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Modellering av avdunstning utgående från markfuktighetsmätningar i moränmark
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Science.
1996 (Swedish)Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesisAlternative title
Modelling of Evaporation Based on Soil Moisture Measurements in Till Soil (English)
Abstract [sv]

En endimensionell SVAT-modell (Soil-Vegetation-Atmosphere) användes för att simulera avdunstning och uppskatta den kritiska vattenpotentialen där reduktionen av vattenupptaget börjar. Detta gjordes i en blandad tall- och granskog i norra Uppland för perioden 1 maj - 31 oktober 1994. Denna period var ovanligt varm och torr och gav därför en unik chans att studera vattenupptag och upptorkning. Som indata till modellen användes markfysikaliska egenskaper och dagliga meteorologiska data. Modellen kalibrerades med TBR-, tensiometer- och grundvattenståndsmätningar för samma period. Den kritiska vattenpotentialen uppskattades till -100 hPa och visade sig vara en känslig parameter i modellen. Reduktionen av vattenupptaget började i slutet av juni. Ytresistansen beräknades med hjälp av Lohammarekvationen och bladyteindex. De markfysikaliska egenskaperna hade stor betydelse för simuleringsresultaten. Dessa egenskaper var mycket osäkert bestämda på grund av svårigheterna att mäta i inhomogen moränmark. Modellsimuleringarnas överenstämmelse med markvattenmätningarna varierade mellan olika djup i marken.

Abstract [en]

A one-dimensional SVAT-model (Soil-Vegetation-Atmosphere) was used to simulate evaporation and estimate the critical soil water potential where the reduction of the water uptake begins. This was done in a mixed pine and spruce forest in the north of Uppland, Sweden for the period 1 May to 31 October 1994. This period was unusually warm and dry and gave a unique chance to study the water uptake and the drought. Driving variables to the model were daily meteorological data and soil physical properties. The model was calibrated with TDR- (Time-Domain Reflectometry), tensiometer and ground water level measurements from the site for the same period. The critical water potential was estimated to -100 hPa and appeared to be a sensitive parameter in the model. The reduction of the water uptake began at the end of June. The surface resistance was calculated from the leaf area index and the Lohammar equation. The soil physical properties were shown to be significantly affecting the results of the simulation. The determination of these properties was uncertain because of the problems to measure in an inhomogenous till soil. The model simulations agreed generally well with the soil moisture measurements in some layers but a good agreement for all layers was not possible to obtain.

Place, publisher, year, edition, pages
1996. , p. 29
Keywords [en]
Evapotranspiration, modelling, critical water potential, soil moisture, till soil, pF-curves
Keywords [sv]
Avdunstning, evapotranspiration, modellering, kritiska vattenpotentialen, markfuktighet, morän, pF-kurvor
National Category
Oceanography, Hydrology and Water Resources
Identifiers
URN: urn:nbn:se:uu:diva-391599OAI: oai:DiVA.org:uu-391599DiVA, id: diva2:1347745
Educational program
Matematisk-naturvetenskaplig linje
Available from: 2019-09-02 Created: 2019-09-02 Last updated: 2019-09-06Bibliographically approved

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