Wetland & Fish Ecology - Enviro Dynamics Namibia

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52 ISSUE POTENTIAL IMPACT UNMANAGED MANAGED IMPACT POTENTIAL UNMANAGED IMPACT EXT DUR INT SIGN MANAGED IMPACT MITIGATION SIGN A Possible salinisation due to salts leaching out of disturbed substrate excavated during construction Increased salinity of water in the channel alongside the dike Most oshana creatures have wide tolerance ranges due to variability of the system and high evaporation rates L ST Min -M L Con Of duration limited Check salinity gradient in substrate beneath iishana to avoid disturbing saline layers if they occur 0 A + B Mixing with water supplied from Kunene Introduction of Kunene species (invasion and genetic pollution) R LT Ser -H M Ong No chance of canal water (NamWater supply) mixing with oshana water Careful construction, ensures NamWater canals and ponds unable to spill downstream L B Reduction in aquatic invertebrates + Fish kills due to eutrophication, algal blooms and resultant local anoxic conditions created in canal in town & downstream Aquatic invertebrates and Fish die as result of stagnant water that has no oxygen L MT MOD -H M Ong No sewage leaks nor leaching from dump sites No algal Prevent build-up of organic waste in storm- water. Repair sewage pipes and move ponds to L Draft Environmental Impact Assessment: Oshakati Flood Mitigation Project Specialist Study: Wetland Ecology and Fish Ecology Imputs July 2012
53 ISSUE POTENTIAL IMPACT UNMANAGED MANAGED IMPACT POTENTIAL UNMANAGED IMPACT EXT DUR INT SIGN MANAGED IMPACT MITIGATION SIGN Impact may extend all the way to Omadhiya wetland Negative effect on piscivorous birds if fish numbers reduced blooms No mortalities fish higher ground. Law enforcement on dumping. Unlikely to affect Etosha Fish mortality in Omadhiya Lower bird numbers Lower fishing success downstream to lakes R MT SER -L M Ong Responsibility of Oshakati Municipality No blooms No mortalities algal fish Use wetlands as green lungs. Keep oshana natural. Water quality biomonitoring of Okatana monthly in summer by town council L Normal fishing downstream and in lakes Annually monitor fish + bird populations in Okatana and downstream to lakes . B Salinisation of water Increased water salinity in Okatana channel + downstream for first few flood seasons, due to construction R MT Min M Con+ Can avoided careful be by Check salinity gradient in substrate beneath iishana to avoid disturbing deeper saline layers, L Draft Environmental Impact Assessment: Oshakati Flood Mitigation Project Specialist Study: Wetland Ecology and Fish Ecology Imputs July 2012
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PROPOSED FLOOD MITIGATION MEASURES
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ii EXECUTIVE SUMMARY The Cuvelai Ri
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iv Decreased surface area of iishan
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vi CONTENTS EXECUTIVE SUMMARY .....
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viii 4.9 IMPACTS OF REMOVAL OF VEGE
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x Figure 4-7 Raised floor of bridge
Page 13 and 14: 1 1 INTRODUCTION 1.1 BACKGROUND: Th
Page 15 and 16: 3 were also still present although
Page 17 and 18: 5 2 LEGAL AND REGULATORY REQUIREMEN
Page 19 and 20: 7 3.1.1 CUVELAI WETLAND SYSTEM: The
Page 21 and 22: 9 Figure 3-1 below is a map of the
Page 23 and 24: 11 In the 1950s and 1960s, a progra
Page 25 and 26: 13 Recommendations to the Departmen
Page 27 and 28: 15 invertebrate fauna by Nakanwe, (
Page 29 and 30: 17 possibly via the Calueque-Oshaka
Page 31 and 32: 19 harvesting fish along the Ondang
Page 33 and 34: 21 from survivors from the last flo
Page 35 and 36: 23 As this underlines the importanc
Page 37 and 38: 25 Discussion with Mr L. Hango, Hyd
Page 39 and 40: 27 A full record of the discussion
Page 41 and 42: 29 Oreochromis macrochir Greenhead
Page 43 and 44: 31 26 June 2012 Site 5 DIKE 10 Oshi
Page 45 and 46: 33 Oshanas at end of canal, Dec 198
Page 47 and 48: 35 Fish species Common names Iishan
Page 49 and 50: 37 Fish species Common names Iishan
Page 51 and 52: 39 The following sizes of fish were
Page 53 and 54: 41 4 IMPACT ASSESMENT (OF THE DIKE
Page 55 and 56: 43 Channing and Griffin (1993) and
Page 57 and 58: 45 A) Impact related to dike and it
Page 59 and 60: 47 ISSUE POTENTIAL IMPACT UNMANAGED
Page 61 and 62: 49 blooms as has happened in Gorean
Page 63: 51 A) Impact related to dike and it
Page 67 and 68: 55 4.4 IMPACTS OF ALTERED FLOWS (VE
Page 69 and 70: 57 Figure 4-3 Inakulo Yomadhiya Gra
Page 71 and 72: 59 High fishing pressure can be exp
Page 77 and 78: 65 During low floods, especially af
Page 81 and 82: 69 Okatana channel of marginal vege
Page 83 and 84: 71 4.6 IMPACTS ON FROGS (PARTICULAR
Page 87 and 88: 75 4.7.2 IMPACT OF DEEPENING AND LI
Page 91 and 92: 79 4.8 IMPACTS OF FLOODGATE OPERATI
Page 95 and 96: 83 4.9 IMPACTS OF REMOVAL OF VEGETA
Page 97 and 98: 85 Although only one study on the e
Page 101 and 102: 89 4.10 IMPACTS OF DEEPENING THE CH
Page 105 and 106: 93 4.11 HEALTH IMPACTS/SPREAD OF BI
Page 107 and 108: 95 POTENTIAL IMPACT UNMANAGED MANAG
Page 109 and 110: 97 4.12 COMMENT ON POTENTIAL FOR FI
Page 111 and 112: 99 This includes following the natu
Page 113 and 114: 101 5 CONCLUSIONS AND RECOMMENDATIO
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103 6 REFERENCES Berry, H.H. (1972)
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105 Geiss, W. (1971). A preliminary
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107 Van der Waal, B.C.W. (2000a). F
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109 Mr Shakelia responded that the
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111 his earlier studies to see whic
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113 Amaranthaceae Nymphaeceae Vahli
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115 Poaceae Poaceae Poaceae Poaceae
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117 Cypercaeae Cypercaeae Cypercaea
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119 Class: Branchiopoda Order: Anos
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121 Sars 1909 Macrothrix spinosa 18
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123 7 1 0 Osprey Pandion haliactus
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125 APPENDIX 3: Field Notes FIELD N
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127 Do not foresee any impacts of w
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129 B) FISH SURVEY RESULTS - ACTUAL
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131 Site 4 Dike 3 Tuesday 25 June T
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133 Site 7 Thursday 28 June - Deep
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Wetland & Fish Ecology - Enviro Dynamics Namibia

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