Examination of the relationships amongst
discharge, suspended and dissolved sediment
discharges of samarU stream, zaria, Kaduna
state.
BY
Yusuf, Yakubu Obadaki
08037022049 & 08075875081
yyobadaki@yahoo.com
and
Igbinigie, Victor Osa
08038216388 & 080
28419620
v
ictoryard@yahoo.com
Department of Geography
Ahmadu Bello University
Zaria.
Abstract
This study examined the relationships amongst discharge, suspended and dissolved sediment discharges of the Samaru
Stream, a 1
st
order basin with a tota
l stream length of 1.05km, basin area of 2.28km
2
, drainage density of 0.46km/km
2
and a relative relief of 30.48m. The stream was monitored for six months by collecting data on sediment concentration
and stream. The data provided the basis of a suspended se
diment discharge (Qs)
–
discharge (Q) rating curve which
revealed the considerable scatter about the straight line relationship, with a coefficient of correlation (r) of 0.666 and
coefficient of determination (r
2
) of 0.443 indicating that the stream discha
rge has a great influence on the level of
suspended sediment discharge. It further provided the basis of a dissolved sediment discharge (Qd)
–
discharge (Q)
rating curve revealing a considerable scatter about the straight line relationship with a very high
coefficient of correlation
(r) of 0.901 and correspondingly high coefficient of determination (r
2
) of 0.812 indicating that stream discharge has a
strong influence on dissolved sediment discharge (Qd). Furthermore, the suspended sediment discharge (Qs) an
d
dissolved sediment discharge (Qd) values for the catchment area were correlated for which they had a positive and
moderately strong correlation value of 0.408 which was significant even at 0.01 level of significance indicating that there
is no significan
t difference between both variables. These sediment discharges have great implication on the Ahmadu
Bello University dam downstream with respect to its water capacity (Siltation problems) and water quality.
INTRODUCTION
The materials carried by a stream o
r river are termed sediment load. Sediment load is composed of eroded materials of
different shapes and sizes, determining their mode of transportation down stream. Sediment load can be categorized into
three: Bedload, Solute load (Dissolved load) and Susp
ended load (Ritter, 2006). In addition, the total amount of
sediments, which are generated or produced within the catchment area of the river is referred to as the sediment yield.
These sediments are subsequently moved from a drainage basin to be deposited
on flood plains, in storage reservoirs, or
carried off to the seas. The greater part of the sediment is made up of the suspended sediment load (Oyebande and
Martins, 1978). Sediment yield is responsible for the sedimentation in reservoirs. (Glymph, 1973),
for example, reported
that some small reservoirs in the United States incure up to 25% percent storage loss annually due to sediment yield into
them. Here in Nigeria, Imevore et. al., (1988) reported that some dams in Nigeria which include the one near I
le Ife at
Oke Odo had become completely silted up and had since turned into weed infested marshes due to rapid urban
development and agricultural practices such as farming at the headquarters of the lake.
Similarly, the Samaru stream, which is a tributar
y of the Kubanni River, across which the ABU dam was constructed,
has had its fair share of the sediment yield problem over the years. Although efforts have been made by the authorities
concerned to nip the problem in the bud, it seems to persist.
RESEARCH PROBLEM
In 1973, the Ahmadu Bello University (ABU) authority started the construction of a small earth dam across the river
Kubanni to forestall the problems of inadequate and irregular water supply for the present and future needs of the entire
university community. The dam was successfully completed in 1974, and had a very impressive storage capacity of 2.6 x
10
6
m
3
with a maximum depth of about 8.5m, a catchment area of 57km
2
, a large lake surface area of 83.4 ha and a
supply capacity of 13.64
million litres per day to cater for about 50,000 people (University Health Service, ABU).
The dam, designed to have a hollow spill way, such that excess water over the storage capacity of the lake spills into this
hollow and is evacuated through pipes un
der the embankment. However, the facility for flushing out sediments was not
provided. As a result, sediments have been accumulating in the dam thereby increasing the thickness of the bottom of the
dam and decreasing the real depth of the dam and the volum
e of water that can be retained in the reservoir over the years
(Yusuf, 2006). Iguisi (1997), in his study of the extent of sedimentation in the dam, recorded a maximum depth of 5.2m,
a far cry from the initial 8.5m which clearly shows that the dam has an
average annual loss of depth of about 14.3cm
which represents a loss of about 3.3m which is about 30 percent loss in storage capacity in 23 years. This is the result of
eroded materials transported and deposited on the dam floor. Consequently, sediments pr
oduction within the basin is
very high.
Furthermore, the Samaru stream which is a tributary of the Kubanni River across which the A.B.U dam was constructed
is expected to produce a great amount of sediments into the dam because of its reduced vegetation
cover and vast ba
r
e
surfaces in its catchment area. These sediments are mainly composed of suspended and dissolved loads (Yusuf, 2008).
Therefore, this study of the examination of the relationships amongst discharge, suspended and dissolved sediment
discha
rges of the Samaru stream is imperative as it will go a long way to contribute to the efforts at getting a permanent
solution to the sediment yield problem of the ABU dam.
AIM AND OBJECTIVES
The aim of this study is to examine the relationships amongst
discharge, suspended and dissolved sediment discharges of
the Samaru stream, Zaria. This aim will be achieved through the following set of objectives:
i.
To determine the suspended sediment concentration
ii.
To determine the dissolved sediment concentration
iii.
To
determine the suspended and dissolved sediment discharges
iv.
To assess the relationships between the discharge, suspended and dissolved sediment discharges.
HYPOTHESES
Deriving from the above objectives are the null hypotheses that:
i.
There is no significant
relationship between stream discharge and suspended and dissolved sediment
discharges of the Samaru stream, Zaria.
ii.
There is no significant difference between suspended and dissolved sediment discharges of the Samaru
stream, Zaria.
STUDY AREA
The study area is in Zaria, Kaduna state, Nigeria. Located in the upper Kubanni drainage basin S.W. Zaria, it is situated
on a plateau, at a height of about 670m above sea level in the centre of Northern Nigeria, about 664km away from the
sea. It is locate
d within latitude 11
0
03’ N and longitude 7
0
42’ E. (see fig. 1).
The study area lies within the tropical wet and dry climatic zone characterized by a strong seasonality of rainfall. It
belongs to the tropical continental type of climate corresponding to Ko
ppen (1963) tropical savannah or tropical wet and
dry climate zone (AW). It has two peculiar seasons: the dry or harmattan season (October to March) and wet season
(April to September). The number of rainy days varies considerably from year to year, but ap
pears to have a long term
average of about 92 days (Hocking and Thomas 1979). The onset of the rainy season is highly unpredictable due to
variability and exceptionally long delay during drought years, although long term averages appears to be first week o
f
May. Similarly, the mean annual rainfall is also variable, but on a long term average of about 1000mm (Owonubi and
Olorunju, 1986). Mean monthly temperature is about 27
0
C but it is highest between the months of March and May,
which represents the hot and
dry period. It is lowest in December/January reaching about 22
0
C.
The soil type in the study area is highly leached ferruginous tropical soils, developed on weathered regolith overlain by a
thin deposit of arid wind blown silt from the Sahara desert dur
ing many decades of the propagation of the tropical
continental air mass into the area (Wright and McCurry, 1970 and Torkarski, 1972). The study area has a natural
vegetation type of the northern Guinea Savannah with shrubs and a few scattered trees. The d
ominant shrub around the
area is
Isoberlina doka
with an average height of 0.5metres. The common grass communities are mostly
Andropogon
spp
. The grasses sprout during the rainy season, shrubs grow very rapidly, but no sooner than the raining season ceased
than they become dry. The tree plants in this area include
Magnifera indica
dotting everywhere,
Parkia clappertoniana
and several others which are found to be useful to man. Unfortunately, this characteristic vegetation cover is hardly
preserved due to cu
ltivation, urbanization and poor management practices like fuel wood harvesting, annual bush
burning, and intensive grazing (Rains, 1963; and Ologe, 1971).
Within the basin catchment area, intensive farming activities and grazing are prominent especially
around the southern
boundary. On the other hand, the northern boundary is dominated by urbanization, mild farming and grazing activities.
Minor fishing activities usually take place especially during the dry season both on commercial and consumption scale
s.
Sand mining is conspicuous with their left over as holes, pit, gullies, etc used as materials for molding bricks and
building of mud houses, for both residential and animal shelter. The university authority restricted farming practices in
the staff resi
dential area in the year 2000, but presently, there is still evidence of farming activities.
Fig. 1: Location of the Study Area on the Kubanni River Basin
METHODOLOGY
Types of Data Collected
To successfully carry out this study, data on susp
ended sediment samples, sediment concentration (i.e. suspended and
dissolved) and stream discharge were collected and derived from the gauging station of the Samaru stream, a minor
tributary of River Kubanni during the study period between May, 2008 and Oc
tober, 2008.
DATA ANALYSES
In order to analyse the data collected for this study, a precise form of rating curve as proposed by Bauer and Tille (1967)
and used by Yusuf (2006)
was used to regress stream discharge on the suspended sediment concentration
by using their
log exponents (log) as shown below:
log Cs = log a + b log Q







(1)
Where:
Cs = suspended sediment concentration in mg/l
Q = stream discharge in m
3
/s
a + b = Constants representing the intercept and slope of the r
ating plot respectively.
The rating curve was also used to regress stream discharge on the suspended sediment discharge, by using their log
exponents (log) as shown below:
log Qs = log a + b log Q





(2)
Where:
Qs = Suspended sedimen
t discharge in mg/s
Q = Stream discharge in m
3
/s
a + b = Constants representing the intercept and slope of the rating plot respectively.
Stream discharge was also regressed on dissolved sediment concentration also referred to as total dissolved solid (T
DS),
by using their log exponents (log) as shown below:
log TDS = log a + b log Q






(3)
Where:
TDS = Total Dissolved solid (Dissolved sediment concentration in mg/l)
Q = Stream Discharge in m
3
/s
a + b = Constants rep
resenting the intercept and slope of the rating plot respectively.
Finally, the rating curve was also used to regress stream discharge on the dissolved sediment discharge, by using their
log exponents (log) as shown below:
log Qd = log a + b log Q





(4)
Where:
Qd = Dissolved sediment discharge in mg/s
Q = Stream Discharge in m
3
/s
a + b = Constants representing the intercept and slope of the rating plot respectively.
Furthermore, the suspended sediment discharge (Qs) and dissolved sedim
ent discharge (Qd) for the catchment area were
correlated using the Pearson correlation analysis. All analyses were carried out by the use of the SPSS statistical
package. The confidence level that was used in accepting or rejecting the hypothesis is 95% c
orresponding to an alpha
value of 0.05.
RESULTS AND DISCUSSION
Discharge
Table 1 shows the daily mean instantaneous discharge values obtained using the AV method. Results of the stream
discharge obtained using the AV method shows that daily mean instantan
eous discharges varied from as low as 0.01m
3
/s
to 0.42m
3
/s with a mean value of 0.165m
3
/s, a standard error of 0.014, a standard deviation of 0.092 and a variance of
0.008. Owing to the fact that discharge values using the current metre for the velocity co
mponent were taken after
rainfall events, discharge data was available for 44 days with missing values for 142 days. This is attributed mainly to the
fact that in the missing value days, the flow of the stream was too low for reading to be taken using the
current metre.
Also, other rain days, with rainfall traces, insufficient to contribute to the discharge of the river were omitted.
Table 1:
Discharge Values in
m
3
/s
for 2008 using the Velocity

Cross Sectional Area Method.
Days
May
June
July
Augus
t
September
October
1.
2.
0.151
0.104
3.
0.307
4.
0.227
0.322
0.129
5.
6.
7.
0.257
8.
0.038
0.247
9.
0.174
10.
11.
0.131
12.
0.109
0.119
13.
0.111
14.
0.117
0.076
15.
0
.099
0.113
16.
0.013
17.
0.031
18.
0.017
0.142
0.161
19.
0.224
0.382
20.
0.099
21.
22.
0.190
0.213
23.
0.202
24.
0.128
25.
0.239
0.206
0.419
26.
0.176
27.
0.029
0.175
0.141
28.
0.024
0.161
0.191
29.
0.132
30.
0.249
31.
0.276
0.212
SUSPENDED SEDIMENT CONCENTRATION (Cs)
Data on suspended sediment concentration obtained from stream sediment samples are shown in table 2. The summary
statistics indicates that suspended sed
iment concentrations varied from as low as 40mg/l on 18
th
of July,2008, to as high
as 720 mg/l on the 27
th
of May, 2008, giving a range of 680 and a mean value of 178.54mg/l with a standard error of 21,
standard deviation of 144 and a variance of 20,869.
SUSPENDED SEDIMENT DISCHARGE (Qs)
The summary statistics illustrates that derived suspended sediment discharges varied from as low as 1.38mg/s on 18
th
May, 2008 to 84.19 mg/s on the 27
th
of August, 2008 giving a range of 82.82 and a mean value of 24.3
1mg/s with a
standard error of 2.87, standard deviation of 19.09 and a variance of 364.6.
DISSOLVED SEDIMENT CONCENTRATION
Data on dissolved sediment concentrations also known and referred to as Total Dissolved Solid (TDS) are shown in table
3
. The summary statistics indicates that dissolved sediment concentrations varied from as low as 40mg/l to 120mg/l,
giving a range of 80 and a mean value of 71.36mg/l with a standard error of 3.92, standard deviation of 26 and a variance
677.
Table 2:
Su
spended Sediment Concentrations Measured from Sediment Samples in mg/l for
2008.
Days
May
June
July
August
September
October
1.
2.
120
160
3.
80
4.
52
160
260
5.
6.
7.
120
8.
120
200
9.
80
10.
11.
120
12.
332
200
13.
120
14.
80
200
15.
480
80
16.
120
17.
80
18.
80
40
80
19.
80
120
20.
400
21.
22.
80
80
23.
160
24.
120
25.
160
160
200
26.
120
27.
720
480
80
28.
520
160
80
29.
160
30.
320
31.
52
240
DISSOLVED SEDIMENT DISCHARGE (Qd)
The summary statistics illustrates that derived dissolved sediment discharge varied from 0.69mg/s to 25.74mg/s giving a
range of 25.06 and a mean value of
11.58mg/s with a standard error of 1.03, standard deviation of 6.89 and a variance of
47.47.
Table 3: Dissolved Sediment Concentrations (Total Dissolved Solids (TDS) in mg/l for 2008.
Days
May
Jun
July
August
September
October
1.
2.
80
80
3.
40
4.
80
80
80
5.
6.
7.
80
8.
80
80
9.
40
10.
11.
80
12.
40
120
13.
80
14.
40
80
15.
40
80
16.
80
17.
40
18.
40
80
120
19.
80
40
20.
40
2
1.
22.
80
40
23.
40
24.
80
25.
40
80
40
26.
80
27.
40
120
120
28.
100
40
80
29.
80
30.
80
31.
80
120
RELATIONSHIPS AMONGST DISCHARGE, SUSPENDED AND DISSOLVED CONCENTRATIONS AND
SUSPENDED AND DISS
OLVED SEDIMENT DISCHARGES.
Suspended Sediment Concentration (Cs)
–
Discharge (Q) Relation.
The rating equation derived from the relationship, using their log exponents, is of the form:
Cs = 10
2.006
Q

0.163
(i.e. Cs = 101.39 Q

0.163
)


5
While the regression equation is of the form:
log Cs = log 2.006
–
0.163 log Q

6
With regression coefficient of correlation (r ) value of 0.196 and coeffi
cient of determination (r
2
) of 0.038 .
Equations
5
and
6
exhibit the fact that there is an indirect relationship between the suspended sediment concentration and
discharge of the catchment area. In order to check the significance of the regression coeffici
ents, a and b (i.e. intercept
and slope), the t
–
ratio test was conducted and in both cases, it was observed that t
a
and t
b
were statistically insignificant
at 0.05 level of significance. Therefore, we concluded that there is weak (poor) relationship betw
een the regression
coefficients in both cases.
The coefficient of correlation (r ) and coefficient of determination (r
2
) measured the strength of the linear correlation
between the two variables and the ratio of the explained variation to the total varia
tion respectively. Both values were
low especially the r
2
(0.038) indicating that discharge is not a strong determinant of the suspended sediment
concentration (Cs).
Suspended Sediment Discharge (Qs)
–
Discharge (Q) Relation
The rating equation der
ived from the relationship, using their log exponents, is of the form:
Qs = 10
1.921
Q
0.772
(i.e. Qs = 83.36Q
0.772
)

7
While the regression equation, is of the form:
log Qs = log 1.921 + 0.772 log Q


8
with a regression coefficient of correlation (r) value of 0.666 and coefficient of determination (r
2
) of 0.443.
E
quations
7
and
8
indicate that there is a direct relationship between Qs and Q of the
catchment area as exhibited in fig.
3. In order to check the significance of the regression coefficients, a and b (i.e. intercept and slope), the t

ratio test was
conducted and in both cases, it was observed that t
a
and t
b
were statistically significant a
t 0.05 level of significance.
Therefore, we can say that there is a strong relationship between the regression coefficient
s
in both cases.
In both cases, using the F
–
ratio (ANOVA) test, the regression coefficient of determination (r
2
) was found to be
st
atistically significant at 0.05 level of significance, indicating that discharge (Q)
,
is a good determinant of the suspended
sediment discharge (Qs).
Discharge (m3/s)
.4
.2
.1
.08
.06
.04
.02
.01
Suspended Sediment Discharge(mg/s)
80
60
40
20
10
8
6
4
2
1
Fig.2: Relationship between Suspended Sediment Discharge (Qs) and Discharge(Q).
Dissolved Sediment Co
ncentration i.e. Total Dissolved Solids (TDS)
–
Discharge (Q) Relation.
The rating equation derived from the relationship using their log exponents is of the form:
TDS = 10
1.841
Q
0.02044
(i.e. TDS = 69.34 Q
0.02044
)


9
While the regression equation is of the form:
log TDS = log 1.841 + 0.02044 log Q

10
with a regression coefficient of correlation (r) value of 0.042 and coefficient of determination
(r
2
) of 0.002.
Equations
9
and
10
exhibit the fact that there is a direct relationship between TDS and discharge (Q) of the catchment
area. To check the significance or regression coefficients, a and b (i.e. intercept and slope), the t
–
ratio test was
c
onducted in both cases, it was observed that t
a
and t
b
were statistically insignificant at 0.05 level of significance.
Therefore, we conclude that there is a weak relationship between the regression coefficients in both cases. The
coefficient of correlatio
n (r ) and the coefficient of determination (r
2
) measured the strength of the linear correlation
between the two variables and the ratio of the explained variation to the total variation. Both values were low especially
the r
2
(0.002) indicating that disch
arge is not a strong determination of the total dissolved solid.
Dissolved Sediment Discharge (Qd)
–
Discharge (Q) Relation.
The rating equation derived from the relationship using their log exponents is of the form:
Qd = 10
1.841
Q
1.020
(i.e. Qd = 69.34
Q
1.020
)



(11)
While the regression equation is of the form:
log Qd = log 1.841 + 1.020 log Q




(12)
with a regression coefficient of correlation (r ) value of 0.901 and coefficient of determination (r
2
) of 0.812.
Equations
11
and
1
2
exhibit the fact that there is a direct relationship between dissolved sediment discharge (Qd) and
discharge (Q) of the catchment area. In order to check the significance of regression coefficients, a and b (i.e. intercept
and slope) the t
–
ratio test w
as conducted and in both cases it was observed that t
a
and t
b
were statistically significant at
the 0.05 level of significance. Therefore, we concluded that there is a good relationship between the regression
coefficients in both cases. The coefficients of
correlation (r) and the coefficient of determination (r
2
) measured the
strength of the ratio of the explained variation to the total variation respectively. Both values were high indicating that
the discharge is a strong determination of the dissolved sed
iment discharge (Qd).
Discharge (m3/s)
.4
.2
.1
.08
.06
.04
.02
.01
Dissolved Sediment Discharge (mg/s)
20
10
8
6
4
2
1
.8
.6
Fig.3: Relationship between Dissolved Sediment Discharge (Qd) and Discharge (Q)
CORRELATIONS
Suspended Sediment Concentration (CS) and Total Dissolved Solids (TDS)
The correlation between suspended sediment concentration and total
dissolved solid is negative with r value of

0.044
and it is not significant at the 0.05 level of significance. This indicates that there is an indirect relationship between
suspended sediment concentration (SSC) and total dissolved solid (TDS).
Suspende
d Sediment Discharge (Qs) and Dissolved Sediment Discharge (Qd)
The correlation between Qs and Qd is positive with r value of 0.408 and it is very significant even at 0.01
significance
level. This implies that as the suspended sediment discharge (Qs) incre
ases; there is an increase in dissolved sediment
discharge (Qd) as well.
DISCUSSION
Discharge
A close look at the discharge values in table 1 reveals the fact that the range of the data is considerably high. The two
events of 25
th
September and 19
th
Sep
tember where peak discharges were observed marked the two occasions where
overbank flow was observed which is strongly connected to the fact that heavy rainfalls were experienced on these days.
These overbank flows were however followed by a high recession
rate as a result of rainfall depletion. It is also observed
that the highest discharge point measurement occurred in the month of August which compares accurately with previous
studies as in the cases of River Kaduna and the Northern tributary of River Ku
banni which recorded peak discharges in
the month of August (Folorunsho, 2004 and Yusuf, 2006).
Suspended Sediment Concentration (Cs)
It is observed that data on suspended sediment concentration varied considerably and this must be responsible for the
hig
h range, standard error, standard deviation and variance. This is caused by several factors that come to play in the
amount of suspended sediment concentration of a particular river. For instance, the maximum suspended sediment
concentration of 720mg/l and
520mg/l were observed on 27
th
May and 28
th
June, 2008 respectively. The high values of
suspended sediment concentration in this period can be attributed to farming activities that seems to persist despite the
ban by the University authority. These farming
activities led to high amount of loose materials on the soil surface and
provision of a surface run off generation potential. This observation can be related to that of Osterkamp et. al. (1991);
Knighton (1998) and Yusuf (2006). Generally, it is observed t
hat as the rainy season becomes well established,
vegetation cover protects the topsoil from further erosion.
Suspended Sediment Discharge (Qs)
–
Discharge (Q) Relationship
The direct relationship between suspended sediment discharge (Qs) and discharge
(Q) and the high coefficient of
correlation (r) and determination (r
2
) may be attributed to the fact that suspended sediment discharge (Qs) has a
component of discharge (Q) which is one of the variable from which it is derived (Gregory and Walling, 1973).
The
statistical significance of the correlation coefficient implying that the independent variable, discharge (Q) is a good
determinant of the dependent variable, suspended sediment discharge (Qs) is exhibited in the low degree of scatter of the
point in f
ig.2. Since there is a direct relationship between them, this further explains the highest suspended sediment
discharge (Qs) value of 84.19 mg/s on August 27
th
which had a corresponding discharge value of 1.75 m
3
/s which is
relatively high as well.
Disso
lved Sediment Concentration
It is observed that data on dissolved sediment concentration has a low variation and this is responsible for the low range,
standard error, standard deviation and variance. This can be partly attributed to the weak relationship
between discharge
and dissolved sediment concentration reflected in their low coefficient of determination (r
2
)
–
(0.02).This means that
discharge does not have a strong bearing on dissolved sediment discharge. This explains why the dissolved sediment
con
centration did not vary much during the study period despite the variation in discharge. The reason for the low range
can also be attributed again to discharge of the catchment area. When there is low river discharge, there is less volume of
water to carry
dissolved minerals in solution, so that invariably accounts for the low dissolved sediment concentration
value. On the other hand, when there is high river discharge, implying high volume of water which instead of carrying
more dissolved sediments tend to
dilute them as you move downstream so much that the dissolved sediment
concentration eventually carried will not differ much from that of the low discharge values.
Dissolved Sediment Discharge (Qd)
–
Discharge (Q) Relationship
The direct relationship be
tween dissolved sediment discharge (Qd) and Discharge (Q) and the very high coefficient of
correlation (r) and determination (r
2
) can be attributed to the fact that dissolved sediment discharge (Qd) has a
component of discharge (Q) which is one of the vari
able from which it is derived (Gregory and Walling, 1973). So, the
statistical significance of the correlation coefficient implying that the independent variable discharge (Q) is a good
determinant of the dependent variable dissolved sediment discharge (Qd
) is exhibited in the low degree of scatter of the
points as shown in fig.
3
. This is expected to be so because availability of water is essential for the dissolution and
eventual transportation of minerals that constitutes the dissolved sediment concentrat
ion making discharge very strong
determination of dissolved sediment discharge (Qd).
Suspended Sediment Concentration (SSC)

Total Dissolved Solids (TDS) Correlation
From the obtained result, it indicated a negative correlation between suspended sed
iment concentration (SSC) and total
dissolved solids (TDS) which is weak as well as insignificant. This implies that an increase in suspended sediment
concentration is likely to lead to decrease in total dissolved solids. This however may not be true in al
l cases because
SSC is directly influenced by discharge. TDS on the other hand, does not depend much on discharge which is reflected in
the indifferent variation between the upstream and downstream concentration which have varying discharges. TDS is
most l
ikely to be influenced by factors of geology and human activities. This tends to explain why the negative
relationship is both weak and insignificant.
Suspended Sediment Discharge (Qs)
–
Dissolved Sediment Discharge (Qd) Correlation
Suspended sediment dis
charge (Qs) and dissolved sediment discharge (Qd) had a moderately positive correlation which
is significant at the 0.01 level of significance, implying a direct relationship between them. This is most likely to be so a
s
both Qs and Qd are being influenced
by a factor of discharge (Q). This implies that when there is an increase in
discharge, it affects both the Qs and Qd. Irrespective of the relationship between SSC and TDS, the effect of discharge
(Q) on both Qs and Qd tends to influence the direct relati
onship between them.
CONCLUSION
Based on the first hypothesis of this research which states that; there is no significant relationship between stream
discharge and suspended and dissolved sediment discharges of the Samaru stream, Zaria, compared with the
obtained
result, we can conclude by rejecting the null hypothesis because there is a significant relationship between discharge and
suspended and dissolved sediment discharges.
Furthermore, based on the second hypothesis of this study which states that
there is no significant difference between
suspended and dissolved sediment discharges of the Samaru stream, Zaria compared with the result obtained, we can
conclude by accepting the null hypothesis because there is a highly significant correlation between
the suspended and
dissolved sediment discharges. Finally, discharge is a very important determination of suspended sediment discharge
(Qs) and dissolved sediment discharge (Qd). However, it is worthy of note that there are other factors other than
dischar
ge responsible for determination of suspended sediment discharge (Qs) and dissolved sediment discharge (Qd).
These factors include, land cultivation, fertilizer application, grazing and other activities that can be surmised as land
used. The geology of the
catchment also plays important role in determining the discharge of the area.
RECOMMENDATION
From field observation, important factors contributing to the suspended sediment discharge (Qs) and dissolved sediment
discharge (Qd) include: vegetation cover
, land use as when cultivation, mining and livestock rearing are observed, these
tend to determine the Qs and Qd. It was observed that farming around the catchment area is still on going inspite of the
ban by the ABU authority and this contributes signific
antly to the suspended sediment discharge (Qs) and dissolved
sediment discharge (Qd) of the catchment area. It is hereby recommended that the ban should be fully enforced which
should also be extended to the prevention of grazing by cattles and sand mining
for construction. Also, the ABU
authority should improve on their afforestation program to cover the catchment area so as to reduce soil loss from the
area which eventually contributes to the dissolved sediment discharge (Qd).
Finally, there is the need
for regular studies of suspended sediment discharge (Qs) and dissolved sediment discharge
(Qd) on the catchment area since it is a tributary to Kubanni River which supplies water to the ABU reservoir which is
the main source of water supply to the Universi
ty community. Regular studies and research will give an idea on the level
of sediment that is being deposited at the ABU reservoir which subsequently has an implication on the storage capacity
of the reservoir and the lifespan of the dam.
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“
Examination of the Relationships Amongst Rainfall, Discharge and Suspended Sediment Discharge
of a Tributary of the Kubanni River, Zaria, Kaduna State, Nigeria
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A Journal Article accepted for Publication
in the
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