Hydrological monitoring installations

Measurement of the outflow of the whole catchment occurs at the outlet point of the pond. The outlet gauge (weir 2) was designed to measure discharge rates up to 250 l/s. This weir is a combination of tipping bucket and compound weir. The tipping bucket is used to measure small fluxes. Discharge exceeding the capacity of the tipping bucket is determined by the compound weir consisting of a rectangular notch with a V-notch cut into the centre of the crest. The discharge from the pond is controlled by the water level of the pond which is automatically recorded by two pressure transducers in the pond, one at the end of the pontoon and one close to the weir.

In the lower part of the catchment, subsurface clay dams were constructed and form a spring area where the groundwater can leak at the surface. At this point weir 1 was installed in August 2005. Weir 1 is designed as a V-notch weir in a rectangle 3.0 m x 0.5 m x 0.5 m concrete channel. Because of the very low discharge at this point, weir 1 is equipped with a 0.1 litre tipping bucket.

Early erosion events resulted in the formation of a network of erosion gullies. Two main gullies cut through the catchment surface down to the subsurface clay dams allowing groundwater exfiltration at the base of the gullies. Runoff components in these gullies are measured using stainless steel (V2A) H-flumes. The water table is scanned by ultrasonic sensors and the level signal is logged and transformed into flow rates. Flume 1 is a 1 FT-Hflume for flow rates up to 55 l s-1 and flume 2 is a 2 FT-H-flume for flow rates up to 315 l s-1. Flume 2 was combined with a 0.1 litre tipping bucket. In a second erosion gully with upwelling groundwater next to the spring area in the eastern part the continuous baseflow is measured by a subsurface drainage gutter (3.0 m x 0.5 m x 0.25 m) across the gully installed in June 2009. Water flux is registered by a 1 litre tipping bucket.

Within the catchment, 21 observation wells were installed to record groundwater levels. 17 of them were installed along the grid points immediately after the completion of the Chicken Creek catchment in September 2005. Additional four groundwater observation pipes were installed close to the permanent soil pits in May 2008. Some of these observation wells are equipped with water level loggers (pressure transducers).