aodis ababa university school of graduate studies the degradation of the abo-kebena river in addis

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AODIS ABABA UNIVERSITY
SCHOOL OF GRADUATE STUDIES
THE DEGRADATION OF THE
ABO-KEBENA RIVER IN
ADDIS ABABA, ETIIIOPIA
TESFJ\YE BERHE
I
JUNE, 19BB
THE DE r, RI lll ,n I 0 tl 0 F TIl E
AnO-KEBEHA RIVER IN
ADDIS ARARA, ETHIOPIA
II THESIS
PRESENTED TO
TilE SCIIOOL OF GRllflUilTE STUDIES
AnDIS AUABI\ UNIVERSITY
IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE
OF MASTER SCIENCE IN BIOLOGY
U~
IlY
HSF,~YE IlERHE
JUNE, 1988
TABLE OF CONTENTS
.'.0:. '.'.: ...
AcknQvl1 edgcrn0nt s •••••••••••••••••••••••.•••• " J
List of Tablp.s ••••••••• )~.i.~,.:J~l.~,:,~.
,o .. oo.o •••••••• : •••
L1 St of Figures ....••. 0 ~ ••• 0 ••••••••••- : ••••• ;" . 0 ,; .': ~ ,.', ~:o:' I,'; i i ,i
. ,, . . :::::' : :: :
Abstract .. ~ ~ ,~ 'rv'" '
& 1 •• " •• 0 ............. " .......... I"' ,'.'• •' .'. . "" .... ",",
I. I NTRO{)llC TI ON ......... " • 1
0 ................... & ••• & ... .
I I. DESCRIPTION OF THE STUDY AREA ................... . 19
I II. t~IITER I ilLS Aim ~lETH()JJS ........................... . 22
1. Site- St;-lpction .......................... , ..... . 22
2. Temp£:,·rature .• ~ 22
fll ........................ 0 ••••
3. 22
22
3.2. flethods d('tenninalion .............. . 22
(jf
4 • Faunal Sampling ..• ". .......................... . 23
4.1. Collection and preservation •••••••••••• 23
4.2. Sorting ... ~~& 23
•••••••••••••••••••••••••••
24
5. Algal Silmpl~s •• " ••••••• ~ ....................... . 25
6. Treatment of Drl.t.:l ...................... ~ ...................... " ~ .. 25
I V. RESULTS ............................... " .......................... ~"""""""" .. ...... 26
1. Tenlperaturt~ ... " 26
& ............................................... 8 ........ ..
2. Cherni cill ... <> " .. Q ................ 0 .. " ......................... ~ 0 ........ . 26
2.1. Nitr~t~-nitrog~n........................ ~6
3.
, !. '.
rli vcrs ity ........... ". ............... c ...... r" ~ -;'.', ,-,. r .. '• • ,:. ~"; '.~' ,.' -34 ..
4. S'!ils'lnal Variation in InYert.?bfat>
't' - '. : '36-
Co mmunl 10S ........................... ~ .. '-... 0-.:.. 0,' ": 0,- t ......., .. ..
5. 1\19ch: of Abo-Kntwna River ..••..••••••••• e •••.
v. OrSCUSIION •••••••••• oeft~ ••• I .................... o ... 45
1. T(~mperdtufe ................................................... " .......... .. 45
'2. Nitrates ilntl OrthlJphosph,ltes ................ . 46
3. 5-day [\i nch(,mi ca 1 Oxygen Dewilnd ••••••••••••••
4. Se~sonal Structure of the Benthic Fauna ••••••
Effl,cts of Organic Pollution on the Fauna .... 49
5.1 Cl r.an w.1tC!r macroi nvertebrates.......... 50
5.2. Effects of light orgilnic pollution...... 51
5.3. Effec,ts of Heavy nrgilnic pollution...... 52
6. Effects of Orgilnic Pllllution on Algae •••••••• 55
VI. COMPIIRISON HITH OTHER J)EGRIIOEO STREI\f·1S !\1m RIVERS
IN AFRICA ................................................. 58
1. Ch,~mi c~ 1 5B
..... ,.oo •••••••••••• e •••••••• oo ••• oo •••
2. Fauna •••• 59
oo •••••••••••••• " ............... o •••••
VII. SUr1WmV OF RESULTS AND INTERPRETATION OF HlPl\CTS ...... 61
VIII. CONCLUSION ANO RECot·l~lENUATION..................... 63
IX.. REFERENCES •••••••• 66
f ................................ .
X. I\PPENDICES •••••••••• 80
oooooo ••••••••••••••••••••••••• e •
I\CKNOWLEDGEHENTS
I \'IQuld like to exprRss my de,-,p grdtitud,' to Prof. H.B.N. Hyn(>s nnd
Prof. il.D. Harri son, my n'sPilrch advisors for tlll'i r C!lnst,lnt guidanc1c, r.\1!f'P
concern nnd for their encouragem~nt I received thr0ughout the pr0paration
of this work, without whom it \'lOuld have, bc(!n very rlifficult, if nllt
impossible!.
Th<: inv,'luabl\' advice and generous help of Prof. G. Hartman is most
gratefully acknoviledged. He has sp(~nt considl'ralJlc time in reading the
first draft of thr> mi1nuscript a,nd offered critici11 suggestions ;Jnd VillUilbl"
commc'nt s.
It is a pleasure' to acknovllt:dgi2 my friends, Hailf'selassh! G. r,\ichael,
Guish G. Hiw6t and Yohann0s G. Michael who were always on the sidp 'If mr
for their assistanc(! ,1nd Qncouragcment. HIJiles(:Ii:\ssi" has done all thE,
graphic and ci1rtographic vlork np.l'ded in the manuscript. Oue thanks also
goes to H/o I\zeb 11ekasha for typi ng thf! manuscri pt nn a
COlllput(~r.
The financial and material assistance including computer facilities madp
by thE.' Canadian International D('velopmf'nt Agency (CIIlI\) thr'1ugh th,"
Freshwater Fisheries ilnd Limnnln9Y Project (FFLP) of the Oepartment of
Biology, Addis Ababa Univfcrsity is also gratefully ~ckno\'t1cdged.
i i
LIST OF TABLES
1. f1ajor grlJups of macroi nvertc'brat\,s cllll ect"o fr;Jm
Abo-Keben~ Riv~r ••••• ~ •••••••••••••••••••••••••• 3<1
2. Numbt'r 01} pcrcentag[: compositi<Jn of faunal sampl,'s
at 8ach statinn (c1ry s(~ason)"'."H''''''.''''<> 39
3. Numbp( (1no percentage compos it i on of f ilunil
samples at each station (wet season) ••••••••••• 40
4. Genera of algae noted in different parts of
,13
50 Summary of results •...• 62
I10 ........................... .
iii
LIST OF FIGURES
L I,lap of Ab<.,-Kebenil R; vcr sho\'l; n9 th,~ I (lCilt i on of
sampling statirJns ..• o........................... 20
2. Temp('rature of I\b»-Kc,bcna R; ver (dry sed son )... ?7
3. TEmp~raturc of Abo-K0b~nft River (wet seas»n)... 28
4. Nutrient level of Abo-Kpbena Riv~r ~s it
fl O>lS thrtlugh Addi 5 Ahaba (clry season) ........ 30
5. Nutrient level of Abo-Kebena River as it
fl()ws through Addis Ababa (\'let s8ason) ••••••• 31
6. HOD profiles of Abo-Kcb0nil River ••••••••••••• 32
7. Numh(~r <Jf t,lxa collected at each station
(dry sf~ason) •• .............................. "' •• ,. 37
8. Number of taxa c01lected at each stdtinn
(Wp.t season) ............... , .................. . 38
9. IJ,Jt"r quality of Abo-KcbEna Riv~r as
d"termim;d by Chandler's Biotic Scor2 ....... 42
i v
Abstract
1\ study of bi 0 I (I'li c(ll an(! ciwmi ea I ch,) ract'.'ri st i CS IWS con<luctf'o on tht'
Aho-Keb~na River, a tropicJI, high altitude m'luntain river, in th~ vicinity
of the city of !\ddis I\bab~, EthitJpia. Ttl<' study WilS carried out over a one
year pr:rioo - ,July 198(j to August 19B5. Observittions wen·, made dt 20
statiuns which had similar features (If depth, substrat~ and velocity. The
20 statiuns covered the stream aver its course from one side of the city to
the other. Though the mountain riv',r \'IdS free 1)1' pollution and thc: upper
part reasonabl'y clean, l'lat"r quality "f the bVlCr part of the river
dc:t"riorated significantly, particularly during the dry season.
llrterioration of watl,r quality caus"d by organic pollution from rloillestic
dnd municipal I'/03St'~5 \'IdS eXilc'~rbat"d by low f11MS and lu\'l dilution during
the dry SG'ason. The biological determination of ~Iatl'r qual ity was marl,~
using macroinvertebrates ,'s indicators. Throughout the study period,
18,934 organisms of 52 tilXil 1'lerL' collect(;<i. The chirl)llornids \'Iere very
important const itu'~nts compri si ng !i4X of th(~ benthi c macroi nvertebrate
community. They uccurred ilt all 5t,ltions throughout the study. The sludy
demonstrilt"d the df,?cts of urgilnic IJOllutants upun str:'am communities.
Plecoptera, Ephemerupteril, Trichoptera, and Colc()pteril \'Iere restricted to
the clean upper part of thi2 river and suppressed in the lower pilrt by water
qual ity conditiJns. Oth(c~r taxa which dominated the pullut('d part of the
river l'll're the Diptera; Ctlironomidae and the Oliguchaet,); Tubifcx spp.
Limnodrilus spp. and Nais spp. 1~lung the ephemernpterans, 8iletis hArrisoni
i'ldS -ubiC]uituus througTi0i"lt the drainage. Simulium spp. \'Ier(' also abundant
in both the cleiln and tilE! polluted part 0(111(, riv,~r. Although represented
by small numbers, Limnnphora lclrvae l'I('r(, found to r'?sist heilvy organic
p')llution in the Abo-Kebena River. There was signific,)nt seasonal
variation (Students t-test) in abundance of macroinvertebrat.,s. Almost ill I
of the benthic fauna \'I(lS found to be ilffected by flol'ls. Thei r nurnl1(,rs
dcclined during the \'let season. The Orthnclild1nac, ~ricotupus spp. I'Icre an
',~xception to this. Th8Y \'Ier.? very abuntlant and <lominated th" faunil during
the ~/fJt season.Nitrilte - nitrogen, orthophosphate ilnd BOOS incrp.asr!d
progressively rlo~lIlstrearn indicating enrichment of the river. A clear
se(lsonal variation in the nutrient level of thl.? rivc:r was al so noted.
Higher cnnwntrations of nutrients \'l<?r0 recQrded during thl.' dry seilson th~n
the wet seHson. The effects of I'rganic pollution 0n the river wcrp much
more severe during the ciry seilson \'Ihen the stream flow I~as low. Possible
sites of pollution have. bl't'n identifireci. The! prl'sl'nt condition uf Abo
Kebena River is compared with other rlegrad(~d streams and rivers in Ilfrica.
It is fl)und thJt organic p')llution has much the Silr.1,' dfects in Ethiopia as
in other cvuntri es. Recomml'ndat ions ha ve il"en mildr~ based on the pres(,nt
data.
1
I. INTRODUCTION
Throughout the world rapid population growth, urb~niz~tion and industrial
development have adversely affected the environment and pollution has
reached alarming proportions. Tne economic development of a count.ry and
its resultant environmental degradation are usually directly related.
!i0l1ever, envi ronmental pollution in general commands a 101'1 priori ty in
terms of national investment, especially in the developing countries.
One of the principdl consequences of man's activities is water pollution
<lnd the consequent deterioration of tllP aquittic environment.
Traditionally, to\'lns and cities ore located on the bilnks of rivers <lnd
streams or in close proximity to them. These water courses serve the needs
of to\'ln dwellers for domestic \'later supply <lS well as waste disposal.
Until recently, the deterioration of I'later courses by pollution was not a
serious problem because fairly small human populations lived in SC<lttered
communities and the wast~s dumped into rivers were subject to dilution and
natural self-purificittion.
I\s human populations multiply and industrialization increases and
diversifies, the problem of water pollution becomes more critical.
Industrialization leads to urbanization, \lith people leaving the land to
work in the ne\'l factories. Domest ic \'Iastes from the rapi dly expandi ng
tm"/lls and 11astes from industrial processes are poured into the nearest
river or stream. Such ~ctivitie5 not only affect the ben0ficial use of the
\'later but they ill so upset the natural balances within the stream ecosystem.
1\ rational approach to the conservation of our \Hlter courses \'Iould be to
understond the nature and the imp<lct of activities ',Ihich cause \'later
pollution; when such understanding is gained about pollution, whether from
single or multiple sources, measures of prevention or abatement can be
taken.
Information on water pollution in the tropics, including high elevation
2
tropical areas such as Ilddis Ilbaba, is scarce or absent (Hynes, personal
communication). Noreover, the knowledge of pollution of ;Ifrican rivers
l'lhich we do have comes mainly from studies done in South Ilfrica, a
subtropical to temperate area. In vie~1 of this, watu pollution
investigations similar to those published dbout the temperate zone, is very
mucll needed for polluted aquatic systems in tropical Africa.
The development of water pollution in the city of I\ddis Ilbaba. follol~s
patterns thdt are evident elsewhere. There has been a rapid population
growth, which is expected to continue to the point where there will be two
million people by the turn of the century. Domestic and municipal wastes
are dumped untreated into ri vers and streams because the sel'lage transport
system in the city is underdeveloped. Furthermore, there is no sewagE'
treatment plant in the city so raw sewage that is collected is only partly
treated. A treatment plant is, hOl'lever, underconstruction and in the
future sewage will receive. primary and secondary treatment before disposal.
Industry, likewise, is no better provided for, nor nre data available on
the quality and quantity of its discharges to the receiving water.
r~onitoring of industrial effluents even on an intermittent basis is
lacking. Thus wastes of unknown quality and quantity are being discharged
into thp. aquatic environment. Unfortunately, we haVf~ no information on tilE'
magnitude of the problem.
This thesis is an attempt to make some contribution to the understanding of
urban pollution effects of a river in il high elevation area of tropical
Africa. The thesis will prp.sent results based on biological and chemical
investigations in the Abo-Kebena River which runs through the city of Addis
Ilbaba. The Kebena River ilnd its tributaries are clean above the city but
the river becomes heavily polluted as it flows through it. The aim of this
paper, therefore, is to show chemical changes along the system, in nitrate,
orthophosphate, and I:lOU5; and to relate these to changes to species
compos it i on and density of macroi nvertebrates.
II study on wilter pollution such as this should properly begin ~lith a
definition of the term. Unfortunately such a definition is not easily