Irrigation water quality of middle awash river basin, Ethiopia

Abstract

The Awash River acts as a major natural drain for several tributaries and hot springs along its course, and it is the main source of irrigation water in Middle Awash Valley. Hence, evaluation of irrigation water quality through time and space could help for salinity control. Two diversion weirs: Metehara and Melka Sadi and two pump sites: Melka Werer and Ambash were sampling sites. Water quality evaluation was caried for seven years. The pH value did not change over years. However, it slightly increased from July-September. ECw value was higher in June than the rest of sampling months. The ECw value from upstream to downstream ranged from 0.25-0.52dS/m. All samples collected from all sites showed values below FAO water quality guidelines for restriction. Thus, no salinity related or cropping problem should be expected because of using the Awash River water for irrigation. The ECw of Awash River water was lower during the rainy season than dry months. Which its water quality was inversely related to its flow. The combined effect of ECw and sodicity values on permeability or infiltration rate was in the recommendable range. However, in the draught years of June month care must be taken in down streams. Particularly, for more sensitive crops to salinity. Specific-ion toxicity hazardous was non-existent in using irrigation water from Awash River. Sodium significantly correlates with ECw and Adj.RNa rather the rest of cations. Sedimentation and siltation in the Middle Awash Valley is becoming great concern for maintenance of canal riverbank and drain to most projects in rainy seasons utilizing it for irrigation and other uses.