**1. Introduction**

Inappropriately managed urbanization and expansion of industrialization are the major causes of river water pollution in urban and pre-urban areas due to the introduction of undesirable materials into soils and irrigation water sources [1]. Contamination of heavy metals and other toxic ions in irrigation water sources is a worldwide problem and harmful for human health and the ecosystems. The excessive accumulation of heavy metals in irrigation water and soils resulted in

contamination of human diets [2]. Heavy metals are entering into the river water and the environment primarily through anthropogenic activities. The main sources of heavy metals and other pollutants entering into the Little Akaki River basin can be industrial effluent, municipal solid waste, oily wastes from garages, and fuel stations. Industries like textile, dyeing, garment, pharmaceutical, ceramic, paint, packaging, etc. discharge their effluents into the rivers could be the causes of heavy metal contamination in the irrigation water sources [3]. Industry expansion has brought severe water pollution in Little Akaki catchment from domestic, commercial, and industrial effluents [4] and the waste management systems of industries and other commercial centers are very poor. According to Addis Ababa environmental pollution Authority 2007 report, 90% of all industries lack waste treatment facilities and subsequently dispose of their effluents into river streams. Lack of proper waste management system in the catchment areas, the irrigation water source in Little Akaki River is highly polluted with point and non-point waste sources.

The rapid urbanization and expansion of industries together with poor effluent management systems have a significant effect on the quality of irrigation water sources in the catchment areas. In the recent few decades, the social and economic structure of Addis Ababa city has changed radically. Rapid urbanization and industries expansion are observed and all other economic activities are also highly concentrated in Addis Ababa city, particularly in the Little Akaki River catchment. Besides the urbanization and industries expansion, the intensification of pre-urban and urban farming activities is also becoming one of the other social and economic features of the city. However, most of these rapid changes are brought without considering the negative environmental consequences. As a result, irrigation water pollution with heavy metals and other undesirable pollutants become an increasingly emphasized problem. Wastes generated from households, industries, fuel stations, hospitals, different business centers, and sewerages are getting into the river streams. Contamination of water bodies from various sources denies current and future generations of a birthright and puts at risk ecological integrity [5].

Little Akaki River is the primary irrigation water source for pre-urban and urban agriculture in the catchment area. The demand for irrigation water is markedly increasing in the study area for the production of fruits and vegetables. Many households are involved in urban farming activities to sustain their life. The use of industrial and municipal wastewater in urban agriculture is a common practice in many parts of the world including Ethiopia [6]. The shortages of safe irrigation water sources in the study area forced the farmers to look for to use contaminated river water for irrigated agriculture and access to quality irrigation water sources is becoming a serious concern these days in the study catchment.

The heavy metals and other pollutant elements are entering the soil because using severely contaminated irrigation water source for prolonged periods in the catchment area affect the physical and chemical characteristics of the soil. The contaminated soil of irrigated farm sites in the catchment area harms vegetables and fruit production. The heavy metals become highly concentrated in the edible parts of fruits and vegetables which alter human health. Heavy metal accumulation in soils, and subsequently, in vegetation by long-term wastewater irrigation has a potentially detrimental effect on humans via their transfer along the food chain [7]. In the existing situation, vegetables and other edible crop products produced in contaminated soil are distributed in the local market of Addis Ababa city. Residents are consuming the infected vegetables subsequently by purchasing from the local market

*Concentration Levels of Heavy Metals and Selected Ions in the Irrigation Water: The Case… DOI: http://dx.doi.org/10.5772/intechopen.103677*

and farmers also use the contaminated vegetables for their home consumption before going to market.

Few studies have been conducted so far in Addis Ababa city particularly in Little Akaki River to investigate the contamination levels of Little Akaki River irrigation water with heavy metals [8–12] but it was still inadequately researched. Because the heavy metal contamination and irrigation water pollution is a very dynamic problem and become progressively increasing. The intensification of industrialization in the Little Akaki River catchment aggravated the progression of river water contamination with heavy metals and toxic pollutants over time. Thus, the dynamism of the problem and the need for updated information about heavy metal contamination are the triggering points for the initiative of this research work. Determination of the existing heavy metals and selected ions is a relatively newer issue or insight to provide possible suggestions. Therefore, this research has focused to investigate the concentration level of heavy metals (Pb, Cd, Cr, and Cu), selected ions (Chloride, Na, Ca, and Mg), and other physic-chemical parameters of the Little Akaki River and to evaluate the suitability of the river water for irrigation uses.
