CHARACTERIZATION OF RAINFALL SPATIAL VARIABILITY AT A SCALE SMALLER THAN 1 KM IN A SEMIARID AREA (REGION OF NIAMEY, NIGER)

A network of 25 raingauges distributed over 1 km(2), in the Niamey reg ion (Niger), was monitored during the 1994 and 1995 rainy seasons. The statistical analysis shows that about 50% of the events present a hig h spatial variability. Three spatial structures can be differentiated by the geostatistical analysis of the recorded rainfields. Ar this sca le, a local measurement is not representative of the mean areal rainfa ll. The difference between the mean areal rainfall and point rainfall represents from 6 to 80% of the mean for the rainfall fields of more t han 10 mm.