Validating the Green-Ampt Analysis of Wetted Radius and Depth in Trickle Irrigation

Abstract

Depth and width dimensions of the wetted volume under trickle irrigation are of considerable practical importance. The depth dimension should coincide with the depth of the root system while the wetted radius should be related to the spacing between emitters and lines. Therefore, the wetted depth and width of wetted volume under an emitter should be an objective rather than an end result of the design process. A three-dimensional Green-Ampt analysis was applied to estimate wetted radius and depth in trickle irrigation for six soil series. A comparison of the measured and estimated results indicated that application of the Green-Ampt analysis of wetted radius and depth in trickle irrigation was appropriate to estimate the wetted radius on soil surface by using soil-saturated hydraulic conductivity, water entry head, soil moisture difference, saturated radius of the emitter source, and application time. An empirical equation was proposed to determine the saturated radius of the emitter source by using emitter discharge, and soil-saturated hydraulic conductivity. Then, by applying saturated hydraulic conductivity, saturated radius of the emitter source, water entry head and the application time, the wetted radius on soil surface may be calculated. Using saturated hydraulic conductivity, the depth of wetted pattern may be estimated by another proposed empirical equation after estimation of the wetted radius on soil surface. The depth of occurrence of maximum wetted radius may also be estimated after estimation of the maximum wetted radius by the third proposed empirical equation, using the saturated hydraulic conductivity of different soils.