INTRODUCTION
Water
is very vital for man's existence hence it is refereed to as the blood of the
earth. Its role in societal growth is crucial. Presently and even more so in
the future the success of such advancements are principally ascribed to water resources.
They include storage lakes, hydro-electricity power production, drinking water,
rain fed /irrigation agriculture, industry and shipping canals. From its
chemical point of view, it is the commonest existing substances that is
experienced and used in the solid, liquid and gaseous states. More than 50% of
plant and animal body weight consist of water. The entire biomass depends on
water.
This
very important natural resources legacy has many factors militating against its
supply and wholesomeness. They include physical factors such as soil erosion,
climatic fluctuation, and drought and soil type, while waste disposal, general
land use at the fringes/surface water bodies' devegetation and irrigation are
some human factors. Soil erosion ranks highest among the factors that
deteriorate water sources in the study area (Eze, 2002). It is geomorphic
hazard that wears off the soil with agents such as water, wind, and glacier for
final disposition at lower terrains. Water however is the usual agent in this
area.
EXTENT OF WATER
SOURCES IN ENUGU NORTH EAST
The
northeastern part of Enugu State is the area reviewed in this study. It lies
between longitude 70I500 and 70I570 east and latitude 70I360 and 70I41 north.
The area occupies a landmass of 1216km2. The population is 259,803 with a
density of 206 persons per square kilometer (2006census).
The area fall
within the tropical wet and dry (AW type) of Koppen's climatic classification.
It records 28oC average temperature and 1506mm annual rain fall. Two thirds of
the area has the loose sandy ferralitic soil type and a loamy clay type in the
rest. The topography is dominated by steeply slopes and prongs of gully
channels that terminate in streams. The vegetation is principally the woodland
grass derived savannah and the forest type, around the water bodies. The
hydrology of the area is mainly dominated by the Ebonyi, Eme, Awra, and Ndene
rivers, most of which flow south eastwards. They are fed by some rivulets,
steams and brooks. Ponds and ephemeral pools are also found in the loamy clay
regions.
Subsistence
agriculture is observed by Kowal and Kassam (1978) as the occupation mainstay
of the area. Wrong agricultural practices such as non-fallowing of land, bush
burning, alignment of farm mounds down slope as well as the sleepy slopes, high
rainfall amount and loose soil material make the area susceptible to soil
erosion. Sheet erosion removes rich plant nutrients and trace chemical elements
from the soil. These are washed into water bodies in the study area causing eutrophication.
The
aggregate effects of the three facets of soil erosion (sheet, rill and gully)
disrupt the soil structure which aids percolation and purification processes of
underground water. Eroded materials deposited in water bodies cause siltation
and pollution. Soil erosion exposes and destroys pipe borne water
infrastructure in the study area. The study area is greatly endowed with
bountiful water sources. Most of the rivers and streams spring from the hilly
northeastern areas. They respond to southeastern flows and are fed by brooks
and streamlets. These in turn converge within their various basins forming
rivers such as Eme, Ebonyi Ngelifi, Olu, Ndene and Awra
Surface Water
Sources: Streams
such as Ederi, Odoru and Okpakeke which flow in the northeastern direction feed
the Ebonyi River. It flows through communities such as Umuosigide, Obollo
Etiti, Obollo Eke, Ikem and Eha-Amufu. The Awo, Nzu and Opu stream as well as
the Amanyi rivulet flow into the Ebonyi River near Ikem. These streams flow
through communities such as Agu Orba, Obinagu Imilike, Ezimo, Mbu and Ogbodu-
Aba. Leke
Onueme, Akpochi, Isiagu, Mbu and Akpoga communities have small brooks and
streamlets that feed the Eme River. The Awra River with its numerous streams
and rivulets flows from the neighbouring Agu Opi in Nsukka Local Government
Area (LGA) through the southeastern fringes of the study area. Communities such
as Agu Mbu, Agu Neke and Agu Umualo fall within this hydrological network.
The
Ayido springs from Obollo Eke in the northern part of the study area. It has
few northerly tributaries and distributaries. Ogo-Ndagu Ikem, is the source of
the Ndene River which flows through Ikem Nkwo and the Mgbede Local railway
station. These hydrological dispositions are in line with the observations of
O.U.C.T. (1990) that streams are members of a complicated network of channels
which form the unit called drainage basin or catchments. The Olu and Ngelifi
Rivers merge with the Ebonyi River between Ikem and Eha-Amufu. Thereafter the
river flows through Umuhali in Isi-Elu L.G.A. Ebonyi State. This Ebonyi River
is the major hydrological feature of the study area.
Ponds
which are usually integral part of drainage basin form small basins where water
supply exceeds loss through evaporation and infiltration in the study area.
Some of these ponds where water flows out from are called intermediate while
others are terminal ponds. These are the characteristics of ponds in the loamy
alluvial and shalyclay areas of Umualo, Agu Neke, Agu Amade, Eha-Amufu and
Obollo Eke. Some of them are fed by small streams, while others are suspected
to have originated from oxbow lake formations in the meandering stream courses.
There are still some that are formed as a result of water accumulation in
depression that have imperious clayey floors. The pond levels lower as the dry
season progresses. Infact the Nkpo pond in Obollo Eke almost maintains its
level throughout the dry season because of the luxuriant forest that shades it
and consequently reduces evaporations. Small perennial ponds and pools are
abounding in the
study area. Some pond levels fluctuate through wide range and each observation
of floating sediment marks on their sides during field trips had to be keyed to
contemporaneous stages of the ponds.
Underground
Water Sources: The
shalyclay soil profile with seams of impervious rock material enhances the
water aquifer's holding capacity in the study area. At depths of 5m, water can
be struck in communities such as Obollo Eke, Ikem, Eha-Amufu, Neke, Mbu, Ogbodu-Aba
to name a few.
The shalyclay
soil inhibits water and the underlying impervious rocks or basal seals keep the
water table at appreciable levels. Seasonal ground water recharge which is the
process of underground water replenishment is in the wet season. The recharging
level is so high that artesian wells sprout sparking water with amazing
pressure flows during such periods.
ANTHROPOGENIC
FACTORS OF WATER POLLUTION
Water
pollution is the introduction of waste material into water such that its
natural self purification processes cannot cope with the situation. Both surface
and underground water are polluted by various pollutant agents (solid, effluent
and gaseous) in the study area. However, the extent of pollution varies with
type of pollutants and other environmental factors such as the degree of water
flow or mobility and the land use factors of the area. The pollutant agents
include plant nutrients disease agents, eroded sediments, solid wastes, sewage,
other oxygen demanding wastes as well as effluents from local industries and
food processing activities.
Plant Nutrients:
The
use of chemical fertilizers and wastes from food processing generate organic
matters that are plant nutrients. These accelerate the growth of weed
infestation and the booming of other aquatic plants in surface water bodies
causing water pollution. This situation suppresses the growth of planktons and
algae which are food for fishes and other water faunae, hence a reduction in
fish population. The clustering of water weeds impede normal stream and river
flows, puts some streams and ponds out of recreational uses and deteriorates
the portability of such stream water.
Eroded
Sediments: Human
activities such as cultivation, road and building construction as well as devegetation
lay the soil bare to erosion. Soil materials are detached from sheet, rilling
and gullying activities. They get entrained in runoff water which feed streams.
Thereafter, they are conveyed into rivers.
Soil erosion is
a serious natural hazard in the study area. Nordin (1995) pointed out that
rivers convey in their flows, the dissolved and solid products of weathering
and erosion from the basin or catchments they drain. These pollute and silt the
water bodies causing low water transparency and clogging of certain fluvial
channels.
Local Industrial
and Food Processing Wastes: Certain areas of streams and brooks such
as Opu and Arikpo in Ezimo, Oshenyi and Egwu near Ogbodu-Aba, Ayido and
Ngele-Okpo in ObolloEke and other brooks and rivulets that feed the Ebonyi
River near Ikem and Eha-Amufu are used for food processing. The food items
include cassava, breadfruit, melon, bitter leaf among others. Local industrial
activities such as oil palm extraction and processing, sponge making, cloth
dyeing, basket weaving as well as wool spinning generate a great deal of
wastes.
Wastes
from food processing activities are also directly introduced into the surface
water bodies while those from local industrial activities are usually either
dumped into these streams or in their catchment areas where they will be latter
washed into the streams. Some of these wastes accumulate and float on the water
surfaces as scums, blocking off sunlight to water flora and fauna. The
biodegradable items increase Biological Oxygen Demand (BOD), producing foul
smelling, gases such as methane CH4, ammonia NH3 and hydrogen sulphide H2S. The
water surfaces and the entire surroundings of such streams are degraded.
Irrigation: Dry season
farming is practiced at the surroundings of some of these surface water bodies.
The crops are usually grown with compost, animal manure or chemical fertilizer.
During irrigation, the wash-off water usually flows directly into these streams
or indirectly by underground seepages.
The constituents
of such wash-off water include loose farm soil, decomposed organic manure,
trace Nitrogen, Phosphorus and Potassium (N.P.K) which are elements of chemical
fertilizer. In situations where pesticides and herbicides are used such as in
the Local Government Agricultural Unit Farm Plots and School farms minute
quantities of these are also washed down into the surface water bodies causing
chemical pollution.
Water
contact uses of streams such as swimming and bathing contribute to water
pollution in the study area. Adults and children alike swim and swagger for fun
in both shallow and fairly deep streams during hot periods. Soap and dirt
generated during laundry activities pollute stream water. Human defecation
within the catchments areas or directly into the surface water bodies are also
sources of water pollution in the area.
EFFECTS OF SOIL
EROSION ON WATER SOURCES
Soil erosion has
grave impacts on water sources in the study area. Human sustenance by water sources
is unspeakable in aspects such as drinking purposes, irrigation agriculture,
food processing and cottage industrial activities, horticulture, domestic uses,
recreation, fishing and other water related hunting, environmental
sustainability among others. These beneficial uses are threatened by soil
erosion's degradation of the water sources in the area. Miller (1988) recounts
that 34% of China's arable land and 1/3 of USA's rich agricultural top soil has
been severely eroded and the resultant siltation of rivers, streams and lakes
are now naturally recognized threats. Soil erosion-induced problems on water
sources in the study area include the following:
Abrasion of
River and Stream Channels: Weathered rock, sharp sand and other loose soil
material in the catchments areas or basins find their way through soil erosion
into streams and rivers. In the August and September peaks of the rains in the
study area, debris laden runoff water swells the channels of rivers and
streams. This optimal soil moisture saturation period, the transporting debris
that hit river channel sides as well as the appreciable river channel gradient
of certain location give way to river channel abrasion. The downward scouring
effects cause the collapsing, slumping and deepening of river and stream
channels or bank erosion. The middle courses of the Ebonyi River at Ikem and
Isu; the Eme River at Mbu Akpochi and around Neke Onueme and the Ndene River at
Ikem Nkwo manifest such features. These river channels posses more variable bank
materials than their bed materials. However, their dispositions downstream show
more uniformity with sand, silt and clay combinations especially at fully
developed flood plain areas.
In areas of
cohesive bank material and vegetation whose fibrous root systems reinforce the
soil, bank erosion is minimal. Nighton (1994) noted that 5cm root reinforcement
affords 20,000 times more protection to erosion than comparable material
without vegetation.
Siltation of
Surface Water Bodies: The transportation of silting material from land
surfaces to the water bodies causes siltation in the study area. This is in
line with Startham (1997) who rationalized this phenomenon into three process
regimes
a. Weathering
regime - physical and chemical breakdown of rock processes
b. Slope regime
- movement of the weathered material by gravity and gradient in mass movement
and by slope wash processes.
c. Fluid
transfer/deposition regime - where water does the transportation and final
deposition of the sediments.
The final
element of the triumvirate processes which is the deposition or aggradations or
siltation takes place as the competence of the streams to transport it
decreases below critical level. The lower courses of the Ebonyi, Ngilife and
Awra have flood plains with features such as sandbars, ripples and dunes.
Back-swamps are areas with deposit of clay and other colloidal materials. They
are commonly observed in streams which are tributaries of the Olu, Amanyi and
Eme River. Such streams include Isi-Amanyi, Ngele- Okpo and Opu. Spawning of
fishes is disturbed since such favourable places and planktophytes which are
food to fishes and their finger lines are destroyed by the accumulating
sediments. Siltation of these surface water bodies also cause the decline in
number of crabs, tortoise, crocodile, water lilies and other aquatic fauna and
flora in the study area. The reducing stream water volume prevents effective
irrigation during dry season farming. Spring sapping and trickling points on
the channel walls of the Nzu, Awo, Ederi and Odoru streams which are sources of
portable water are often times blocked off by silting materials and require a
great deal of manual labour to dredge them. Ponds and pools on the shaly clay
depressions of Umualo, Neke, Agumade and Mbu often times have inflowing streams
which introduce eroded materials into them. This causes siltation of such ponds
as their floor levels get raised. Where the ponds are intermediate, the
out-flowing streams lower the pond rims through erosion.
Eutrophication: This is an
insidious form of water pollution that causes progressive deterioration of surface
water sources. Human excrement, dead organic matters, domestic and agricultural
wastes, ashes from bush burning, minute elements of agrochemicals are washed by
soil erosion into surface water bodies. This over enrichment with nutrients
that support aquatic flora results in an overabundance of plant life or
eutrophication. Mac - Caull (1994) observed that eutrophication brings about
certain drastic changes in the ecology of lakes, streams and ponds.
Decomposition of such organic matters cut down the amount of dissolved oxygen
in the water which results in the destruction of aquatic animals.
Eutrophication also thins down the population of some water plants that do not
thrive in overcrowded situations. The recreational and other water-hunting uses
of such water bodies are put off.
Water Pollution
and Disease Transmission: Solid wastes dumped into gullies, rills, refuse
dumps, drains, domestic sewage and other externalities from human activities
are washed down into bodies in the stream, causing water pollution. Domestic
sewage has a strong composition of pathogenic pollutants (Table 1). The
micro-organisms that decompose these biodegradable wastes increase Biological
Oxygen Demand (BOD).
The water's
portability is lost and it turns turbid and putrid. Water samples were
collected from the water bodies after rainstorms for laboratory analysis
(Table 2).
Table 1: Typical
Composition of Domestic Sewage (Values in mg/litre)
Constituents Strong Medium Weak
Solid:
Total 1000
500 200
Volatile 700 350
120
Fixed 300 150 80
Suspended
Total 500
300 100
Volatile 400
250 70
Fixed 100
50 30
Dissolved
Total 500
200 100
Volatile 300
100 50
Fixed
200 100 50
BOD (5 - day
200c) 300 200 100
Oxygen Consumed 150 75 30
Dissolved Oxygen
0 0 0
Nitrogen
Total 85
50 25
Organic 35 20 10
Free
ammonia/inorganic nitrogen 50 30 15
Nitrates NO2 0.1 0.0 5 0
Nitrates NO3 0.4
0.2 0.1
Chlorides 175 100 150
Alkalinity 200 100 50
Fats 40
20 0
Source: Babbit and
Baumann (1995)
The stagnant
water bodies in the study area such as ponds, pools as well as slow flowing streams
which are recipients of pollutants degenerate with time into transmitters of
water related diseases. When the water can no longer cope with their natural
self purification processes such pollutants form bacterial and viral agents
which transmit diseases such as typhoid fever, dysentery, cholera, hepatitis,
gastroenteritis among others.
Bilharzias
which are a debilitating disease from water snails are sometimes transmitted
from stagnant water. Hence water the sustainer and necessity of life can become
a transmitter of disease organisms both organic and inorganic chemical
contaminants to man.
Table 2: Laboratory Test
Results of After Rainstorm Water Samples from the Study Area
Sample Tests
Nzu Stream 1 Odoru Stream 2 Ebonyi
River 3 Amanyi River 4 Ndene River
5 Eme River 6
Total solids (mg/l) 760 900 11300 850 820 860
Suspended solids (mg/l) 480 580 700 520 500 540
Dissolved solids (mg/l) 260 320 430
330 320 260
BOD (mg/l) 72 70 63
83 84 73
Colifor (100ml) 38 41 45 47 40 44
PH 6.4 6.7 6.8 6.7 6.9 6.3
Turbidity (JTU) 8 7 9
8 8.4 7.7
Colour (Pt/Co) 14 12 16 12 13 15
Sample Mean, = 204.0 242.09 300.35 232.09 24.04 218.25
Source: Eze 2002
Materials and Methods
The
laboratory test results on table 2 which gave sample means of 2040, 242.09,
300.35, 232.09, 224.04 and 218.25 were obtained from the Nzu and Odoru streams
as well as Ebonyi, Amanyi, Ndene and Eme rivers respectively. The grand means,
obtained was 29.62 when these results were subjected to the Analysis of
Variance (ANOVA) statistical method. Also in the same order, the sum of squares
within, (SSW), of 546984.64, 78678.04, 1238298.34, 680234.04, 621590.05 and
629724.46 were obtained for the streams and rivers. This gave a total of
449951.57. The sum of squares between (SSB) gave 2108006.25. The mean of square
within (MSW) obtained was 107131.40 while the mean of square between, MSB gave 421601.25.
Hence the ratio of MSW and MSB which is the variance estimate of F-test or Fcal
becomes 7.4. With a degree of freedom of 5 (numerator) and 42 (denominator) and
at 95% confidence level, the F?, obtained was 2.44 since Fcal > f?. Hence
the pollution in the water sample is significant.
The values of the magnitude of water
pollution from soil erosion as ranked are presented on table 3.
Table 3: Ranked Value of
Water Pollution Extent from Soil Erosion in the Study Area
Water Sample Values
of Sum of Squares within SSW Ranking
Nzu Stream 546984.64
6
Odoru Stream 786769.04
2
Ebony River 1238298.34 1
Amanyi River 680234.04
3
Ndene Rivers 621509.05
5
Eme Rivers 625724.46
4
Effect on
Underground Water Sources: Underground water composition is subject to the
source of surface water that percolates into it and the interaction of the
surface water with the soil and rock materials along its path. The Nzu and
Okpakeke streams flow through dolomite and soft talc areas, hence their turbid
and low transparency qualities. The streams as well as underground water show
chalky sediments in transparent containers.
Gullies in
Agu-Ezimo that rip through such soft chalky rocks cause intrusion of such
chalky materials into pure underground water held on aquifers below. Artesian
well water in such areas shows such sediments mainly in the rainy seasons. In
the growing clustered settlement areas such as Obollo Eke, Eha-Amufu,
Ogbodu-Aba and Ikem, solid wastes dumped into gullies as well as other eroded
materials are washed down the catchment areas until they get to the shale seams
where they can infiltrate into the ground and contaminate underground water.
Moran, Morgan and Wiersma (1990) observed that soil erosion also lowers the
water table in aquifers by agrading eroded materials in the area, and this
impedes percolation of water through existing pervious surfaces for final
storage as underground water.
CONCLUSION AND
RECOMMENDATIONS
Land use
management should be given greater considerations. This would guarantee optimal
delivery of water from the water shed. Tackling the problem from the source is
more rewarding than wasting resources in dredging silted reservoirs streams and
rivers. The following recommendations will alleviate the environmental problem.
Soil
Conservation: The
fundamental tenet of soil conservation with a view to arresting soil loss into
water bodies are that soil surfaces be maintained in a receptive condition for
the infiltration of rainfall. Also, surplus runoffs are to be channeled along
gentle gradients such as permanent grass covered areas and circumvent
obstruction. There should be an agreement on how the drainage routes should
transit boundaries of individual land or properties and serve the catchment
area as an entity. The optimal application of these measures requires the
co-operation of all rural dwellers. Extension officers from the state ministry
of environment should oversee these arrangements.
These must be
strict adherence to cultivation on the contours, planting of grassed water
routes and construction of drains to cut off water from higher terraces. Where
cultivation is done on sleepy slopes the ridges and mounds should be aligned
across slopes and terracing should be practiced. The cost of these structures
should be subsidized by government. There should be
belts of
fallowing and tree planted plots between farm plots to boost infiltration of
water. These measures will stem soil loss and inflow of debris into surface water
bodies in the study area.
Watershed
Protection: The
highest points or rims of catchments are the peaks where precipitation gets
into the ground. It is from there that water percolates to the lower base of
the basin from where springs sprout and latter flow as streams and rivers. Such
points or watershed should be protected with forest reservations to enhance the
conservation of water and steady flows from the springs.
Reservation of
Land Strips Close to Water Bodies: There should be reservation and outright
ban to cultivation on the lowest third portion of land in all catchment areas
towards surface water bodies. Such undisturbed soil and vegetation rich areas
would enhance infiltration of rain water, prevent the generation of runoff
water and its associated soil erosion and purify percolating rain water. To
maximize land use in this face of growing population and food insecurity, small
patches of such reserved areas can be put into dry season irrigation farming.
The precautionary measure in this instance is strictly regulated irrigation
such as to prevent back flow or wash off sediments into the water bodies.
Livestick
Fencing: In
already established gullies, livestick fencing methods are to be applied to
hold further deposition of sediments into the water bodies. It involves staking
of livesticks across gully channels from the points where the scouring
activities starts receding. Palm fronds and other fast establishing wattles are
tied across the lowest portion of the staked livesticks such as Indian Bamboo
Bambus vulgaris. This is repeated at distances of 100- 150m down the gully
channels. They hold the transported sediments, thereby reducing siltation of
the receiving streams. Indian bamboos Bambus vulgaris and other live sticks
will spring into luxuriant vegetation strips across the gullies and this will
in the long run, aid gully stability.
Monitoring: Local government
environmental protection officials should monitor these management measures and
not to leave it to the care of the rural farmers. This is because the marginal
economic situation of the subsistent farmers of the study area does not incline
them to see with these long-term but rewarding control measures.
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