1 3 Irrig Sci DOI 10.1007/s00271-014-0439-z ORIGINAL PAPER Numerical investigation of the influence of texture, surface drip emitter discharge rate and initial soil moisture condition on wetting pattern size Boštjan Naglic ˇ · Cedric Kechavarzi · Frederic Coulon · Marina Pintar Received: 24 July 2013 / Accepted: 22 May 2014 © Springer-Verlag Berlin Heidelberg 2014 content caused larger wetting pattern sizes in all direc- tions. When compared to the 2D tank experimental results, Hydrus-2D/3D predicted the wetting pattern dimensions with a relatively small root mean square error not exceed- ing 2.6 cm. The numerical data obtained for a wide range of textures provided the opportunity to refine the parame- ters of the Schwartzman and Zur model, which, when com- pared to experimental data from the literature, provided good estimates of wetting pattern dimensions. This sug- gests that this simple model, for which the only soil param- eter required is the saturated hydraulic conductivity, could provide a valuable and practical tool for irrigation design. Introduction Water withdrawal for irrigation represents more than 90 % of worldwide consumptive water use (Bates et al. 2008). For countries in development, a 14 % increase in irrigation water withdrawal is expected by 2030 without taking into account the impacts of climate change (Bruinsma 2003). Therefore, improvements in irrigation techniques as well as in water management will play a very important role in the near future in assuring the availability of water for both food production and competing environmental and human needs. Because of several advantages over other irrigation systems including its potential to save water, drip irriga- tion has become increasingly popular in the past decades. According to various estimates, the world area irrigated by microirrigation has increased from 6 Mha in 2006 (Rein- ders 2007) to 10.3 Mha in 2013 (ICID 16.7.2013). The general goal of drip irrigation system design is to provide irrigation water efficiently and uniformly to a crop and to help meet the evapotranspiration (ET) needs. At the same time, maintaining the desired water content within Abstract Knowledge of the dimensions of the wetted zone formed under point source surface drip irrigation is essential to the design of cost-effective and efficient irri- gation systems. Numerical simulations were carried out with Hydrus-2D/3D to investigate the influence of emitter discharge rates and initial soil moisture conditions on the wetting pattern dimensions of a series of soils with vary- ing textures. Numerical simulations of simple 2D soil tank irrigation experiments were also conducted on two soil types. Based on the simulation results, the parameters of the Schwartzman and Zur model were refined. The results showed a small influence of discharge rates >1 L h -1 on the size of the wetting pattern. The only major difference was observed for the rates lower than 0.5 L h -1 , where the larg- est wetting patterns were observed. Higher initial soil water Communicated by A. Furman. B. Naglic ˇ Plima d.o.o., Cesta Žalskega tabora 2, 3310 Žalec, Slovenia e-mail: bostjan.naglic@ihps.si C. Kechavarzi (*) Department of Engineering, University of Cambridge, Trumpington Street, Cambridge CB2 1PZ, UK e-mail: ck209@cam.ac.uk F. Coulon Department of Environmental Science and Technology, Cranfield University, Cranfield MK43OAL, UK e-mail: f.coulon@cranfield.ac.uk M. Pintar Biotechnical Faculty, Chair for Agrometeorology, Agricultural Land Management, Economics and Rural Development, University of Ljubljana, Jamnikarjeva 101, 1000 Ljubljana, Slovenia e-mail: marina.pintar@bf.uni-lj.si