UPPER NIGER BASIN RECORDED LOWEST FLOW IN MARCH 2003

1.0 GENERAL COMMENT

Along the Upper Niger Basin in Mali at Koulikoro, downstream the Selengue dam in Mali,, the flow has been reduced to its lowest in recent years. The low flow has been on for some time and continued to have drastic effect on the downstream in the Middle and the Lower Niger.

Most of the tributaries have ceased flowing and the river Niger besides the base flow, is now being sustained by releases from major dams such as the Selengue in Mali, the Kainji, Jebba and Shirroro dams in Nigeria and the Lagdo dam in Cameroun along the river Benue, the biggest tributary of the Niger.

Unless there is early rainfall this year, it is feared that the continued low flow condition of the river Niger may be among the worst in the recent year that could have adverse effect the downstream population, fauna and flora..

For the analyses that was carried out on data recorded in March 2003, the Niger Basin was subdivided in 3 sub-basins with data in Table 1 analysed on the 4 reference stations namely; Koulikoro on theUpper Niger basin; Niamey and Kandadji on the Middle Niger; Lokoja on the Lower Niger basin.

Fig. 1 to 4 showed the hydrographs of these representative stations from December 2002 to March 2003 and compared with records of the hydrological years 1967/1968, 1984/1985, and 2001/2002. The 1967/1968 has the highest flood flow records in the past 50 years and the year 1984/1985 was the driest record in the series.

2.0 DATA COLLECTION AND ANALYSES

Hydrological data for the month of March 2003 were received from the following network stations:

Mali : Koulikoro, Ansongo, Dire, Banan koro and Nantaka along River Niger and Douna along river Bani;

Niger : Niamey and Kandadji stations along River Niger;

Nigeria: Lokoja along the river Niger

The selected stations for the hydrological data analyses for the month of March 2003 in the basin are as follows :

The Upper Niger Basin : Koulikoro along River Niger in Mali;

The Middle Niger Basin :Niamey and Kandadji alongriver Niger in Niger.

The Lower Niger Basin :lokoja along river Niger in Nigeria.

2.1 THE UPPER NIGER BASIN

2.1.1 KOULIKORO (MALI)

At Koulikoro the mean daily water level (H) during the month of March, year 2003, has the maximum, mean and minimum of 54 cm, 35 cm and 20 cm respectively, with their corresponding discharge of 113 m3/s, 79 m3/s and 55.8 m3/s. The maximum flow (113 m3/s) occurred on the 5th March 2003 and the minimum (55.8 m3/s) on the 31st March 2003.

Fig 1. shows the comparative hydrographs with different years 1967/1968, 1984/1985, and 2001/2002 with 2002/2003 from December 2002 to March 2003.

The flow recorded in March 2003 was among the lowest in recent years and is sustained by base flow and releases from Selengue dam upstream. These flow are lower than those of the years of comparison during the same period as shown in Fig 1.

Column 2 on Table1 is observed data recorded at Koulikoro in Mali during the month of March 2003.

2.2 MIDDLE NIGER BASIN

2.2.1 KANDAJI (NIGER REPUBLIC)

At Kandaji the mean daily water level (H) during the month of March, year 2003, has the maximum, mean and minimum of 310 cm, 262 cm and 232 cm respectively, with their corresponding discharge (Q) of 271 m3/s, 170 m3/s and 113 m3/s. The maximum flow (271 m3/s) occurred on the 1st March 2003 and the minimum (113 m3/s) on the 31st March 2003 as shown on Table 1.

Fig 2 shows the comparative hydrographs from December 2002 to March 2003, with the different years 1994/95, 2000/2001, and 2001/2002.

At Kandadji the flow recorded in March 2003 was also the lowest which is clearly lower than those of the preceding years during the same period as shown in Fig.2. Column 4 on Table1 is real time data recorded at

Kandadji in Niger during the month of March 2003.

2.2.1 NIAMEY (NIGER REPUBLIC)

At Niamey the mean daily water level (H) during the month of March, year 2003, has the maximum, mean and minimum of 231 cm, 191 cm and 163 cm respectively, with their corresponding discharge (Q) of 302 m3/s, 187 m3/s and 113 m3/s. The maximum flow (302 m3/s) occurred on the 1st March 2003 and the minimum (113 m3/s) on the 31st March 2003.

In Niamey the flow recorded during this month of March 2003 was also characterised by continuous decrease. The flow recorded was clearly lower than those of the preceding years during the same period with the exception of the 1984 (the driest period).

Column 3 on Table1 is observed data recorded at Niamey in Niger during the month of March 2003.

2.3.2 LOKOJA (NIGERIA)

Lokoja station, situated at the confluence of the river Niger and the Benue river has the maximum, mean and minimum mean daily water level during the month of March, year 2003, as 286 cm, 269 and 254 cm respectively, with their corresponding discharges of 2,740 m3/s, 2,473 m3/s and 2,240 m3/s. The maximum flow (2,740 m3/s) occurred on the 5th and 6th March 2003 and the minimum (2,240 m3/s) on the 29th and 30th March 2003.

Fig 4 shows the comparative hydrographs from December 2002 to March 2003, with different years 1967/1968, 1984/1985, and 2001/2002.

The flow recorded at Lokoja during March 2003 was characterised by fluctuation due to releases from Kainji, Jebba, Shirroro and Lagdo dams upstream. Flow at Lokoja this month is about nomal when compared with records those selected years as shown in Fig.4.

Column 5 on Table1 is real time data recorded at Lokoja in Nigeria during the month.

3.0 INFORMATIONS FROM OTHER DCP STATIONS IN THE BASIN

3.1 River Niger at Ansongo (Mali)

The maximum, mean and minimum flow discharge recorded during the month of March 2003 along river Niger at Ansongo in Mali were 364 m3/s, 195 m3/s and 105 m3/s respectively. The maximum occurred on 1st March and minimum on 31st March 2003.

3.2 River Niger at Dire (Mali)

The maximum, mean and minimum flow discharge recorded during the month of March 2003 along river Niger at Dire in Mali were 138 m3/s, 90 m3/s and 57 m3/s respectively. The maximum occurred on 1st March and the minimum on 31st March 2003.

3.3 River Niger at Nantaka-(Mopti (Mali)

The maximum, mean and minimum flow discharge recorded during the month of March 2003 along river Niger at Nantaka (Mopti) in Mali were 105 m3/s, 60 m3/s and 30 m3/s respectively. The maximum occurred on 17th March and the minimum on 27th and 28th March 2003.

3.4 River Bani at Douna (Mali)

The maximum, mean and minimum flow discharges recorded during the month of March 2003 along river Bani at Douna in Mali were 1.28 m3/s, 0.28 m3/s and 0.39 m3/s respectively. The maximum occurred on 1st March and the minimum on 27th to 31st March 2003.

4.0 CONCLUSION

Flow along the river Niger with the exception of Lokoja (the confluence of river Niger and Benue) has generally been reduced to its lowest in recent years. Unless there is early rainfall this year, it is feared that continued low flow condition of the river Niger may be among the worst in the recent year that could have adverse effect the downstream population, fauna and flora.

It should also be noted that except the river Benue, the major tributaries have ceased flowing and the river Niger besides the base flow, is now been sustained by base flows and releases from major dams such as the Selengue in Mali, the Kainji, Jebba and Shirroro dams in Nigeria and the Lagdo dam in Cameroun which serves the river Benue.

For more detailed information and your comments please, contacts us through either of the following e-mail addresses: cip@abn.ne .This Bulletin can also be found on the Niger Basin Authority's Web-site: http//www.abn.ne on the AOCHYCOS Websit: http//aochycos.ird.ne.