used include Ca2+, Mg2+, K+, Na+, CO32−, HCO3−, SO42−, Cl−, EC, pH, and TDS. Nir station at the upstream of the Yamchi dam (length of data records, 1972–2014) and the Poleh-Almas station at the downstream of the dam (time length of data is 2005–2014). Also, in Sabalan Dam, the Arbabkandi station at the upstream of this dam with a 20-years period (1999–2014) and Dostbeiglu station at the downstream of the dam with a length of dataset records of 2005–2014. It should be noted that due to the fact that the dams have been under operation since 2005, therefore, at the downstream stations of these dams (Pol-e-Almas and Dostbeiglu), the data from 2005 were used to determine the effect of dams on water quality parameters of studied rivers.

Also, the independent T-test was conducted to investigate the effect of Yamchi and Sabalan dams on the flow discharge and also the water quality parameters at the studied watersheds (Irenosen et al., 2012).

Statistical test is used to evaluate the difference in average flow and water quality variables in different sites and datasets. This test was also used when the standard error of the dataset was unknown and the standard error of the samples was known. Normality of data is the prerequisite assumption of the variables. Through the T-test the significant difference between the two groups of data has been examined (Derrick et al., 2017; Fay & Proschan, 2010).

2.2.1 AqQA software

AqQA software is able to perform six data homogeneity tests based on AWWA-1030-E standard methods. The AqQa tools easily create 11 different plots, including time series, Schoeller diagrams, ion balance, Durov, Piper, Stiff. In addition, carbon balance calculations, TDS, Density and EC, and organic, inorganic, biological, isotopic, and radioactive analysis make AqQA platform an appropriate tools for analyzing water quality data (Hosein Salehi et al., 2016). In this regard, the following is explained regarding the diagrams prepared in this study.

2.2.1.1 Schoeller diagram

The Schoeller semi-logarithmic diagram presents main ions (mEq/L) and illustrate the chemical difference in water quality parameters. The Schoeller diagram is usually used in hydrological reports for drinking water classification (Hosein Salehi et al., 2016; Schoeller, 1964). In the present study, this diagram is used to evaluate the quality of water for drinking.

2.2.1.2 Piper diagram

One of the most common methods for determining the chemical water facies is the Piper curve (Piper, 1944). Based on the Piper chart, eight chemical facies can be distinguished that are derived from the combination of Na+, HCO3−, Ca2+, Mg2+ and Cl−. These eight facies can be classified into three fresh, salty, and combined water types.

2.2.1.3 Durov diagram

The Durov chart to determine the type and source of groundwater based on the values of major cations (%) and anions (%) of water (Durov, 1959; Hosein Salehi et al., 2016).

2.2.1.4 Stiff diagram

This chart is used to evaluate the qualitative changes in water condition in a given place and distinguished periods. This diagram consists of four parallel horizontal axes that cut off their zero-valued vertical axis (Stiff, 1951).

For this purpose, the water quality data of each river gauge station has been prepared based on AqQA input format. Then, Schoeller, Piper, Durov and Stiff charts were prepared to evaluate the water quality parameters. In conjunction with the Stiff chart, only the graphs for 2013 year are presented as sample. In addition, the chemical characteristics of water at the stations studied were extracted from AqQA software. Also, the desirable (utility) level of Schoeller water quality parameters was investigated. Finally, histogram of SAR and ESR parameters were prepared at each station using MS Excel software. Quantitative values of mean and coefficient of variation statistics in each river gauge station based on each parameter were presented in Table 1. Also, Table 2 shows the criteria for drinking water quality according to Schoeller diagram.

Table 1 Quantitative values of average and coefficient of variation in each river gauge station, Ardabil province, Iran
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Table 2 Schoeller drinking water quality criteria
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3 Results and discussion

The effects of Yamchi and Sabalan Dams construction on the water quality of the Balikhlouchai and Gharehsou rivers in Ardabil province were analysed with the help of AqQA software and statistical test.

The results of T test on the effect of Yamchi and Sabalan dams on flow discharge and also the parameters affecting water quality in the pre- and post-dam construction periods were presented in Tables 3 and 4.

Table 3 The results of independent t-test in investigating the effect of Yamchi and Sabalan dams on flow discharge, Ardebil province, Iran
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Table 4 The results of independent t-test in investigating quality parameters changes affected by the Yamchi and Sabalan dams, Ardebil province, Iran
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Based on the results presented in Table 3, it can be said that the construction of Yamchi and Sabalan dams had a significant effect on the river flow discharge. The discharge values in the post-dam period had a significant reduction at the level of 1%, which is due to the regulating effects of the dam operation. Also, among the parameters affecting water quality, the construction of Yamchi Dam had a significant effect on Ka, Na, Mg, Ca, SO4, Cl, HCO3, CO3 and pH parameters at the 99% confidence level (α < 0.01). Meanwhile, Ka, Na, Mg, Ca, SO4, Cl, HCO3, EC and TDS parameters were also affected under the influence of Sabalan dam construction at 99% confidence level (α < 0.01) (Table 4).

The results of an independent t-test examining the impact of Yamchi and Sabalan dams on flow discharge shows that the F statistic is significantly different for both dams (Yamchi: 1067.28, Sabalan: 1302.66), indicating a substantial difference in flow discharge. The t-test results confirm this difference, with a t-value of 49.98 for Yamchi and 34.39 for Sabalan, both associated with a p-value of 0.00. The mean difference in flow discharge between the two dams is noteworthy, with 2.85 for Yamchi and 6.69 for Sabalan. According to Table 4, the results of an independent t-test investigating changes in water quality parameters affected by the Yamchi and Sabalan dams. Across various water quality parameters, significant differences are observed due to the influence of dam. For instance, in the parameter K, there is a considerable difference (t = -14.12) between Yamchi and Sabalan dams, with a mean difference of -7.75. Similar patterns can be observed in Na, Mg, Ca, SO4, Cl, HCO3, CO3, pH, Ec, and TDS, all indicating substantial differences between the two dams.

Comparatively, Yamchi and Sabalan dams exhibit notable differences in their impact on water quality parameters. Yamchi, for example, shows more pronounced variations in several parameters, emphasizing its unique challenges. Sabalan, while still presenting differences, tends to have a comparatively smaller impact in certain parameters. In this regard, it can be stated that the impact of dam construction on water quality parameters is heavily influenced by dam operation and the reduction in flow discharge downstream of the dam. In other words, since the Yamchi dam is more influenced by human activities and water supply for various purposes, it has exerted a more significant impact on water quality.

The results of water quality parameters at the stations studied are presented in Table 5.

Table 5 Values of water quality parameters at the stations studied using AqQA software
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According to the results of Table 5, TDS and EC values at Nir, Poleh-Almas, Arbabkandi and Dostbeiglu stations are 312, 789, 1288, 1372 mg/l and 448, 1130, 1845 and 941 mhos/cm, respectively. The value of Mg2+ at Arbabkandi station is at the highest level. The largest amount of TH is also related to Arbabkandi station. The graphs of Schoeller, Piper, Durov and Stiff diagrams in relation to water quality parameters are shown in Figs. 2, 3, 4 and 5.

Fig. 2
figure 2

Schoeller diagram of the studied stations, a Pre-dam Yamchi, b Post-dam Yamchi, c Pre-dam Sabalan, d Ppst-dam Sabalan

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Fig. 3
figure 3

Piper diagram of the studied stations, a Pre-dam Yamchi, b Post-dam Yamchi, c Pre-dam Sabalan, d Ppst-dam Sabalan

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Fig. 4
figure 4

Durov diagram of the studied stations, a Pre-dam Yamchi, b Post-dam Yamchi, c Pre-dam Sabalan, d Ppst-dam Sabalan

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Fig. 5
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Stiff diagram of the studied stations, a Pre-dam Yamchi, b Post-dam Yamchi, c Pre-dam Sabalan, d Ppst-dam Sabalan

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In similar research, Kurunc et al (2006) found that the Kilickaya Dam in Turkey impacted Kelkit Stream's water quality, causing a modest decline in most constituents, excluding Na + and Cl − . The study attributed these changes to the reservoir's prolonged hydraulic residence time and dilution effects from winter snowmelt and spring rainfalls and stated that the Kilickaya Dam significantly influenced the water quality of Kelkit Stream. Moreover, Bayram et al. (2012) conducted a study evaluating the impact of the Torul Dam on water quality in NE Turkey through analysing 13 physico-chemical parameters and found to have a positive effect, decreasing annual average concentration values and demonstrating significant correlations among the studied parameters.

Based on the Schoeller diagrams in each station, it can be concluded that water quality classified as desirable in all four studied rivers (Fig. 2). In this regard, (Salehi & Zeinivand, 2016; Hosein Salehi et al., 2016) found water quality to be appropriate in similar conditions to the present rivers. Also, according to the Piper diagram, the amount of Na+, Cl− and SO42− at the station of the Poleh-Almas (downstream) increased compared to the Nir station (upstream). In this regard, (Hosein Salehi et al., 2016) in Saqez city also examined water quality and reported a decrease in these parameters. The Durov diagram which can be used to determine the type and origin of water indicates that the type of water at the upstream station of the Yamchi dam (Nir) is Carbonate and the water had the lower TDS content. The amount of TDS has increased at the station after the Yamchi dam (Poleh-Almas). The pH of the water is neutral in the Arbabkandi station, but at the Dostbeiglu station (after Sabalan dam) has shifted toward alkaline condition.

In Fig. 6, the Wilcox water quality diagram for irrigation purposes is presented at two stations, Poleh-Almas and Dostbeiglu, located downstream of the Yamchi and Sabalan dams, respectively.

Fig. 6
figure 6

Wilcox water quality diagram for irrigation purposes at two stations, a Poleh-Almas, and b Dostbeiglu

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Table 6 shows the values for the classified type of drinking water quality in the studied stations. Also, the spatial arrangement of some important parameters of water quality in studied stations was presented in Fig. 7.

Fig. 7
figure 7

Spatial arrangement of some important parameters of water quality in studied stations, Ardabil province

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Table 6 Desirable level of drinking water quality in the studied stations in Ardabil province (According to Schoeller)
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According to the results of Table 6, it can be said that only at the Nir station, the water quality had a suitable condition for drinking, while in consequent downstream stations some water quality parameters have been moderated and drinking water type changed to acceptable level. Also, the histogram (Fig. 7) shows that the SAR values was 0.46, 0.83, 0.95, 0.58 and ESR was 0.9, 1.13, 0.96, and 0.8 respectively at Nir, Poleh-Almas, Arbabkandi and Dostbeiglu river gauge stations.

In a two-decade study of the Lancang River, Wei et al. (2009) found that the construction of Manwan and Dachaoshan Dams initially worsened water quality in Manwan Reservoir. However, subsequent years demonstrated improvement through self-purification processes. The cooperative operation of the dams positively impacted the below-dam segment, while downstream flowing segments were unaffected. Also, Santucci Jr et al. (2005) studied the impact of multiple low-head dams on the Fox River, Illinois, spanning a 171-km reach with 15 dams. Dams impounded 55% of the river's surface area, restricting upstream movements of 30 fish species. The Illinois index of biotic integrity (IBI) and macroinvertebrate condition index (MCI) showed higher values in free-flowing areas, highlighting the adverse effects of dams on warm water stream ecosystems. Bouaroudj et al. (2019) extensively assessed water quality at Algeria's Beni Haroun Dam, and found that despite the suitability for irrigation by certain indices, 39% of samples surpassed standards due to elevated SAR and EC values. Their study emphasizes the necessity for protective measures to counteract potential adverse effects of irrigation water on agricultural lands.

4 Conclusion

In this study, the potential impacts of Yamchi and Sabalan dams on the water quality parameters of Balikhlouchai and Gharehsou rivers were assessed using AqQA software and statistical methods. There was a significant reduction (α < 0.01) in discharge values during the post-dam periods, leading to potential alterations in the concentration of certain water quality parameters. The statistical analysis revealed that the construction of Yamchi Dam significantly influenced parameters such as Ka, Na, Mg, Ca, SO4, Cl, HCO3, CO3, and pH at a 99% confidence level (α < 0.01). Similarly, the construction of Sabalan Dam had a significant impact on Ka, Na, Mg, Ca, SO4, Cl, HCO3, EC, and TDS parameters at a 99% confidence level (α < 0.01). Despite these changes, the water quality for drinking purposes was classified as being in good condition based on the study results. Also, in each of the four stations studied, the type of water is NaCl. In the stations affected by the dam (Poleh-Almas and Dostbeiglu), the amount of HCO−3 increased compared to the upstream stations (Nir and Arbabkandi), while the pattern of changing other parameters at the downstream stations of Yamchi and Sabalan dams is the same. In relation to the effect of Yamchi and Sabalan dams on the amount of Na+ and Cl− parameters, Yamchi dam increased the amount of these parameters, while Sabalan dam had negligible effect on Na+ and Cl− parameters. Regarding the TH, the Yamchi dam has a negative impact on the quality of the Balikhlouchai River and has increased 126% of the TH at the Poleh-Almas Station. The effect of Sabalan and Yamchi dams on the amount of TDS has reduced the water quality considering drinking suitability in Gharehsou and Balikhlouchai rivers, so that the TDS at post-dam stations is modest and acceptable in terms of utility.

The Stiff diagram at the stations showed that the values of HCO−3 decreased at the Poleh-Almas station. While, the value of So42−, Mg2+ and Ca2+ increased at the Poleh-Almas, which confirms the results of the Piper diagram on increasing the TH in the station is located next to the Yamchi Dam, which confirms the results of Piper's diagram on increasing TH at the station after the Yamchi Dam. Also, in the upstream and downstream stations of Sabalan dam, it can be seen that Ca2+ and Mg2+ have increased. Another negative effect on Mg2+ is that at the station after the dam, about 12% of the risk of Mg2+ has risen to the station before the dam. In general, it can be said that changes in water quality parameters of the Balikhlouchai and Gharehsou rivers occurred in the post-dam period, and the negative impacts of the Yamchi Dam on the water quality of the Balikhlouchai River were higher.

5 Limitations

Regarding the effects of the dam construction, other water quality parameters related to the river's biological status can be measured to determine the comprehensive status of water quality, so that more detailed information on the change in water quality can be obtained. Moreover, this research does not provide details about the initial state of the rivers prior to dam construction, limiting a thorough evaluation of the dams' impacts. The study depends on numerical and visual comparisons, possibly neglecting more intricate biological analyses that could enhance comprehension of water quality changes. The absence of recorded data also means the study did not assess the impact of dam construction on nutrient levels (N, P, K), emphasizing the need for more comprehensive investigations in this regard.

6 Potential solutions to adapt/mitigate negative effects of dams on water quality

Given the impact of dam construction on changes in water quality parameters, it is essential to consider measures to improve quality, such as appropriate water treatment for drinking purposes. Additionally, since water from the downstream flow of the dam is used for agricultural irrigation, it is necessary to implement measures in line with adaptive management. This involves utilizing agricultural species that are compatible with the altered water quality, thereby preventing a reduction in agricultural production.

Given that water from the downstream flow of the dam is allocated to meet the environmental needs of Lake Shorabil, a comprehensive environmental impact assessment plan should be developed, taking into account the impact of changes in water quality on aquatic organisms and potential damages to the lake. Installing a river water quality monitoring system downstream is crucial for recording water quality changes and being aware of the trend of changes in shorter time intervals.

Due to the impact of reduced water flow downstream on aquatic organisms and the river ecosystem, adhering to environmental flow release is essential to mitigate the adverse effects of water quality decline and ensure the river's vitality. It is worth noting that, due to the lack of recorded data, the impact of dam construction on nutrients affecting water quality (including nitrogen, phosphorus, and potassium) was not assessed in this study. Considering the considerable impact of dam construction on nutrient dynamics, it is necessary to address this aspect in future research works.

In summary, the studied dams play a significant role in the economic vitality of the region. The Yamchi Dam, in the study area, serves as a primary source for Ardebil's drinking water and economically supports over 5,000 hectares of downstream agricultural lands. The Sabalan Dam, with a storage capacity of approximately 105 million cubic meters, provides water for 86 villages and has the capability to irrigate 15,000 hectares of downstream lands. Therefore, it is crucial to implement management measures for water conservation downstream and to prevent the cultivation of crops with high water demands through thoughtful crop pattern management. This is essential for mitigating the negative impacts of utilizing these dams on water supply, preserving water quality, and maintaining the river ecosystem downstream.