1
Hydrological and climatic data availability and preliminary analysis in Rwanda
O. Munyanezaa,b,1, S. Uhlenbrookb,c, S. Maskeyb , U. G. Walia and J. Wenningerb
a
National University of Rwanda, Department of Civil Engineering, P.O. Box 117, Butare,
Rwanda
b
UNESCO-IHE Institute for Water Education, P.O. Box 3015, 2601 DA Delft, The Netherlands
c
Delft University of Technology, Department of Water Resources, P.O. Box 5048, 2600 GA
Delft, The Netherlands
ABSTRACT
Proper planning for sustainable development of water resources requires the use of long term
meteorological and hydrological data. The main aim of this study is to review the hydro-climatic
data availability and to analyze the hydro-climatic variability in Rwanda. This study also presents
the assessment of spatial and temporal variability of hydro-climatic data in Rwanda primarily
based on pre-1994 period data. Data were collected from many stakeholders in the field of water
and environment in Rwanda, such as MINIRENA, MININFRA, ELECTROGAZ, NBDF and
NUR-WREM Project. Stream flow data, mainly daily water level measurements, were obtained
from 39 gauging stations. Daily rainfall data were obtained from 136 gauges, whereas other
climatic variables (temperature, relative humidity, solar radiation, evaporation, sunshine duration,
wind speed and direction) were collected from 13 stations. The lengths of these data sets vary
significantly, most of them begin in the 1930s and end in early 1994 as a result of the Rwanda
Genocide. There are only 11 meteorological stations and 22 hydrological stations that are
operating around the whole country after 1994, of which most have resumed operation only
recently. Moreover, there are significant amounts of missing data in these data series. The
assessment of the data availability shows the severity of the problem currently faced in the
country in planning, management and research activities in the water resources sector. Large
variability within a year and between the years has been observed for the daily rainfall and stream
flows. The average monthly rainfall in Rwandan catchments from 1970 to 1993 is 101
mm/month, with the mean maximum monthly rainfall of 203.8 mm in April and mean minimum
of 10.5 mm in July. The hydrograph peaks occur in April and May, roughly one month in lag of
precipitation. The minimum flows occur in the months of July and August, summer season.
Keywords: Hydrological and climatic data, Rwanda, spatial variability, temporal variability
Introduction
The world population has tripled in the twentieth century, while, over the same period, water use
has increased sixfold. Currently, about 1 billion people live in water-scarce or water-stressed
regions, and by 2025 this number is expected to increase by a factor 3.5 (Wagener et al., 2008).
The magnitude of this water scarcity and its variations in both space and time are largely
unknown because of lack of hydro-climatological data (Oyebande, 2001; Kipkemboi, 2005).
Though the needs for hydrological and meteorological information are increasing, there is a
decline in technical and human capacities by the reduction in number of hydrological and
1
Corresponding author. Address: National University of Rwanda (NUR), Department of Civil
Engineering, P.O. Box 117, Butare, Rwanda.
E-mail address: o.munyaneza@unesco-ihe.org ; munyoma2000@yahoo.fr (Omar Munyaneza)
2
meteorological stations in Africa during the last 30 years (Bonifacio and Grimes, 1998). This
decline was also observed in Rwanda where only 136 meteorological stations are operational in
1994 out of the 147 existing stations in 1960 to 1990 (Dushimire, 2007). This decline continued
during and after the 1994 genocide and at present, only 11 meteorological stations are functioning
in the whole country (NWRMP, 2008).
The main objective of this work was to presents an overview of the spatial and temporal
variability of temperature, precipitation and stream flow data availability in Rwanda.
Description of the study area
This study was carried out in Rwanda. Rwanda is a small, mountainous country with relatively
high rainfall, and is situated in Central Africa, bordered by Burundi in the South, the Democratic
Republic of Congo in the West, Uganda in the North and Tanzania in the East. The total area of
Rwanda is about 26 338 km2 out off which about 24,948 km2 is land and 1,390 km2 is covered by
water (5.3%). In 2007 the population of Rwanda was estimated to be 9.3 million (NISR, 2008).
This gives an estimated population density of about 342 persons/km2, the highest in Africa
(NELSAP, 2006).
The mean annual rainfall in Rwanda is about 1120 mm and varies from 700 mm in the NorthWest to about 1600 mm/year in the South-West. The mean altitude is 1250 m above sea level
with a general slope oriented from west to east (FAO, 2005). The altitude increases progressively
from the south-eastern plateau to the north and west where it gets the highest altitudes in the
“Congo-Nile Crest” with elevations varying between 2200 m and 3000 m and the chain of
volcanoes with the highest point of 4507 m at the Karisimbi volcano (NELSAP, 2006).
Rwanda has a moderate climate with an annual average temperature of 190 C. It is divided into
three agro-climatic zones: i) high-altitude region, ii) central plateau, and iii) plateau of eastern
lowlands and the west (FAO, 2005). The country has an annual cycle of four seasons that are
distributed as follows:




a short rainy season, locally known as “Umuhindo” runs from
September to November, with November characterized by heavy precipitation;
a short dry season, locally known as “Urugaryi” runs from December to February;
a long rainy season, locally known as “Itumba” runs from March to May, this
bringing about 14 to 61% of the total annual precipitation;
a long dry season, locally known as “Icyi” runs from June to August.
Figure 1 shows the location of Rwanda within the Nile Basin and the distribution hydrological
network in the country.
3
Figure 1 The hydrologic networks of Rwanda and the spatial distribution of meteorological
stations and River gauging stations
Rwanda is head water of the two of the main African Basins: Congo Basin and Nile Basin.
Roughly 80 percent of the country is located within the Nile Basin, while the remaining portion
forms part of the Congo Basin (MINAGRI, 2000). Two main Rivers, Nyabarongo and Akanyaru
and their numerous tributaries, make up the Akagera River which drains most of the Rwandan
waters to the Lake Victoria and then the River Nile.
Methodology
This study presents the baseline information of the spatial and temporal variability of
temperature, precipitation and stream flow in Rwanda. Data used in this study were provided by
the Ministry of Natural Resources (MINIRENA) and Rwanda Meteorological Office. Some
additional data were obtained from other institutions like MININFRA, ELECTROGAZ, REMA,
NBDF and NUR-WREM Project.
The period of available data records is given in Table 1 for some selected stations, within the
period of data availability the data set exhibit some significant discontinuity. In many cases the
missing values ranges from several some months to several years. Because of that, a manual
screening method was used to select as set of dataset with reasonably long period of time series
with minimum missing values, which is presented in Table 1. The locations of these selected
stations are presented in Fig. 2.
Table 1: Selected stations used for hydro-climatic analysis
Station
Parameter
No
Station name
Period of data availability
Alt.
Time series
4
Rainfall
Temperature
Stream flow
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
Rulindo
Murehe
Kigali Airport
Rubilizi
Rushashi
Nyakibanda
Gakoma
Butare airport
Kansi ENT
Kansi Parish
Save ETI
Cyanika
Kaduha
Kibeho
Kitabi
Mbazi
Mweya
Nyange
Muramba Parish
Muramba Cyabingo
Rwankeri
Nemba
Remera-Ruhondo
Rwesero
Gisenyi Airport
Kamembe Airport
27
1
2
3
Byimana
Kigali Airport
Butare Airport
Ruhengeri Airport
4
Station
No
1
5
Gikongoro
River/Former
Province
Kagitumba/Umutara
Ururumanza/Gitara
ma
Rusumo/Ruhengeri
Nyabugogo 3/Kigali
Rural
Nyabugogo 1/Kigali
City
6
Mwogo 1/Butare
2
3
4
1970-1993
1975-1993
1970- 2008
1970-1975; 1978-1993
1979-1993
1970-1993
1971-Jan 1994
1970-1993
1977-Feb 1994
1970-Feb 1994
1974-Feb 1994
1970-1993
1970-Jan 1994
1970-1973; 1975; 1978-1993
1974-Jan 1994
1977-Feb 1994
1977-1993
1970-Feb 1994
1970-1973; 1975-Jan 1994
1970-1973; 1976-1993
1970-1993
1971-1993
1975-1993
1970-Jan 1994
1975-Feb 1994
1971-March 1994; 1998-1999
1970-1989; 1991-1993; 19961999
1971-2000
1971-1993
1977-1992
1990-1993; 1997-1999; Sept
2000
24 years
19 years
39 years
22 years
15 years
24 years
23 years
24 years
20 years
24 years
20 years
24 years
24 years
21 years
20 years
17 years
17 years
24 years
23 years
22 years
24 years
23 years
19 years
24 years
19 years
25 years
1800
1575
1495
1400
1620
1750
1500
1768
1650
1670
1750
1950
1900
1894
1900
1700
1700
1600
1950
2200
2250
1675
1850
1475
1554
1591
28 years
30 years
23 years
16 years
1830
1495
1768
1878
7 years
1900
Alt.
Period of data availability
1970-1971; 1973-1988
Time series
18 years
1284
1970-1990
1971-1989; 1990; 1999
21 years
20 years
1450
2045
1970-1988; 1995-2000
25 years
1971-1982; 1984-1988; 19951997; 2000
19 years
1970; 1972-1982; 1984-1989;
1995-2000
24 years
1439
1380
1525
5
13
14
Mukungwa
1/Gisenyi
Akanyaru 1/Butare
Akavuguto/Gikongo
ro
Nyabarongo
5/Ruhengeri
Nyabarongo
4/Gitarama
Nyabarongo
3/Kibungo
Nyabarongo
2/Kigali City
Akagera/Kibungo
15
16
Sebeya 2/Gisenyi
Migina/Butare
7
8
9
10
11
12
1971-1985; 1987-1988; 19952000
23 years
1971-1991; 1995-2000
27 years
1400
1406
1971-1993; 1995-2000
29 years
1970; 1974-1984; 1986-1989;
1995-2000
26 years
1700
1971-1990; 1995-1996; 1998
23 years
1475
1971-1990; 1995-2000
26 years
1337
1970-1990; 1995-2000
1970-1990; 1995-1996
1972-1990; 1992; 1995-1997;
1999-2000
1970-1990
27 years
23 years
1352
1325
25 years
21 years
1775
1547
Figure 2 Spatial distributions of selected climate stations and River gauging station
Preliminary results of hydrological and climatic data analysis
Spatial and temporal variability of daily hydro-climatic data
Figure 3 shows daily total rainfall and daily mean stream flows for the year 1985 from several
gauging stations. Similarly, Figs 4 and 5 show mean daily temperature for several stations and
mean yearly rainfall averaged from selected stations, respectively.
1400
6
The daily rainfall and stream flows show large variability within a year and between the years, as
exemplified by Figures 3 and 5. There rainfall and stream flow data are continuous and complete
for the year 1985. Because of that, 1985 data were selected for demonstration in this paper. A
consistent decrease in summer runoff (June to August) in the upstream was observed on Sebeya
River located upstream of the Congo Basin and Ururumanza River for Nile basin (see Figure 3).
Butare Airport
12
/1
/8
5
11
/1
/8
5
10
/1
/8
5
9/
1/
85
8/
1/
85
7/
1/
85
6/
1/
85
5/
1/
85
4/
1/
85
3/
1/
85
2/
1/
85
65
60
55
50
45
40
35
30
25
20
15
10
5
0
1/
1/
85
Total daily rainfall (mm/day)
Kigali Airport
Date
Ururumanza
Mukungwa 1
Akanyaru 1
Nyabarongo 3
5
/1
/8
5
12
/1
/8
5
11
/1
/8
10
1/
85
9/
1/
85
8/
1/
85
7/
1/
85
6/
1/
85
5/
1/
85
4/
1/
85
3/
2/
1/
1/
85
360
330
300
270
240
210
180
150
120
90
60
30
0
1/
85
Mean dailly discharge (m 3 s-1)
Sebeya River
Date
Figure 3 Intra-annual variability of daily precipitation and mean daily stream flows data in
Rwanda primarily based on the pre-1994 period, illustrated for the data of the water year 1985
Akagera
7
Figure 3 shows that there are two rainy periods in Rwanda (March to May and October to
December) and two dry periods (June to September and January) in a year.
Inter-annual variability of temperature covering the period of 1970-1993 is shown in Figure 4.
Butare Airport
Ruhengeri Airport
Gikongoro
22
21
20
19
18
17
16
15
19
70
19
71
19
72
19
73
19
74
19
75
19
76
19
77
19
78
19
79
19
80
19
81
19
82
19
83
19
84
19
85
19
86
19
87
19
88
19
89
19
90
19
91
19
92
19
93
Mean daily Temperature (
o
C/day)
Kigali Airport
Time (year)
Figure 4 Inter-annual variability of temperature, based on selected stations of Rwandan
catchments (Kigali, Butare, Ruhengeri and Gikongoro); data covers 1970-1993
Figure 4 shows the record of daily mean temperature data for 1970-1993 with mean yearly
temperature of 18.60C. For the selected time series data records, mean maximum daily
temperature occurred in 1987 (20.90C, 19.20C and 17.40C at Kigali Airport, Butare Airport and
Ruhengeri stations, respectively). The mean minimum daily temperature occurred in 1984
(16.60C at Ruhengeri station).
The mean minimum daily temperature in the whole time series at Kigali airport station is 19.4 0C
and occurred in 1971. Ruhengeri station present lower temperature values compare to Kigali
airport station due to the topography of these two different catchments. The altitude of Kigali
airport station is 1495 m whereas the altitude for Ruhengeri station is 1878 m (see Table 1). The
impact of topography on temperature variation was also found by Mul et al. in 2008.
8
Total annual Rainfall (mm/yr)
1450
1350
1250
1150
1050
950
850
750
3
19 2
35
19
38
19
41
19
44
19
47
19
50
19
53
19
56
19
59
19
6
19 2
65
19
68
19
71
19
74
19
77
19
80
19
83
19
86
19
89
19
9
19 2
95
19
98
20
01
20
04
20
07
19
16
19
19
19
19
19
10
13
650
Time (year)
Figure 5 Inter-annual variability of rainfall, based on selected stations in all Rwandan
catchments; the first meteorological station was installed in 1910 at Save, southern Province of
Rwanda, currently 11 meteorological stations are operating in the whole country, years time
series records (1910–2008) with cut-off periods of 1920 to 1930 and 1994
Figure 5 shows that the maximum annual rainfall in Rwandan catchments from 1910 to 2008 is
1450 mm/a in 1951 and minimum is 677 mm/a in 1919. The years of 1995, 1996 and 2001
presented drought period in Rwanda. During these drought years, remarkable decrease in water
level was also observed in some lakes like Bulera and Ruhondo located in the northern of
Rwanda (MINITERE, 2005).
Spatial and temporal variability of monthly hydro-climatic data
Intra-annual variability of total monthly rainfall and mean monthly temperature from selected
climate stations, illustrated for the data of 1970–1993, is presented in Fig. 6.
Kigali Airport
Butare Rirport
Byimana
Kansi Parish
Rulindo
Rushashi
Nyakibanda
Total Monthly Rainfall (mm/month)
250.0
225.0
200.0
175.0
150.0
125.0
100.0
75.0
50.0
25.0
0.0
Jan
Feb
Mar
Apr
May
Jun
Jul
Time (month)
Aug
Sept
Oct
Nov
Dec
9
Kigali Airport
Butare airport
Gikongoro
Ruhengeri
Mean Monthly Temperature ( o C)
21.5
21.0
20.5
20.0
19.5
19.0
18.5
18.0
17.5
17.0
16.5
16.0
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sept
Oct
Nov
Dec
Time (month)
Figure 6 Intra-annual variability of total monthly rainfall and mean monthly temperature,
illustrated for the data of 1970–1993
Mean monthly Discharge (m 3 s-1)
Figure 6 shows the summer rainfall (June-July-August) and winter rainfall (March-April-May)
across the whole country. The average monthly rainfall in Rwandan catchments from 1970 to
1993 is 101 mm/month, with the mean maximum monthly rainfall of 203.8 mm in April and
mean minimum of 10.5 mm in July. The rains are mainly concentrated between November and
April. Intra-annual variability of mean monthly stream flows for selected stations in 1985 is
shown in Fig. 7.
Sebeya
Ururumanza
Nyabugogo 3
Mwogo 1
Mukungwa 1
Akanyaru 1
Nyabarongo 3
Akagera
Aug
Oct
11000
10000
9000
8000
7000
6000
5000
4000
3000
2000
1000
0
Jan
Feb
Mar
Apr
May
Jun
Jul
Sept
Nov
Month of 1985
Figure 7 Intra-annual variability of mean monthly stream flows for selected stations in 1985
The hydrograph peaks occur in April and May, roughly one month in lag of precipitation. The
minimum flows occur in the months of July and August.
Dec
10
Conclusions
Hydrological and climatic data availability in Rwanda has been reviewed and analyzed. Hydroclimatic data in Rwanda are scarce in time and space with around one station per 30km x 30km,
and many data gaps (duration often more than one year) within the record 1910-2008 were
detected. The data in Rwanda is not all compiled in data bases. Some data sets can be found as
hard copy and others can be found with private persons according to the research they were doing
for their personal interests. Large variability within a year and between the years has been
observed for the daily rainfall and stream flows. A consistent decrease in summer runoff (June to
August) in the upstream of Rwandan catchments was observed and the hydrograph peaks occur in
April and May. In order to address some of these problems, the data reconstruction and the build
up of an updated complete Rwanda data base are needed. It is strongly recommended that more of
these hydro-climatic stations are urgently rehabilitated and new installed in different catchments
of Rwanda.
Acknowledgements
This study was supported by a grant from the National University of Rwanda (NUR) through
NUR-Sida-Research Commission. A Nuffic/NPT Fellowship provided support to facilitate the
research. The authors would like to thank various institutions and government agencies for
providing data: the Meteorological Service of Rwanda; the Water Resources Management
Department of Rwanda, and the Rwandan Ministry of Natural Resources (MINIRENA) and
Ministry of Infrastructures (MININFRA).
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