Water quality Bodensee/Lake Constance
Current focus
The group is currently trying to specify its data formats so that the technology developers can see how the Lake Constance data is stored. This will enable the exchange of data with the ongoing Bodensee (Bodensee being the German name for Lake Constance) online database. At the moment there is no specific research work being undertaken at Lake Constance, as GENESIS is currently in phase 2 of the overall project, in which Kobus-Partner is notvery strongly involved.
Preparatory work
Nevertheless there is a great deal of work to do to prepare for the Summer meeting of the GENESIS partners, which some potential end-users of the technology from Lake Constance will also attend.
This work is at an early stage, and issues like project coordination are still being discussed, as well as just which end-users should attend. Kobus-Partner's role within GENESIS is centred largely on phase 3, where the GENESIS tools will be tested.
Testing phase
The results from the first two phases of the project will have a significant impact on the testing phase, the plans for which are subject to ongoing change in line with the emergence of new research. At this stage it is difficult to say exactly how GENESIS will be applied and in how much detail, because of course there are several different pilot sites within the project, each of which faces different problems.
Contingency planning
Lake Constance is a major resource of drinking water, used by more than 4 million people, and unforeseen weather events can have a significant impact on key parameters. Water speed increases during floods, while measurements also show that this also causes turbidity to rise, a key issue for drinking water suppliers.
Drinking water is typically taken from a depth of around 60 metres, yet flood events have an impact on water quality at both the surface and greater depths. The work of the GENESIS project in monitoring and assessing water quality, as well as warning of possible health risks, will help address the water quality issues floods often cause.
Project Overview
Lake Constance is a well-observed and well-monitored lake and so this pilot provides the opportunity to validate the IT-developments of GENESIS and receive feedback from possible end users of GENESIS. The pilot directly addresses the central objectives of GENESIS to study the spatialisation of the diffuse pollution index to support drinking water, inform the public about current bathing water quality, and enhance information flow in cases of accidents with hazardous substances.
The role of the Bodensee/Constance Lake pilot in GENESIS
- To test and verify the principles of methodologies elaborated on the two other pilot sites.
- To evaluate the ownership capacity of results and IT tools.
Lake Constance
Lake Constance, a large pre-alpine lake, is an unregulated natural water body of very high ecological value, a unique tourist attraction and an important drinking water resource. More than five million inhabitants are currently supplied with drinking water from Lake Constance and therefore the lake water quality has to be protected from pollutions, and the risk of accidents from hazardous substances needs to be minimised. This is the aim of the AWBR, Arbeitsgemeinschaft Wasserwerke Bodensee Rhein (Association of Waterworks Lake Constance-Rhine), a politically and economically independent organisation of all water suppliers around Lake Constance.
Map of Lake Constance
Lake Constance is under a common responsibility of all riparian countries: i.e. Germany, Austria and Switzerland while the International Commission of Lake Water Protection Bodensee (IGKB) takes care of the environmental development of the lake and compiles guidelines to the local legislatives.
The average annual inflow to Lake Constance is 370 m3/s and 90 per cent of its inflow is discharged from the Alpine Rhine. Due to the alpine catchment, low water level conditions occur during the winter season, with the highest water level reached in early summer caused by snowmelt. Lake Constance consists of two lakes, the larger Upper Lake and the smaller Lower Lake. The main basin in the Upper Lake has a maximum depth of 350 m. The Lower Lake is only 40 m deep.
The watershed of the lake is shared by Germany, Austria, Switzerland and Liechtenstein. The watershed has an extension of 11.500 km2, of which more than 50 per cent is located in the upper alpine region.
Ecological Development
Observed phosphorous concentration in Lake Constance between 1951 and 2005
Due to the industrialisation and the population growth in the watershed of Lake Constance the nutrient load increased in the 1960's and the 1970's. The result of this was bad water quality with large algae plumes in summer time. Over the last 40 years the aforementioned eutrophication process has been stopped by enhancing the sewage treatment systems in the complete watershed. Due to this, the sewer network is now at a very high standard and all wastewater is treated in sewage plants. The success of these international efforts can be identified by the development of the yearly monitored total phosphorous concentration in the lake. For example, the highest phosphorous concentrations of the seventies, with values of more than 70 µg/l have decreased to values similar to before the eutrophication started.
Current Monitoring and Lake Management
The current information and communication flow for Lake Constance takes place dependent on the different issues of management. The following capabilities are installed:
- Hydrology : The hydrology data, such as inflow to the lake, is collected from the different hydrological services. The data is presented via web services with access to real-time measurements. The common internet-platform provides the public with links and information about the inflow conditions and water table of Lake Constance. In cases of flood events, the flood event forecast centre provides the end user with information about the lake level and the discharge of the tributaries from federal state Baden-Wuerttemberg. Similar services are acting in the other riparian countries.
- Damage defence for Lake Constance: In case of accidents in the watershed or on the lake the local authorities, both the water police and the fire brigade are informed. A digital alarm map containing all sensitive locations such as drinking water abstractions is also available.
- Monitoring: The lake is monitored by the Institute of Lake Research in Langenargen under contract of IGKB. A monitoring routine has been established and the data garnered through it is published in yearly reports concerning the current status of lake water quality.
Hazards and Risks
Constance is presently under substantial pressure from intensive tourism, increases of population, enlargement of industrial areas in the watershed and intensive agricultural use. This is causing an increase of micro pollutions in the lake and because the lake water is directly used for drinking water without chemical treatments, an impact on human health must be excluded and the development of the micro pollutions has to be monitored and analysed.
The main sources of hazards and risk for the water quality are accidents by transportation on the railways and roads around the lake, and the air traffic to and from the airport Zuerich Kloten. Indeed, history demonstrates that no potential risk can be neglected with two airplane crashes occurring over the last 25 years in the local region of Lake Constance or above the lake. These accidents were the basic motivation for the BodenseeOnline project.
Further risk can be identified from the following sources:
- The intensive use of Lake Constance by sailors
- Industrial use of lake water (heating and cooling)
- Accidents in the watershed near tributaries
- Inflow of treated waste water or storm water overflow
Due to lake precautions for handling the potential risks, a decision support system for hydrodynamics and lake water quality has been developed in a scientific project between 2005 and 2008. The aim of this project was to install a decision support system for the assessment of hydrodynamics and water quality in Lake Constance. The decision support system consists of a large database with all relevant measured hydrological and meteorological data and water quality data. Further, numerical models support the interpretation of the lake's current hydrodynamic situation and the water quality. These numerical models are updated daily and a forecast for the next 78 hours is calculated. The observed data and simulation results are then available for testing by GENESIS.
Movie of the simulated temperature development in a vertical cross section along the longitudinal axis of Lake Constance during a wind event
Conclusion
Overall, Lake Constance is well-observed by continuous monitoring stations and long-time historical water quality data collected over the last 20 to 40 years. The protection of the lake water is the responsibility of all its riparian countries. The aim of GENESIS is to provide these responsible stakeholders with new tools for decision support. The pilot is used to evaluate the IT tools of GENESIS. The consideration of local end users will provide verification and validation for the methodologies developed in the two other pilot sites.
Interview with application pilot responsible Ulrich Lang
Dr Ulrich Lang describes the Lake Constance thematic pilot
A trans-boundary lake at the Northern foot of the Alps, Lake Constance suffered from severe water quality problems in the 1960s, yet sustained action since has led to significant improvement. Nevertheless, the proximity of industrial areas demands continued monitoring, as Dr Ulrich Lang of kup, a key GENESIS partner, explains
Patrick Truss: How does Lake Constance differ from the other fresh water pilot sites in GENESIS?
Dr Ulrich Lang: There are three fresh water pilot sites in GENESIS, and they are each completely different. The Oder Estuary suffers from significant water quality problems, with algae plume growth in Summer and large eutrophication problems due to the nutrient load from the Oderso river, while Lake Villerest has problems with cyanobacteria and bathing water quality.
Lake Constance doesn't suffer from these kinds of problems, it is more or less clear and the water quality is good. We had water quality problems in the 1960s and 70s, there was significant algae growth, but the water authorities around the lake (Lake Constance is a trans-boundary lake which Germany, Switzerland and Austria all border) cleaned up the surrounding waste water and the nutrient inflow was reduced. The phosphorus concentration load today is more or less the same as the 1950s we have a very clean lake and we can use it for drinking water, recreation, and bathing for most of the Summer.
PT: What are the main environmental problems around Lake Constance?
Dr UL: The area around Lake Constance is very industrialised. We have to be aware of the possibility of accidents, and if an accident does occur around the lake then we need a warning system. In that case we want to be able to use the GENESIS applications. We also sometimes have water quality problems at locations near the tributaries when we have bad weather and floods occur.
PT: Do you have a lot of historical data on water quality in the lake?
Dr UL: We have a lot of data, going right back to the 50s. Of course we don't have as much data from then as we have on water quality today, but one parameter tells us a lot about the eutrophication of the lake, phosphorus concentration. This is measured annually when we have a total turnover of the lake, which gives an average value of the phosphorus concentration. Currently it's about 8 microgrammes per litre, whereas in the 70s it was 80 microgrammes per litre. In the 50s it was at 8, so we are now back at the level of the 50s. This is quite a significant improvement.
PT: But although the water quality is better now you cannot say that the problem is solved? It is important to continue monitoring the lake?
Dr UL: Yes. The problem of the eutrophication of the lake is over for now, but the question is what will happen in future, when changes to our climate are likely to have a significant impact on the lake.
The problem is that the lake has an annual turnover, it is totally mixed in Winter, and we have just had a very severe Winter. But what will happen when the air temperature increases and we don't have this turnover annually, and it only happens every ten years or so?
PT: What do you mean by turnover?
Dr UL: In summer the lake is stratified, meaning that on the surface the water temperature is about 20º, and at the deepest part, about 250 metres, it is around 4º. So the density of the water on the surface is lower than in the deeper part, the so-called hypolimnion.
Warm water rises, and in these circumstances water is not exchanged between the surface and the bottom. It is only in Winter that the water temperature at the surface is the same as it is at the bottom, and at that time we get a mixing in the lake. During this mixing fresh water will go from the surface to the bottom of the lake, as does oxygen.
This might not happen in a few years time. Biological activity at the bottom of the lake might cause the oxygen concentration to decrease, and if the turnover takes too long then there will be no oxygen left at the bottom of the lake.
PT: What are the key criteria by which you are assessing the GENESIS tools?
Dr UL: I think one of the most important criteria is the views of end-users. The end users of the GENESIS tools are administrative people around the lake, such as water authority personnel and sanitary inspectors, as well as people who rely on the lake for drinking water. They should be able to work with these complex GENESIS solutions. If they are able to manage the GENESIS system easily then we would consider that a great success, so the system should be accessible for all the end-users.
PT: What are the main sources of data you are using in your work?
Dr UL: We use data measurements from around the lake, which are important in terms of meteorological conditions, as well as water quality data from inside the lake through the uptake of drinking water suppliers. There are 16 such locations around the lake, and they deliver parameters on water quality.
Additionally we had a research project before GENESIS started called Bodensee Online. In that research project we collected all the data, put it together, and ran lake models to simulate the flow and water quality processes in the lake, as well as the hydrodynamic processes in the lake and its water quality. Bodensee Online currently delivers 3-D information about hydrodynamics and water quality to users daily. This might be one of the most important data sources for GENESIS.
PT: What are the main sources of inflow into the lake? Does its position at the bottom of the Alps mean it gets water from glacier run-off?
Dr UL: Yes, that's important. In Summer the main tributary is the Alpine Rhine, which accounts for 60 per cent of the total inflow. This water comes from the Swiss Alps.
We have measurements of the inflow from the Alpine Rhine directly in the inflow to Lake Constance. So we use this measured information to simulate the lake, which centres only on the lake itself, not the catchment.
PT: Does this work involve modelling the quality of the water, or is it more about the quantity?
Dr UL: We are simulating the flow and the quantity; we have clear information about the most important water quality parameters, which are dependent on the inflow. This equation then gives us information about the inflow of phosphorus or nitrate depending on the discharge.
PT: What general effect does inflow from the Rhine have on the overall quality of water in the lake?
Dr UL: The water from the Rhine is very clean in comparison to the other tributaries. Less nutrients come from the Rhine, but when floods occur the Rhine has a very strong impact on sediment load.
The Alpine Rhine has a very high sediment load, and the density of its water is higher when it floods. The high sediment load means the density of the water will remain high, even during floods. That means that the flow of the Rhine takes place at the bottom of the lake, so Rhine water comes in the deeper part of the lake, but only during flood events, not during average conditions.
