Initially a henrispherical sprinkler type of rainfall sirnulator with manual oscillation was developed following the one used at IIT Kharagpur, West Bengal, India. The tests conducted revealed that distribution of sirnulated rain was not unform over the soil and the intensity of the rain could not be varied. Apart from the above, the drop size was also not uniform with respect to space and time. Considering various types of sintulators available, efforts were therefore made to correct the above deficiencies and develop an indigenous rainfall simulator by introducing a v-jet nozzle for uniform drop size connected to automatic oscillation system ( l6 oscillations per minute) fitted with a Solenoid value attached to a timer for spraying to effect changes in the solenoid valve attached to a timer for intermittent spraying to effect changes in the intensity of simulated rainfall, The clean water is pumped using a reciprocating pump having a facility to deliver the water at a constant pressure. The specification and treatment of rainfall simulator is presented below.

· Type of rainfall simulator: nozzle type

· Tray size – 1.5 x 1.00 m

· Time of operation- 15 minutes

· Antecedent condition : Dry and wet

· Treatment Slope - Vertical mulch with 0.5 m interval @ 6 t/ha with 6 cm

height across the

· slope 1 to 2 %

· Observations- Runoff and soil loss observations* were taken in bare and

vertical mulched plot

· Soil type- Vertisols

The Initial characteristics of the soil determined were Bulk density 1.33 g per cc, particle density 2.04 g per cc, pore space 34 percent, hydraulic conductivity 0.8 mm per hr, clay 545.5 g per kg, sand 232.7 g per kg and silt 211.5 g per kg.

Dear Ashok Kumar Singh, thank you for your answer.

For my part, I have already used in laboratory experiments, a rainfall simulator equipped with a conical jet nozzle (TEEJET and VEEJET types) fixed at 3.6 m high above the soil flume test, connected to an oscillation system in order to ensure the watering of the total soil surface. My results gave excellent similarity to those of Laws. Currently, I am working on another model of rainfall simulator equipped with several nozzles but the constraint is that these nozzles are placed at 50 cm from the soil surface.

Best regards.

It depends on the type of the simulator (nozzles):

1- under pressure (falling with an initial velocity)

2- without pressure (free fall)

If you use the without pressure nozzle, the height of the nozzle is very important as the simulated raindrops needs at least 7-8 meters to reach the critical velocity equal to the natural raindrops. While in case of the under pressure nozzles, the velocity depends more on the initial pressure not the height of the nozzles.

In addition, the height of the nozzles may change the raindrop diameter and the density of the raindrops in a given area on the soil surface. All these changes can affect the kinetic energy of the rainfall and rainfall erosivity.

In this paper, we attempted to review the soil erosion studies conducted throughout the globe using Revised Universal Soil Loss Equation (RUSLE). We searched the SCI, Scopus, Web of Science, Google Scholar database and various theses for this study. Though RUSLE is the most widely used model for estimation of soil erosion, the factors, namely rainfall erosivity, soil erodibility, slope length and steepness, cover management and conservation practice; vary greatly over different climatic zones, soil properties, slope, land cover and crop phase, respectively. Depending upon those variations, researchers have developed various sets of equation for different factors of RUSLE. These equations can be useful to map soil loss for many places on this planet.

Article A Review of RUSLE Model

What are the stages adopted in this methodology?

The use of artificial rain provided by conical jet nozzles fixed at different heights and evenly distributed over a 2m² floor pan.

The nozzles are then supplied by a water tank with a regulated flow rate and a given pressure.

The soil put in place is initially watered to saturation so that runoff is generated instantly upon impact of raindrops.

Once the flow is established, the sediment rate (soil particles) is measured at the end of the soil tank at regular time intervals.

Issam Benali

Abdulvahed Khaledi Darvishan

Exactly.

In a previous study, we concluded that the kinetic energy of the rainfall (which depends on the mean raindrop diameter and its mass, in other words its density) is the most important factor to consider as responsible for soil surface erosion.

However, in a recent study, which is underway, we have found that the effect of kinetic energy is not at all the same when working in rill and interrill soil erosion, instead of sheet soil erosion.

Yes, it is logical.

Because the raindrop kinetic energy is main and dominant detachment and transport factor when you study sheet erosion, while the energy of runoff (detachment and transport the soil particles inside the rills) may play the most important role when you study the rill erosion. @Aziz Maaliou

Which is interpreted by the close relationship between the rain power (rainfall) and the stream power (runoff). Thanks for your clarification Abdulvahed Khaledi Darvishan