ARS | Publication request: Measured and simulated soil weeting patterns under porous clay pipe subsurface irrigation

Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 21, 2008
Publication Date: June 1, 2009
Repository URL: http://www.ars.usda.gov/SP2UserFiles/Place/53102000/pdf_pubs/P2266.pdf
Citation: Siyal, A.A., Skaggs, T.H. 2009. Measured and simulated soil weeting patterns under porous clay pipe subsurface irrigation. Agricultural Water Management. 96:893-904.

Interpretive Summary: Many less-developed regions of the world lack adequate water resources and would benefit from the implementation of water-saving agricultural practices such as drip irrigation. However, modern drip irrigation technology is typically cost-prohibitive in these areas. A low-cost alternative is to irrigate with buried baked-clay pipes. With this technique, water seeps through buried porous pipes and into the soil. Applying the water below the soil surface helps minimize evaporative water losses. Maximizing the efficiency of clay pipe irrigation requires guidelines and criteria for system design and operation. In this research, we combined field data obtained in a rural area of Pakistan with computer simulations performed at the U.S. Salinity Laboratory to investigate the performance of pipe irrigation systems. The information provided by this study is helpful for determining the most cost-effective installation depth and system water pressure. This research will assist engineers and other workers trying to develop and implement water-saving irrigation methods for less-developed parts of the world.

Technical Abstract: Subsurface irrigation with porous clay pipe can be an efficient, water saving method of irrigation for many less developed arid and semi-arid regions. Maximizing the efficiency of clay pipe irrigation requires guidelines and criteria for system design and operation. In this study, experimental and simulated (with HYDRUS-2D) soil wetting patterns were investigated for subsurface pipe systems operating at different water pressures. Predictions of the soil water content made with HYDRUS-2D were found to be in good agreement (R2 = 0.98) with the observed data. Additional simulations with HYDRUS-2D were used to study the effects of various design parameters on soil wetting. Increasing the system pressure increased the size of the wetted zone. The installation depth affects the recommended lateral spacing as well as the amount of evaporative water loss. . For a given water application, the potential rate of surface evaporation affected the shape of the wetted region only minimally. Soil texture, due to its connection to soil hydraulic conductivity and water retention, has a larger impact on the wetting geometry. In general, greater horizontal spreading occurs in fine texture soils, or in the case of layered soils, in the finer textured layers.