The sensitivity of a catchment model to soil hydraulic properties obtained by using different measurement techniques
✍ Scribed by Sharon H. Davis; Robert A. Vertessy; Richard P. Silberstein
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 236 KB
- Volume
- 13
- Category
- Article
- ISSN
- 0885-6087
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✦ Synopsis
Most studies on the use of physically based hydrological models have identi®ed saturated hydraulic conductivity (K sat ) as one of the most sensitive input parameters. However, K sat is also one of the most dicult landscape properties to measure accurately, casting doubt on the ability of modellers to estimate this parameter a priori for catchment simulations. Several studies have shown that K sat estimates are greatly in¯uenced by the measurement method used, primarily because of scale eects. In this paper, we evaluate the eect of K sat measurement method on catchment simulations aimed at predicting water yield from forested catchments. A series of simulations are conducted using the Topog Dynamic catchment model, with K sat estimated by means of the constant head well permeameter, small core 6Á3 cm  7Á3 cm and large core 22Á3 cm  30 cm methods. These were applied in a deep, permeable forest soil in which macropore ¯ow has been noted to occur. The three measurement methods yielded very dierent K sat estimates and these had a large eect on model results. The model predictions based on small core and well permeameter measurements were extremely poor, as these methods did not adequately account for preferential ¯ow through the soil. The large core estimates of K sat , which were one to three orders of magnitude higher than the values obtained by the other two techniques, produced good predictions of catchment discharge and known spatial patterns of water table depth. Our results highlight the need for caution when applying soil hydraulic measurements to catchment-scale models.