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Measurement modeling of soil‐water dynamics evapotranspiration of drained peatland soils
Author(s) -
Schwärzel Kai,
Šimůnek Jirka,
van Genuchten Martinus Th.,
Wessolek Gerd
Publication year - 2006
Publication title -
journal of plant nutrition and soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.644
H-Index - 87
eISSN - 1522-2624
pISSN - 1436-8730
DOI - 10.1002/jpln.200621992
Subject(s) - lysimeter , soil water , evapotranspiration , environmental science , water table , peat , groundwater recharge , groundwater , hydrology (agriculture) , soil science , water content , soil horizon , geology , aquifer , ecology , geotechnical engineering , biology
Natural peat soils serve as important sinks for nutrients, organic components, and water. Peat soils can pose major environmental problems when they are drained for agricultural production, which may change their role in the landscape from a sink to a source. To successfully restore and conserve peat soils, it is important to understand the soil‐moisture dynamics and water demand of drained peat soils for different climate and groundwater conditions. For this purpose, we conducted a series of lysimeter experiments with peat soils subject to different groundwater levels. Evapotranspiration (ET) rates and upward capillary fluxes in peat soils under grass were measured, while TDR probes and tensiometers were used to monitor the soil‐water dynamics in the lysimeter during the growing season. The lysimeter data were simulated using an extended version of HYDRUS‐1D to enable ET calculations using the Penman‐Monteith equation. A physically based approach was tested to predict the canopy resistance as a function of the average pressure head of the soil root zone. The numerical simulations closely followed the observed soil‐moisture dynamics in the lysimeter and were consistent with measured differences in ET rates for different groundwater levels. Besides average climate conditions, the effects of extreme dry and wet weather conditions on ET and groundwater recharge during the growing season were evaluated using the calibrated numerical model for different groundwater levels. Evapotranspiration rates during dry years depended very much on upward capillary flow from the water table and hence on the soil hydraulic properties. During wet years, however, ET was controlled mostly by the evaporative demand of the atmosphere, and much less by the soil hydraulic properties.