The physico-chemical and algal characteristics of the upper reaches of Ebonyi River were studied in four stations over a four- month period from September to December 2014. The physico-chemical parameters: air and water temperatures, colour, depth, rate of flow, transparency, pH, Total Dissolved Solids (TDS), alkalinity, Biochemical Oxygen Demand (BOD5), Dissolved oxygen (D.O), silica, potassium, phosphate, nitrate, chloride, calcium, lead, iron and mercury were studied using standard methods. Parameters such as colour, calcium, pH, total dissolved solids, alkalinity, chloride, dissolved oxygen, silica, biochemical oxygen demand, phosphate, nitrate, potassium and lead did not significantly differ between the locations (P ≤

0.05). Air temperature, depth, rate of flow and transparency differed significantly between locations. All parameters differed significantly between months except depth and rate of flow which did not significantly differ between the months. Mercury was not detected during the study period. A total of twenty nine (29) taxa of algae were observed in the study. Algal abundance showed the following order: Heterokontophyta > Chlorophyta > Cyanophyta > Euglenophyta > Cryptophyta. Based on Shannon-Wiener diversity index, the water in the four locations studied is moderately polluted. The study revealed that though Ebonyi River is not heavily polluted, the fluctuations of the investigated parameters along the sampling points could be as a result of both anthropogenic and natural activities.

Rivers as water bodies are important by being involved in maintaining a balance in the ecosystem through supporting diverse plankton (phytoplankton and zooplankton) and other organisms in the food chain. In the last decades, there has been a growing necessity for the conservation of our resources, especially water. At the same time, growing populations, progressive industrialization and intensification of agriculture are leading to increased pollution of our surface waters (Mohammad and Saminu, 2012).

Adequate and safe water supply is therefore a pre-requisite for significant socio-economic development of any community. Unfortunately, in many areas of the world, especially developing countries including Nigeria, it is difficult to obtain a steady source of clean water for drinking and for agricultural uses (Akpan-Idiok et al., 2012). Rivers are equally useful in generating electricity, fisheries, irrigation and for domestic animals (Zakariya et al., 2011). Water required for domestic consumption should be free from suspended solids and dissolved impuritiesetc. (Alexander, 2008). Rivers constitute one of the major sources of water supply in the world (Akpan-Idiok et al.,2012).

The assessment and continuous monitoring of the quality of water sourced from rivers can be used to define existing conditions, detect trend and or establish sources of pollution. The quality of water is often affected by rocks, soil and surface through which it flows and anthropogenic (e.g. industrial, agricultural and mining) activities (WHO, 1996; Ibeto and Onianwa, 2011).