Assessment of irrigation suitability of water in Hirakud reservoir and Bargarh main canal, Odisha, India: A multivariate analysis

Due to widespread water pollution from increased industrialization and urbanization, maintaining water quality for various human purposes is gradually becoming a big challenge across the globe. Although 71% of the total earth's surface is occupied by aquatic bodies, the percentage of accessible freshwater suitable for human use is a meager 0.5% of the total available water. For human consumption such as drinking, agricultural, industrial, and recreational purposes, 60% of the total freshwater comes from rivers, lakes, and wetlands (Wada et al. 2014; Abbott et al. 2019). The easy accessibility for disposal of wastewater makes most of the surface water aquatic bodies vulnerable to pollution. The quality of surface water in a region is mostly determined by natural processes like erosion, precipitation input, as well as anthropogenic exploitation of water resources for various purposes such as industrial activities, mining, urban development, and agriculture (Haidary et al. 2013; Ayari et al. 2021, 2023). In Vietnam, groundwater quality was assessed for drinking purposes using the integrated water quality index (IWQI). The water samples were analyzed for pH, TDS, nitrate (NO₃⁻), ammonium (NH₄⁺), iron (Fe), manganese (Mn), arsenic (As), mercury (Hg), lead (Pb), and total coliform and weighed parameters assigned for IWQI calculation (Nguyen et al. 2022).

Prolonged irrigation with poor-quality water leads to reduced crop productivity, and poor quality of crop products affects the health and well-being of consumers as well as farmers coming in direct contact with the irrigation water. Water quality parameters (pH, TDS, and turbidity) were measured in secondary treated wastewater and were infiltrated through the soil matrix to remove contaminants (Raji & Packialakshmi 2022). Alteration in soil characteristics and crops on prolonged irrigation reflects the quality of the irrigation water (Jain et al. 2007; Etteieb et al. 2017). Total dissolved solids (TDS), electrical conductivity (EC), and concentration of major ions (Ca²⁺, Mg²⁺, Na⁺, K⁺, CO₃²⁻, HCO₃⁻, SO₄²⁻, Cl⁻, and NO₃⁻) dictate the quality of water for irrigation (Acharya et al. 2020). The dissolved ions in irrigation water within the permissible limit are essential for the soil permeability and growth of plants, while the concentration above the permissible limit causes salinity and sodicity hazard in soil (Kumari 2017; Zaman et al. 2018; Acharya et al. 2020). Irrigation water with more than 60% sodium content may disrupt the soil's physical properties (Singh et al. 2018). On the other hand, surface water quality is highly susceptible to human activities such as mining, industries, and direct discharge of urban and agricultural wastes, which alters its physical, chemical, and biological characteristics (Gupta et al. 2016; Reddy et al. 2020). The chemical facies of river basins have been shown to reflect natural and anthropogenic interferences in the catchment. The primary source of riverine Ca²⁺, Mg²⁺, HCO₃⁻, and SO₄²⁻ is natural, while trace metals, NO₃⁻, and NH₄⁺ are induced by anthropogenic activities (Gibbs 1970; Haidary et al. 2013; Hussain et al. 2020). Several researchers in the past have used electrical conductivity (EC), sodium adsorption ratio (SAR), percent sodium (%Na), residual sodium carbonate (RSC), magnesium hazard ratio (MHR), and permeability index (PI) classifications for irrigation water quality index in many parts of the world (Sundaray et al. 2006; Brindha et al. 2013; Panda et al. 2014; Kumari 2017; Reddy et al. 2020). SAR (sodium adsorption ratio) is an effective monitoring index of sodium in irrigation water (Li et al. 2018; Tayyab et al. 2022). While high contents of magnesium may increase alkalinity, high contents of chlorides and the presence of boron may induce plant toxicity, and other constituents such as heavy metals may be toxic for crops and humans. High salinity reduces plant growth and makes it difficult for the plant roots to absorb water because of the high osmotic pressure of the water caused by a high concentration of water-soluble ions around the plant roots (Adejumobi et al. 2022). Regular monitoring of irrigation water quality is therefore essential for managing soil as well as human health in the affected area (Aziz et al. 2021).

The Hirakud Dam is located on the Mahanadi River in the state of Odisha, India, and has a reservoir capacity of 5,375 million m³/year. The command area is principally irrigated by two main canals (i) Sason canal and (ii) Bargarh canal. Bargarh main canal irrigates 135,000 ha of land with 115 m³/s capacity serving as a lifeline to around 90,000 farmer families residing in the area (Mahapatra 2014). Water from the reservoir and upstream rivers is heavily polluted due to increased urbanization and the associated increase in domestic and industrial wastewater. In a lotic system like a river, the pollutants deposited in the sediments during nonmonsoon seasons generally get resuspended and are carried downstream increasing the pollutants load near the ocean/reservoir, resulting in deterioration of reservoir water quality (Sahu et al. 2023). The impact of poor-quality irrigation water from reservoirs varies depending on climate, soil type, and crops grown (Singh et al. 2018). Earlier studies on the Mahanadi River around Hirakud investigated seasonal variations in microbiological and physicochemical parameters (Kar et al. 2010). In the Mahanadi River estuarine system, extensive studies on spatial and temporal variations in nutrient and chemical characteristics for irrigation suitability were conducted (Sundaray et al. 2006, 2009). In the Hirakud Command Area, groundwater aquifer has been assessed for physicochemical quality (Dhar et al. 2014). Many industries such as iron and steel plants, aluminum smelting plants, and ore processing plants have mushroomed in the upper head of the river basin. Tributaries of the river upstream of the Hirakud reservoir discharge a broader set of trace metals into the river basin. Earlier, surface water quality has been assessed with reference to trace metal concentration (Sundaray et al. 2012; Hussain et al. 2020). However, the irrigation suitability of the Hirakud reservoir and Bargarh Main Canal has not been investigated although it has irrigated thousands of hectares of land in the Bargarh district for the last 50 years. Hence, in the present study, water quality from the reservoir and Bargarh main canal was assessed for irrigation suitability, and their seasonal variation was determined to evaluate the possible adverse impact on soil in the irrigated area.

The present study was conducted in the Hirakud reservoir and Bargarh main canal, a part of the Hirakud canal command that extends from 21°05′N to 21°55′N latitude and from 83°55′E to 84°05′E longitude. The Hirakud canal system consists of three canals, namely, Bargarh Main Canal, Sason Main Canal, and Sambalpur distributary command area. The Hirakud dam project is a multipurpose scheme intended for flood control, irrigation, and power generation, which is the first major multipurpose water resource project after the independence of India. It is built across river Mahanadi at about 15 km upstream of Sambalpur town in the state of Odisha on the eastern coast of the country (Dhar et al. 2014).

The climate of the command area is tropical monsoon with four distinct seasons: (a) summer – March to May, (b) monsoon – June to September, (c) postmonsoon – October to November, and (d) winter – December to February. The area gets rain from the southwest monsoon. The annual average rainfall is 1,250 mm, and 75% dependable annual rainfall is 816 mm. The mean maximum and minimum temperatures are 42 and 13 °C, respectively (Rath & Swain 2018).

All physicochemical analyses were performed according to the protocol laid by FAO (2003), WHO (2006), and APHA (1995). Measurements for water temperature, pH, and electrical conductivity (EC) were done onsite, and total dissolved solids (TDS) were measured gravimetrically after evaporating 100 mL-aliquot dried at 105 °C. The concentrations of Na⁺ and K⁺ were measured using the flame photometer. Ions (Ca²⁺, Mg²⁺, Cl⁻, and HCO₃⁻) were determined by volumetric titration methods and sulfate (SO₄²⁻) and nitrate (NO₃⁻) were determined by spectrophotometer. For the analysis of trace metals such as Fe, As, Cu, Cr, and Hg, atomic absorption spectrophotometry was used.

Descriptive statistics (mean, interquartile range, standard deviation) were determined for the physicochemical parameters, trace metals, and water indices. One-way ANOVA (analysis of variance) was used to test the variations of physicochemical parameters and indices between seasons. The correlation matrix was determined using the SPSS. Factor analysis was done using the principal component analysis (PCA) method. The PCs with eigenvalues > 1.0 were only considered, and highly loaded variables having absolute values > 0.6 were retained under each PC (Abuzaid & Jahin 2022).

Most of the water samples from the canal show specific charge balance denoted as normalized inorganic charge balance (NICB = (TZ⁺ − TZ⁻)/TZ⁺)) within ±10%, which suggested that all the samples were well balanced, where TZ⁺ and TZ⁻ represent the total positive and negative inorganic charges, respectively.

Physico-chemical parameters and trace metal concentration in the reservoir and main canal are mentioned in Table 1. The pH of the water in the reservoir and canal ranged from 5.55 to 8.45. During the premonsoon season, the average pH was found to be 7.58 ± 0.60, while during the monsoon and postmonsoon seasons, it was found to be 7.00 ± 0.31 and 7.70 ± 0.50, respectively. Electrical conductivity (EC) ranged from 61.76 to 129.60 μScm⁻¹. It ranged from 61.76 to 75.22 μScm⁻¹ and was lower during the monsoon season than the nonmonsoon season. On the contrary, it ranged from 82.44 to 129.60 and from 92.62 to 119.04 μScm⁻¹ during premonsoon and postmonsoon seasons, respectively. TDS of water ranged from 98.09 to 314.82 mgL⁻¹, in the reservoir and canal. TDS during the premonsoon season was found to be higher compared to other seasons. During the premonsoon season, it ranged from 168.24 to 314.82 mgL⁻¹, while it ranged from 98.09 to 187.11 mgL⁻¹ and from 163.98 to 229.82 mgL⁻¹ during monsoon and postmonsoon seasons, respectively. The temperature of the water in the reservoir and canal ranged from 15.4 to 39.13 °C. During the premonsoon season, the temperature was as high as 38.67 °C. The concentration of the major anions (HCO₃⁻, SO₄²⁻, and Cl⁻) constituted around 75% of TDS. Carbonate and bicarbonate concentrations of water ranged from 10.48 to 89.36 mgL⁻¹. It ranged from 61.86 to 89.36 mgL⁻¹ during the postmonsoon season and was higher than other seasons. It ranged from 10.48 to 14.66 and from 18.44 to 23.28 mgL⁻¹ during premonsoon and monsoon seasons, respectively. The concentration of sulfate ranged from 2.13 to 224.86 mgL⁻¹ in the reservoir and canal water. It ranged from 8.79 to 224.86 mgL⁻¹ during postmonsoon and was higher than the other seasons. It ranged from 3.16 to 189.21 and 2.13 to 187.16 mgL⁻¹ during premonsoon and monsoon seasons. The concentration of chloride ranged from 0.31 to 21.27 mgL⁻¹ in reservoir and canal water. During the postmonsoon season, it ranged from 7.82 to 21.27 mgL⁻¹ and was higher than in the other seasons. It ranged from 4.23 to 8.88 and from 0.31 to 1.19 mgL⁻¹ during premonsoon and monsoon seasons, respectively. The concentration of nitrate in water ranged from 0.22 to 6.63 mgL⁻¹. During the monsoon season, it ranged from 4.16 to 5.64 mgL⁻¹ and was higher than the other seasons. It ranged from 1.18 to 4.07 and from 0.22 to 6.63 mgL⁻¹ during premonsoon and postmonsoon seasons, respectively. On the other hand, the major cations constituted around 25% of total TDS. The concentration of calcium ions ranged from 1.08 to 19.57 mgL⁻¹. It ranged from 8.71 to 19.57 mgL⁻¹ during the postmonsoon season and was higher than in the other seasons. It ranged from 3.40 to 9.75 and from 1.08 to 1.28 mgL⁻¹ during premonsoon and monsoon seasons, respectively. The concentration of magnesium ion in water ranged from 1.22 to 14.66 mgL⁻¹. It ranged from 5.57 to 14.66 mgL⁻¹ during the postmonsoon season and was higher than in the other seasons. It ranged from 1.22 to 5.36 and from 2.23 to 4.02 mgL⁻¹ during premonsoon and monsoon seasons, respectively. Similarly, the concentration of sodium ion in water ranged from 3.39 to 14.11 mgL⁻¹. It was higher during the postmonsoon season than other seasons. The concentration of potassium ion in reservoir and canal water ranged from 1.21 8.33 mgL⁻¹. It was higher during the postmonsoon season and ranged from 1.45 to 8.33 mgL⁻¹. The reported concentration of major ions followed a typical trend for cations (Ca²⁺> Na⁺> Mg²⁺ > K⁺) and anions (HCO₃⁻ >Cl⁻ >SO₄²⁻ >NO₃⁻).

The pH is the measure of acidity and alkalinity of water in terms of hydroxyl ion concentration and is one of the most important water quality parameters. It describes the acidic and basic properties of the water because it controls the solubility of different metallic pollutants. It depends on various factors such as the carbonate system present in water (concentration of carbon dioxide and carbonates present in water), erosion of acidic or alkaline compounds from the soil or rock, and release of wastewater effluent. The seasonal variations in pH control the weathering pattern and availability of dissolved ions in the lake water. At some sites, the pH of the canal water was found to be alkaline, which could be due to the presence of alkaline earth metals that combine with soluble CO₂ forming carbonate and bicarbonates. Further increase in pH of canal water could lead to the formation of trihalomethanes. Electrical conductivity (EC) represents the ionic strength and is contingent upon the concentration, volume, and movement of ionic entities. It represents the degree of chemical weathering that occurs in the catchment area. An increase in the dissolved ion concentration will increase the electrical conductivity. Therefore, it provides overall insight into the water quality. Also, temperature has a profound effect on electrical conductivity as the movement of ionic components is also affected by temperature variation. The large variation in EC is due to the geochemical processes and anthropogenic contribution dominating the area (Ghazaryan & Chen 2016). The solid content of water depends on the size, type, and concentration of solids, both organic and inorganic present in the water. TDS can originate from various sources such as wastewater, storm flow, and urban runoff (Acharya et al. 2020). Fluctuations in the levels of dissolved solids serve as an indicator of climatic influence on the intensity of processes occurring in the source region. Elevated total dissolved solids (TDS) encompass both natural and human-induced pollutants in water, affecting its color, total alkalinity, and conductivity. This elevation poses risks to both cultivated land and aquatic ecosystems (Aziz et al. 2021). Higher TDS in irrigation water increases the osmotic potential of soil affecting the water absorption capacity of the plants. Higher salt concentrations during the premonsoon days may be due to evaporation. Increased evaporation during premonsoon season could have elevated the total dissolved salts in the water samples. Solubilization of solids at high temperatures during summer could also contribute to higher solid content during premonsoon (Ghazaryan & Chen 2016). However, in a study conducted in the Pokhara Valley of Nepal, the mean EC and TDS were found to be highest during postmonsoon and lowest during the monsoon period due to the dilution effect of monsoon rainfall (Khadka & Ramanathan 2012). Evaluation of groundwater and surface water for agriculture and drinking purposes conducted in south India showed a concentration of different ions was in the order of Na⁺ > Ca²⁺ > Mg²⁺ > K⁺ for cations and Cl⁻ > HCO₃⁻ > SO₄²⁻ > F⁻ for anions (Sakram & Adimalla 2018). The general chemistry of Tarim River water in China suggested that anions and cations were in the order of Na⁺ > Mg²⁺ > Ca²⁺ > K⁺ and SO₄²⁻ > Cl⁻ > HCO₃⁻ > CO₃⁻ (Ghazaryan & Chen 2016). In the present study, the major anions such as HCO₃⁻, SO₄²⁻, and Cl⁻ constituted about 75% of the total TDS in the irrigation water. The source of bicarbonate could be the dissolution of carbonate and/or silicate minerals by carbonic acid (Gupta et al. 2016). Previous investigation reported that the primary bedrock in the Mahanadi River basin is Proterozoic limestones. Major ion chemistry in the basin is affected by silicate weathering with minimal contribution of carbonate weathering (Bastia et al. 2020). The highest HCO₃⁻ concentration observed in the reservoir water during the postmonsoon season could be a measure of intense chemical weathering of the silicate rocks and in turn parent mineral composition. The concentration of HCO₃⁻ was lower during the monsoon season due to the dilution effect. In addition, studies show that a high concentration of HCO₃⁻ in the surface water contributes to the accumulation of Ca²⁺ and Mg²⁺ in the surface and subsurface soil when irrigated for a prolonged period (Reddy et al. 2019). Sulfate ions (SO₄⁻) present in the surface water are due to the presence of sedimentary rock such as gypsum and anhydride. A study on sources of riverine sulfate suggests that gypsum is the primary source of sulfate ions in the Mahanadi River basin (Rout & Tripathy 2024). During the monsoon period, lower SO₄²⁻ concentration could be due to the dilution effect of monsoon and lower agriculture-to-lake ratio. The agriculture-to-lake ratio refers to the spatial relationship and balances between agricultural lands and adjacent water bodies like lakes, reservoirs, or wetlands and is an important factor in understanding the interactions between agricultural production and riparian zone ecology. Chloride (Cl⁻) concentration during the monsoon season was very low in the reservoir as well as canal water. Low concentration of Cl⁻ suggested minimal anthropogenic contribution such as industrial discharge and domestic wastewater (Reddy et al. 2020). Depending on the chloride concentration and sensitivity of the crop, its toxic effect on soil varies. During the monsoon periods, NO₃⁻ concentration was higher due to the leaching of fertilizers in the areas where agricultural activities were intensive. The major cations constitute 25% of the TDS predominated by Ca²⁺ and followed by Na⁺ in the irrigation water. During the monsoon period, Ca²⁺ concentration was lower than in the nonmonsoon seasons, which could be due to the dilution effect and phytoplankton consumption (Mukherjee 2020). The decay of phytoplankton during the postmonsoon season could result in the release of Ca²⁺ and an increase in the concentration. Weathering in the river basin could also increase the concentration. The presence of multivalent metallic cations is responsible for hardness in water. At high pH, much of its quantities may get precipitated as CaCO₃. The concentration of sodium was found to be the highest in postmonsoon days. The sources of Na⁺ include various rocks, weathering product of silicate rocks, and its displacement from the absorbed complex of rocks and soils by calcium and magnesium (Gupta et al. 2016). Potassium (K⁺) is an important parameter for water quality. It was higher than the maximum allowable limit according to Ayers & Westcot (1994). Sources of potassium are potash feldspar (KAlSi₃O₈), mica [(KAl₂)(AlSi₃O₁₀)(F(OH)₂)], and less commonly sylvite (KCl). The geological characteristics of the river basin are in accordance with the facts. Various rocks such as precambrian khondalites, charnockite, granite, and gneiss; proterozoic shale and limestone; gondwana shale, sandstone, and conglomerate; and the recent deltaic alluvium of the river and laterite are the predominant geological formations in the Mahanadi River basin. Feldspar is the major constituent of khondalites (Bastia et al. 2020). Despite being a populated area, the concentration of nitrate does not exceed the maximum allowable limit prescribed by Ayers & Westcot (1994) for irrigation.

Trace metal concentration in reservoir and canal water varied between 28.69 and 1,892.51 μgL⁻¹ for Fe, 1.67 and 214.82 μgL⁻¹ for Zn, 0.09 and 8.09 μgL⁻¹ for As, 1.65 and 60.16 μgL⁻¹ for Cu, and 1.17 and 139.19 μgL⁻¹ for Cr. To see the detailed variation in trace metals in the Hirakud reservoir and canal water, maximum, minimum, and average concentrations along with standard deviation are presented in Table 1. The concentration of all the trace metals was above the permissible limit. It might be an indicative trend of anthropogenic and geogenic activities in the basin as well as a bank of the reservoir (Hussain et al. 2020). The relative abundance of trace metals in the irrigation water was found to be Fe > Zn > Cr > Cu > As. The results also corroborated with the findings of previous studies on the Mahanadi River (Sundaray et al. 2012; Hussain et al. 2020). It could be due to anthropogenic activities, which include indiscriminate discharge of industrial waste, sewage effluents, lead recovery processing from small batteries, and coal mining. The metal concentration during the postmonsoon season was higher for Fe, Zn, Cu, and Cr primarily due to anthropogenic activities and secondarily due to geogenic activities. The concentration range of Fe (28.69–1,892.51 μgL⁻¹) was a concern for all the sampling sites around the year. Of many possibilities, direct discharge of untreated effluents from metal electroplating industries, iron leachates from iron mines, and urban wastes from nearby places could have ended up in such a surge in Fe concentration. The Cr and Cu pollution was observed in both premonsoon and monsoon seasons at all sites with concentration ranges of 1.65–60.16 and 1.17–139.19 μgL⁻¹, respectively. Cu pollution could be due to geogenic activities as a significant source of pollution. The fact that supports the above observation is that Sambalpur districts have potential copper minerals such as chalcopyrite and azurite. Many copper manufacturing units such as those present in Sundergarh directly discharge their waste in the basin. Except for W4, W7, and W9, the concentration of Hg was undetectable in all sites. The temporal variation in trace metal concentration across the studied sites suggested the combined impact of anthropogenic (mainly industrial) and natural (weathering and leaching) factors. The overall concentration of dissolved ions and metals was higher than found in the Mahanadi River in earlier studies (Sundaray et al. 2012; Hussain et al. 2020). One-way ANOVA test indicates that SO₄²⁻, Zn, and As showed no significant difference among sites. The concentration of all the parameters (pH, EC, TDS, temperature, Na⁺, K⁺, Ca²⁺, Mg²⁺, HCO₃⁻, Fe, Cu, Cr, Na%, SAR, MH) showed significant differences (p < 0.05) in all the studied seasons.

A positive correlation of Cl⁻ with the major ions indicated the dominance of the precipitation mechanism. A similar phenomenon was observed in the major rivers of Western Ghat (Reddy et al. 2020). In all seasons, alkaline earth elements (Ca²⁺ and Mg²⁺) showed a strong correlation with alkalis (Na⁺ and K⁺). The strong positive correlation of the main exchangeable ions (Na⁺-Ca²⁺, Na⁺-Mg²⁺) supported the fact that the precipitation–dissolution reaction is the primary mechanism that controls the water quality in the reservoir and Bargarh main canal (Masoud 2013). A strong positive correlation was observed between Cu and Cr in the water, which might be due to similar geogenic activities and mobilities of the ions in the region.

Principal component analysis (PCA) helps classify the original dataset and reduce the large volume of data. The geological interpretation of factors gives an insight into the main hydrological process, which controls the distribution of the measured variable of water in the reservoir and main canal. From this multivariate study, the factor loading of each variable within three selected factors which explains 92.1% of the variability of data, represents a possible source of variation in the hydrochemistry of canal water (Table 2). PC1 explained 41.13% of the total variance and showed higher negative loading of pH, Na⁺, Ca²⁺, K⁺, Mg²⁺, HCO₃⁻, Cl⁻, and Cr. It can be attributed to anthropogenic sources. PC1 can be called an ionic component. PC2 had 21.09% of total variance and showed higher positive loading of EC and TDS while negative loading of Fe and NO₃⁻. PC2 can be called a salinity component. PC3 explained 18.21% of the total variance. It shows higher loading of SO₄²⁻, Zn, As, and Cu and can be called a heavy metal component. Both PC2 and PC3 showed loading for HCO₃⁻, which signifies geogenic attributes such as weathering of mineral-bearing rock, soil erosion, and surface runoff during the rainy season. The Hirakud Dam accounts for a significant dilution and assimilation of dissolved ions and trace metals due to precipitation and wetland activity. In the last decade, there has been an intense increase in Industrial as well as agricultural activities in and around the upstream of Hirakud reservoir, mixing of the effluent and runoff from industries such as coal-fired thermal power plants, steel, aluminum, sponge Iron could have led to the observed alteration of the physicochemical properties of the surface water.

Irrigation water if not properly monitored may negatively affect soil properties, crop productivity, and public health of farmers and consumers viz. direct contact and consumption. So, it is essential to assess irrigation water for its suitability. Various water quality parameters such as sodium adsorption ratio (SAR; Richards 1954), sodium percent (% Na; Wilcox 1955), residual sodium carbonate (RSC; Eaton 1950), and magnesium hazard ratio (MR; Raghunath 1987) were calculated by using Equations (1)–(4), where all ions are expressed in meq/L. SAR assesses the impact of sodium hazard which dictates the cation exchange capacity of the soil about calcium and magnesium reaction (Thomas et al. 2015; Banerjee & Ghosh 2016). The classification of irrigation water was carried out based on different values of parameters and indices (Table 3).

High SAR values in irrigation water make the soil compact and impermeable as sodium replaces calcium and magnesium, and hence, it reduces water and air movement (Ghazaryan & Chen 2016). It ranges from 1.58 to 4.64 meq/L (Table 1). SAR in postmonsoon seasons was higher than in monsoon days. Furthermore, sodium concentration is also expressed in terms of percentage (% Na). Percentage Na higher than 80 is unsuitable for irrigation as it causes deflocculation and impairments of tilth and permeability of soil (Amiri et al. 2015). The % Na values were found to be higher in monsoon seasons than in nonmonsoon samples. It may be due to evaporation. Similar observations were found in the Western Ghats (Reddy et al. 2020). During postmonsoon days, 35% of water samples fall into the good category. During premonsoon days, at the S9 site, one sample belongs to the doubtful category. A total of 35% water sample belongs to the permissible category. It may have some negative impact on soil permeability and texture. For mitigation in the irrigated area, some steps such as the use of organic matter, crop residues, subsoiling, and high leaching can be used. RSC is one of the crucial parameters to assess groundwater as well as surface water worldwide (Eaton 1950; Richards 1954). It is evident from Table 1 that bicarbonate ions register a higher concentration than the rest of the ions. Hence, carbonate ions have a profound impact on irrigation water through the precipitation of alkaline earth matter (Ca²⁺ and Mg²⁺). RSC during postmonsoon seasons was considerably higher in the studied area. During premonsoon days, water samples fall into a bad category and generally require proper treatment for irrigation. Such conditions prevail due to the impact of different anthropogenic activities such as the intensive discharge of domestic and agricultural wastes (Bouderbala 2015; Thomas et al. 2015). The suitability of irrigation water is also affected by excess magnesium as it alters the properties of soil (Amiri et al. 2015).

In the present study, the water from the Hirakud reservoir and Bargarh main canal was found to be slightly alkaline. Factor analysis suggested that geogenic and anthropogenic activities could combinedly affect the irrigation water quality. Irrigation water from the reservoir and main canal was found to be suitable for irrigation in terms of salinity, SAR, % Na, and MH. However, most of the water samples came under bad category in terms of their high RSC value, indicating the dominance of bicarbonate ions in the irrigation water. Trace metal concentration in the water was found to be above the permissible limit across the seasons. The ongoing unregulated disposal of industrial, municipal, as well as agricultural waste directly to the Mahanadi River and Hirakud reservoir without prior treatment could lead to the deterioration of water quality. This could be a potential threat to hectares of irrigated land in the command area as poor-quality water negatively affects soil health, crop quality, and productivity.

The authors thank the Odisha State Higher Education Council, Odisha, for providing financial assistance under the MRIP Scheme (Sanction No. 426/190/OSHEC). Special thanks are due to the Indian Institute of Technology, New Delhi, and NIT, Rourkela for providing infrastructural research facility for the analysis of heavy metals. Ms Syed Nikhat Ahmed thanks the Ministry of Minorities, Government of India for providing the Maulana Azad National Fellowship.

All relevant data are included in the paper or its Supplementary Information.

The authors declare there is no conflict.