WUR colloquium by Martine Broer

Geplaatst: 23-10-2008

Vermue & Van de Voorde [2005] examined the hydrological situation around the observatory and Niessen & Wesselius [2005] constructed a steady state 3D-model of the area directly around the observatory.

The objective of this study was to get a grip on water storage and water flow on the hill slopes around the observatory and to create a dynamic linear reservoir model for the hill slopes. This reservoir model is needed to transform the steady state 3D-model into a transient model.

 

During a short intensive field campaign emphasis was set to get information on the spatial variability of the area (vegetation, geology, hydrogeology) and on response times. This was done on the relatively steep slope east of the gravimeter, which is closest to the gravimeter, and on the less steep slope west of the gravimeter.

 

No distinct spatial variability of the upper soil layer was found. An infiltration experiment was performed, in order to test the transmissivity of the parent material (shales). On this small plot, the cracks were able to transport 0.3 l/s during 20 hours towards the valley. The water level below the gravimeter – downstream of the experiment – showed a quick rise after the start of the experiment with a maximum of  0.53 m water level rise five hours after the start of the experiment.

 

A linear reservoir model was constructed to be able to predict the amount of water flowing into the valley. The model consists of different reservoirs that represent layers on both the eastern and western slope. Not all model parameters could be quantified in the field. The canopy is an important reservoir in the model, because a large amount of precipitation can be stored in this reservoir. The western slope reacts faster on precipitation then the eastern slope, due to the lack of a weathered layer on the western slope. Base flow is not included yet in this model. As a result the outflow from the parent material in the valley can stop during long dry periods. Discharge measurements in the Silberleite show that also during longer lasting dry periods water is discharged, indicating at least some base flow conditions.

 

The calibration in this study was done for the eastern slope and shows promising results. A calibration for the western slope could still be carried out.


WUR colloquium by Martine Broer
Date: Thursday  30th  of  October  2008
Time: 13.30 uur  - 14.15 hrs
Venue: C45 (A109) Atlas Building, Droevendaalsesteeg 4, Wageningen
Supervisors: Roel Dijksma en Henny van Lanen