Camber Bed Cultivation of Ground-Water (VLEI) Soils: II—Modifications of the System.

Abstract

Since the publication of a description of the camber-bed system of cultivation of vlei soils (Robinson et al. 1955), a considerable area of vlei land has been treated in this way, and the experience gained brought out points which required further investigation. Observations during the past two years have shown that the run-off from camber beds can be very high, and it is clear that before the system is put into operation the area should be examined to see if the run-off can be safely discharged into protected drainage ways without risk of damage to roads, culverts, cultivated land etc. In order to test these observations, a six-inch Parshall flume and a recording run-off gauge were installed at the Coffee Research Station, Ruiru, on a camber bed 30 feet wide and 566 feet long, with a fall of 1.15 feet. During the period 5th April to 5th May the rainfall was fairly light, with low intensity, and run-off was so small that it was not recorded, the total rainfall being 9.39 inches in 18 days. From 6th to 16th May, however, 14.84 inches of rain fell in 11 days, sometimes with considerable intensity, and the data in Table I were recorded. From 13th to 16th May, there was a constant flow which was just too low to be recorded, but it was estimated at about 1,500 gallons a day. If this flow is taken into account the percentage run-off is increased to 100 per cent over the greater part of this period. Even discounting this unrecorded flow, it will be seen from the table that the run-off can be as high as 90 per cent.