Length and Slope Effects on Runoff from Sodium Dispersed,Campacted Earth Microcatchments

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The effects of micro-catchment slope and length on runoff and erosion rates were studied under 18 rain storms to get information .. for design of water harvesting systems. Two replicates of a two factor experiment, including 1,5, 10, and 15~ slopes and 3-and 6- m lengths, were built on a gravely sandy clay loam (mixed mineralogy) using 11.2 t ha-I of mixed into the surface 2 to 5 cm of soil folowed by compaction with a 6-t roller after a heavy rain. Both slope and length had effects on runoff significant at the O.I~ probability level but the effect of rainfall intensity was not significant. The best fit linear model of runoff, Q, (em) n. rainfall, P, (em) was Q = O.858(P - 0.34) which explained about 98% of the variability in runoff on individual plots for individual storms but which explained no differences in runoff among treatments. A nonlinear model incorporating slope, J, (m/m) and length, or, (m) accounted for about 96% of the .. riability in average total runoff among treatments. This model, Q - ( ... .tel x-U13 + 0.183)(P - 0.339), shows that the important differences in runoff among treatments can be explained by slope and length alone for our conditions. Water quality analyses indicated that only a minor salinity problem but slight to moderate permeability problems might be expected. However, no apparent problems have arisen in 12 yr of grape and fruit tree (Prunu sp.) cultivation in a water harvesting system using our catchment on the same soil.
Soil Science Society Of America. Journal, 49, p. 734-738