Dissolved matter fluxes in the inner delta of the river Niger

1998

Colloque

Bricquet Jean-Pierre, Gourcy Laurence, Mahé Gil, Orange Didier, Picouët Cécile, Olivry Jean-Claude

Johnson A.I. (ed.), Fernandez-Jauregui C.A. (ed.), Hydrology in the humid tropic environment (La hidrologia en el medio tropical humedo)

Wallingford : AIHS, 1998, p. 435-445 (AIHS Publication ; 253).

Hydrology in the Humid Tropic Environment : Symposium, Kingston (JAM), 1996/11

This study is part of the EQUANIS programme, the objectives of which are (a) estimating inputs from the River Niger to the inner Delta ; (b) computing the hydrological balance ; and (c) monitoring the quality of water in the central lacustrine basin. Eleven sampling locations were selected near gauging stations, both on the Niger River and its main tributary of the Bani River. Those sites have been sampled weekly since July 1990. The inner delta of the Niger River is a system particularly subject to sahelian and sub-desert climatic conditions and characterized by large flood plains. Time series of input water volumes in the inner delta, and of the water losses within it, show that the water losses are high, due to the intense evaporation, and vary from 6 to 40 km3. The water losses reach their maximum during the wettest years - up to 47%, and minimum during the driest years - only 32%, due to the reduction of the flooded area. The surface of the flooded area is inferred from the hydrological balance. The preliminary results of this study indicate that the Niger and Bani rivers have low levels of dissolved element concentrations. The mean conductivity values, ranging from 50-80 microSiemens/cm, increase regularly during the low water stage and decrease drastically with rising water. The pH values are slightly basic, ranging from 7.1 to 8. silica and bicarbonates are the main dissolved species ; they always represent more than 75% of TDS. In May, when the rising water stage begins, the waters are poorly mineralized at the input of the delta, while they have been enriched during the dry season in the delta. A good mass balance is found between inputs and outputs through the delta. However, a disequilibrium appears at the sampling sites within the basin, which could be partially linked to poor mixing between the Niger and Bani river waters... (D'après résumé d'auteur)

Transports solides et qualité physico-chimique des eaux [062MECEAU04]

COURS D'EAU ; MATIERE EN SOLUTION ; MATIERE EN SUSPENSION ; SOLUTE ; BILAN HYDROLOGIQUE ; FLUX HYDRIQUE ; EVAPORATION ; QUALITE DE L'EAU ; CYCLE HYDROLOGIQUE ; VARIATION SAISONNIERE ; ETUDE REGIONALE

MALI

Fonds IRD [F B010021124] ; Montpellier (Maison des Sciences de l'Eau)

fdi:010021124