Soil erosion by water and the impact of sediment transport on lakes and streams, can seriously degrade soil and create problems for both agricultural land and water quality. The present study has been carried out to assess suspended sediment yield in Mellegue catchment, northeast of Algeria. Regression analysis was used to establish a relationship between the instantaneous water discharge (Q) and the instantaneous suspended sediment concentration (C) based on all recorded data and seasonal ratings for the period 1970–2003. The regression technique used in this paper involved a division of data into discharge – based classes, the mean concentrations and discharges of which are used to develop power regressions, according to single and season ratings, through log-transformation. Sediment loads estimated by stratified rating curves reduced underestimations to a range from 2 to 4%. The mean annual sediment yield during the 34 years of the study period was 589.23 t·km−2·y−1. Sediment transport is dominated by fall rainstorms accounting for 41% of the annual load. The big supply of sediment during this season confirms the intense geomorphic work by fall storms caused by high intensity rainfall and low vegetation cover.

In Algeria, soil erosion has experienced a spectacular extension, it is therefore imperative to assess the effects of this phenomenon. The purpose of this study is to assess soil loss rate using a GIS/USLE approach at the Mellegue watershed, northeast of Algeria. Geographic Information System techniques have been adopted to process data obtained at the study watershed, of reasonable spatial mapping, for the application of the RUSLE model. The model is a multiplication of the five erosion factors, namely rainfall erosivity, soil erodibility, slope and length of slope, plant cover and anti-erosion practices. Each of these factors has been expressed as a thematic map. The resulting soil loss map, with mean erosion rate of 20.40 T/ha/year, shows very low erosion (≤ 7 T/ha/year) which covers 64.60% of the total area of the basin, and very high erosion (> 60 T/ha/year) which does not exceed 4.80% of the basin area. The results indicate that Chabro and downstream Mellegue sub-watersheds face the greatest risk of soil erosion compared to Meskiana sub-basin, with contributions of 14.20 % and 12.90 % of their basin areas respectively. This is mainly due to natural factors and anthropogenic activities without appropriate conservation practices of agricultural land.