A method for surface irrigation design based on infiltration using the border strip as an infiltrometer

Abstract

Design for irrigation schemes requires a knowledge of the infiltration characteristics of the soil. This thesis summarised design procedures for border strip irrigation used in New Zealand to the late 1970's and the methods used to determine infiltration characteristics. Three farm sites representing up to 70% of the irrigable soils on the Canterbury Plains were used to obtain field data. The data was analysed by the Finkel and Nir method to obtain depth of water infiltrated with respect to time. A number of recognised infiltration equations was used to describe the data to which the Jobling equation fitted with the least error. A computer programme was written to carry out the calculations and a linear programme method was also used to analyse the field data. Relationships have been developed between the depth of water ponded on the strip and the unit flow of water down the strip and the height of pasture growing on the strip. The initial infiltration coefficient of the Jobling infiltration equation had a negative correlation with the antecedent soil moisture and was dependent on the soil type while the final infiltration rate (infiltration capacity) had a positive correlation with the height of water ponded on the strip. The infiltration characteristics were used together with other hydraulic data to develop tables which form the basis for surface irrigation design.