RAINFALL EROSIVITY AT ROMA, LESOTHO

Information on rainfall intensity is regarded as one of the essential factors for predicting soil erosion. Since many sites lack information regarding the intensity of rains, estimates have to be made. The study investigates the relationship between daily amounts of precipitation and rainfall intensity based on a discontinuous series of charts from 1985-1992 at Roma Campus, Lesotho. Records of daily precipitation during the period 1962-1992 were used to determine the frequency distribution of daily precipitation for individual months. Relationships between total daily amount and maximum storm intensity during 15, 30 and 60 minutes were established which may be used for intensity estimates at sites lacking intensity records. It is also shown that standard erosivity indices may severely underestimate the number of days with erosive conditions. If, in contrast, the actual infiltration capacity of the soils is compared to rainfall intensity, the number of days with erosive conditions for grazing land increase from 1.6 to 68 days/year. The corresponding figure for farmed land would be 6-7 days/year.