In this paper we investigated the effects of fresh water (F as a control), wastewater (W) and magnetized wastewater (M) on furrow erosion. Experimental design was randomized complete blocks consisting of four replication blocks and three water quality treatments. Five irrigation events with 4 days' irrigation interval were practiced in each furrow. The erosion was monitored and measured in the second, fourth and fifth irrigation events for each furrow. Water quality parameters measured during the irrigation ventsd included cations, anions, EC, pH, total-coliform, TSS, DO and COD. The applied intensity of the magnetic field was 10 mili-Tesla. Furrows spacing, length and slope were 0.6 m, 42 m and 0.11 %, respectively. Inflow rate was 0.8 l/s for all the irrigation evens. To determine the net erosion in furrows, water samples were taken from runoff after its start at different time intervals. The net erosion was calculated at each time after determining soil mass in the samples and the net erosion vs. time chart was plotted. The mean erosion was calculated from this chart. The erosion indexes investigated in this study include mean erosion and maximum depth of the furrow crosssection. The results showed that, in all of the water treatments, the net erosion decreases with time in each irrigation., There is also a significant decrease in the mean erosion values in W and M treatments, compared with F treatment, in the second and fourth irrigation events at the 1% (p < 0.01) and 5% (p < 0.05) level, respectively, but there no significant difference between W and M treatments. The effect of irrigation event on the mean erosion was not significant in any treatment. The effect of water treatment on the basic infiltration rate and the maximum depth of furrow cross-section were not significant, but the basic infiltration rate was in most cases higher in M treatment than in F and W treatments in most cases. Also the changes in the maximum depth of furrow cross-section due to subsequent irrigation events were smaller in M and W treatments than in F treatment.