Vegetation have good role to reduce surface run off and soil erosion, as the effect of reducing energy kinetic and increase infiltration. Therefore, vegetation is assumed could reduce sediment rate and reduce the fluctuation of river discharge, the research was done in Cijambu small watershed, Sumedang, West Java, since Januari 1994 until November 1994, the research was devided into three period. The land cover for each period were : first period was shrubs after clear felling ; second period was taungya system, where Pinus merkusii is the main crop ; third period was Pinus merkusii and cover crop such as Eupatorium inulifolium, Lantana camara, Melinis minutiflora and Ceropterid tartrea. The research result showed that : (1) Vegetation is effective in reducing fluctuation of river discharge. It was proved that the ration of the mean maximum discharge and the minimum discharge in the period shrubs after clear felling, taungya system and after taungya system. It means the condition of watershed became better after the land cover is more dense. (2) Run off coefficient is influenced by the density of land cover. This condition was proved by research result that coefficient run off in the harvesting area, taungya system and after taungya system were 58,5% , 52,17% , and 35% respectively. The same case also found for quick flow in earc period with the value of 976,8 mm, 666,6 mm and 387 mm respectively. It meant, better land cover will decrease surface run off and oil erosion/sedimentation. (3) The increase land cover by the vegetation will reduced peak discharge andc sediment concentration and increase delayed flow from 693,0 mm in the Pinus merkusii harvest area, 710,7 mm in the taungya system and 718,7 mm after taungya system. It means, the increase land cover by the vegetation could increase water yield in a certain watershed. From the above result, could be shown the important of vegetation in a certain watershed. It can reduce peak flow and sediment concertration and prevent flood down streams and increase and prolong base flow and hence prevent drought and assure availability water in dry seasond.