Keywords

1 Introduction

In order to meet the needs of fresh water for different uses, the most logical solution is the surface water storage in dams. To ensure its independence and guarantee its water resource needs [1], Algeria has already taken this problem very seriously. In 1962, there were only 15 dams to store 450 million m3 of water mainly for irrigation use. Currently, there are 79 [2] for a total capacity of about 8 billion m3 of water. These dams are located within 17 watersheds (Fig. 2) which some of them are the aim of this study, (1) the endorheic basins occupying the High Plains whose waters are largely lost by evaporation in the chotts. The annual flow is estimated at 700 hm3 and (2) the Saharan basins with an average intake of 650 hm3 per year [1]. This surface water collected in dams may be polluted and contain important levels of salts, toxic ions, heavy metals, and organic residues [3]. Accumulation of these pollutants when in water and soils may cause a threat to agricultural production and the environment [4]. For example, release of phosphorus and nitrogen into watercourses then in dams can lead to severe pollution problems, such as eutrophication [5, 6], which cause profuse algal blooms, excessive growth of harmful plants, oxygen depletion, habitat degradation, and problems related to water treatment [7, 8]. In addition to contributing to eutrophication, forms of nitrogen such as ammonia, nitrite, and nitrate have the potential for direct toxicity [8, 9].

Organic matter content in water comes generally from crop wreckage, food waste, other degradable solid wastes [10], and fecal matters [11]. Algal and phytoplankton growth is enhanced by nutrients which are supplemented by fertilizers and finally results in eutrophication [12].

Monitoring the water quality for human consumption and/or irrigation purpose becomes necessary to protect human health, soil, plants, and water bodies and to prevent the deterioration of irrigation and treatment infrastructures [13].

Many studies have been published concerning the assessment of water quality in rivers [14,15,16,17,18,19] and dams [20,21,22,23,24,25] using physical, chemical, and biological parameters and permitted (1) the assessment of water quality in these water bodies and (2) the identification of the pollutants discharged into and their effects on water quality. This way of doing can give warnings to consumers in order to prevent dangerous and unhealthy situations.

The aim of this study concerned the assessment of water quality of ten dams belonging to Tafna and Macta watersheds. The prime objectives were to evaluate physical and organic chemical characteristics of water, to identify polluted dams, and to assess the difference in water quality of dams and watersheds. The second objective was the assessment of spatial and temporal variability in the water quality and their suitability for irrigation purposes.

2 Materials and Methods

The study dams (Fig. 1) are located in the northwest of Algeria. They administratively belong to four wilayas: Tlemcen, Ain Temouchent, Mostaganem, Sidi Bel-Abbes, and Mascara. Their basins are limited by the Oran coastal watersheds at north, by Morocco at west, by Chott Ech Chergui watershed at south, and to the east by Chelif watershed .The dams covered by this study are included in Tafna (5) (Fig. 2) and Macta (5) (Fig. 3) watersheds.

Fig. 1
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Location of study area

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Fig. 2
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Location of Tafna watershed dams

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Fig. 3
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Location of Macta watershed dams

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Table 1 summarizes the dams of concern, the watersheds they drain, and the water use.

Table 1 Different water uses of the study dams [2]
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The analyzed parameters were pH, dry residue (DR), dissolved oxygen (DO), nitrate (NO3−), nitrate (NO2−), ammonium (NH4+), phosphate (PO43−), biochemical oxygen demand (BOD5), chemical oxygen demand (COD), and organic matter (OM). Analyses were done monthly during January–December 2013 year.

For Tafna watershed, analyses concerned water dams of Sidi-Abdelly (SA), Sikkak, Meffrouch, Hammam Boughrara (HB), and Beni Behdel (BB) (Fig. 2). As for Macta basin, analyzed water concerned Fergoug, Bouhanifia, Ouizert, Cheurfa, and Sarno dams (Fig. 3). These surface waters are generally used for human consumption and irrigation purposes (Table 1).

3 Results and Discussion

Tables 2 and 3 summarize the minimum and maximum values of the analyzed parameters of the water dams.

Table 2 Minimum and maximum values of the analyzed parameters of Tafna dams
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Table 3 Range of values of the analyzed parameters of Macta dams
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3.1 Physical and Chemical Characterization

3.1.1 Variations in pH and Dissolved Oxygen

The recorded pH values in Tafna (7.36–8.97) (Fig. 4a) and in Macta (7.01–8.62) (Fig. 4b) watershed dams show that all water dams are alkaline (Tables 2 and 3).

Fig. 4
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pH spatial variations at (a) Tafna and (b) Macta dams

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Depletion of dissolved oxygen in water can encourage the microbial reduction of nitrate to nitrite and sulfate to sulfide and cause an increase in the concentration of ferrous iron [19]. Its consumption results from excessive algae growth and decomposition caused by phosphorus and nitrogen compounds [26]. Dissolved oxygen values (Tables 2 and 3) range from 36.3% to 154.3% in Tafna dams (Fig. 5a) where the highest values were recorded at HB (in January) and Sikkak (in July) dams. As for Macta watershed, DO levels were greater than in Tafna dams. They vary from 54.4 (in January) to 160.3% (in September) (Fig. 5b) in Cheurfa dam. DO can be affected directly by biochemical and chemical demands; the greater the BOD5, the more rapidly dissolved oxygen is depleted in the water bodies. This means that less oxygen is available to aquatic life forms [27]. BOD5 refers to the amount of oxygen required for the destruction of decomposable organic matter by biochemical processes. It is a measure of the dissolved oxygen consumed by microorganisms during the oxidation of reduced substances [27]. High BOD5 levels can cause water quality deterioration and generate problems such as eutrophication leading to severe DO depletion [28].

Fig. 5
figure 5

DO spatial variations at (a) Tafna and (b) Macta dams

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3.1.2 Dry Residue

Dry residue contents are greater in Macta watershed dams (400–4,000 mg L−1) than in Tafna one (200–1,200 mg L−1) (Fig. 6a). Important concentrations were observed at Sarno dam (Fig. 6b) located upstream of the confluence of Mekerra and Sarno wadis and where values were between 2,700 and 4,000 mg L−1 (Avg., 3,161.7 mg L−1; SD, 668.8 mg L−1) (Fig. 6a) during all the sampling period except in December (1,600 mg L−1).

Fig. 6
figure 6

DR spatial variations at (a) Tafna and (b) Macta dams

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3.1.3 Variations in MO, BOD5, and COD

In Tafna Basin, the highest BOD5 (5.4–38 mg L−1; Avg., 11.9 mg L−1; SD, 9.4 mg L−1) and COD (7.1–96 mg L−1; Avg., 43.8 mg L−1; SD, 21.7 mg L−1) contents were recorded at HB dam with BOD5 and COD maximum values in July and December, respectively (Fig. 7d). This dam receives, among others, wastewater of the complex of greasy substance via surface water flow of Mouillah wadi [29]. Organic matter contents were also maximum at HB dam (5.2–16 mg L−1; Avg., 8.8 mg L−1; SD, 3.8 mg L−1) compared to those of Meffrouch (2.8–6.0 mg L−1; Avg., 4.1 mg L−1; SD, 1.1 mg L−1), SA (3.4–8.4 mg L−1; Avg., 5.2 mg L−1; SD, 1.5 mg L−1), Sikkak (4.4–8.3 mg L−1; Avg., 6.3 mg L−1; SD, 1.2 mg L−1), and BB (1.8–6.2 mg L−1; Avg., 4.0 mg L−1; SD, 1.4 mg L−1).

Fig. 7
figure 7figure 7

Variations of organic parameters of (a) SA dam, (b) Sikkak dam, (c) Meffrouch dam, (d) Boughrara dam, (e) BB dam

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As for Macta watershed, maximum BOD5 (17.1–37.9 mg L−1; Avg., 24.1; SD, 6.4) and COD (75–154 mg L−1; Avg., 104 mg L−1; SD, 26.5 mg L−1) values were found at Cheurfa dam (Fig. 8d). Organic matter levels were high than in Tafna dams. The maximum values (1.7–20.5 mg L−1; 12.9 mg L−1; 4.8 mg L−1) were found at the aforementioned dam. The high contents of MO, BOD5, and COD may probably be due to agricultural runoff, waste disposal, and wastewater effluent discharged into the watercourses feeding the dams.

Fig. 8
figure 8figure 8

Variations of organic parameters of (a) Fergoug dam, (b) Bouhanifia dam, (c) Ouizert dam, (d) Cheurfa dam, (e) Sarno dam

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3.1.4 Nitrate, Nitrite, and Ammonium

Nitrates come to water dams through surface water flow. They probably originate from the fertilizer uses as well as human and animal wastes. Nitrate concentrations range between 1 and 35 mg L−1 in the ten study dams. In Tafna watershed, nitrate ions were found in the following concentrations: HB (1–35 mg L−1; Avg., 5.9 mg L−1; SD, 9.6 mg L−1) (Fig. 7d), Meffrouch (1–8 mg L−1; Avg., 3.0 mg L−1; SD, 1.9 mg L−1) (Fig. 7c), SA (1–6 mg L−1; Avg., 2.6 mg L−1; SD, 1.5 mg L−1), Sikkak (2–15 mg L−1; Avg., 8.2 mg L−1; SD, 5.2 mg L−1) (Fig. 7b), and BB (1–6 mg L−1; Avg., 2.8 mg L−1; SD, 1.5 mg L−1) (Fig. 7e). The maximum content (35 mg L−1) was recorded at HB during July.

In Macta watershed NO3− ions were found with the following concentrations: Cheurfa (1–20 mg L−1; Avg., 9.3 mg L−1; SD, 7.2 mg L−1) (Fig. 8a), Ouizert (1–18 mg L−1; Avg., 8.8 mg L−1; SD, 6.7 mg L−1) (Fig. 8c), Fergoug (1–9 mg L−1; Avg., 4.6 mg L−1; SD, 2.6 mg L−1) (Fig. 8a), Bouhanifia (1–8 mg L−1; Avg., 4.1 mg L−1; SD, 2.4 mg L−1) (Fig. 8b), and Sarno (1–11 mg L−1; Avg., 3.3 mg L−1; SD, 2.8 mg L−1) (Fig. 8e).

Nitrites and ammonium ions were also present with concentrations varying from 0.01 to 2.1 mg L−1 and 0.06 to 4.46 mg L−1, respectively (Figs. 7a–e and 8a–e). In Macta watershed, the concentration of NH4+ was at a maximum at Cheurfa dam during November. However, the values of this parameter were lower than those obtained in HB dam where NH4+ contents were between 0.07 and 4.46 mg L−1(Avg., 1.73 mg L−1; SD, 1.71 mg L−1). The highest values were recorded in HB dam during the first semester (Fig. 7d). Ammonium concentrations lowered during the sampling period inversely to pH values. These two parameters are negatively and well correlated (r = −0.7). The same situation was observed at SA with a correlation coefficient of −0.63.

3.1.5 Orthophosphates (PO43−)

At Tafna watershed, the maximum PO43− concentration values ranging between 0.1 and 1.86 mg L−1 (average: 1.01 mg L−1) were found at HB dam. The maximum value was recorded during March in the aforementioned dam. In the other dams belonging to Tafna watershed, PO43− contents were less than 0.16 mg L−1 with values ranging from 0.05 to 0.15 mg L−1 (average, 0.08 mg L−1) at Meffrouch, 0.05 to 0.19 mg L−1 (average, 0.09 mg L−1) at SA, 0.06 to 0.16 mg L−1 (average, 0.11 mg L−1) at Sikkak, and 0.02 to 0.12 mg L−1 (average, 0.07 mg L−1) at BB (Fig. 7a–e).

As for Macta, PO43− concentration values recorded at Cheurfa dam were between 0.22 and 1.16 mg L−1 (average: 0.71 mg L−1) (Fig. 8a–e). The yearly average PO43− concentration values for the other dams were less than 0.71 mg L−1; the calculated averages were 0.15, 0.13, 0.11, and 0.09 mg L−1 for Fergoug, Ouizert, Bouhanifia, and Sarno dams, respectively. The presence of phosphates in water dams is due to domestic wastewater discharges, particularly those containing detergents, fertilizer runoff, and industrial effluents.

3.2 Water Pollution

To understand the overall evolution of organic water pollution and the biodegradable matter proportion, we have calculated the organic pollution index (OPI) developed by [30] and the COD/BOD5 ratio.

The principle of the OPI is to divide the pollutant values into five classes (Table 4), then to determine, from its own measurements, the corresponding class number for each parameter, and then to average it.

Table 4 Classes of parameters allowing the OPI calculation
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The limits of the OPI classes are as follow [30]:

5.0–4.6: no organic pollution

4.5–4.0: low organic pollution

3.9–3.0: moderate organic pollution

2.9–2.0: strong organic pollution

1.9–1.0: very strong organic pollution

The calculated OPI values for the ten dams during the study period indicated, generally, moderate to strong pollution. OPI values of SA (OPI, 3–3.75; average, 3.3), Meffrouch (OPI, 3.0–3.5; average, 3.25), and BB (3.0–3.5; average, 3.2) dams show that organic pollution is moderate. As for Sikkak (OPI, 2.5–3.25; average, 2.8), pollution is considered to be moderate from January to April and strong during the remainder of the year (Table 3, Figs. 9a and 10). Among the Tafna dams, HB dam water is the most polluted one. Calculated OPI values show a strong to very strong (March, July, and November) pollution.

Fig. 9
figure 9

OPI variation of (a) Tafna dams and (b) Macta dams

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Fig. 10
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Spatial variation of IPO

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Water of Fergoug (2–3.25; average, 3.25), Ouizert (2.25–3.0; average, 2.1), Cheurfa (OPI, 1.25–2.50; average, 2.6), and Bouhanifia (OPI, 2.25–3.25; average, 2.8) dams is generally strong polluted compared to that of Sarno dam (2.75–4.00; average, 3.40) which reveals a strong pollution during May and December months and moderate to low during the rest of the year (Table 3, Figs. 9b and 10).

Calculated COD/BOD5 ratios vary between 3.7 and 7.2 (Table 5) and were greater than 3. They revealed that all waters are more or less difficult to biodegrade in the study dams. Water with BOD5 levels greater than 10 mg/L are considered to be polluted and less than 4 mg L−1 to be reasonably clean [31].

Table 5 OPI and COD/BOD5 values of water of Tafna and Macta dams
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In Macta watershed BOD5 values were, in general, above 10 mg L−1 and can be considered to be polluted. As for Tafna dams, they generally vary between 4.8 and 21.6 mg L−1 and were more or less polluted except for Meffrouch (in January, February, March, and May) and Sikkak (in March) dams where BOD5 contents were less than 4 mg L−1.

4 Conclusions

In this study, surface water quality data for 14 parameters collected from the monitoring of 10 dams located within two northwestern Algerian watersheds (Macta and Tafna) were monthly analyzed during 1 year (2003). The waters of all dams were alkaline, with pH values ranging between 7.01 and 8.97. The highest DR contents were found at Macta watershed. The maximum yearly average (3,161.7 mg L−1) was recorded at Sarno dam located upstream of the confluence of Mekerra and Sarno wadis. In the other Macta dams, yearly averages were between 1,101.7 and 1,858.3 mg L−1. Tafna watershed registered lesser contents varying between 279.2 mg L−1 at Meffrouch dam and 1,081.7 mg L−1 at HB.

As for BOD5, COD, and MO average contents, they were maximum at Cheurfa (BOD5, 24.1 mg L−1; COD, 104 mg L−1; 12.9 mg L−1) and HB (BOD5, 11.9 mg L−1; COD, 43.8 mg L−1; OM, 8.8 mg L−1) dams and minimum at Sarno (BOD5, 10.6 mg L−1; COD, 53.3 mg L−1; 12.9 mg L−1) and Bouhanifia (MO, 6.9–10.6 mg L−1) in Macta watershed and BB (BOD5, 5.8 mg L−1; COD, 31.9 mg L−1; 4.0 mg L−1).

The calculated organic pollution index values during the study period evidenced the pollution state of the dams. They indicated moderate to very strong pollution in the water of the two watersheds. In Tafna dams, OPI averages of SA, Meffrouch, and BB dams, exhibited moderate organic pollution. As for Sikkak, pollution is considered to be moderate from January to April and strong during the remainder of the year. Water of HB was strongly to very strongly polluted.

Waters of Fergoug, Ouizert, Cheurfa, and Bouhanifia dams were generally strongly polluted except that of Sarno dam, which indicated a strong pollution only during May and December months. Indeed, water of the two watersheds was more or less difficult to biodegrade.

5 Recommendations

To ensure good water quality in order to preserve dams against pollution, several measures must be taken.

Following the observations made during the processing of the acquired information, it is important to frequently analyze other water parameters at watershed and dams, such as heavy metals, to get more information and to identify the emerging water quality issues and the extent to which existing criteria and recommendations can address these problems.

More accurate monitoring is recommended for watercourses, and setting up of mandatory regulations for polluters by requiring them to clean their wastewater by sewage treatment plants before pouring them into streams is needed.

Necessary measures must be taken to avoid the eutrophication of the dams which is the consequence of the poor quality of water and the presence of pollution.

It is also important to create treatment plants for each dam inlet regardless of the destination of these waters, as it is necessary to adjust the treatment in relation to the water quality and according to their uses.