the united republic of tanzania ministry of water lake nyasa basin water board basin annual ...

59 Pages·2014·3 MB·English

THE UNITED REPUBLIC OF TANZANIA
MINISTRY OF WATER

LAKE NYASA BASIN WATER BOARD

BASIN ANNUAL HYDROLOGICAL REPORT
NOV.2012 – OCT.2013

LAKE NYASA BASIN WATER BOARD
P.O. BOX 240
TUKUYU
Tel: [phone]
Fax: [phone]
E-mail: [email protected]
Website: www.lakenyasabasin.com JANUARY, 2014
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TABLE OF CONTENTS
EXECUTIVE SUMMARY ………………………………………………………………………………………………………………1
1.0 GENERAL INTRODUCTION ............................................................................................................... 4
1.1 Objectives of the Report ..................................................................................................................... 4
1.3 Physiography ....................................................................................................................................... 4
1.3.1 Topography .................................................................................................................................. 4
1.3.2 Geomorphology ........................................................................................................................... 5
1.3.3 Drainage Patten ............................................................................................................................ 6
1.3.4 Land Use/Cover ........................................................................................................................... 6
1.3.5 Soils.............................................................................................................................................. 7
1.4 Main Features in the Basin.................................................................................................................. 7
2.1.1 Data Management ..................................................................................................................... 17
2.1.3 Processing of Data ..................................................................................................................... 17
2.2 Rivers water level Data ..................................................................................................................... 18
2.3 Water Quality Data ........................................................................................................................... 21
2.4. Data Management ........................................................................................................................ 22
2.4.1 Temporal and Spatial Coverage of Measuring Stations ............................................................. 23
2.4.2 Water Quality Management ....................................................................................................... 23
2.5 Lake Nyasa information .................................................................................................................... 23
2.6 Groundwater Data ............................................................................................................................. 23
2.6.1 Data Management ...................................................................................................................... 24
2.6.2 Temporal and Spatial Coverage of Borehole/Groundwater Stations ......................................... 24
2.6.3 Processing of Data ..................................................................................................................... 24
2.7 Water Use/Abstraction Data ............................................................................................................. 24
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2.7.1 Data Management ...................................................................................................................... 24
2.7.2 Temporal and Spatial Coverage of Water Use/Abstraction Points ............................................ 25
2.7.3 Processing of Data ..................................................................................................................... 25
3.0 HYDROLOGY OF THE BASIN ......................................................................................................... 26
3.1 Climate .............................................................................................................................................. 26
3.2 Runoff Distribution ........................................................................................................................... 26
3.3 Sediment Transport ........................................................................................................................... 26
3.4 Water Storage .................................................................................................................................... 27
3.5 Groundwater Occurrence .................................................................................................................. 27
3.6 Pollution sources ............................................................................................................................... 27
4.0 WATER AVAILABILITY AND UTILIZATION IN THE BASIN .................................................... 28
5.0 GENERAL REMARKS AND WAYFORWARD.......................................................................... 28
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Tables
Table 1.1: Area of each country in Lake Nyasa Basin………………………………………….……………………4
Table 2.1: shows statistical water use customers...........................................................................25
Figures
Figures 2.1(b):Tenende monthly total rainfall for (Nov.2011-Oct.2012) annual hydrological
year………………………………………………………………………………………………12
Figures 2.1(a): Tenende monthly total rainfall for (Nov.2012-Oct.2013) annual hydrological
Year………………………………………………………………………………………………12
Figure 2.2(b): Unyamwanga monthly total rainfall for 2011-12 and 2012-13 annual hydrological
year……………………………………………………………………………………………….13
Figure 2.2(a): Unyamwanga monthly total rainfall for 2011-12 and 2012-13 annual hydrological
year………………………………………………………………………………………………13
Figure 2.3(b):Madaba monthly total rainfall for (Nov.2011-Oct.2012) annual hydrological
year………………………………………………………………………………………………14
Figure 2.3(a):Madaba monthly total rainfall for (Nov.2012-Oct.2013) annual hydrological
year………………………………………………………………………………………………14
Figure 2.4(b): Masigira monthly total rainfall for (Nov.2011-Oct.2012 ) annual hydrological
year……………………………………………………………………………………………….15
Figure 2.4(a): Masigira monthly total rainfall for (Nov.2012-Oct.2013) annual hydrological
year……………………………………………………………………………………………….15
Figure 2.5 (b): Ileje Maji yard monthly total rainfall for (Nov.2011-Oct.2012) and 2012-13
annual hydrological year………………………………………………………………………...16
Figure 2.5 (a): Ileje Maji yard monthly total rainfall for (Nov. 2012-Oct.2013) annual
hydrological year………………………………………………………………………………...16
Figure 2.6: Kiwira River water level at Ipyana………………………………………….…….....18
Figure 2.7: Ruhuhu river water level at Masigira (upstream)…………………………….……...19
Figure 2.8: Ruhuhu River water level at Kikonge (down stream)…………………………..…...19
Figure 2.9 (a): Lake Nyasa water level at Itungi Port (Nov.2012-Oct.2013)…………………....20
Figure 2.9 (b): Lake Nyasa water level at Itungi Port (Nov.2011-Oct.2012)…….……….…..…20
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Plates
Plate 1.1; show Ngozi Crater Lake……………………………………………………………......9
Plate 1.2; show Kaparogwe Falls ……………………………………………………………..….9
Plate 1.3; show the Natural Bridge (Bridge of God)…………………………………………….10
Plate 1.4; show the Lake Masoko………………………………………………………………..10
Plate 2.2: A washed gauge stuff due to flash flood at Luhekei river at Nangombo (March,
2013)……………………………………………………………………………………………..21
Plate 2.1: construction of Water level gauging station Lufilyo at Ipinda
(Downstream)………………………………………………………………….………………...21
Plate 2.3:Coal transportation at Lake Nyasa at New Kiwira port in Kyela district………………….23
ANNEXES....................................................................................................................................24
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EXECUTIVE SUMMARY
The Lake Nyasa Basin has plenty of water sources which are greatly found through springs,
rivers, wetlands, reservoirs and lakes. The basin receives heavy annual precipitation for both its
surface and groundwater. Most of the rivers are perennially flowing into Lake Nyasa. During this
reporting period the basin has experienced moderate rainfalls in most part of the basin. Data have
been collected at different operating hydrometric and rainfall stations distributed in the basin.
During this reporting period rainfall has been recorded ranging between 900-2300mm per
annum. Normal rainfall ranges between 1000-2800mm per year. This indicates that rainfall was a
little bit below normal average. Day temperatures experienced an average of 12- 21oC during
rainy season, while 19 - 28 oC during dry season. The onset of the rain season has become
unpredictable while the long dry spells within the rain season has increased across the basin.
Since the basin has much water from the rivers which flow throughout the year the population is
easily getting water, but most areas they lack proper technology only to gain an improved water
supply. But most of these perennial rivers their amount of water keep decreasing especially
during dry season. Lake Nyasa and rivers water levels recorded indicate the situation of this
year. However, there was discharge measurements computed from Lilondi river at Lingatunda
falls, Mngaka river at Paradiso, Lutukira at Litumbandyosi (tributaries of Ruhuhu river), Luswisi
river at Bwenda (a tributary of Kiwira river), Kiwira river at Natural Bridge, Kiwira river at
Kiwira Village, Chiwindi river at Mtupale, Mbawa river at Mkali, Songwe river at Kasumulu.
Other discharge measurement were conducted on spot gauging for the purpose of water
allocation, see the annex-vi below.
Lake Nyasa is a big water body in the SADC region and has an outlet of Shire river only towards
Zambezi river basin. Lake Nyasa on Tanzania side receives inflow from rivers which contribute
about 59%, compared to shared countries of Mozambique and Malawi. A portion of 2%
catchment area Tanzania contribute to Zambezi River basin, while 11.3% volume of water
through Shire River.
Generally the Water quality in Lake Nyasa Basin has remained normal due to most sources of
pollution are originated from agrochemicals, industry, municipal waste waters, disposal of solid
waste etc.
Lake Nyasa Basin has 38 hydrometric stations (35 are River gauges and 3 are Lake Level
gauges), all stations are operational; 6 Meteorological stations were constructed and
rehabilitated, but only 4 Meteorological stations are working fully; 4 Automatic rainfall stations
were constructed, but only 3 are in operational, 12 manual rainfall are existing and operating.
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Rainfall is a primary source of freshwater in the basin and most of the rural communities, who
make the majority, also depend directly on water in rivers, wetlands and Lakes for domestic
water supply and income generating activities. A changing climate will affect all aspects of life
in the basin in which the majority of farmers depend on rain-fed agriculture for their livelihoods.
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1.0 GENERAL INTRODUCTION
1.1 Objectives of the Report
In Hydrological aspect of the basin offers the best opportunity as an appropriate unit, for
analytical and coordinated water resources management. The information collected enable in
decision making, planning and development in the basin.
1.2 Location of the Basin and Administrative Units
Lake Nyasa Basin is a trans-boundary basin and is located between coordinates 90S to 120S
latitudes and 330E to 360E longitudes in the southern highlands of Tanzania. Lake Nyasa basin
encompasses all land whose rivers drain water into Lake Nyasa. The main rivers that pour their
water into Lake Nyasa from the Tanzania side with respective catchment sizes include Ruhuhu
(13,490Km2), Songwe (3550 Km2), Kiwira (1660 Km2), Rufirio (1350 Km2), and Lumbira (1414
Km2). Other river systems include Mbaka, Nkiwe, Malisa, Mnyamaji, Mbawa, Luika, Luhekei
and Mchuchuma. Administratively, there are twelve (14) districts, in three regions of Mbeya,
Njombe and Ruvuma regions all of which fall partially within Lake Nyasa Basin. Districts falling
fully into Lake Nyasa basin are Rungwe, Kyela, Ileje, in Mbeya region, Ludewa in Njombe
region. Districts with partial coverage into Lake Nyasa include Mbozi (10%), Mbeya Rural (6%),
Makete (about 80%), Njombe (about 45%), Songea (50%), Mbinga (about 50%), Nyasa (80%),
Momba (8%), Wanging’ombe (5%) and Namtumbo (20%). The population is estimated to be 2.2
million inhabitants
1.3 Physiography
1.3.1 Topography
Lake Nyasa Basin forms the south-west part of Tanzania with common borders of
Mozambique and Malawi territories. The total area covered is approximately 165,109
Km2 (inclusive of lake waters (33,457 Km2), land area (131,652 Km2) distributed as
follows:-
Table 1: Area of each country in Lake Nyasa Basin
Total Area Part of Total area (Km2)
Km2
Malawi Tanzania Mozambique
Land Area 131,652 89,745 39,140 2,767
Lake Area 33,457 19,372 8,105 5,980
Total 165,109 109,117 47,245 8,747
The Tanzania portion of the basin is 47,245 Km2). The basin is generally mountainous
and hilly, with Rungwe, Kipengere mountains being the highest over 2,000 metres above
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sea level. The lowest land is around the Lake Nyasa which is 470 metres above sea level
on the average. The mountainous areas of Ruvuma region are of lesser altitudes than
those of Njombe and Mbeya regions and most of the region is covered by undulating
hills.
The characteristic features of the basin, apart from the Rift Valley system, are the
surrounding uplifted and warped plateaus, covering nearly 90 percent of the total basin
area. The plateaus represent by far the most common land form. They are separated by
fault-lines and erosion scarps, and is the result of steady erosion that has taken place since
the late Jurassic period.
The oldest plateaus are found at the highest levels from 1800 to 2700 m above sea level
(i.e. the Mporoto and Kipengere ranges ) the remaining parts of the basin is occupied by
areas where deposition of the material has taken place notably in the Rungwe Volcanic
and around Rungwe district.
The Rungwe Volcanic, with the Rungwe Mountain (2960 m.a.s.l.) as its centre of
eruption, forms an area of pronounced topographical relief. The craters, lava flows and
volcanic ash covers make the volcanic area completely different from the rest of the
Basin.
1.3.2 Geomorphology
Most of the Basin consists of African Land surface with Gondwana remnants being found
in the higher areas of Songea and Mbinga districts. Towards Lake Nyasa, Congo surfaces
are found with also some scraps in the north of Mbinga and Songea districts. The Karoo
formation of the Basin (i.e. north Songea, Ludewa, Ileje, Rungwe and Kyela) is of
particular geomorphologic interest since the easily eroded rock system result in
permeable sub-strata and high aquifer recharge.
About 68 percent of the basin area is underlying by crystalline rocks belonging to the
Basement Complex. The remaining 32 percent is underlying by sedimentary rocks of the
Karroo System and (volcanic formation) mainly of Neogene age.
Intensive in-situ chemical weathering by circulating groundwater has produced a thick
mantle of overburden across the plateaus. This overburden in some places effectively
masks the exact geological nature of the underlying rocks, as well as their tectonic and
structure features.
At an early stage of the study, it became apparent that in the basement complex,
groundwater occurred in the lower part of the in-situ weathered rock zone, and that the
distribution of the landforms played an important role in determining the hydrogeological
conditions. The factors controlling the hydrogeology of the basement complex were
therefore found to be uniquely related to the geomorphology of the given area, and by