Macroscopic root-water-extraction models often do not adequately account for the non-uniform distribution of roots in the soil profile. We developed an exponential root-water-uptake model, which was derived from a measured root density distribution function. The model, incorporated in the Soil-Water-Atmosphere-Plant (SWAP) simulation model, was tested on a clay loam soil cropped to soybeans and on a sandy loam soil cropped to corn, near Ottawa. Comparisons of measured and simulated soil water contents with the exponential model, a linear depth-dependent model and a constant-extraction-rate model were also made. The exponential model performed satisfactorily (average relative errors 3 cm−3) and underestimated them (maximum error −0.09 cm3 cm−3) in the lower part. The exponential model and the linear model performed fairly similarly at the lower depths, but the exponential model gave better results in the near-surface horizons. The exponential model was sensitive to the root distribution coefficient and to the rooting depth, when the latter was approximately less than 40 cm. The results of this study suggest that the exponential root-water-uptake model as incorporated in SWAP is an improvement over those models, which do not account for the root distribution in the soil. Key words: SWAP, soil water simulation, root distribution, corn, soybeans, sensitivity analysis