Published on International Journal of Biology, Physics & Mathematics
Publication Date: May 1, 2019
Aquatic Animals Biodiversity, Ethiopian Biodiversity Institute
Addis Ababa, Ethiopia
The people on globe are under tremendous threat due to undesired changes in chemical, physical, and biological characteristics of air, soil and water. Next to air we breathe, water is humankind most important substance. The diverse uses of rivers are seriously impaired due to pollution. The increased human population, rapid urbanization, industrialization, old agricultural practice, over uses of chemicals and man-made activity are highly polluted water with different harmful contaminants. Thus, the study has been carried out to assess water quality with physico-chemical parameters in River Berga, Ethiopia. Three sites were selected following the rapid bio assessment protocol criteria and Physico-chemical parameters Sampling was performed in December, 2016, February and April, 2017 months. Physico-chemical parameters, such as dissolved oxygen, conductivity, temperature and pH were measured in-situ, and total phosphorous, soluble phosphorous, ammonia-nitrogen, nitrate-nitrogen and COD were determined in Laboratory of Ambo University. Totally, nine water samples were collected from the sites and analyzed for physico-chemical parameters such as (temperature, Conductivity, pH, nitrate-nitrogen (NO3-N), ammonia, soluble phosphorus and Total phosphorus, DO, BOD, Total suspended solids and COD). Some physico-chemical parameters (water temperature, soluble phosphorus, pH, and NO3-N) were negatively correlated with the benthic macroinvertebrate metrics in the study area. Pressure from livestock, poor farming methods, destruction of riparian forest, cattle grazing, watering, wallowing and wading along the river shore, washing clothes and domestic wastes were the major environmental stressors identified in impacting the water quality of river Berga. This observation was confirmed by ETHbios threshold values where the upper sites fell in high water quality and the downstream site as highly polluted. Thus, mitigate measures should be taken to prevent the further deterioration of river Berga.
Keywords: River Berga, physico-chemical parameters and Specific stressors.
The people on globe are under tremendous threat due to undesired changes in the chemical physical and biological characteristics of water, air and soil. Water is one of the most important and abundant compounds of the ecosystem. It is always the vital commodity for humans, used for drinking, cooking, agriculture, transport and recreation, among other purposes. Next to air we breathe, water is humankind most important substance (Lawson, 2011). In addition, the water plays an important role in the world economy, its functions as a solvent for a wide variety of industrial cooling, chemical substances, and transportation. It also serves as a receptor of industrial waste, domestic waste and wastewater resulting from other uses of water (Chapman, 1996). Water obtained from two principal natural sources: Surface water such as fresh water, lakes, rivers, streams, etc. and ground water such as borehole water and well water (Mendie, 2005). As of now only earth is planet having about 70 – 75% of water. The Rivers are vital and vulnerable freshwater systems across the in world, providing main water resources for domestic, agricultural purposes and industrial. Living organisms on earth need water for growth and their survival.
Diverse uses of rivers are seriously impaired due to the pollution. Pollution of the river first affects its chemical quality and systematically destroys the community disrupting the delicate food web. Water quality parameters which affect the survival, reproduction, growth and production of aquatic species are called water quality variables (Chhatawa,1998). In the past, ‘Water’ that basic amenity for living organisms was pure, virgin, undisturbed, uncontaminated and basically most hospitable for living organisms. However, in recent years due to increased human population, agricultural activities, changes in land use and industrialization, have resulted in increased pollution on water, since these things result in habitat loss, excessive addition of pollutants into the water bodies and functioning in an ever alarming way in different parts of the world (Roy and Gupta, 2010). This affects the natural balance of the aquatic ecosystem, the physical and chemical condition of many stream waters (Pringle et al., 2000). The situation is not different in Ethiopia where organic pollution from residential, agricultural and industries are damped into rivers and streams (Zinabu Gebremariam and Elias Dadebo, 1989). River pollution has effective monitoring, several dimensions and control of river pollution requires the expertise from various disciplines. Accurate and timely information on the quality of water is necessary to shape a sound public policy and to implement the water programs efficiently. Many researchers’ have been conducted an analysis to evaluate the quality of river water in the country. However, because of rapid urbanization, industrialization, old agricultural practice, over uses of chemicals, etc. our rivers are still at high risk. This study investigate the water quality parameters for river Berga under the consideration of effluents from soap, unsuitable agricultural activities, cattle grazing and watering of river and lack of good marginal vegetation along the Berga sides which all cased discharge of pollutants in to the river.
2. Materials and Methods
2.1 Study area
The study area is situated in the Ethiopian central high land lying between latitude 9o1’40″N–9o1’30″N and longitude 38o21’0″E–38o21’15″E (Fig.1). It focuses on the river Berga, major tributary of river Awash in the upper section. River Berga is perennial river which originates from the central highland of Ethiopia around Addea berga weroda and flows southwards to join Upper Awash. It is about 60 km from the capital Addis-Ababa on the way to Ambo town and 80 km on the way to Mugger. River Berga River catchment is about 303 km2 (Hussen Endre, 2006). Dobbi, Addama, Fachi and Kerbo are among the most tributaries and the river provides several services, on which the people depend for domestic and irrigation along its gradient from the head water to the junction with river Awash. Furthermore, people use the river water for drinking and washing their clothes in the upper section and intensively used for livestock watering.
Fig. 1 Map of the study area showing the sampling sites
Three important sites were selected based on land use pattern, vegetation cover, habitat types, substrate structure and other human activities, such as washing clothes, grazing animals, watering and agricultural activities. Thus, the selected sites were following the rapid bio assessment protocol criteria (Barbour et al., 1999). Site one (S1) is located at the river reach called Cecafe. The selection of the site was based on observation of minimally impacted physical habitat, low human population pressure; no known discharge and good vegetation cover. The substrates were dominated by megalithal, macrolithal, mesolithal, microlithal, sand and a muddy mixed with decaying leaf litter in pool area. The banks were moderately covered with herbs, shrubs and trees on both sides. Site two (S2) is located in Cirri, particular name called melka Fiche 300 meters in length downstream of site one. The substrate of the river was dominated by megalithal, macrolithal, mesolithal, microlithal and muddy. Bank of the river scattered steep with herbs, shrubs and trees on the left side and eroded on the right side. At this site, agricultural activities and bathing were common practices. Site three (S3) is located in near Kimoye village, above the main bridge on Addis Ababa to Ambo town high way at the distance of 400 meters downstream from the site two. The banks of the river were eroded. Anthropogenic activities such as grazing, washing clothes, cattle watering and bathing are common practices. The structural habitat of the river is dominated by microlithal, mesolithal, macrolithal and megalithal at riffle; sand and mud are the dominant habitats in pools.
2.2 Sample collection
2.2.1 Physico-chemical parameters
Physico-chemical parameters Sampling was performed in December, 2016, February and April, 2017 months. During the period, geographical locations (latitude, longitude and altitude) of the sites were also recorded with GPS (Garmin model 60). The substrate composition of the river was visually estimated from microlithal to megalithal following the categories given in Moog (2007b). Physical and chemical variables including conductivity, dissolved oxygen, pH and water temperature were measured in the field using a portable multi-parameter probe. In Laboratory Ammonia-nitrogen (NH4+-N), nitrate-nitrogen (NO3-N), soluble phosphorus (PO4), COD and Total phosphorus (TP) were analyzed from the collected samples, following standard methods described in APHA (1998). Accordingly, Nitrate-Nitrogen was determined by UV spectrophotometric while Ammonia-Nitrogen by phenate spectrophotometric method, Phosphorus (PO4), by ascorbic acid spectrophotometric method and Total Phosphorus by digestion and ascorbic acid spectrophotometric method. Whereas, Chemical Oxygen Demand (COD) was determined by openreflux method. To retain the chemical properties, all the samples were protected from heat and direct sunlight during transportation until estimated.
3. Results and Discussions
3.1 Correlation of physico-chemical parameters with biological metrics
The result of correlation analysis shown that Shannon diversity index is strong (negatively) correlated to water temperature with r value of -0.998 and p value of 0.037 at 0.05 confident levels and with soluble phosphorus at -1.00 r value and 0.005 p value at 0.01 confident level. pH had a significant negative relationship with Margalef index and average score per taxa. These negative relations suggest the presence of organic pollution from anthropogenic source. This observation was in agreement with the explanation of Aschalew Lakew (2014) who correlated water quality deterioration with lack of proper soil and water conservation measures, high number of cattle grazing, deforestation, siltation, and conversion of forest land into farmlands.
3.2 Physico-chemical parameters
The assessment of ecological conditions in the sampling sites provided a better knowledge of the physical and chemical characteristics. Physico-chemical parameters measured in the field during the sampling period and determined in the laboratory were summarized in (Table 1). The level of dissolved oxygen among the sites had a little variation in the study area. The lowest mean dissolved oxygen value 7.22±1mg/L was recorded at site one and the highest 7.42±0.92 mg/L at site two. DO can also be expressed in terms of percentage saturation and it was relatively low at site one (99%) and maximum (105%) at site two (Table 1). The concentration of dissolved oxygen recorded in all sites were higher than the minimum amount 5mg/l (Chapman and Kimstach, 1996), required for survival and functioning of biological communities. Thus, it was not limiting factor to the survival and growth of benthic organisms. In most natural waters, total phosphorus ranges from 0.005 to 0.02mg/L. Concentration as low as 0.001mg/L may be found in some pristine waters and as high as 200mg/L in some enclosed saline waters (Chapman and Kimstach, 1996). The average phosphorous concentrations recorded at site three was higher than concentrations in most natural waters 0.005 to 0.02mg/L. In the study area the high level of phosphorus (3.3±1.5 mg/L) at S3, inferred that this high value could be due to the mixing of domestic wastes (cattle urine, detergents etc.) and land drainage from the surrounding areas.
In the study area, concentration of COD varied among sites. The highest value was determined at site three (42.33±19mg/L) whereas, the least value was observed at site one 25±5mg/L (Table 1). High COD concentration recorded in site three might be due to the use of detergents, from the washing clothes and urine of cattle which are organic or inorganic, that is oxygen-demanding in nature. However, the COD values were within the standard limit as recommended by the Federal Ministry of Environment.
Site one mean value of pH was 8.7±0.22 while at impaired S2 and S3 were recorded 8.74±0.2 and 8.74±0.18, respectively. The higher values were found at impacted sites. When streams become excessively acidic or alkaline, the change can adversely impact the biota. The pH of river Berga water was slightly above 7 implying basic water. In this study, pH was higher than the neutral value, so the problem of low and extreme pH on the aquatic animals’ structure was improbable. Also the pH values recorded in all sites meet the EPA (2003) standards for surface water 6.0-9.0.
Conductivity was a numerical expression of the ability of an aqueous solution to carry electric current. This ability depends on the presence of ions, their total concentration, mobility, valence, relative concentration and temperature. The mean conductivity of S2 and S3 recorded were 617±34.93 µs/cm and 623±28.53 μs/cm, respectively. According to Chapman and Kimstach (1996), the electrical conductivity in fresh water ranges between 10-1000 µs/cm for surface waters. Increase in conductivity possibly occurs as additional wastes containing ions that enter the stream. It is generally known that watershed disturbance (associated erosion) and urban organic loading increase stream water ionic concentrations and subsequently conductivity (Dow and Zampella, 2000). Thus, runoff from urban areas, which might bring multitude of wastes, such as point discharge of residential wastes contributes to this elevated conductivity and can add high amounts of sediment to receiving streams. The results of this study agree with this idea especially which justified at S3.
Temperature is another important physical property of water, because it regulates the amount of dissolved oxygen, the rate of decomposition of organic matter, photosynthesis and ionization of ammonia (Colt and Tomasso, 2001). Natural variation in water temperatures mainly occur in response to seasonal and regional climate. During this study, the mean water temperatures recorded were 18.8±1.5oC, 19.9±2.86 oC and 20.33oC at S1, S2 and S3, respectively. The temperatures recorded at all sites were found to be within a range of WHO (1995) guideline values 12-25oC for fresh water bodies. The lowest value recorded at S1 may be due to the shading effect of riverine vegetation’s. Water temperature influences the type of plants that grow in the water and the types of animals that live in the water.