Potential soil erosion and sediment yield in Bovilla watershed. Soil erosion and sediment yield in Bovilla watershed

VALMIR BALOSHI1, FRAN GJOKA1*, ELVIN TOROMANI1, NEHAT ÇOLLAKU1

1Agricultural University of Tirana, Kodër Kamëz, Tirana, Albania

*Corresponding author e-mail: rimlav_2004@hotmail.com

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Abstract:

Sediments and chemical pollutants generated by soil erosion penetrate into the water bodies damaging their quality. In this study, the potential soil loss and sediment yield has been investigated at the sub-watershed level within Bovilla watershed located in the northeast of Tirana municipality. This reservoir provides most of the potable water for Tirana city. Data on local rainfall, soil type, topography, land cover and conservation practices were used for soil erosion modelling using the integration of RUSLE and ArcGIS tools. The sediment delivery ratio was determined by several models to obtain the sediment yield. The potential annual soil loss was highly variable, ranging from 2.46 to 37.72 t/ha/year. The lowest value (0.2 t/ha/year) in annual soil loss is reached in the Bulcesh sub-watershed and highest (1.2 t/ha/year) in Ranza sub-watershed because of the presence of steep slopes. The mean sediment yield in this watershed for the four tested models ranged from 7.15 to 43.25 t/ha/year. This high variation is the result of the diverse land covers/uses, wide range of land slopes and distances to drainage channels within each sub-watershed. The sub-watershed ‘Ranxe’ with the highest slope had the maximum sediment yield, contributing to approximately 30% of the total sediment yield in Bovilla watershed. Several sub-watersheds like “Ranxe”, “Vilez” and “Zall-Bastar” were identified as critical erosion areas, accounting to 78% of the total sediment yield at watershed level, threatening the water quality of Bovilla reservoir. In these critical areas, immediate measures are needed to protect soil and improving water quality. However, further research is needed to quantify soil losses at experimental plots as well as to determine the chemical parameters of water quality in the watershed scale.

Keywords: land cover, RUSLE, sediment yield, soil erosion, water quality.

 

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