Abstract
Scarcity of water has urged farmers, managers and engineers in the field of water resources engineering to explore the
parameters of drip irrigation for its high performance and optimal working. Wetting pattern of soil under drip emitter is one of
the most important parameters affecting the efficiency of the drip irrigation system. In this paper standard sand box model
experiments were executed to identify the wetting pattern of various soils under different emitter discharges. The tests were
performed on four types of soil including sandy loam, loam, clayey loam and clay. Equal volume of water was supplied in
each experiment. The wetted diameter and depth of soil for a single emitter were monitored with the help of sand box model.
The wetted radius on surface of soil and at some depth where it was maximum were measured in every experiment. Similarly,
the maximum wetted depth and the depth of maximum wetted diameter were recorded. The volume of wetted soil was estimated
using the measured data. The soil samples were collected and tested in the laboratory. The percentage of moisture in soil
samples was recorded by gravimetric method in laboratory. Finally, the optimal emitter discharge and conditions for an
efficient drip-irrigation system were obtained. The emitter discharge of 4 l/h was found to be the optimal for sandy-loam
whereas 3 l/h produced optimal results for the other three types of soil. Empirical equations were developed to determine the
maximum wetted radius and depth on the basis of different parameters including emitter discharge, irrigation time, soil bulk
density, hydraulic conductivity, initial and final soil-moisture-contents and percentage of sand, silt and clay in soil formation.
Subsequently additional data was obtained (for sandy loam and clayey loam) by varying emitter discharge over a broader range
(1.0 to 30.0l/h) to improve the effectiveness of equations. Values of the empirical parameters of the equations were determined
using “Generalized Reduced Gradient Non-Linear Optimization Technique”. The empirical equations with these parameters
performed well and produced reasonable accuracy (Nash and Sutcliffe coefficient up to 99%). The equations can be useful to
predict data for design of an efficient drip irrigation system in absence of resources to perform experiments.
