A study of some aspects of the hydrology of some irrigated soils of western New South Wales

Abstract

In an investigation of soil degeneration in an irrigation area adjacent to a channel, piezometric techniques were used to establish that seepage from the channel was the main source of water contributing to an abnormally high water-table, and by graphical integration methods it was possible to establish a rate of seepage which was verified using a numerical solution of the approximate equation äz/ät = KH/f . ä2z/äx2 The two-well method of Childs, Collis-George, and Holmes (1957) was used to establish that there was little or no difference in horizontal permeability between various sites but that the areas with no or degenerate vegetation were isotropic, while the normal areas in terms of plant behaviour and soil surface stability were anisotropic with a value for the horizontal component of permeability greater than that of the vertical component. These observations, together with observations of a high water-table and high rate of potential evaporation, are used to propose a consistent theory to explain the incidence of and the increase in size of degenerate areas predisposed to become saline.