Seal formation at soil surfaces is significantly affected by raindrop kinet
ic energy (KE). Soil sealing enhances runoff and soil erosion. It has been
hypothesized that in soils exposed to vain (i) runoff and interrill erosion
levels in soils previously irrigated with effluents differ from those in s
oils previously irrigated with fresh water (FW), and (ii) that the differen
ce in runoff and interrill erosion between the previously irrigated effluen
t and FW samples depends on rain KE. The effects of four droplet KE levels
(3.6, 8.0, 12.4, and 15.9 kJ m(-3)) of distilled water (DW) on runoff and w
ash erosion of four smectitic soils that had been irrigated for many years
with fresh water or effluents was studied with a drip-type rain simulator.
The soils used were a loamy loess (Calcic Haploxeralf) from Be'er Sheva Val
ley, a dark brown sandy clay vertisol (Chromic Haploxerert) from the Pleshe
t Plains (vertisol HH), and two dark brown heavy clay vertisols (Chromic Ha
ploxerert) from Zevulun Valley (vertisol Y) and Western Galilee (vertisol E
), Israel. For all soils, total runoff and wash erosion values increased wi
th the increase in rain KE. Total runoff levels were lower for the FW-irrig
ated samples than for the effluent-irrigated soils, except for the highest
KE where no differences in runoff between the two types of soils was noted.
Conversely, for each soil and each rain KE, wash erosion was higher in the
effluent-irrigated samples than in the FW-irrigated ones. Total runoff was
affected mainly by changes in rain KE at the lower to medium range of the
KE studied. Thus, the effects of irrigation water quality (i.e., effluents
vs. FW) on total runoff was pronounced mainly at the low-to-moderate rain K
E range; at high rain KE, the effects of irrigation water quality on runoff
were negligible. Wash erosion was affected mainly by changes in vain KE at
the medium-to-high KE range studied. That wash erosion increased markedly
at the high rain KE values, despite the negligible change in runoff level,
suggested that for KE greater than or equal to 12.4 kJ m(-3), seal formatio
n was completed, and the contribution of runoff in facilitating transport f
or the entrained material was secondary to the role of soil detachment in d
etermining wash erosion. The dependence of wash erosion (through soil detac
hment) on rain KE was greater than its dependence on the quality of the irr
igation water that the soil was exposed to in the past (FW vs. effluent).