LOW FLOW DISCHARGE MEASUREMENT EXERCISE

LOW FLOW DISCHARGE MEASUREMENT EXERCISE

The Nigeria Hydrological Services Agency, in line with one of her mandates embarked on a Nationwide River Discharge Measurement on all the Hydrological Stations (Gauging Sites) on Rivers Niger and Benue and their tributaries.

Considering the widths, depths and the flow patterns of the Rivers Niger and Benue and their tributaries and to obtain the best result, the Agency deployed the use of Acoustic Doppler Current Profiler (ADCP), one of the best equipment in the field of Hydrometry that measures real-time flow rates. Two methods of deployment were used as follows:

• Manned Boat using Riverboat
• Over a bridge using Riverboat and Hydrolink SL Series Wireless Data Transceivers with a range of 20 miles.

The choice of the method of deployment to engage at a specific site was based on the location of the site, safety and convenience in other to obtain the best result. In accordance with global best practices, four transects were usually taken at each gauging station.

POST FIELD PROCESSED DATA

The raw data obtained from the fieldwork was meticulously processed and the results of the discharge measurement data carried out on rivers Niger and Benue and their tributaries are been used in  updating rating tables/curves for flood forecasting, mitigation and control for sustainable water resources management.

BRIEFS ON SOME IMPORTANT HYDROLOGICAL STATIONS VISITED

1. RIVER NIGER AT JIDEREBODE: The station is in Kebbi state, close to the border of Nigeria and Benin/Niger Republics. The station monitors the flow of River Niger into the country from Niger Republic. The station is equipped with a Data Collection Platform (DCP) and Staff Gauge. Discharge (Q) measured on 12/02/2018: Q=663m³/s , Water Level=1.62m
2. RIVER NIGER AT KAINJI: Kainji Dam is the first Dam on river Niger within the Nigerian portion of the River Niger, with Jebba Dam 100k downstream. The station is on the Dam crest equipped with DCP to measure the inflow to the Dam and Staff Gauge to measure the tail raise (outflow). Discharge (Q) measured on 14/02/2018: Q =1,250m³/s , Water Level=104.09m

• RIVER NIGER AT BARO: the station is located about 100km upstream of Lokoja station on river Niger. Discharge (Q) measured on 4/03/2018: Q =3,540.422m³/s , Water Level=5.35m

660. RIVER NIGER AT LOKOJA: The station is located in Nigeria Inland Water Authority (NIWA) and equipped with DCP. Discharge (Q) measured on 3//03/2018: Q=1,660.809m³/s , Water Level=3.023m
661. RIVER NIGER AT ONITSHA: The station is downstream of the Confluence of Rivers Niger and Benue. Discharge (Q) measured on 1/03/2018:

Q =1,847.679m³/s , Water Level=2.52m

1. RIVER BENUE AT WUROBOKI: This is the station that monitors the flow of River Benue from Cameroon into Nigeria. It is equipped with DCP and manual staff gauge. Discharge (Q) measured on 22/02/2018:

Q =295.392m³/s, Water Level=2.77m.

The field work is an on-going exercise which is done at least twice in a year to capture the high and the low flows in the months of February/March and September/October respectively.