Hydrological Assessment and Discharge Determination of River Jarkwami for Sustainable Water Resources Management in Kwami Local Government Area, Gombe State, Nigeria
Abstract
Reliable river discharge information is essential for flood prediction, irrigation planning, reservoir management and sustainable water resource development. However, most tributaries within the Gongola Basin in semi-arid Northeastern Nigeria lack gauging stations. This study characterizes the discharge regime of River Jarkwami, a seasonal tributary of River Morom that drains into Dadin Kowa Reservoir on the Gongola River in Gombe State, using inexpensive staff-gauge and float techniques suited to data-limited developing regions. The upstream catchment was delineated with ArcGIS 10.1 and the SRTM Digital Elevation Model. Field observations of water level, flow velocity and channel breadth were conducted twice daily, at 07:00 and 18:00, from May through October 2023, representing the 2023 hydrological year, at the Jarkwami Bridge gauging station. Flow velocity was estimated using the float method and verified with Manning's equation. Cross-sectional area was calculated as depth × breadth, discharge was obtained using Q = A × V, and a stage-discharge rating curve was established. The results indicate that the upstream catchment covers 225 km2 and has a dendritic drainage network consisting of 70 streams: 57 first-order, 9 second-order, 3 third- order and 1 fourth-order streams. The mean bifurcation ratio is 3.82, drainage density is 1.21 km/km2 and total stream length is 271.8 km. The catchment comprises 25 sub-basins ranging from 0.76 to 59.93 km2, with a mean stream length of 13.73 km. At the gauging station, the channel measures 17.1 m in breadth. Mean float velocity was 0.18 m/s, ranging from 0.07 to 0.37 m/s, with the maximum recorded in September (0.37 m/s) and the minimum in October (0.07 m/s). Monthly water level averaged 21.3 cm, reaching its lowest value in May (1.27 cm) and its highest in September (58.2 cm, with a peak of 85.34 cm on 10th September). Mean instantaneous discharge was 5.76 m3/s, ranging from 0.60 to 20.7 m3/s, while cumulative IIARD International Journal of Geography & Environmental Management seasonal discharge totaled 368.8 m3/s over 64 effective flow days. September accounted for 40.1% of the total seasonal discharge, indicating a single-maximum regime characteristic of tropical continental climates. Discharge was influenced by rainfall intensity and duration, catchment size and elongated form, highly permeable sandy ferruginous soils, undulating terrain (370-670 m), sparse derived savanna vegetation and anthropogenic activities such as open grazing, farming, soil excavation and sand mining. The staff gauge and float techniques were effective, cost-efficient and reliable for small-medium seasonal rivers, exhibiting excellent performance, as demonstrated by the rating curve Q = 0.42h^1.65 (R2 = 0.87). Although turbulence, debris, water surges and limited vertical range presented limitations, these were addressed through strategic site selection. The study establishes baseline information for forecasting inflows into Dadin Kowa Reservoir, scheduling irrigation on the Kwami Fadama lands, issuing early flood warnings, and evaluating affordable techniques for ungauged basins in semi-arid Nigeria.
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