Assessment of the Spatio-Temporal Trend of Awash River Water Quality to Address Emerging Irrigation Water Quality Issues in Awash Basin, Ethiopia

Abstract

Awash is the most intensively used river in Ethiopia for agriculture, with irrigation water that spatiotemporally varies in the transport pathways. Ever-increasing anthropogenic activities and climate change have brought challenges, of which, salinity and the degradation of water quality are the prime examples. Information regarding recent water quality and suitability dynamics of the Awash is very limited, and thus, this study was conducted in due time. Samples were gathered from ten water quality monitoring stations, three times a year, for seventeen consecutive years, and analyzed for quality parameters. Results indicate that pH values over the years ranged from 7.4 to 8.4; lying within a slight to moderately alkaline range of water. The EC values ranged from 0.21 to 1.16 dS/m within the 2004–2014 period. The average ion concentrations northwardly spread in the sequence of Ca2+>Na+>Mg2+>K+, HCO3->Cl-> SO42- and Na+>Ca2+>Mg2+>K+. Spatial trend analysis revealed an increasing progression of ECw, SAR, RSC, and ionic constituents. Water quality parameters are found to temporally vary often, with a progressively degrading trend over the study period, confirming the control of water quality mainly by anthropogenic factors. The result further showed a prevalence of slight to moderate sodicity hazards in all samples. The observed space-time variabilities of water quality suggest the proper usage of updated water quality evaluation and spatiotemporal dynamics and trend analysis results in designing appropriate water management strategies in river systems near intensive agricultural, industrial, and urban development areas before unforeseen determinant ground facts hinder development plans in this sub-basin.

Summary of key messages of this paper

• The Awash River is the longest inland river and one of the intensively used rivers in Ethiopia for domestic, industrial and agricultural purposes.
• The water quality of Awash River is under a spatially and temporally continuous and trended change.
• Continuous monitoring and evaluation of water quality are mandatory for timely management actions.

Keywords: Temporal trend, Spatial trend, Awash River Basin, water quality, Ethiopia

DOI: 10.7176/IKM/13-4-01

Publication date:July 31^st 2023