Investigating the Effect of Water Quality and Soil Texture on the Hydraulic Conductivity of Clay Pipes in Subsurface Irrigation

Considering the obscurity and variability observed in the characteristics of clay subsurface irrigation when utilizing saline water in different soil types, a comprehensive 2-year study was conducted to examine the impact of two water qualities (EC = 0.87 and 3.78 dS/m), on the seepage behavior of clay pipes. Laboratory and field tests were carried out under three distinct soil types, namely clay loam, sandy loam, and loam, with a hydrostatic pressure of 2 m. The laboratory-based seepage measurements enabled the development of a multivariable model capable of predicting the long-term seepage performance of clay pipes. Notably, water salinity significantly influences the model parameters, substantiating its effect on reducing the water yield of clays. Particularly noteworthy is the substantial decrease in the initial seepage rate observed with increasing irrigation water salinity. Moreover, a mathematical regression relationship characterized by a strong correlation was established to estimate the total volume of water passing through the pipes. The declining trend of seepage over time was consistent across all clay types, with regression models displaying a high coefficient of determination. The observed decrease in seepage values under both laboratory and field conditions highlights the sensitivity of these clay pipes, even when exposed to water of low salinity. This phenomenon can be attributed to the accumulation of solutes within the clay body pores over time, leading to a reduction in water permeability. Consequently, the diminished water permeability of clay pipes makes them unsuitable for sustainable long-term use in meeting the water requirements of agricultural and garden plants.