Comparative analysis of the actual evapotranspiration of Flemish forest and cropland, using the soil water balance model WAVE

Abstract

Abstract. This paper focuses on the quantification of the green -vegetation related -water flux of forest stands in the temperate lowland of Flanders. The underlying reason of the research was to develop a methodology for assessing the impact of forests on the hydrologic cycle in comparison to agriculture. The tested approach for calculating the water use by forests was based on the application of the soil water balance model WAVE. The study involved the collection of data from 14 forest stands, the calibration and validation of the WAVE model, and the comparison of the water use (WU) components -transpiration, soil and interception evaporation -between forest and cropland.For model calibration purposes simulated and measured time series of soil water content at different soil depths, period March 2000-August 2001, were compared. A multiplesite validation was conducted as well. Actual tree transpiration calculated with sap flow measurements in three forest stands gave similar results for two of the three stands of pine (Pinus sylvestris L.), but WAVE overestimated the actual measured transpiration for a stand of poplar (Populus sp.).A useful approach to compare the WU components of forest versus cropland is scenario analysis based on the validated WAVE model. The statistical Profile Analysis method was implemented to explore and analyse the simulated WU time series. With an average annual rainfall of 819 mm, the results reveal that forests in Flanders consume more water than agricultural crops. A 30 years average of 491 mm for Correspondence to: W. W. Verstraeten (willem.verstraeten@vito.be) 10 forests stands versus 398 mm for 10 cropped agricultural fields was derived. The WU components, on yearly basis, also differ between the two land use types (transpiration: 315 mm for forest and 261 mm for agricultural land use; soil evaporation: 47 mm and 131 mm, for forest and cropland, respectively). Forest canopy interception evaporation was estimated at 126 mm, while it was negligible for cropland.

An efficient workflow to accurately compute groundwater recharge for the study of rainfall-triggered deep-seated landslides, application to the Séchilienne unstable slope (western Alps)

“…In addition, pedotransfer functions can also be used for runoff estimation. Lastly, vegetation coefficients are available from local surveys (Gochis and Cuenca, 2000;Verstraeten et al, 2005;Hou et al, 2010), but can also be found in the literature for many species (Allen et al, 1998).…”

“…2a). The ET c is a lumped parameter including potential transpiration, potential soil evaporation and canopy interception evaporation (Verstraeten et al, 2005). In the proposed computation diagram workflow (Fig.…”

“…For K c estimation, the proportion of beeches and conifers is assumed to be identical for the Séchilienne forest (each 50 % of forest subarea) and other species are ignored. K c values are set to 0.71 and 0.97 for conifers, and to 0.78 and 0.9 for beeches according to Verstraeten et al (2005). Most pastures are anthropogenic and consist of grass.…”

“…The minimum and maximum K c values are estimated from the literature and are assigned respectively to 4 February (middle of winter) and 6 August (middle of summer) of each year. A daily linear interpolation is performed for K c between these two dates (Verstraeten et al, 2005).…”

Remotely sensed soil moisture integration in an ecosystem carbon flux model. The spatial implication

“…Fortunately, in situ soil moisture data for 1998 were made available by the University of Tuscia (except for the NL1 site made available by Wageningen University and the BE2 site obtained from Verstraeten et al 2005).…”