Anthropogenic Influence and Climate Change: Water and Nutrient Dynamics in the Kebir- Rhumel Basin, (Northeastern Algeria)

doi:10.21203/rs.3.rs-3221535/v1

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Anthropogenic Influence and Climate Change: Water and Nutrient Dynamics in the Kebir- Rhumel Basin, (Northeastern Algeria)

https://doi.org/10.21203/rs.3.rs-3221535/v1

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This study investigates Anthropogenic Influence and Climate Change: Water and Nutrient Dynamics in the Kebir-Rhumel Basin in Northeastern Algeria. Integrating 10 physicochemical variables, a PCA analysis highlights two distinct factors accounting for 80.90% of the total variance and identifies a strong positive correlation between various variables, particularly NH₄ and PO₄. Two contrasting river areas were noted: Oued Radjas and Oued Rhumel rivers, displaying evidence of anthropogenic activities, and Oued Kebir and Oued El-Kotone rivers, indicative of pristine conditions. Seasonal fluctuations were noted in atmospheric temperature, precipitation, humidity, and wind speed, as well as in physical parameters and nutrient concentrations of surface water, suggesting the potential impact of human activities on water quality and ecosystem health. High EC and TDS values in the Oued Radjas River point to anthropogenic pollution, and high nitrogen nutrient concentrations in the Oued El-Kotonne River hint at potential eutrophication. The study underscores the importance of understanding the interplay between human activities and natural processes in managing water resources and ecosystems. Further research is needed to identify specific human contributors to water quality degradation and nutrient imbalances and to explore mitigation measures for sustainable development.

Anthropogenic activities

Kebir-Rhumel basin

Nutrient

Physicochemical variables

Water quality

Identification of human-induced influences, such as agricultural runoff, urbanization, and industrial pollution, on the water quality and nutrient dynamics of different rivers in the Kebir-Rhumel basin.
The high nutrient concentrations, specifically NH₄ and PO₄, and low SiO₄ levels reveal significant anthropogenic activities impacting the water quality in the basin.
Human activities have resulted in discernible water quality degradation, specifically manifested in high levels of EC, TDS, NH₄, and PO₄, particularly in the Oued Radjas and Oued Rhumel rivers.

Climate change is one of the most pressing global issues of our time. The increasing levels of greenhouse gases in the atmosphere lead to temperature, precipitation patterns, and sea level changes, with wide-reaching consequences for human and natural systems.As the world continues to grapple with the impacts of climate change and urbanization, it is becoming increasingly evident that these factors significantly impact precipitation patterns at the regional level(Deng et al., 2023). As the earth's surface temperature increases, it is expected to impact precipitation patterns and atmospheric moisture levels significantly. The reasons for this are linked to changes in air circulation, an uptick in the hydrological cycle, and the atmosphere's capacity to hold more water (Dore, 2005; Terink et al., 2013). Therefore, Global warming directly impacts changes in precipitation and heavy rains. As temperatures rise, evaporation increases and causes surface drying, leading to more intense and prolonged droughts. However, the atmosphere's ability to hold water also increases by around 7% per 1 degree Celsius of warming, which results in more water vapor and has the most considerable influence on precipitation(Kunkel et al., 2013; Trenberth, 2008). Under global warming, changes in the hydrological cycle with far-reaching effects on humans and ecosystems are predicted to occur globally(Padrón et al., 2020).

Water is a vital component of the hydrological cycle, which is impacted by multiple processes, including the effects of climate change and human activities. On the one hand, Climate change has a major influence on ecosystems and human life, and it impacts the quantity, distribution, and quality of water resources(Oliazadeh et al., 2022). Human activities can have direct and indirect effects on water quality. Direct impacts are those that alter the quality of water by the addition of a chemical element, physical property, or biological component. The discharge of wastewater into a stream has a direct effect on the chemistry of the stream. While the indirect consequences include altering the terrain (building, mining, and farming), which influences hydrological routes that modify the rates at which water interacts with the environment and flushes materials from the landscape(Peters et al., 2005).

Furthermore, dams' effects on the flow of water and nutrients to the coast can also be influenced by water quality. When constructed, dams can impede the natural flow of water, leading to alterations in water temperature and dissolved oxygen levels. This can harm aquatic species' health and make the water less acceptable for human consumption. In addition, a slowdown in water flow can lead to the accumulation of pollutants and sediments upstream, which can have a severe effect on water quality(Baumgartner et al., 2022; Liermann et al., 2012; X. Zhang et al., 2022a). Besides, one of the factors that can impact the environment is the construction and operation of dams.The impact of dams is not limited to the immediate changes in water flow and ecology downstream but also extends to the surrounding estuarine and marine habitats. Building dams can provide benefits and difficulties as an aspect of comprehensive watershed management. The conversion of flowing rivers into stationary reservoirs as a result of damming can greatly impact the hydrography and physical changes of rivers by altering the speed of flow, water quality, temperature, cloudiness, and other physical and chemical characteristics of the river water(Best, 2019; Pearson et al., 2016; Wei et al., 2017; Zarfl et al., 2015; S. Zhang et al., 2019; X. Zhang et al., 2022b).

In addition, dams can significantly disrupt the natural flow of nutrients through biogeochemical cycles, impacting downstream wetlands, estuaries, deltas, and marine ecosystems. In terms of temperature and precipitation, the recent global warming may also increase the detrimental ecological and environmental effects of dam construction(Donald et al., 2015; Iyakaremye et al., 2021; Ullah et al., 2022; van Cappellen & Maavara, 2016). How to reconcile environmental concerns with the development of dams has become an urgent problem for many individuals and organizations.Similarly, the use of fertilizers and pesticides can also have an impact on surface water.The use of pesticides has several benefits, including a dramatic decrease in vector-borne illnesses and higher crop/food yield. Contrarily, overuse of fertilizers poses widespread contamination of groundwater and surface water. When irrigated fields get more precipitation than they can absorb, the surplus water flows off the land as runoff. Surface runoff and leaching are two pathways that pesticides use to get into water sources. The hydrologic cycle links these two essential processes that occur on Earth (Cooper, 1993; Kaur & Sinha, 2019).

Freshwater and sediment inputs from rivers are crucial in preserving estuarine and coastal ecosystems. These inputs, such as river nutrients, enhance biological productivity in estuaries and coastal waters. River sediments also help stabilize deltas and coastal zones, maintaining ecosystems along the land's margins. However, human activities over the past several decades have significantly altered the character and quantity of these inputs. The global influx of mineral nutrients, like phosphate and nitrate, into the oceans has increased by over two times(Ittekkot et al., 2000).The ecological status of lakes and coastal waters is determined by the balance of silicates (Si), nitrogen (N), and phosphorus (P) loads and their relative proportions. These bodies of water act as biogeochemical reactors within the hydrological network, controlling the retention and movement of these essential nutrients(Scibona et al., 2022).Most research on eutrophication causes has centered on nitrogen and phosphorus, primarily because human activities release both nutrients. However, silicate is also crucial for algae growth and species composition. For example, silicate availability determines the growth rates of diatoms (silica-shelled phytoplankton). In recent years, scientists have observed decreaseddissolved silicate concentration in many coastal marine regions worldwide(Conley et al., 1993).

As mentioned before, Climate change and human activities are among today's most significant challenges. The impacts of rising greenhouse gas emissions and human actions, including the building of dams and utilization of fertilizers and pesticides, have a notable effect on the movement of water and nutrients to the northeastern coast of Algeria. The alterations in water temperature, dissolved oxygen levels, and the accumulation of pollutants and sediments upstream can negatively impact aquatic species' health and make the water less acceptable for human consumption. Additionally, the disruption of the natural flow of nutrients through biogeochemical cycles can also impact downstream wetlands, estuaries, deltas, and marine ecosystems. In this research, we aim to investigate Anthropogenic Influence and Climate Change: Water and Nutrient Dynamics in the Kebir-Rhumel Basin and how to reconcile environmental concerns with the development of human activities in the region. Despite the importance of these issues, there is a lack of research on the specific climate Change and Human Activities on the flow of water and nutrients to the coast of northeastern Algeria.

2.1. The study area:

The Kebir Rhumel Watershed is located in northeast Algeria. It borders the Mediterranean Sea to the north, Constantine and Oum El Bouaghi to the east, Batna to the south, and Setif to the west. It covers an area of 8843 km² between 5°40' and 6°40' E longitude and 35°50' and 36°40' N latitude. It is considered a major watershed in the country, home to the largest dam in Algeria, with a capacity of nearly 1∙10⁹ m³.The watershed is divided into the western Oued Enndja Basin and the eastern Oued Rhumel Basin. The Oued Enndja Basin covers an area of 3454.85 km² and has a mountainous topography with high precipitation (681.33 mm/y). The average elevation is 819.50 m, ranging from 114 to 1659 m. The Oued Rhumel Basin extends from the south to northeast, is characterized by a softer topography, and has moderate precipitation (600 mm/y). It covers an area of 4062.42 km² with an average elevation of 775.27 m, ranging from 127 to 1722 m. The confluence of the Oued Enndja and Oued Rhumel forms Oued El Kebir (Zeghmar et al., 2022).A Mediterranean climate, with mild, rainy winters and hot, dry summers, characterizes the study area. The climate varies from semi-humid in the north to semi-arid in the south and has diverse water resources, including rain, hail, and snow. Snowfall occurs mainly in high mountain areas, and rainfall is the primary factor that affects river flow. The average annual rainfall in the Kebir Rhumel Watershed is between 638–738 mm, with more rainfall in the north declining as one moves southward. The average annual temperature is 21.24°C with a maximum temperature of 31.3°C and a minimum temperature of 12.15°C.The topography of the Kebir Rhumel Watershed is primarily mountainous, with steeper slopes found mainly in the northern region. The average height is 745.12 m, with the lowest and highest points being 0 and 1723 m, respectively (as shown in Fig. 1). The average slope is 15.66%, with areas of very steep slopes (over 30%) covering 14.55% of the total area, primarily located in the northwest. Agriculture, such as growing wheat, barley, and animal feed crops, is an everyday activity in the area. The northern part of the watershed is covered with forests of oak and cork trees, while vegetation decreases towards the south. The lack of vegetation has contributed to soil erosion.

The Beni Haroun Dam is crucial in the northeast region of Algeria, near Mila (as shown in Fig. 1). The surrounding area features mountainous regions in the north and a mix of plains and highlands in the south. Constructed in 2003, the dam collects water from a catchment area of 8815 km2 and has a storage capacity of 795 million cubic meters. The water stored in the dam serves two main purposes: (1) irrigation, providing water to approximately 40,000 hectares of agricultural land in the High Plains of Constantine region, including the 2272-hectare Ouled Hamla area, which is mainly used for growing crops such as cereals, and vegetables, and (2) supplying drinking water to six provinces including Constantine, Jijel, Mila, Oum El Bouaghi, Khenchela, and Batna, providing for a population of over 2.5 million people(Bouaroudj et al., 2019). The Beni Haroun Dam (BHD) is fed primarily by precipitation from the Rhumel and Nedja River watersheds and untreated domestic and industrial wastewater from the Constantine and Mila provinces discharged into the reservoir through the hydrographic network. The BHD also receives treated wastewater from the Sidi Marouane treatment plant, which has a daily capacity of 20550m³. The region has a semi-arid climate with two distinct seasons: a cold and wet winter with an average temperature of 7.3°C in January and a hot and dry summer lasting four months, with the warmest month being August with a temperature of 24.2°C. Rainfall in the area is irregular, ranging from 4mm in July to 89mm in January(Soltani et al., 2020).

2.2. Analytical methods:

The speed of the river water flow was evaluated using the CM-2 current meter from Toho Dentan Co. Ltd, Tokyo, at the time of sampling from the same water mass. The water's electrical conductivity (EC) and total dissolved solids (TDS) were measured using the multiparameter probe WTW 197i. To calculate the flow rate (m³ s^− 1), the water velocity (m s^− 1) was multiplied by the total surface area (m²) of the river's transect at the outlet station. Two liters of water were collected from the middle of the flow for nutrient analysis. These water samples were frozen in polyethylene bottles and processed within two days of collection. In the laboratory, the samples were filtered through Whatman GF/C glass filters (0.5µm porosity), and the concentrations of dissolved inorganic nitrogen (DIN), including ammonia (NH₄), nitrate (NO₃), and nitrite (NO₂), as well as silicates (SiO₄), were determined using standard colorimetric methods described in Parsons et al. (1989).

From January 2022 to March 2022, hydrological parameters and nutrient levels were measured monthly at eight stations within the KR basin (Fig. 1). These stations were strategically located at the entrances of Endja, Radjas, El-Kotonne, and Rhumel branches, as well as at the Beni-Haroun dam's exit and the Kebir-Rhumel River outlet. To determine the instantaneous fluxes of nutrients, their concentrations were multiplied by the river's flow. The estimation of wet seasonal loads for nutrients using the method of average instantaneous loads, as described by Preston et al. (1989).

$$F=K\sum _{i=1}^{n}\frac{CiQi}{n}$$

Where F is the wet seasonal load (tons/wet season), Ci is the concentration of nutrients (µM converted to kg m^− 3), Qi is the concomitant instantaneous flow (m³ s^− 1 converted to m³ day^− 1), n is the number of days with concentration and flow data, and K is the conversion factor to consider the period (90 days) and unit of estimation.

2.3. Statistical analysis:

The multivariate technique known as correspondence analysis (CA) was employed to examine potential associations between inorganic nutrients across the aquatic continuum of a river system, spanning from the dam openings to the river outlet. CA offers several advantages over other multivariate techniques like principal component analysis (PCA) and is better suited for the collected data. Presenting the variables and objects together in a biplot graphic interprets the cloud points and associations easier. CA is essentially a dual principal component analysis conducted on both the variables (columns) and objects (rows), comparing them through a double Euclidean distance (Khi-square distance). Unlike PCA, there is no need for data normalization, which can often distort reality (Dervin, 1988). The CA technique was performed using the statistical software SPSS. The contingency table analyzed with CA consists of a matrix showing the monthly average of six nutrient loads (variables) observed at eight sites (objects), including the dam entrance and exit of the Kebir-Rhumel basin.

3.1. Mean changes in atmospheric temperature (T, in °C), precipitation (PP, inmm), humidity (H, in %), and wind speed (V, in m/s) for the period from 2010 to 2020 in the Kebir-Rhumel basin:

Temperature (T)

The mean temperature increases from January to July, with the highest temperature observed in July (28.6°C). It then decreases from August to December (Fig. 2), with the lowest temperature observed in January (8.9°C). This pattern indicates seasonal temperature fluctuations, with warmer temperatures in the summer and cooler temperatures in the winter months.

Precipitation (PP)

The highest mean precipitation occurs in February (99 mm) and March (96 mm), suggesting that these are the wettest months in the Kebir-Rhumel basin (Fig. 2). Precipitation decreases from April to July, with the lowest value in July (7 mm), indicating that this is the driest month precipitation increases from August to November, followed by a slight decrease in December.

Humidity (H)

The highest mean humidity values are observed in the winter months of January (74%), February (76%), and December (76%). Humidity decreases from March to July (Fig. 2), reaching its lowest value in July (43%). It then increases from August to December, suggesting a higher moisture content in the air during the cooler months.

Wind speed (V)

The highest mean wind speeds are observed in February (22 m/s) and September (22 m/s), while the lowest wind speeds occur in June (16 m/s) and July (17 m/s). Wind speed generally decreases from the beginning until mid-year and then increases again towards the end of the year (Fig. 2). This data shows that the Kebir-Rhumel basin experiences seasonal temperature, precipitation, humidity, and wind speed fluctuations. These factors can influence the flow of water and nutrients to the northeastern coast of Algeria and the impact of human activities on the region's water and nutrient cycles.

3.2. Physical parameters of surface water in the Kiber-Rhumel basin and water delivery to the Jijel coastal region during the wet period of 2022:

Electrical Conductivity (EC) and Total Dissolved Solids (TDS) are water quality indicators, representing the concentration of dissolved ions and salts in the water. Generally, higher values indicate increased dissolved salts and lower water quality. In the Kiber-Rhumel basin, the highest EC and TDS values are consistently observed in the Oued Radjas River (ORa-R), suggesting that it may have the poorest water quality among the rivers in this area (Table 1). The pH of the surface water in the basin varies between slightly acidic (7.1) to slightly alkaline (8.9) conditions. Most of the sampling stations exhibit slightly alkaline pH values, with the Oued Rhumel River (ORh-R) showing the lowest pH (7.1) in January and the Oued Endja River (OE-R) is having the highest pH (8.9) in March.Dissolved Oxygen (DO) is a key factor in determining the health of aquatic ecosystems, as it is essential for the survival of aquatic organisms. The DO levels in the Kiber-Rhumel basin are relatively high across all sampling stations, ranging from 32.7 mg/l to 41.5 mg/l (Table 1). This suggests that the water bodies in the basin generally have good oxygen levels and can support aquatic life.The water delivery values indicate the volume of water (in 106 m3) transported to the Jijel coastal region by the rivers during the wet period (Table 1). The Oued Rhumel River (ORh-R) delivers the highest volume of water, with the highest value recorded in January (750). Water delivery generally decreases from January to March for most rivers, except for the Month Kebir-Rhumel River (M-KRR), which has an increase in water delivery from February (300) to March (462).

Table 1

Physical parameters of surface water in the Kiber-Rhumel basin and water delivery to the Jijel coastal region during the wet period of 2022:
January 2022	Station	EC (µs/cm)	TDS (mg/l)	pH	DO (mg/l)	Water delivery (10⁶ m³)
	S1 :Oued Endja River (OE-R)	1614	811	7.9	40.8	136
	S2 :Oued Radjas River (ORa-R)	5350	3340	7.2	34.6	20
	S3 :Oued El-Kotonne River (OK-R)	1481	795	8.0	40.6	61
	S4 :Oued Rhumel River (ORh-R)	2200	1170	7.1	33.4	750
	S5 :Downstream dam (D-D)	1550	887	8.2	40.7	225
	S6 :Milia River (M-R)	1400	787	7.7	40.3	/
	S7 :Month Kebir-Rhumel River (M-KRR)	1018	543	7.7	37.1	330
	S8 :Jijel Offshore (J-OS)	1748	941	7.9	40.3	/
Fabruary 2022	S1 : Oued Endja River (OE-R)	1788	936	8.45	39.3	113
	S2 : Oued Radjas River (ORa-R)	7180	3870	7.60	39.6	15
	S3 : Oued El-Kotonne River (OK-R)	1472	782	8.30	40.0	42
	S4 : Oued Rhumel River (ORh-R)	2100	1140	8.20	33.8	359
	S5 : Downstream dam (D-D)	1548	826	8.40	40.2	225
	S6 : Milia River (M-R)	1548	828	8.26	40.3	/
	S7 : Month Kebir-Rhumel River (M-KRR)	1355	723	8.10	33.4	300
	S8 : Jijel Offshore (J-OS)	1130	670	8.10	40.5	/
March 2022	S1 : Oued Endja River (OE-R)	1413	753	8.90	40.8	380
	S2 : Oued Radjas River (ORa-R)	5850	3180	8.17	36.6	20
	S3 : Oued El-Kotonne River (OK-R)	1252	670	8.90	40.7	56
	S4 : Oued Rhumel River (ORh-R)	1809	983	8.63	34.6	313
	S5 : Downstream dam (D-D)	1245	684	8.86	41.5	250
	S6 : Milia River (M-R)	1208	681	8.70	32.7	/
	S7 : Month Kebir-Rhumel River (M-KRR)	989	532	8.81	40.8	462
	S8 : Jijel Offshore (J-OS)	46	27	8.61	41.3	/

3.3. Nutrient concentration (in mg/l)in the Kebir-Rhumel basin during the wet period of 2022:

Ammonium (NH₄), Nitrite (NO₂), and Nitrate (NO₃) are essential for the growth of aquatic plants and algae, but their excessive concentrations can lead to eutrophication and water quality issues. The levels of these nutrients vary across sampling stations and months, with some of the highest concentrations observed in the Oued El-Kotonne River (OK-R) for NO₃ in February and March and the Oued Rhumel River (ORh-R) for NH4 in January (Table 2). Dissolved Inorganic Nitrogen (DIN) represents the combined availability of nitrogen as ammonium, nitrite, and nitrate. The highest DIN concentration was observed in the Oued El-Kotonne River (OK-R) in February, indicating high levels of nitrogen nutrients in this river, which could potentially contribute to eutrophication and water quality degradation.Phosphate (PO₄) is another essential nutrient for aquatic life, but excessive levels can also lead to eutrophication. The PO4 concentrations are generally low across all sampling stations, with the highest values observed in the Oued Radjas River (ORa-R) and Oued Rhumel River (ORh-R) in February.Silicate (SiO₄) is an essential nutrient for the growth of diatoms, a group of algae that plays a vital role in aquatic ecosystems. The SiO4 concentrations are highly variable across the sampling stations, with the highest values observed in the Oued El-Kotonne River (OK-R) in February and March (Table 2).

Table 2

displays the nutrient concentration (in mg/l) in the Kebir-Rhumel basin during the wet period of 2022.
January 2022	Station	NH₄ (mg/l)		NO₂ ( mg/l )	NO₃ ( mg/l )	DIN ( mg/l )	PO₄ ( mg/l )	SiO₄ ( mg/l )
	S1 : Oued Endja River (OE-R)		0.43	0.41	0.78	1.62	0.04	11.22
	S2 : Oued Radjas River (ORa-R)		0.49	0.17	0.58	1.24	0.40	14.90
	S3 : Oued El-Kotonne River (OK-R)		0.39	0.02	1.52	1.93	0.10	14.61
	S4 : Oued Rhumel River (ORh-R)		0.69	0.39	0.82	1.89	0.49	13.52
	S5 : Downstream dam (D-D)		0.18	0.01	0.55	0.75	0.00	7.35
	S6 : Milia River (M-R)		0.53	0.11	0.38	1.02	0.02	12.15
	S7 : Month Kebir-Rhumel River (M-KRR)		0.56	0.13	0.63	1.32	0.02	15.66
	S8 : Jijel Offshore (J-OS)		0.58	0.16	0.42	1.16	0.01	14.45
Fabruary 2022	S1 : Oued Endja River (OE-R)		0.48	0.27	2.52	3.27	0.08	1.28
	S2 : Oued Radjas River (ORa-R)		0.68	0.48	1.65	2.81	0.72	13.93
	S3 : Oued El-Kotonne River (OK-R)		0.48	0.59	5.29	6.36	0.30	19.95
	S4 : Oued Rhumel River (ORh-R)		0.44	0.53	2.61	3.57	0.67	15.71
	S5 : Downstream dam (D-D)		0.06	0.00	0.64	0.71	0.03	12.37
	S6 : Milia River (M-R)		0.61	0.20	0.58	1.39	0.01	3.31
	S7 : Month Kebir-Rhumel River (M-KRR)		0.48	0.31	0.81	1.59	0.02	3.79
	S8 : Jijel Offshore (J-OS)		0.19	0.00	0.06	0.24	0.01	0.44
March 2022	S1 : Oued Endja River (OE-R)		0.03	0.50	2.90	3.43	0.07	9.42
	S2 : Oued Radjas River (ORa-R)		0.14	2.03	2.95	5.11	0.33	8.91
	S3 : Oued El-Kotonne River (OK-R)		0.10	0.11	7.01	7.23	0.23	16.15
	S4 : Oued Rhumel River (ORh-R)		0.22	1.21	0.56	1.99	0.38	10.25
	S5 : Downstream dam (D-D)		0.17	0.02	0.67	0.86	0.02	5.49
	S6 : Milia River (M-R)		0.35	0.26	0.68	1.28	0.03	9.13
	S7 : Month Kebir-Rhumel River (M-KRR)		0.17	0.33	0.88	1.38	0.04	8.83
	S8 : Jijel Offshore (J-OS)		0.04	0.06	0.25	0.34	0.03	1.80

3.4. Nutrient loadings (t/wp) at Beni-Haroun dam and the Kebir-Rhumel river outlet during the wet period 2022:

Ammonium (NH₄), Nitrite (NO₂), and Nitrate (NO₃) loadings vary across sampling stations, with the highest loadings observed in the Oued Rhumel River (ORh-R) for NH₄ and NO₃, and the Oued Endja River (OE-R) for NO₂ (Table 3). These high nutrient loadings could result from human activities in the watershed, contributing to eutrophication and water quality issues in the downstream areas.The highest DIN loading is found in the Oued Rhumel River (ORh-R), followed by the Oued Endja River (OE-R). This suggests that these two rivers are the primary sources of nitrogen nutrients in the region and may significantly impact water quality and ecosystem healthon the northeastern coast of Algeria.The PO4 loadings are highest in the Oued Rhumel River (ORh-R) and the Milia River (M-R). High phosphate loadings can lead to eutrophication and other water quality issues in downstream areas. The SiO₄ loadings are relatively low across all sampling stations (Table 3). Nonetheless, the highest SiO₄ loading is observed in the Milia River (M-R), which could influence the growth of diatoms and other algae in the receiving waters.

Table 3

Nutrient loadings (in tons per wet period, t/wp) in the Beni-Haroun dam and the outlet of the Jijel coastal region during the wet period of 2022.
Wet period	Station	NH₄ (t/wp)	NO₂ (t/wp)	NO₃ (t/wp)	DIN (t/wp)	PO₄ (t/wp)	SiO₄ (t/wp)
	S1 : Oued Endja River (OE-R)	324	220.5	907.2	1451.7	33.3	11.22
	S2 : Oued Radjas River (ORa-R)	58.5	40.5	55.8	154.8	16.2	14.90
	S3 : Oued El-Kotonne River (OK-R)	130.5	45.9	415.8	592.2	25.2	14.61
	S4 : Oued Rhumel River (ORh-R)	1917.9	675.9	1008	3601.8	604.8	13.52
	S5 : Downstream dam (D-D)	378	6.3	253.8	638.1	9.9	7.35
	S7 : Month Kebir-Rhumel River (M-KRR)	1049.4	153.9	495	1698.3	26.1	15.66

3.5. Statistical analysis results:

For the PCA analysis, we included ten physicochemical variables: pH, CE, TDS, soluble DO, NH₄, NO₃, NO₂, DIN, PO₄, and SiO₄. The correlation analysis of these variables revealed that most exhibited substantial and statistically significant correlations (Fig. 3). The PCA applied to these parameters resulted in two distinct factors that accounted for 80.90% of the total variance. Factor 1 (F1) alone explained 55.70% of this variance (Fig. 3). The variables with the highest factorial charges were EC (0.835), NH₄ (0.639), PO₄ (0.928), SiO₄ (0.644), and TDS (0.828). Factor 2 (F2) accounted for 25.20% of the total variance, and the remaining variables also displayed strong relationships, as indicated by their high factorial charges.The asterisk (*) denotes the strongest correlations in the matrix. Consequently, a robust positive correlation is observed between SiO₄ and NH₄, as well as between DIN (dissolved inorganic nitrogen) and NO₃. Furthermore, NH₄ exhibits a relatively strong positive correlation with DIN and PO₄ (Fig. 3).The factorial plan projection F1 × F2 from the correspondence analysis reveals two distinct areas: the Oued Radjas and Oued Rhumel rivers characterized by high levels of pH, TDS, EC, NH₄, and PO₄ resulting from various anthropogenic activities in their watersheds, in contrast to the Oued Kebir and Oued El-Kotone rivers, which display high levels of NO₂, NO₃, and SiO₄, indicating pristine river conditions. Notably, the studied rivers are characterized by elevated NH4 and PO₄ levels, particularly in the Oued Radjas and Oued Rhumel rivers, while SiO₄ levels are deficient. These biogeochemical conditions are likely to have significant impacts on the river systems and the functioning and productivity of the Ben Haroune dam, which receives water from these rivers.

The present study investigates the Anthropogenic Influence and Climate Change: Water and Nutrient Dynamics in the Kebir-Rhumel Basin located in Northeastern Algeria by analyzing meteorological data, physical parameters of surface waterin the Kebir-Rhumel Basin from 2010 to 2020, and nutrient concentrations during the wet season of 2022. Our findings reveal notable seasonal fluctuations in atmospheric temperature, precipitation, humidity, and wind speed, which could significantly impact the flow of water and nutrients in the region and the effects of human activities on the water and nutrient cycles.These findings are broadly consistent with other studies showing that higher water temperatures also affect chemical processes in lakes with increasing pH (Psenner and Schmidt, 1992). As well as the seasonal differences in Sur-Counter surface runoff, precipitation, inflow, groundwater flow, andthe pumped-in and outflows strongly influence River discharge and the concentrationofPollutants in river water (Vega et al.,1998).The data on physical parameters of surface water (EC, TDS, pH, DO) and nutrient concentrations (NH₄, NO₂, NO₃, DIN, PO₄, SiO₄) indicate potential influences of human activities on water quality and ecosystem health in the Kebir-Rhumel basin.The highest EC and TDS values observed in the Oued Radjas River suggest poorer water quality in this area, which may be attributed to human-induced factors such as agricultural runoff, urbanization, or industrial pollution. In addition, the highest concentrations of nitrogen nutrients (NH₄, NO₂, NO₃, DIN) are found in the Oued El-Kotonne River, potentially contributing to eutrophication and water quality degradation.

Numerous recent research papers concur that the levels of nitrogen and phosphorus in surface waters are substantially affected by human-related factors linked to land cover, land use, and specific source points (for example, as suggested by Castillo et al. 2000; Ferrier et al. 2001; Valiela and Bowen, 2002). His seasonal variations in nutrient concentrations highlight the importance of understanding how human activities interact with natural processes to shape water and nutrient flow in the region.

For instance, the elevated levels of DIN in the Oued El-Kotonne River during February may be due to increased agricultural runoff during the wet season, which could exacerbate eutrophication and adversely impact aquatic ecosystems. Similarly, the low phosphate concentrations across most sampling stations may be influenced by human activities such as using phosphate-free detergents or wastewater treatment processes that remove phosphate from effluents. Conversely, agricultural operations that aren't well-managed can lead to the pollution of both surface and groundwater due to the presence of nutrients and pesticides (as discussed by Spalding and Exner, 1993; Pereira et al., 1996; Kolpin et al., 1998; Novotny, 1999; Gunningham and Sinclair, 2005). Habitual usage of these agricultural substances can lead to their dispersion into the environment through means such as drift, runoff, and drainage (as found by Kolpin et al., 1998; Guzzella et al., 2006; Papastergiou and Papadopoulou-M, 2001). This can ultimately lead to the detection of these residues in groundwater (Lacorte and Barcelo, 1996), river waters (Irace-Guigand et al., 2004; Claver et al., 2006), as well as coastal waters and lakes (Konstantinou et al., 2006). These findings suggest that these residues can mobilize and be found considerable distances from their original application points.The data on water delivery to the Jijel coastal region reveals that the Oued Rhumel River contributes the highest volume of water during the wet period, which suggests that this river may play a crucial role in transporting nutrients and other contaminants to the coastal area. Understanding the factors that drive changes in water delivery, such as seasonal precipitation patterns or human interventions like water extraction and dam construction, is essential for managing water resources and protecting the ecological integrity of the northeastern coast of Algeria.

This study underscores the importance of understanding the complex interplay between human activities and natural processes in shaping the flow of water and nutrients in the Kebir-Rhumel basin. By identifying the key drivers of water quality and nutrient dynamics, our findings can inform targeted management strategies to mitigate the impacts of human activities on the region's water resources and ecosystems. Future research should focus on elucidating the specific human activities contributing to water quality degradation and nutrient imbalances, as well as exploring potential mitigation measures and management strategies to promote sustainable development on the northeastern coast of Algeria.

The significant characteristics of the studied rivers are the high values of NH₄ and PO₄, contrary to SiO₄ levels that were remarkably lowered because of their retention in dams. The other particularity is that direct wastewater inputs from the neighboring big cities and several villages heavily polluted the dams. Surprisingly, the KR and KW dams’ entrances, supposed to be protected, were heavily polluted by vital inputs of NH₄ and PO₄.

The findings underscore the urgent need for targeted intervention strategies to balance the anthropogenic activities contributing to water quality degradation and nutrient imbalances. Future research should focus on identifying specific activities causing these imbalances, exploring potential mitigation measures, and promoting management strategies for sustainable development.

PCA	Principal Component Analysis
pH	Potential of Hydrogen
EC	Electric Conductivity
TDS	Total Dissolved Solids
T	Temperature
NH4	Ammonium
NO2	Nitrite
NO3	Nitrate
DIN	Dissolved Inorganic Nitrogen
PO4	Phosphore
SiO4	Silicates

Authors contribution: Noureddine Bouchareb: Conceptualization, Methodology, Software, formal analysis, Writing - Review & Editing. Sabri Bousbia: data curation, writing-original draft, Writing - Review & Editing. Abdelhak Lefilef: writing-original draft, Review & Editing. Alaeddine Akboudj: data collection, data analysis. Marwa Chardib: data collection, data analysis. Rawiya Bouguenna: data collection, data analysis.

Data availability: All the data examined in this research are incorporated within this published paper along with its supplementary information materials.

Competing interests: The authors declare no competing interests.

Ethics approval: The stated authors have agreed to be authors, have readand approved the work, and have given their consent for the manuscriptto be submitted and published in the future. The author of this articlefurther warrants that they will abide by Springer’s publishing guidelinesand agrees to submit it for publication as any sort of open-accessarticle, thereby reaffirming their commitment to the subscriber accesscriteria and licensing.

Consent to participate: Not applicable.

Funding: This paper was not financially supported.

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No competing interests reported.

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Anthropogenic Influence and Climate Change: Water and Nutrient Dynamics in the Kebir- Rhumel Basin, (Northeastern Algeria)

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1. Introduction

2. Material and Method

2.1. The study area:

2.2. Analytical methods:

2.3. Statistical analysis:

3. Results

3.3. Nutrient concentration (in mg/l)in the Kebir-Rhumel basin during the wet period of 2022:

3.5. Statistical analysis results:

4. Discussion

Conclusion

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