1
Competing for Water Research Programme
Preliminary Report : Hydrological Study
Danish Institute for International Studies
DIIS.
Groupe d’Etudes et de Recherche en Droit
et Sociologie Appliquée – GERSDA Tél :
00 (223) 279 66 36. E-mail :
gersda@yahoo.fr Bamako / Mali
Author : Adama Tiémoko DIARRA – Hydrologue. Tél : 00 (223) 671 28 48 E.mail :
atdiarra56@yahoo.fr
February 2008
2
Contents
1. INTRODUCTION .............................................................................................. 3
2.AVAILABILITY OF HYDROLOGICAL DATA................................................. 3
2.1.
Meteorological data ...................................................................................3
2.2.
Hydrological data .......................................................................................5
2.2.1.
Surface water ...........................................................................................5
2.2.2.
Underground water .................................................................................8
2.3.
Simplified hydrological assessment ..........................................................9
2.4.
Data on quality of water ...........................................................................12
2.5.
Standards for the evaluation of water demands .....................................15
3. CONCLUSIONS ............................................................................................ 16
4. BIBLIOGRAPHY ............................................................................................ 18
5.
ANNEXES ............................................................................................ 19
3
1. INTRODUCTION
This report consists of an evaluation of water resources in the Douentza district,
Mopti region, in Mali, in the framework of the « Conflict and cooperation in local water
governance » research programme. Led by the Danish Institute for International
Studies (DIIS), this interdisciplinary programme collaborates with research partners
in Africa, Asia, Latin America and Europe.
The aim of the preliminary phase of this hydrological study is to assess the data on
water resources in the case study area of the Douentza district, Mali.
More specifically, this study will :
-
Dress an inventory of the current knowledge on water resources in the study
area.
-
collect available data from relevant technical services on climate, hydrology
and hydrogeology in the district
-
Analyse and process collected data on water resources (surface and
underground water)
-
Establish a simplified hydrological assessment on the study area.
This analysis of existing data will complement the sociological inventories and
analyses and aims at identifying technical and physical factors playing a role in water
conflicts.
2.
AVAILABILITY OF DATA ON WATER RESOURCES
2.1. Meteorological data
The climate of the study area is sahelian, with the following three seasons :
• rainy season, from May to October
• cool dry season, from November to January
• warm dry season, from February to April
The average annual rainfall in the study area is spatially and temporally variable, and
ranges from 400 to 500 mm, with 62% rain falling during July and August.
4
The average annual temperature is 28°C, with a monthly maximum temperature of
38°C in April and an average monthly minimum of 15°C in January ; seasonal
variations are not high but during the warm dry season there can be a high variability
during the day.
Potential evapotranspiration is 2190 mm per year, but is irregular during the year,
with peaks in March and April (235mm and 230mm) and at its lowest in July and
August (150mm).
The meteorological data are tracked by the network of the Direction Nationale de la
Météorologie (DNM), which has a regional office in Mopti.
The meteorological network includes the Mopti and Hombori stations and the rainfall
station of N’Gourma in Douentza. Rainfall is the main data collected by these stations.
Table : Rainfall stations representative for the study area
Station
Locality
Coordinates
Altitude
Longitude
Latitude
Date of
Creation
N’Gouma
Douentza
03°22W
15°38N
267
1954
Hombori
Hombori
01°41W
15°20N
287
1920
Mopti
Mopti
04°06W
14°31N
271
1921
The data collected by the meteorological stations of Mopti and Hombori are the
following :
Table: Climatic parameters, Mopti and Hombori stations
Available parameters
Characteristics
Rainfall
Level and intensity
Temperature
Maximum ad minimum temperature (at 2m)
Ground temperature
Relative humidity
Maximum and minimum
Solar radiation? Insolation?
Daily duration
Wind
Speed and direction (at 2 m and 10 m)
Atmosphere pressure
pressure
5
Evaporation
Piche, class A pan evaporation
Inter-annual variation of rainfall
The following graph shows the average annual variation of rainfall from 1945 to 2005.
A dry period started in 1968, with reduced and very variable rainfall, both spatially
and temporally.
The drought of the 1970’s and 1980’s had a very strong negative impact on the study
area’s ecology and profoundly modified the water resource regime.
One of the main consequences is a low rate of storage and a bad functioning of the
water tanks/reserves which are the main water resources of the zone.
Low rainfall has degraded and even destroyed the vegetation cover, which in turn led
to an increase in surface runoff and a decrease in infiltration of rain water.
2.1. Hydrological data
2.1.1. Surface water
The Douentza district is situated in the Niger basin but the Niger River does not run
through the district.
Directly available water resources come from temporary water courses, lakes
and water reservoirs/tanks (retenues)? The largest lakes (Kourarou, Aounkoundou
and Korientze) are supplied by the Kolli Kolli, an arm of the Niger river, and by rain
6
water. The water level and the flood duration in the lakes and other water storage
points depend on the hydraulicity of the Niger river.
Apart from the above-mentioned lakes, other surface water resources are small and
temporary ponds.
Table : temporary water courses and ponds in Douentza
Temporary water
Locality
Types of zones
courses and ponds
Hydrological
regime
Ibissa
Commune Ibissa
Natural source
temporary
Kikara
Commune Kikara
Natural source
temporary
Mokeïna
Commune de
Forest /pond
temporary
Pond/livestock
temporary
Mokeïna
Borko
Boré
watering point
Boni
Boni
Storage dam
temporary
7
Dioulouna
Dioulouna
Pond
temporary
Inani
Commune de Inani
Forest/pond
temporary
Source : Plan d’Action National de Gestion des Zones humides (PAZU), Etude d’inventaire et de
caractérisation des zones humides au Mali, Avril 2007.
Economic activities around these water points are agriculture, fishing and livestockrearing. Most of the lakes and ponds are unfortunately small and dry.
Hydrometric data collection and tracking has only been done on the Kolli Kolli, an
arm of the Niger River supplying the main lakes. The water levels measured on the
Kolli Kolli are presented in annex. The level of the Kourarou lake has been tracked
only during one hydrological year. We do not have data on other water points in the
study area.
The hydrological stations of Mopti and Konna situated on the Niger river, outside the
study area, could serve as control/relay stations in the analysis of the seasonal
variability of water resources. Data on water level and water flow since 1922 are
available from these stations.
Table : Hydrological stations representative for the study area
Station
River
Longitude
Latitude
Altitude
Basin area
(Km2)
Creation
Korientze
Kolli Kolli
W 003 4700
N 15 25 00
257
-
1959
Diona
Kourarou
Lake
W 003 1500
N 15 20 00
-
-
-
Mopti
Niger
W 004 1200
N 14 30 00
261
281 600
1922
8
The following graph shows a high correlation between the water level measured on
the Niger River in Mopti and the Kolli Kolli in Douentza.
2.1.2. Underground water
Underground water is used for people and livestock. In Douentza, surface water is
mostly non perennial and is therefore only available during part of the year.
9
The drought taking place in Mali since the 70’s lowered the level of the water table,
and caused water depletion of the traditional water points ( temporary ponds and
shallow wells). As a consequence, new water points (wells and water drilling) have
been developed, in order to harvest water from deep aquifers, therefore less
dependent on climatic changes.
According to the information system « SIGMA 2 » on underground water points, the
Douentza district has 272 wells, of which 215 are permanent. For these wells, the
following data are available :
-
Depth and diameter
-
Static level
-
Hydraulic conductivity
The Douentza district also has 279 water drillings, out of which 224 equipped. For
these drillings, data are available on depth and diameter, static level, hydraulic
conductivity, and also on water flow, which has been measured during pumping
trials.
The spatial and temporal variability of underground water aquifers in Douentza is
difficult to assess due to the lack of tracking of the hydraulic gradient level.
Average characteristics of drillings and wells in Douentza
Average depth of
Success rate
Success rate
Average depth of
drillings (m)
Q≥1m /h
Q≥5m /h
wells (m)
64
63%
31%
31
3
3
2.2. Simplified hydrological assessment
The following hydrological assessment is based on the difference between the
average rainfall and the watershed flow, and corresponds to flow loss :
Pm = Le + ETR + R1 - Ro
Pm is the average level of annual rainfall in mm in the basin.
10
Le is the annual runoff depth in mm, i.e. volume of flow in comparison to the size of
the basin, at a level comparable with rainfall level.
ETR is the real average annual evapotranspiration in mm.
R1 and R0 are respectively the runoff stored in the ground or in the underground
aquifers and runoff returned by these aquifers during a certain period.
Lack of hydrological data makes modelling difficult. The simplest relations use rainfall
level as variables for runoff depth. The basic relation is :
Vapports  K e  Pm  S
Vapports: Supply (m3)
Ke : runoff coefficient
Pm : average rainfall
S : watershed size
Runoff depth
Runoff depth and average rainfall :
Le(mm) 
31,53x103 xQ(m3 S 1 )
S ( Km2 )
Q represents the flow and S the size of the watershed.
Runoff coefficient and runoff deficit
The inter-annual runoff coefficient Ke constitutes a characteristic/distinctive feature of
the hydrology of the basin, as it only depends on inter-annual runoff depth and
rainfall level in the basin :
K e (%) 
Le
 100
P
11
According to research by ORSTOM, the runoff coefficient in the study area is about
14%.
Runoff deficit
The runoff deficit corresponds to the water used by evapotranspiration and the
difference between water stored in underground aquifers and the volume given
back/returned by these aquifers.
De= P - Le = ETR + R1 - Ro
In a yearly assessment, storage and return tend to reach an equilibrium for a long
time period of observation (R1≈R0) and the average runoff deficit represents the only
parameter ETR (average value of real evapotranspiration in the zone)
De= P - Le = ETR
The table below contains all ten-year hydrological assessments since 1950.
Table: components of the simplified hydrological assessment
Decades
Rainfall
Runoff depth
Deficit = ETR
(mm)
(mm)
(mm)
1950-1960
572,89
80,20
492,68
1961-1970
487,72
68,28
419,44
1971-1980
431,22
60,37
370,84
1981-1990
354,78
49,66
305,11
1991-2000
439,49
61,52
377,96
1950-2000
458,73
64,22
394,51
The gap analysis in relation to averages established from 1950 to 2000 shows that
the deficit is higher during the last 30 years.
12
2.3. Data on water quality
Surface water (rivers, ponds, tanks) is polluted by men and animals. There is no
pollution from industry and very little pollution from agriculture.
There are almost no data on the quality of the surface water of the study area. The
only data available come from a few water samples taken during research
programmes by the « Institut Français de Recherche pour le Développement » (e.g.
ORSTOM). Results of the measures taken in 1999 on the Kolli Kolli, which supplies
in water all the main lakes in the study area, are below:
Date of
sample
Suspended
solids (g/m3)
Conductivity
at 25° C (µs)
pH
Temperature
(°C)
02/02/1999
45,2
57,7
7,5
21,2
Underground water is less polluted. Most of the localities are supplied by water
drillings or wells which harvest underground water without processing/treating it.
13
Table: Physical and chemical features of underground water in Douentza
Locality
Commune
DANGOL BORE /BORE
DOUENTZA/
Date of
analysis
CATIONS (mg/l)
Ca
Mg
Na
Anions (mg/l)
K
Fe
Mn
HCO3
Cl
S04
NO3
TAC
TH
Cond
mg/l
mg/l
µS/cm
pH
27/12/82
30
113
0
0
0
0
5
52
636
0
45
540
1632
8
18/04/82
61
90
0
4,3
0
0
606
21
216
0,1
496
524
1344
8
18/04/82
0
18
0
62
0
0
210
26
32
1,4
174
165
441
8
17/12/82
56
160
0
0
0
0
616
52
820
0
505
800
1981
7
11/12/82
38
65
0
0
0
0
499
20
192
0
407
364
1118
7
08/06/87
38
91
0
0
0
0
650
0
11
0
532
468
1204
8
17/12/84
52
0
0
0
0,6
0
71
32
36
0
58
132
589
6
26/04/88
35
18
0
0
0,6
0
115
5
20
0
94
160
414
8
26/04/88
48
39
0
0
0,8
0
412
10
283
0
277
280
1026
8
Douentza
HAIRE/
Nokara
HOMBORI/
Hombori
Korarou/
Ibrizaz
Source: Base de données sur les eaux souterraines « SIGMA 2 » de la Direction Nationale de l’Hydraulique.
15
2.4. Standards for the evaluation of water demands
Water resource (surface and underground water) uses:

Human consumption

Livestock watering

Agriculture (rice and horticulture)

Making banko for house building

Refill of groundwater tables
Human consumption
In Mali, the following standards are used to estimate demands for human
consumption.
Category of locality
Standards from the Schema
Optimum needs
Directeur l/day/pers
l/day/pers
Bamako
54
100
Urban centres
46
80
semi-urban centres
31
55
Rural centres-villages
20
45
Water needs of population are assessed according to the standards in table above
i.
Village (less than 2000 inhabitants): 20 litres/person/day, i.e. 1 modern
water point for 400 inhabitants (modern water points have a flow of 8
m3/day.)
ii.
Rural centre (2000 inhabitants to 5000 inhabitants) : 31 litres/pers./day
iii.
Semi-urban centres (5000 and 10.000 inhabitants) : 31 litres/person/ day
iv.
Urban centres (more than 10.000 inhabitants) : 45 l/pers/day
It is generally admitted that for localities with more than 2000 inhabitants in rural
areas, water supply networks such as water towers and water taps are appropriate
drinking water supply installations.
16
Animal consumption
Livestock watering with surface water is the most common use by livestock keepers,
who prefer it to using underground water.
Water needs of livestock depend on the species, on the quality of forage and on
climate. Specific consumption is variable but gaps are not significant.
Field studies led by the Comité Inter Etats d’Etudes Hydrauliques (CIEH) cite the
following figures:

cattle: 39,2 l/d/head

sheep :

goats : 4,3 l/d/head

donkeys :

horses : 23 l/d/head
4,3 l/d/head
30 l/d/head
Agricultural consumption
Estimation of water needs estimation for irrigated agriculture (horticulture and
orchards) is based on the following standards:

large areas (double rice cultivation) : 20 000 m3/ha/year ;

small areas (double rice cultivation and horticulture) : 15 000 m3/ha/year ;

improved lower-depth areas (bas fonds améliorés) (complementary supply
during the rainy season) : 5 500 m3/ha/year ;

Horticulture: 8 000 m3/ha/year.
3. CONCLUSIONS
Water resources in the study area are mostly ponds and temporary water courses, as
well as lakes fed by the high water of the Niger River.
Hydrological data on the study area are not available, due to a lack of measurement
networks. This situation can prevent the planned modelling. This gap can be partly
corrected with hydrological data available from the Mopti station on the Niger River.
17
The hydrological data on the Niger in Mopti, even if outside the study area, can
contribute to analysing the variability of water resources in relation to water conflicts.
Indeed, the main lakes in Douentza depend on the Niger River.
Meteorological data are available from the Mopti, Hombori and N’Gourma stations, all
representative of the study area.
The next phase of the hydrological study will aim to:
-
Assess water needs or demands from different socio-economic sectors
-
Establish hydrological assessments and apply water allocation model in order
to explain variability factors in water resources and satisfaction levels in the
analysis of water related conflicts.
-
Identify technical and physical factors linked to water conflicts in order to
complement the sociological inventories and analyses.
18
4. BIBLIOGRAPHY
1. Monographie hydrologique du fleuve Niger, Tome 1 – Niger Supérieur,
Brunet-Moret, Y.; Chaperon, P.; Lamagat, J.P.; Moliner, M.; Edition
l’ORSTOM Monographie Hydrologues No 8, ISBN 2-7099-0790-9/2-70990791-7;1986
2. Influence des aménagements hydrauliques et hydro-agricoles du Niger
supérieur sur l’inondation du delta intérieur du Niger (Mali), Adamou
Hassane, juin 1999.
3. ORSTOM/DNHE. Projet MLI/90/002. Evaluation des ressources en eau non
pérennes du Mali. Rapport final Bamako, Novembre 1992, Mali.
4. Ministère de l’environnement. Plan d’Action National de Gestion des Zones
humides (PAZU), Etude d’inventaire et de caractérisation des zones humides
au Mali, Avril 2007.
19
5. ANNEXES
Average water levels on the Koli Koli in Korientze
Year
level(cm)
01/07/1959
01/07/1960
01/07/1961
01/07/1962
01/07/1963
01/07/1964
01/07/1965
01/07/1966
01/07/1967
01/07/1968
01/07/1969
01/07/1970
01/07/1971
01/07/1972
01/07/1973
673
614
466
451
506
450
497
645
514
494
564
656
557
517
550
Year
01/07/1974
01/07/1975
01/07/1976
01/07/1977
01/07/1978
01/07/1979
01/07/1980
01/07/1981
01/07/1982
01/07/1983
01/07/1984
01/07/1985
01/07/1986
01/07/1987
01/07/1988
Level (cm)
415
350
272
279
235
320
253
262
219
163
147
191
151
123
185
year
Level (cm)
01/07/1989
01/07/1990
01/07/1991
01/07/1992
01/07/1993
01/07/1994
01/07/1995
01/07/1996
01/07/1997
01/07/1998
01/07/1999
01/07/2000
01/07/2001
01/07/2002
01/07/2003
156
157
168
143
143
189
216
191
153
205
190
211
58
249
237
Source : Direction régionale de l’hydraulique de Mopti
Average water levels on the Niger in Mopti
Year
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
level(cm)
289,81
322,43
363,76
326,88
321,46
307,88
335,71
396,72
427,16
427,80
437,85
453,83
389,46
388,94
426,37
386,45
369,42
357,68
Year
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
Level
(cm)
354,39
368,88
385,89
394,98
340,56
369,23
380,84
359,86
336,05
291,39
280,91
229,75
269,83
300,13
302,08
267,32
288,70
305,28
Source : Direction Nationale de l’hydraulique
year
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
Level
(cm)
252,28
277,10
259,67
222,20
205,39
229,36
217,26
219,81
233,94
219,26
195,14
241,46
236,43
231,89
317,85
308,71
282,17
273,93
year
1998
1999
2000
2001
2002
2003
2004
2005
2006
Level
(cm)
300,23
310,30
320,56
295,67
258,82
299,15
263,68
279,13
293,58