Effect of riparian land use on environmental conditions and riparian vegetation in the east African highland streams

Agricultural land use is expanding and at an accelerated rate. In Ethiopia, most of this expansion has occurred in highland areas and involve deforestation of natural riparian vegetation. However, the impacts on the water quality of streams are poorly understood, especially with regard to the influence of land use patterns on highland streams. In this study, we investigated the effects of land use modifications on the water quality and riparian condition of highland streams and examined whether the preservation of riparian vegetation would help mitigate the negative impacts of intensive agriculture practices. Our results show significant differences in the water quality of streams with different land use. Several parameters commonly used to indicate water quality, such as the concentrations of orthophosphate, turbidity, and suspended solids were significantly higher in the agricultural streams than in the forest stream. The preservation of riparian vegetation in the surrounding highland streams was associated with overall better riparian condition, floristic quality, and water quality such as lower turbidity, total suspended solids, orthophosphate, and higher dissolved oxygen. We conclude, that increases in vegetation cover improved riparian condition and water quality relative to other non-vegetated areas. Therefore, we strongly recommend the preservation of riparian vegetation in tropical highland streams surrounded by intensive agriculture. More studies on the effects of best management practices in areas dominated by agriculture can greatly improve our capacity to prevent the degradation of water quality in tropical highland streams of Africa.