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Hydrology
The Study on Rural Water Supply JICA in Mwanza and Mara Regions in the United Republic of Tanzania KOKUSAI KOGYO CO., LTD.
A1-82
Meteorology and Hydrology,Meteorology and Hydrology,River Discharge MeasurementRiver Discharge Measurement
Kazuyuki SUENAGA Kazuyuki SUENAGA (JICA Study Team)(JICA Study Team)
OutlineOutline
Calculation of observation data
Computation by Tank Model
Estimation of potential recharge to groundwater
4. Water balance analysis
Measurement of river discharge on site
Cross checking of existing dataThinking for possibility of
recharge to groundwater
3. River discharge measurement
Analysis of existing data
Understanding of hydrological situation2. Hydrology
Analysis of existing data
Understanding of meteorological situation1. Meteorology
MethodPurposeItem
1. Meteorology1. MeteorologyLocation of StationRainfallEvaporationTemperature
Location of Meteorological StationsLocation of Meteorological Stations
76 St.Mwanza region (49 St.)
Mara region (24 St.)Shinyanga region (3 St.)
19 St. selected for meteorological analysis
Observation at selected stationsObservation at selected stationsRainfall
All St. (19)
Evaporation5 St.
Temperature2 St.
Monthly Rainfall Monthly Rainfall (mm/month, 1985(mm/month, 1985--2005)2005)
MwanzaMwanza MusomaMusomaUkereweUkerewe
NyehungeNyehunge
BuslwangiriBuslwangiri
MasuwaMasuwa
MugumuMugumuSumveSumve
Average Monthly Rainfall Average Monthly Rainfall (1985(1985--2004)2004)
MaxUkereweUkerewe
239 mm/month
April
MinMasuwaMasuwa0 mm/month
July
Average Annual RainfallAverage Annual Rainfall
The Study on Rural Water Supply JICA in Mwanza and Mara Regions in the United Republic of Tanzania KOKUSAI KOGYO CO., LTD.
A1-83
EvaporationEvaporation
100110120130140150160170180
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
month
Ave
rage
Mon
thly
Eva
pora
tio(m
m/m
onth
)
Musoma Airport
Mwanza Airport
rainy season: high at Musomadry season: high at Mwanza
Annual Musoma MwanzaMax : 2058 mm (1984) 2057 mm (1999)Min : 1662 mm (1991) 1703 mm (1994) Ave: 1817 mm 1800 mm
TemperatureTemperature
14
16
18
20
22
24
26
28
30
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecMonth
Tem
pera
ture
(℃)
Musoma A.P.MaxMusoma A.P.AveMusoma A.P.MinMwanza A.P.MaxMwanza A.P.AveMwanza A.P.Min
Monthly Musoma MwanzaMax : 31.1℃ (Sep. 1997) 32.1℃ (Sep. 1997)Min : 14.6℃ (July 1999) 11.6℃ (July 1998)
total Ave: 24.8℃ 24.4℃
decrease (rainy season)increase (dry season)
2. Hydrology2. Hydrology
• River System• Observation Station• Rating Curve
(water level – river discharge)• River Discharge
River SystemRiver System
8 river basin8 river basinEast Shore
MaraGrumeti
MbalagetiSimiyu
Magogo-MoaneIsanga
South shore
Observation Stations Observation Stations (water level)(water level)Establishment
15 st.
Under observation
7 st.4 (Mara)
3 (Mwanza)
Available rating curve
9 st.5 (Mara)
4 (Mwanza)
Rating Curve Rating Curve (Discharge (Discharge –– Water level)Water level)Mori river at Utegi (1970-1981)
y = 5.4568x2 + 5.5748xR2 = 0.7719
010203040506070
0.0 1.0 2.0 3.0Water Level (m)
Dis
char
ge (m
^3/s
ec)
Simiyu river at R.B. (1969-1985)
y = 9.4638x2 - 15.656xR2 = 0.8718
0
20
40
60
80
100
120
0.0 1.0 2.0 3.0 4.0 5.0Water Level (m)
Dis
char
ge (m
^3/s
ec)
Grumeti river at R.B. (1970-1982)
y = 4.0407x2 + 0.4808xR2 = 0.9723
0
20
40
60
80
100
0.0 1.0 2.0 3.0 4.0 5.0Water Level (m)
Dis
char
ge (m
^3/s
ec)
Mbalageti river at R.B. (1970-1982)
y = 3.9378x2 - 3.8394xR2 = 0.6811
010203040506070
0.0 1.0 2.0 3.0 4.0Water Level (m)
Dis
char
ge (m
^3/s
ec)
River DischargeRiver DischargeMori river at Utegi
0
10
20
30
40
50
60
Jan-
70
Jan-
72
Jan-
74
Jan-
76
Jan-
78
Jan-
80
Jan-
82
Jan-
84
Jan-
86
Jan-
88
Jan-
90
Jan-
92
Jan-
94
Jan-
96
Jan-
98
Jan-
00
Jan-
02
Jan-
04
year/month
mon
thly
ave
rage
Dis
char
ge(m
^3/s
ec)
0
100
200
300
400
500
600
mon
thly
Rai
nfal
l(m
m/m
onth
)
Shirati 9133002Mori at Utegi
Grumeti river at R.B.
0
20
40
60
80
100
120
Jan-
70
Jan-
72
Jan-
74
Jan-
76
Jan-
78
Jan-
80
Jan-
82
Jan-
84
Jan-
86
Jan-
88
Jan-
90
Jan-
92
Jan-
94
Jan-
96
Jan-
98
Jan-
00
Jan-
02
Jan-
04
year/month
mon
thly
ave
rage
Dis
char
ge (m
^3/s
ec) 0
100
200
300
400
500
600
mon
thly
Rai
nfal
l(m
m/m
onth
)
Seronera 9234005Grumeti at R.B.
River DischargeRiver DischargeMbalageti river at Mara mine
0
10
20
30
40
50
60
Jan-
70
Jan-
72
Jan-
74
Jan-
76
Jan-
78
Jan-
80
Jan-
82
Jan-
84
Jan-
86
Jan-
88
Jan-
90
Jan-
92
Jan-
94
Jan-
96
Jan-
98
Jan-
00
Jan-
02
Jan-
04
year/month
mon
thly
ave
rage
Dis
char
ge (m
^3/s
ec)
0
100
200
300
400
500
600
mon
thly
Rai
nfal
l(m
m/m
onth
)
Seronera 9234005Mbalageti at R.B.
Simiyu river at R.B.
0
50
100
150
200
250
300
Jan-
70
Jan-
72
Jan-
74
Jan-
76
Jan-
78
Jan-
80
Jan-
82
Jan-
84
Jan-
86
Jan-
88
Jan-
90
Jan-
92
Jan-
94
Jan-
96
Jan-
98
Jan-
00
Jan-
02
Jan-
04
year/month
mon
thly
ave
rage
Dis
char
ge (m
^3/s
ec) 0
100
200
300
400
500
600
mon
thly
Rai
nfal
l(m
m/m
onth
)
Masuwa 9333005Simiyu at R.B.
The Study on Rural Water Supply JICA in Mwanza and Mara Regions in the United Republic of Tanzania KOKUSAI KOGYO CO., LTD.
A1-84
3. River discharge measurement3. River discharge measurement•• Location ofLocation of
River discharge measurementRiver discharge measurement•• Result of river dischargeResult of river discharge
Location of River measurementLocation of River measurement(only available for discharge data, as of may 2005(only available for discharge data, as of may 2005))
River basin River Downstream Upstream
East shore Mori non Utegi (new and existing)
East shore Suguti Suguti (new) R.B. (new)
Grumeti Grumeti R.B. (existing) Fort Ikoma (new)
Mbalageti Mbalageti R.B. (new and existing) non
Simiyu Duma Sayaka (existing) Baridai R.B. (new)
Simiyu Simiyu Lumeji (new) Malita (new)
Magogo-Moame Moame Pambani (new) non
South shore Nyamkama R.B. (new) non
Location of River measurementLocation of River measurement★
Existing7
(function)
○
New10
ResultResult of River Discharge of River Discharge (May 2005)(May 2005)
Max10.339 m³/sec (Duma river,
Baridai-Ramadi R.B.)
Min0.006 m³/sec(Moame river,Pambani)
ResultResult of River Discharge of River Discharge (Sep 2005)(Sep 2005)
Dry up (Duma river,
Baridai-Ramadi R.B.)
Dry up(Moame river,Pambani)
4. Water balance analysis4. Water balance analysis
Tank ModelComponents of Tank ModelVerification and Accuracy of the Model
Calculation of observation dataP = Rr + E + R
P: Rainfall (mm/month)Rr: Ratio of Runoff (mm/month)E: Potential Evapotranspiration (mm/month) R: Recharge to Groundwater (mm/month)
Tank ModelTank ModelThe tank model is widely used
for estimation of water balance in Japan.The tank model is applicable in
both the flood runoff analysisand the log-term runoff analysis.
proposed by Sugawara (1972)
Rainfall↓
↑Evapotranspiration
SurfaceSystem
↓Deep Aquifer
System
Discharge →
SoilSystem
a 1
ShallowAquiferSystem Groundwater Flow →
Recharge to Groundwater↓
S 1
a 5
a 4
a 3
a 2b 1
b 3
b 2
S 2
S 3
Z 1Z 2
Z 4
Z 3
Z 5
Components of Components of Tank ModelTank Model
a: coefficient of the outlet on the side
b: coefficient of the outlet on the bottom
Z: height of the outlet on the side
S: depth of the water
Input
Output
The Study on Rural Water Supply JICA in Mwanza and Mara Regions in the United Republic of Tanzania KOKUSAI KOGYO CO., LTD.
A1-85
Verification and Accuracy of the ModelVerification and Accuracy of the ModelCollection of raw data is essential.Each parameter should be carefully set up.Potential recharge to groundwater will be decided after agreement of good correlation with observed data and computed data.
So far, arrangement of input data has not been prepared well yet.Computation of the tank model will be carried out for evaluation of potential recharge to groundwater after arrangement of data.
Calculation of observation dataCalculation of observation data
Rainfalls per unit river basinwere calculated by Thiessen Method
Rr = D / ARr: Ratio of Runoff (mm/month)
D: River Discharge (mm3/month)A: Catchment Area (mm2/month)
Potential evapotranspirationwas calculated by Thornthwaite method
The result of CalculationThe result of CalculationAnnual potential
recharge to GWMax: 136.37mm
at South shore basinMini: 51.78mm
at Mara basin
Annual percentage recharge to GWIn Rainfall
Max: 7.54%at South shore basin
Mini: 3.07%at Mara basin
0
10
20
30
40
50
60
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Decmonth
Pote
ntial
Rechar
geto
GW
(m
m/m
onth
)
East Mara Grumeti Mbalageti
Simiyu Magogo-Moame Isanga South
05
101520253035
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Decmonth
Perc
enta
ge R
echar
geto
GW
(%)
ConclusionConclusionRainfall: low in central part of study areaEvaporation: high, especially in dry season
River System: 8 river basinDischarge: almost river are dry up in dry season
Potential recharge to groundwater:generally low, especially in dry season
(Comparison by the river basin)slightly high in Grumeti, Mbalageti and South shoreconsiderably low in East shore and Mara
The recharge deference by the basin: due to the deference of the surface geology