Environmental and Social Impact Assessment Ruzizi 3 Regional Hydropower Project (P178685) (English)

Table of Contents

• Climate ............................................................................. 7-1 2
• Geology ........................................................................... 7-4 2
• Hydrogeology ............................................................... 7-15 2
• Geomorphology ........................................................... 7-17 2
• Water Quality ............................................................... 7-33 2
• Hydrology ..................................................................... 7-36 2
• Aquatic Ecology .......................................................... 7-70 2
• Terrestrial Ecology ................................................... 7-120 3
• Climate 9
• Janv. Fév. Mars Avril Mai Juin Juil. Août Sept. Oct. Nov. Déc. 10
• Geology 12
• General Geological Context 12
• Seismicity 15
• Geodynamic Context 15
• Regional and Local Seismicity 15
• Slope Stability 17
• Potential Landslide Identification 17
• Previous Investigations 2008-2009 17
• 2020-2021 Investigations 18
• Interferometry Data and SAR Analysis 19
• Risk Assessment 20
• Hydrogeology 23
• Generalities 23
• Types of Aquifers 23
• Aquifer Potential 23
• Groundwater Exploitation 24
• Geomorphology 25
• General Area Description 25
• Lake Kivu Outflow to Ruzizi-II Dam 26
• Ruzizi-II to Ruzizi-III Dam Site 27
• Reach to be Occupied by the Proposed Ruzizi-III Dam and Reservoir 29
• Reach Bypassed by the Ruzizi-III Headrace Tunnel 31
• Ruzizi-III Powerhouse to the confluence with the Ruhwa River 32
• Tributaries Sediment Input in the Ruzizi Downstream from the Project 34
• Estimate of Sediment Loading in the Ruzizi River at the Ruzizi-III dam Site 37
• Sediment Inflow from Lake Kivu 38
• Measurement of Suspended Sediment Concentration in the Ruzizi River 38
• Measurement of Bedload Sediment Particle Size Distribution 39
• Assessment of Sediment Load 39
• Contribution from Landslides 40
• Water Quality 41
• Generalities 41
• Lake Kivu and its catchment area 41
• The Ruzizi River and its Tributaries 42
• Hydrology 44
• Introduction 44
• Monthly Inflows 46
• Introduction 46
• Feasibility Study Analysis 2020 46
• Other Analysis 52
• Ruzizi I and II Production Data 54
• Summary 54
• Study Area Hydrology 57
• Introduction 57
• Water Level Monitoring 57
• Modelled Hydrological Hydraulic Characteristics 60
• Flood Risk 76
• Aquatic Ecology 78
• Regional Context 78
• Hydrogeomorphological Types 79
• Aquatic Biotopes 83
• Distribution of Aquatic Biotopes 83
• Water Levels 88
• Water Quality 88
• Benthic Diatoms 89
• Aquatic Flora 90
• Aquatic Macroinvertebrates 92
• Diversity 92
• Abundance 92
• Present Ecological State 92
• Ecological Sensitivity 94
• Fish 104
• Current Threats to Ruzizi River 125
• Aquatic Habitat Status 127
• Terrestrial Ecology 128
• Protected and Internationally Recognised Areas 128
• Protected Areas 128
• Key Biodiversity Areas 128
• Ramsar Sites 128
• Regional Context 132
• Terrestrial Ecoregions 132
• National Conservation Priorities for Rwanda 132
• Regional Vegetation Types 132
• Vegetation Communities 135
• Riparian Thicket 135
• Riparian Wetland 136
• Cultivation Secondary Shrubland Mosaic 142
• Hillslope Thicket Forest 142
• Hillslope Grassland Savannah 143
• Flora of Conservation Concern 147
• Threats to Vegetation and Flora 150
• Observations of Landcover Change between 2022 and 2024 153
• Birds 154
• Bird Diversity and Habitat Types 154
• Priority Bird Species 156
• Threats to Birds and Bird Habitats 161
• Mammals 167
• Diversity and Habitat Types 167
• Priority Mammal Species 168
• Hippopotamus Hippopotamus amphibius 168
• Angolan Colobus 169
• Threats to Mammals 174
• Herpetofauna 175
• Diversity and Habitat Types 175
• Priority Herpetofauna Species 175
• Threats to Herpetofauna 179
• Terrestrial Ecological Importance 180
• Ecological Importance 180