internal drainage basin water resources fact sheet · tanzania mainland is comprised of nine...
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THE UNITED REPUBLIC OF TANZANIA
Ministry of WaterWater Resources Division
Physiographic Profile
143,200 km2Basin Area (inside Tanzania)
9No. of Sub-basins
7No. of Major Lakes
107
52,827 Km2
Protected Areas
No.
Area
Sandy LoamDominant Soil Texture
Migmatite/
Granitoide/
Meta-Sediment
Complexes
Dominant Productive
Formation
0.25Mean Vegetation Index
-1.52 %/yrForest Cover Change (2000-2015)
4.6%Average Slope
5,895 m.a.s.l*
573 m.a.s.l
1,312 m.a.s.l
Altimetry
Highest
Lowest
Mean Elevation
Water Resources Fact SheetThe Internal Drainage Basin
Map of the Internal Drainage Basin
Socio-Economic Profile (2019)
7.47 millionPopulation52 person/km2Population Density
933 m3/yrWater per Capita
Hydro-Climatic & Water Resources Profile*
701 mm/yrAverage Precipitation21.7 CAverage Temperature
1,667 mm/yr
646 mm/yr
Average Evapotranspiration
Potential
Actual6,968 mcm/yr
6,084 mcm/yr
884 mcm/yr
Average Renewable Water
Resources
Surface Water
Groundwater
5,634 mcm/yr
1,087 mcm/yr
Water Demands
Averaged Total
Human Consumptive
16 %Water Resources
Vulnerability Index
Tanzania mainland is comprised of nine hydrologic basins. The Transboundary Internal Drainage Basin is Tanzania’s 2nd Largestbasin (considering total area of the basin shared with Kenya); however, regarding part of the basin that is located inside Tanzania,it is the 3rd largest basin that encompasses more than 15% of the area of the country. The basin is stretched from central parts ofTanzania to the north-east, where it crosses borders with Kenya. Waters that run from precipitation, flow into several lakes andswamps scattered in the basin.
19%
45%
13%
6%
6%3% 1% 4% 3%
Area of Subbasins (%)Bahi Swamp
Lake Eyasi
Lake Manyara
Lake Natron
Masai Steppe
Monduli A
Monduli B
Namanga
Olduvai
71% of basin area lies between 1000-1500 m.a.s.l
* m.a.s.l: meters above mean sea level
Internal Drainage Basin Water Demands Key Figures
The Falkenmark Water Stress Indicator
Water ResourcesDivision
20
9.5
84
.5
51
.9
30
.5
29
.9
28
.9
13
.0
6.5
5.6
0
50
100
150
200
250
Irri
gate
d A
rea
(1,0
00
ha)
Area of Irrigation Schemes in Basins
11%
89%
Share of Irrigated Area
Internal Drainage
Other Basins
9,5
80
2,1
86
1,9
73
1,3
74
1,1
53
96
2
92
0
80
3
62
8
0
2,000
4,000
6,000
8,000
10,000
Cu
bic
me
ters
pe
r ye
ar
Renewable Water Resources per Capita in Sub-Basins (2019)
IndicationAvailable Renewable
Water per Capita (m3/yr)
Water Stress< 1700
Water Scarcity< 1000
Absolute
Water Scarcity< 500
Country Average: 2,250 m3/yr/cap
3%12%
1% 2%2%
80%
Water Demands by Sector (%)Internal Drainage Basin
Domestic (200 mcm)
Irrigation (687 mcm)
Hydropower (47 mcm)
Livestock & Aquaculture (99 mcm)
Industries & Mining (101 mcm)
Ecosystem & Wildlife (4,547 mcm)
0 200 400 600 800
Lake Eyasi
Lake Manyara
Bahi (Manyoni)
Namanga
Lake Natron
Masai Steppe
Olduvai
Monduli A
Monduli B
mcm per year
Water Demands in Sub-Basins*(human consumptive demands)
* exclusive of environmental & hydropower demands
Ecosystem is the largest water user in the Internal Drainage Basin. About 65% of the renewable water resources in the basin isrequired for replenishment of environmental demands, and nearly 16% is currently utilised for domestic, industries, irrigation, andlivestock sectors. In the latter portion, Irrigation sector accounts for about 63% of human-consumptive uses, which makes it thesecond rank in total water demands.
3 rd
Ị
* According to the Internal Drainage Basin IWRMDP, 2015
Internal Drainage Basin:
Rank in Irrigated Area3 rd Tanzania,s Total Irrigated Area:
460,300 ha
8%
92%
Human Consumptive Water Demands
Internal Drainage
Other Basins
0 10 20 30 40 50
0 10 20 30 40 50 60 70
500-750750-1000
1000-12501250-15001500-17501750-20002000-22502250-25002500-30003000-40004000-6000
Area Percentage (%)
Area (thousand km2)
Ele
vati
on
Cla
sse
s (m
.a.s
.l)
Land Hypsometry○ 17% of people in IDB are experiencing water stress.
○ 80% of people in IDB are confronted with water scarcity.
BahiSwamp
-
Internal Drainage Basin Water Resources Key Figures
Annual Renewable Water Resources: 6.97 km3
19
19.5
20
20.5
21
21.5
22
22.5
23
19
001
905
19
101
915
19
201
925
19
301
935
19
401
945
19
501
955
19
601
965
19
701
975
19
801
985
19
901
995
20
002
005
20
102
015
Tem
per
atu
re (
°C)
Historic Average Air Temperature (1900-2016)
Averaged for the Internal Drainage Basin; Source: Climatic Research Unit, University of East Anglia, UK; http://www.cru.uea.ac.uk/data
Long Term Rainfall Variation
703 mmRainfall Average 1900-1930
680 mmRainfall Average 1985-2016
- 23 mmDifference in Long-term Average
Long Term Temperature Variation
21.30 CTemperature Average 1900-1930
22.32 CTemperature Average 1985-2016
+ 1.02 CDifference in Long-term Average
Difference in Rainfall*: - 3.3% Difference in Temperature*: + 4.8%
* Over 85 Years (30-yr average values, centered on 1915-2000)
87%
13%
Surface Water
Groundwater
The Internal Drainage Basin receives in average an annual precipitation of 100 km3 out of which as much as ca. 93 km3 returnsback to the atmosphere and 6.97 km3 (about 7%) turns into surface and ground water as renewable freshwater resources.
27
09
12
90
12
00
11
44
20
2
15
0
11
9
11
6
40
0
500
1000
1500
2000
2500
3000
An
nu
al V
olu
me
(m
cm) Average Total Renewable Water
Resources in Sub-Basins
6%
94%
Total Water Resources
Internal Drainage
Other Basins
Share of Internal Drainage Basin in Tanzania’s Renewable Water Resources
15%
85%
Basin Area
Internal Drainage
Other Basins
0102030405060708090
100
Spe
cifi
c R
un
off
(m
m) Average Surface Water
Runoff in Sub-Basins Average Country-wide Specific Runoff: 111 mm
Water ResourcesDivision
There is a large variation of runoff production within different sub-basins in the Internal Drainage Basin:• Lake Natron sub-basin as high as 221% of average• Namanga sub-basin as low as 44% of average
(6.08 km3)
(0.89 km3)(inside Tanzania borders)
Internal Drainage Basin Water Infrastructure Key Figures
Water Infrastructure Profile
11,957
16,285
Water Points
No. of Water Points
No. of Taps
5
57
46
31
No. of Monitoring Stations:
Weather
Rainfall
Hydrological
Hydrogeological
119No. of Dams and Reservoirs
119.2 mcmReservoirs Capacity
315
51,872 ha
Irrigation Schemes
No.
Area
30%Irrigation Efficiency
Maize, Sorghum,
Wheat, Beans
Main Crops (irrigated)
37%
23%
17%
11%
1%2%
9%
Water Points by Sources of Water
Borehole Shallow WellSpring River/ StreamLake DamRainwater Harvesting
Functioning Water Taps: 11,820 73%
CED Pumps: Conventional Energy-Driven Pumps (includes Thermal Electricity, Hydroelectricity, Gasoline & Diesel)
NCD Pumps: Non-Conventional Energy -Driven Pumps (includes Solar Electricity, Windmill(
Hand Pumps: (includes Lever Pumps, Mono Pumps, Rope Pumps, Play Pumps)
Water supply access in Tanzania – mainly in rural areas – is realised through "water points", i.e. usually a public place for peopleto obtain clean water.Water from water points is potable water consumed for the people or livestock. Means of access to water at the supply points areusually in form of communal standpipes. However, other shapes of access to water are present such as water kiosks, water tanks,hand pumps, developed or undeveloped springs, and cattle troughs.
Water Points Supplied by Groundwater and Springs
Water Points that Need Energy for Extraction of Water 62%
Water ResourcesDivision
0 10 20 30 40
0 5 10 15 20
2-3
3-4
4-5
5-6
6-7
7-8
8-9
9-10
10-11
11-12
12-13
13-14
Cumulative Reservoir Capacity (mcm)
Count of Dams
He
igh
t o
f D
ams
(m)
Count
Volume
There are 119 man-made dams constructed in the Internal Drainage Basin with a total reservoir capacity of about 119.2 mcm. The largest reservoir belongs to Mwamapuli Dam with a height of 10 m and capacity of 28 mcm on Cheli River, Tabora Region.
Statistics of Dams in the Basin
77%
20%
1%
41%
38%
Extraction Technologies at Water Points
CED Pumps
NCD Pumps
Hand Pumps
Gravity
400
500
600
700
800
900
1000
1100
19
001
905
19
101
915
19
201
925
19
301
935
19
401
945
19
501
955
19
601
965
19
701
975
19
801
985
19
901
995
20
002
005
20
102
015
Pre
cip
itat
ion
(m
m)
Historic Annual Precipitation (1900-2016)
IDB average = 43 mmAverage Internal Drainage
Basin’s Specific Runoff: 43 mm
Average Gross Area per Water Point: 12 km2