the effectiveness of variable and constant wetted perimeter on simulation and uniformity of furrow irrigation

infiltration in furrow irrigation is 2-d which depends on both time and surface characteristics at which infiltration occurs. however, in many furrow irrigation models, infiltration is determined as a function of infiltration time opportunity, assuming the variation of weted perimeter is low along furrow. in order to compare the proposed asumptions, two zero-inertia furrow irrigation models were developed; one was ziwpv model, which considers the effectiveness of wetted perimeter, and the other was ziwpc model, which assumes a constant surface for wetted perimeter. solution of finite-difference equations is obtained with an explicit scheme. the results of two models were compared together using schwankl’s field data. the ziwpv model predicted well the advance time which was measured 157 minutes in the field. but ziwpc model understimated it which was 10.8%. cu and du were estimated 77.4 and 68.5 by ziwpv model and 93.1 and 89.4% by ziwpc model, respectively. however, they were measured in the field 77 and 64%, respectively. the average infiltrated depth in the field was measured 7.47 cm. but it was estimted 8.6 and 7.43 cm by ziwpv and ziwpc models, respectively. thus, taking into account the wetted perimeter effectiveness to calculate infiltration during irrigation improves infiltrated water uniformity, but overestimated the average depth of infiltration. also, furrow irrigation models which assume infiltration to be 1-d, predict well the average infiltration depth. but, they overstimated infiltrated water uniformity.