Abstract

A detailed and intensive study was made within the Ultuna watershed during the months of November 1996 through February 1997. Groundwater levels and soil temperatures were measured as well as the total watershed discharge. A one-dimensional mathematical model was used to simulate the hydrological conditions in the field and study the effects of changes of soil physical parameters on simulated ground water levels (sensitivity analysis). A comparison was made between model calculations and field measurements to establish which model and soil parameters most influence ground water simulations. A comparison was also made of simulated and measured discharge to determine the relationship of one soil as compared to an expected range of spatial heterogeneity within the whole watershed. More extensive measured climate data was required for reliable winter simulations, especially measured longwave radiation and snow cover. Without such data the model simulated soil temperatures that tended to be lower than measured, especially during periods of snow. The changing of parameter values influenced the behaviour and movement of ground water. Changes in the saturated matrix conductivity (influencing sorption properties) of a soil had little or no effect on the results. The partitioning of the infiltrating water into bypass flow or saturated matrix flow induced no great changes in the simulated ground water level. This was explained by the fact that the infiltrating water caused changes in the saturated zone with the same delay independent of the partitioning of velocities in different pore sizes. The only observed difference was in the response time of the ground water level to infiltration, while the overall shape of the curve remained the same. Changes in the total saturated hydraulic conductivity, however, strongly affected simulated ground water levels, not only in the overall shape of the curve, but also in its response time and mean change of depth. Simulated discharge was three times greater than measured. This may be explained both by the watersheds topography and water storage capacities. The watersheds areal mean storage capacity may be larger than for the specific investigation plot. Measured data also implied that a certain amount of water was lost below the drainage system and this was not measurable at the discharge station

Keywords

hydraulic properties; ground water; clay soil; fluctuations

Published in

Avdelningsmeddelande / Sveriges lantbruksuniversitet, Institutionen för markvetenskap, Avdelningen för lantbrukets hydroteknik
1997, number: 97:3
Publisher: Institutionen för markvetenskap, avdelningen för lantbrukets hydroteknik, Sveriges lantbruksuniversitet

UKÄ Subject classification

Fish and Aquacultural Science
Agricultural Science

Permanent link to this page (URI)

https://res.slu.se/id/publ/29597