THE UNITED REPUBLIC OF TANZANIA
MINISTRY OF WATER
LAKE TANGANYIKA BASIN WATER BOARD
ANNUAL BASIN HYDROLOGICAL REPORT
(REVISED)
NOVEMBER 2012-OCTOBER 2013
Lake Tanganyika Basin Water Office
P.O. Box 105
Tel. No. 255 28 2802697
Fax No. 255 28 2804901
Email:
KIGOMA MARCH, 2014
EXECUTIVE SUMMARY
Lake Tanganyika Basin is divided into two climatic regions i.e. a semi-arid part comprising areas of Shinyanga and Tabora regions and semi tropical areas comprising of Kigoma, Katavi, Kagera, Geita and Rukwa regions. Water stress is experienced in those areas within semi-arid area where most formerly perennial Rivers i.e. Igombe, Pangale & others are now becoming seasonal. The trend is further depicted in as you move westwards through Lakes Nyamagoma and Sagala within the Malagarasi Moyowosi Wetland to the western semi tropical area. The current work being conducted by SMEC International Pty Ltd as part of the preparation of the IWRM planning and Development indicates the two lakes to be shrinking from their origin dimensions and the drying up of surrounding Rivers and Streams. The impact is strongly increasing the dependency of groundwater into the area. Among the factors contributing to the decline of water resources include anthropogenic activities i.e. Agriculture, forestry degradation etc and decline of rainfall intensity.The declining trend of surface water can be associated with rainfall trends. The rainfall trend analyzed from 7 stations in the Basin, 3 Stations in the semi arid area have indicated a rainfall decline of between -20.12% to -33.40% against a rise of between 2% to 16.04% while data collected from the Western Semi tropical area indicate a decline of only -5.24%.
During the reporting period, the Lake Tanganyika water levels continued to rise. From 2004 the Lake levels depicts an average annual rise of 0. 3meters. Recorded highest mean monthly water level from station No. 4/1 of the Lake Tanganyika during the year was 775.01 meters (m.a.s.l), this is higher by 0.49m above the highest reading of 774.54m (m.a.s.l) recorded in 2011/12 Hydrological year.
Furthermore during the year it was only water levels that were collected from the 28 hydrometric stations; representative data have been taken from 4 Hydrometric stations i.e. Mkuti, Wala, Makere and Igombe Rivers and two dams of Igombe and Kazima. Flow and sediment data could not be measured due to technicality emanating from lack of necessary accessories especially the heavy duty winches for big rivers like Malagarasi, Luiche, Kalambo and Lugufu. The flatter Boats we have are not good for sailing in such rivers; the durable ones are the Fiber Boats which we don’t have. Trial to use other methods was also impossible due to River complexity in terms of; width, flow current and roughness.
Water quality in the Basin is being monitored through the available selected 14 hydrometric stations and is relatively good. The water quality status is revealed through the analysed 140 samples collected from different sources, a serious effects indicated by over 50% of the collected samples reveal that fecal coliform is the major degradation problem impacting water resources in the Basin, major sources of pollution are attributed to poor environmental sanitation and poor hygiene education among communities.
TABLE OF CONTENT
EXECUTIVE SUMMARY ii
LIST OF ABREVIATIONS………………………………………………………………………………………………………………………..…………………….III
LIST OF ILLUSTRATIONS IV
1.0 GENERAL INTRODUCTION 1
1.1 Purpose and Objectives of the Report 1
1.2 Location of the Basin and Administrative Units 1
1.3 Physiographic 3
1.3.1Topography 3
1.3.2 Drainage Pattern 3
1.3.3. Land Use/Cover 5
1.3.4. Soils 5
1.4 Geology 5
2.0 Main Features in the Basin 5
3.0. HYDROLOGICAL DATA 6
3.1. Rainfall and Other climatic Data 6
3.1.1. Temporal and Spatial Coverage of Measuring Stations 6
3.2 River Discharge and Sediment Data 9
3.2.1. Temporal and Spatial Coverage of Measuring Stations 9
3.4. Reservoirs/Lakes Information 12
3.5. Water Use/Abstraction 16
4.0. HYDROLOGY OF THE BASIN 16
4.1. Climate 16
4.1.1. Rainfall 16
4.1.2. Temperature and Evaporation 20
4.1.3. Runoff Distribution 20
4.1.4. Groundwater Occurence 22
4.1.5. Groundwater recharge 22
4.1.6 Water Quality. 23
5.0. GENERAL REMARKS AND WAY FORWARD 26
ANNEX 1: Mean Monthly WATER lEVEL for Lake Tanganyika xxiv
ANNEX 2: RAINFALl DATA FROM; URAMBO, IGOMBE. UYOWA, LUMBE, TABORA AND KIGOMA MAJI YARD STATIONS 2011/12 - 2012/13 xxv
ANNEX 3: IGOMBDE DAM WATER LEVEL 20O3/04 -2012/13 xxvi
ANNEX 4: Mean monthly water level for selected rivers 2011/12 - 2012/13 xxvi
ANNEX 5: climatic stations in lake tanganyika 2012/13 xxvi
ANNEX 6: artificial man made resorviors 2012/13 xxvi
ANNEX 7: Water quality sampling results as a part of iwrm 2012/13 xxvi
ANNEX 8: Water quality sampling results 2012/13 xxvi
LIST OF ABBREVIATIONS
Cur / CurrentLat / Latitude
Long / Longitude
LTRIMP / Lake Tanganyika Regional Integrated Management Programme
l/sec / Liters per second
M3/day / Meter Cubed Per Day
LMMP / Long Term Mean Monthly Precipitation
m.a.s.l / Mean Above Sea Level
MCM/yr / Metric Cubic Meter/yr
MMP / Mean Monthly Precipitation
mg/l / Milligram per liters
Rbg. / River Bridge
Rec. / Record
Stn / Station
T/day / Ton per day
WMP
µS/cm / Water Master Plan
Micro-Siemen per centimeter
LIST OF ILLUSTRATIONS
Figure 1 / Location Map of Lake Tanganyika BasinFigure 2 / Catchment Map of Lake Tanganyika Basin
Figure 3 / Map of gauging stations
Figure 4 / Lake Tanganyika Water levels during 2010/11 & 2011/12
Figure 5
Figure 6 / Part of Shunu Dam in Kahama
Igombe Dam Water level analysis
Figure 7 / Tabora Maji yard Water level analysis
Figure 8 / Kigoma Maji Yard Met Station Rainfall analysis
Figure 9 / Igombe Dam Station Rainfall analysis
Figure 10 / Lumbe Dam Station Rainfall analysis
Figure 11 / Uyowa Met Station Rainfall analysis
Figure 12 / Urambo Met Station Rainfall analysis
Figure 13 / Igombe Dam Water Level Analysis 2004/05- 2012/13
Figure 14 / Wala River Water level Analysis 2011/12-2012/13
Figure 15 / Makere at Makere Rbg Stn Mean Monthly Water level Analysis for 2010/11 -2012/13
Table 1 / Climatic & Rainfall Stations
Table 2 / Rain gauge Stations
Table 3 / River Gauging Stations Status
Table 4 / Rainfall variation against Long term Mean Monthly precipitation
iv
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1.0 GENERAL INTRODUCTION
1.1 Purpose and Objectives of the Report
This annual hydrological report, covering the period November 2012 to October 2013, describes the existing surface water hydrometric network and major changes to the network during the year. It also provides an overview of the trends in rainfall, river flows, lake and wetland levels and notable hydrological events of the year. Other Climate elements like temperatures, winds, humidity, atmospheric pressure, sunshine were not recorded due to technical error of the PDA instrument. It has been not possible to download the data from the stations.
1.2 Location of the Basin and Administrative Units
Lake Tanganyika basin is located in the western part of Tanzania between latitudes 20 45″ and 80 45′ and longitudes 290 35′and 340 00′. The total catchment area of the basin is 238,000km2. The total surface area of the Lake Tanganyika is 32,600 km2 of which 45% is in Democratic Republic of Congo; 41% in Tanzania; 8% in Burundi and 6% in Zambia. It is 670 km long and 50 km wide with a maximum water depth of 1,470 m at its deepest point and a mean depth of 570 m, and has a volume of 18,800 km3. It is the second deepest lake in the World and holds almost one sixth of the world’s free fresh water resources. The lake is a unique environment (Sven Erik Jorgensen et. al, 2006). The land surface of the basin on Tanzania side is 151,900km2, which contribute 60% of the total runoff to Lake Tanganyika.
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Figure 1: Location Map of Lake Tanganyika Basin (source: Lake Tanganyika: Experience and Lessons Learned by Sven Erik Jorgensen et. al, 2006)
1.3 Physiographic
1.3.1Topography
The Basin is a gently inclined plateau with steep hills rising very sharply from 773 m.a.s.l at the level of Lake Tanganyika to altitudes of 1, 800 m.a.s.l to the East descending from the North and East into gently rolling hills with eight major perennial rivers of Malagarasi, Luiche, Ruchugi, Lugufu, Luegele, Luamfi, Samba and Kalambo. The first two rivers comprise the major drainage area. The descent leads to river valleys at 1000 m.a.s.l, and swampy and flat delta area at 800masl where the rivers join the lake. From the water-shed gently rolling country bisected by broad defined drainage lines (known as mbugas) drain into Ugalla River in the south west and the Igombe and later the Malagarasi River and Lake Sagara which form the western boundary of the Basin.
1.3.2 Drainage Pattern
The basin is composed of seven sub-catchments that are Malagarasi, Ugalla, Ruchugi, Luiche, Lugufu, Luegele and the South Western lake shore catchment. The Malagarasi catchment is the largest in the basin, covering nearly 130,000 km2 and drains approximately 30,000 km2 of the Kigoma region (Fig. 2). Additionally the river drains 93,300 km2 of Burundi, and Shinyanga, Tabora and Rukwa Regions in Tanzania. The river originates in the mountainous landscape area close to the border of Tanzania and Burundi at an altitude of 1750 m.a.s.l from where it runs northeasterly through hilly and mountainous landscape and then Southwards into flatter area east of the Kasulu – Kibondo Road. Due to low gradient in this reach, the river flows in large meanders before entering the Malagarasi swamps in the southeast.
Figure 2: Catchment Map of Lake Tanganyika Basin (Source: Consultancy Services for the
preparation of IWRM in Lake Tanganyika Basin, SMEC 2012)
1.3.3. Land Use/Cover
Vegetation consists of upland vegetation which includes closed and open woodland, bush-land thicket, bushy grassland; lowland or wetland vegetation consisting of wooded grassland and swamps. Woodland is the natural vegetation over most of the basin and can be divided into two groups: Miombo woodland and Acacia, Cambretum and Albizia species. Bushland, bushed grassland and bare land considered being a degraded form of a number of different vegetation types which have been cleared, browsed and selectively grazed for many years are the most widespread types in the basin with extremity in the North East of Tabora region where tobacco farming has been practiced over years. Subsistence farming of food crops i.e. banana, maize, cassava, beans, and season paddy dominate the area, in low lands along the Lake Tanganyika shore palm oil dominate the area .
1.3.4. Soils
The soils of the basin can generally be categorized as follows: Along the lake shore the soils are deep and well drained comprising the dark reddish brown fine sandy loams, and sandy loams partly stony and severely eroded. The heavy black soils are found in permanently waterlogged areas with black clayey soils which have a high proportion of sand in swamp fringes subject to seasonal water logging. These are highly fertile areas because of high proportion of sand and silt. However, these soils are not subject to seasonal wetting and drying like the cotton soils because the water table is high. In the low relief areas the soils are dark reddish clay loams with fairly good internal drainage while the black and brown alluvial soils are mostly found in areas of high relief. On the west of the basin soil varies widely, ranging from sandy loam to heavy (black/dark brown) soils in poorly drained areas especially in the Northern part of Tabora region.
1.4 Geology
The oldest rocks of the area are gneisses and schists, which occur in the northwest and intermittently along the shores of the Lake Tanganyika to the south (Halligan, 1960; Norconsult, 1982b). The rocks are exactly similar in type to rocks of Ubendian system. They represent an ancient series of sediments, probably shales, sandstones and greywackes, which have been altered by regional metamorphism and migmatization to their present high grade. Overlying these rocks with unconformity is the Kigoma quartzite. This thick formation consists almost entirely of coarse-to-medium grained, white, occasionally, cream, pure quartzites and sandstones, with occasional bands of quartz pebbles. There are few horizons of shaly beds, which often show signs of shearing, and thin basal conglomerates are also sometimes developed.
2.0 Main Features in the Basin
An outstanding hydrological feature of the Basin is the Lake Tanganyika itself and the Malagarasi/Moyowosi Ramsar Site covering nearly 32,500 km2 close to Kigoma -Tabora Regions boundary (Nkotagu et. al; 2000). This area consists of large plains with scarce vegetation and forested patches that dry up during the dry season. At the end of the rainy season, most of the area is wet and swampy, and Lake Sagara and Lake Nyamagoma have increased their areas manifold. The swamps act as regulators on stream flows within the area. Because of low infiltration rates, they change from small, scattered ponds in the dry season to shallow, temporary lakes during the wet season. However of recent the two lakes areas are exhibiting shrinking trend, the fact is evidenced by growth of grass around the lakes a phenomena which is suspected to early stages of ecological succession where an ecosystem can change from one form to another i.e. an open water area becoming a marshland or grassland, a bare land becoming a shrub or grassland.
3.0. HYDROLOGICAL DATA
3.1. Rainfall and Other climatic Data
3.1.2. Temporal and Spatial Coverage of Measuring Stations
For easy of management of the measuring stations in 2011/12 the Basin identified 13 climatic stations and 45 rainfall stations to serve for delivering necessary and representative climatic data for its area. During the reporting period the same stations have continued to be used for providing this important climatic information for the Basin.
Table: 1. Climatic & Rainfall Stations
SN / CODE / STN. NAME / LAT / LONG / RECORDING PERIOD / MAP[mm] / Status of the station /
/ EARLY REC. / CUR REC. /
1 / 9530008 / Uvinza Met- Stn. / 05°.91 / 30°.39 / Rehabilitated & installed with automatic Weather equipment since May 2013
2 / 9530005 / Nguruka Met- Stn. / 05°.56 / 31°.04
3 / 9331001 / Ushirombo Met- Stn. / 03°.12 / 31°.90 / Not available / Not available / 977.7
4 / 9430009 / Kagera Nkanda Met-Stn. / 04°.74 / 30°.58 / 76-89 / 2012-2013 / 1176
5 / 9532030 / Urambo Met- Urambo / 05°.27 / 32°.07 / 2004- 2013 / 1063
6 / 9332023 / Kahama-Met Stn. / 03°.00 / 32°.05 / 28-88 / 1136
7 / 9532026 / Sikonge Met- Stn. / 05°.05 / 32°.75 / 64-88 / 2004- 2013
8 / 9432005 / Ushetu-Ushetu / 04°.62 / 32°.27 / 899
9 / 943102 / Uyowa Met Stn. / 04°.05 / 31°.96 / 2004- 2013 / 1132
10 / 933007 / Kibondo Met- Stn. / 04°.61 / 31°.12 / 2004- 2013 / 924
11 / 953108 / Lumbe Met-Stn. / 05°.00 / 36°.48 / 2004- 2013 / 929 / Need a major Rehabilitation and total installation of equipment
12 / 9630007 / Karema Met- Stn. / 06°.12 / 31°.44 / 1057
13 / 9831023 / Kasanga Met- Stn. / 08°.74 / 31°.17 / 899
Table 2: Raingauge Stations