Infiltration and hydraulic behaviour of an anguiform furrow in heavy texture soils of Iran

Abstract

Surface irrigation is used in smooth and land-levelled areas. Since land levelling is costly and it is not technically feasible in sloping lands, farmers in these areas in the Islamic Republic of Iran use anguiform (snake-shaped) furrow in traditional fashion instead of a straight furrow, particularly in heavy texture soils. Hydraulic and geometric parameters are different for anguiform furrow irrigation compared with the straight furrow irrigation. Research was conducted to determine the parameters of the Lewis–Kostikov infiltration equation and flow hydraulic and geometric parameters for an anguiform furrow in comparison with those for a straight furrow irrigation. The furrow geometric parameters were found to be variable in various furrow types and irrigation events. Differences were more pronounced between irrigation events than between furrow types. The Manning roughness coefficient in the anguiform furrow with real flow path was lower than that in the straight furrow in both the first and the next irrigations. The recession time in the anguiform furrow is higher due to greater water storage in upstream end stations. The basic infiltration rate in the anguiform furrow is higher (22 and 48% in the first and the next irrigations, respectively) than that in the straight furrow. The infiltration coefficients k were higher (two orders of magnitude) and the exponents a are smaller (about half) in the anguiform furrow than the straight furrow. Further more, it was indicated that the flow hydraulics in the anguiform furrow can be estimated by Fok–Bishop equation using the water surface hydraulic gradient, corresponding furrow geometry parameters and infiltration equation with the real water flow path.