Transport of carbon, nitrogen, phosphorus, and major solutes in the Gambia River, West Africa1

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Abstract
Transport of solutes and particulate materials and their variation with discharge were studied for 1 year (July 1980–June 1981) in the Gambia River in the tropical savanna of West Africa. The water is a dilute (flow‐weighted mean total solutes, 40.6 mg·liter‒1) solution of SiO2 and HCO3‒ (75% of total solutes by weight). Na+, K+, Cl‒, and total dissolved nitrogen showed no significant relation with discharge. Ca2+, Mg2+, HCO3+, conductivity, and SO42‒ decreased as discharge increased, while total dissolved phosphorus increased with discharge. After an initial increase SiO2 was independent of discharge. Dissolved organic carbon displayed counterclockwise hysteresis with rising and falling discharge. Particulate phosphorus and total particulate materials displayed clockwise hysteresis. Total transport amounted to 9.66 t·km‒2·yr‒1. The transport rates of both dissolved and particulate organic C are among the lowest ever reported. The low transport of total particulates and solutes is attributed to lack of relief and the lithology of the catchment.