Sediment Transport and Its Impacts on Lake Kivu, Gihira Water Treatment Plant and Various Hydropower Plants along Sebeya River in Rwanda

Abstract

Complex processes of sediment transport in a river impact on overall aquatic system and result in the productivity decrease of socioeconomic development projects taking the river as a source of water. The present study was designed to estimate Sebeya river sediment load and assess its impacts on Lake Kivu, Gihira water treatment plant and various hydropower plants constructed in Sebeya catchment located in Western Province of Rwanda. Water samples were hand-collected from five different sampling points along Sebeya river during rainy and dry seasons. Laboratory analysis for turbidity, total suspended solids, sieve analysis for bed load materials and NPK content of water samples were conducted. The results revealed that the average turbidity was found to be high during rainy season compared to dry season. The same trend was found in total suspended solids concentrations. At all 5 sampling sites and during rainy season compared to dry season, the average mass flowrates of bed load materials were 7.84 and 2.96 kg/hr respectively. Sieve analysis results showed that all bed load sediments were mainly composed of high proportions of fine sand of more than 70% which adversely causes damages on hydropower turbines and the effect of high soil erosion rates on Gihira water treatment plant was traduced by high turbidity of raw water and excessive costs of reagents. At Sebeya outlet, nutrients load and high turbidity reduce significantly the aesthetic quality of Lake Kivu, having a harmful impact on recreation and tourism, aquatic life

Quantification of sediments and delineation of their sources in Nyabugogo Stream, RWANDA: Relationship with economic development activities

“…For instance, large amount of sediments which are being conveyed in the rivers are transported by soil erosion globally at a rate of 2.3 billion tons per year. The sediment being conveyed in rivers depend proportionally to the erosion rate, river runoff, the land slope, type of soils in most water bodies in Rwanda while soil nutrients (organic materials, nitrogen, phosphorus, and potash) were lost due to soil erosion at rates of 945, 200, 41, 210, 200, and 3055 tons/year respectively (Majoro et al, 2020).…”

Analysis of Pollutant Load Carrying Capacity of the River Tapi Using QUAL2Kw for Surat City

“…The effluent of various urban, industrial, and agricultural pollutants that exceeds the river capacity of the self-purification process causes the river ecosystem to deteriorate [2] [3]. The high concentration of sediments in water negatively affects the country's economy, and polluted water harms people and adversely affects aquatic life [4]. An increase in population, agricultural and industrial activities, and disturbed climate are threats to the global hydrologic cycle and the world's water quality is under threat [5].…”