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