As predicted last weekend heavy rain fall occured in eastern Austria. Also the HOAL was affected by high precipitation rates.
In 24 hours around 90mm of rainfall occured and this led to a discharge rise at the catchment outlet from 2 l/s to around 1000,0 l/s. Compared to the mean rates (820mm/year mean annual precipitation; 4,0 l/s mean annual runoff) this was a high event which we were happy to catch with our sensors and installations. Several water samples were taken automatically and are currently under analysis for chemical and physical parameters in the laboratory.
Due to the old age of the H-Flumes and the poor condition, new ones were dimensioned, designed, manufactured and installed. A total of eight new "modified H-Flumes" made of stainless steel were installed. The measured data can be used for calculating the flow paths, but also for the parameterization of various hydrologically models.
Around the start of this year the disicion was made to install new measuring weirs. These weirs are designed according to the "Field manual for research in agricultural hydrology" from the United States Department of Agriculture (Handbook number 224). By evaluating the existing measurements over the past eight years, it was decided to use modified H-Flumes. These modified H-Flumes can measure higher flows through raised walls. Other advantages are less welding work and therefore little warping of the stainless steel, and not to forget the price-performance efficiency.
The calibration process for establishing the water level-discharge relationship can be seen in the pictures.
Shallow core drilling to confirm the occurence of biogeochemical hotspots delineated with geophysical imaging
On 14th of November, two boreholes with depths of 8 and 6 m respectively, were drilled at the HOAL site next to the stream in the alder forest area. Previous geophysical investigations in this area have revealed a significant anomaly characterized by high induced polarization signatures, which so far has been interpreted as the accumulation of biominerals such as iron sulfides associated to the occurrence of a biogeochemical hot-spot.
Such hot-spots are spatially constrained areas associated with disproportional high rates of microbial activity and the enhancement of biogeochemical processes, such as the precipitation of minerals as metabolic products. As part of the research activities, we have been working on the development of geophysical methods to delineate the occurrence and geometry of such hot-spots; thus, the two boreholes were planned to compare the geochemical status of the sediments from material recovered within the expected biogeochemical hot-spot, and a control point away of the geophysical anomaly.
Initial analysis of the sediment reveal large contents of organic matter in the materials within the geophysical anomaly, which are not observed in the material recovered in the control drill. Further analysis in the laboratory will be conducted to gain detailed information about physical and geochemical parameters, as required to for the quantitative interpretation of the geophysical data.
On the 5th of June, a group of students of the Vienna Doctoral Programme on Water Resource Systems, with a research interest focusing on hydrology, visited the Hydrological Open Air Laboratory, HOAL. They got an introduction about the history and ongoing projects of the Institute for Land and Water Management Research. Then they visited the laboratories of the Institute, to learn about the experiments and physical and chemical measurements conducted there. Then the Hydrological Open Air Laboratory was introduced by the HOAL manager, which was followed by an excursion to the catchment, where the students learnt about the long-term and specific field measurements and the general instrumentation of the catchment. Some pictures from the day: