HOAL Petzenkirchen

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Map of the catchment area

The Hydrological Open Air Laboratory (HOAL) Petzenkirchen



The catchment is situated in Petzenkirchen, in the western part of Lower Austria (48° 9’ N, 15° 9’ E).

Catchment size

The catchment area is 66 ha.


The climate can be characterised as humid with a mean annual temperature of 9.5 °C and a mean annual precipitation of 823 mm/yr from 1990 to 2014. Precipitation tends to be higher in summer than in winter. Crop evapotranspiration (ETc) estimated by the FAO (1998) method using local climate data and crop growth information for this period was 471mm/yr. Annual evaporation estimated by the water balance ranged from 435 to 841 with a mean of 628 mm/yr (1990-2014). The natural surface water outlet of the catchment is known as the Seitengraben stream. Mean annual flow from the catchment in this stream is 4.1 l/s (or 195 mm/yr) (1990-2014). Mean flows tend to peak in the spring. The largest flood events on record occurred in 1949 and 2002 with estimated peak discharges of 2.8 and 2.0 m³/s, respectively. The highest discharge in recent times occurred in summer 2013 with 0.66 m³/s.


The subsurface consists of Tertiary sediments of the Molasse zone and fractured siltstone. The dominant soil types are Cambisols and Planosols with medium to poor infiltration capacities. Gleysols occur close to the stream.


The elevation of the catchment ranges from 268 to 323 m a.s.l. with a mean slope of 8%.

Vegetation/Land use

At present, 87% of the catchment area is arable land, 5% is used as pasture, 6% is forested and 2% is paved. The crops are mainly winter wheat and maize.

Context of investigation

The purpose of the HOAL project is to advance the understanding of water related flow and transport processes involving sediments, nutrients and microbes in small catchments. The HOAL catchment is ideally suited for this purpose, because it features a range of different runoff generation processes (surface runoff, springs, tile drains, wetlands), the nutrients inputs are known and it is convenient from a logistic point of view as all instruments can be connected to the power grid and a high speed Local Area Network (glassfibre). A number of innovative measurement techniques are being tested or will be tested including video cameras, distributed temperature sensing, soil moisture clusters, genetic markers as well as a range of isotopic techniques. The HOAL is operated jointly by the Vienna University of Technology and the Federal Agency for Water Management and takes advantage of the "Vienna Doctoral Programme on Water Resource Systems" funded by the Austrian Science Foundation.


See the basic instrumentation of the catchment here.

The basic infrastructure and monitoring in the HOAL consists of

- Atmospheric processes: four raingauges are installed to monitor spatial rainfall patterns. Three of the raingauges are distributed within the catchment and one is located close to its boundary.

- Atmospheric and soil processes: Monitoring at the weather station located approximately in the centre of gravity of the catchment includes air temperature, air humidity, wind speed and direction (all at three heights), incoming and outgoing solar and long wave radiation, wind load on the construction, rain drop size distribution, snow depths, soil heat flux and soil temperatures at different depths.

- Surface water: A total of 12 flumes were installed within the catchment to monitor discharge at 1 minute resolution from the inlet piped stream, tile drains, erosion gullies, springs and tributaries from wetlands. These flumes are the backbone of the HOAL. All flumes were calibrated in the Hydraulic Laboratory of the TU Wien to obtain a reliable stage-discharge relationship.

- Surface water: At the catchment outlet, the existing H-flume (dating from 1945 with a number of changes since) was upgraded in 2009. The maximum discharge capacity was increased and a number of additional sensors were installed including water temperature, electrical conductivity, turbidity (two probes from different makes), chloride, pH, nitrate. Grab samples are taken weekly for a range of chemical analyses including suspended solids and various compounds of nutrients. Additionally, autosamplers take water samples during events. A video camera was installed to monitor the water level in the flume and the functioning of the instruments.

- Groundwater: 23 piezometers were installed within the catchment where groundwater level and water temperature are monitored. Most of the piezometers are located along transects perpendicular to the stream to help understand stream-aquifer interactions. Two additional air pressure sensors were needed to correct the readings of the pressure transducers for the air pressure fluctuations.

Links to project webpages


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