Extreme low and high flow situations can lead to limitations of inland waterway transport.
We use novel climate data and derived high and low flow indicators as input to a well established workflow that allows monitoring and projecting river flow changes and effects on costs of inland waterway transport.
We focus on the middle Rhine area which is one of the most relevant bottlenecks for inland waterway transport.
Vessel on the Rhine River south of Koblenz (Middle Rhine area) during a low flow situation in 2015.
Case Study Description
Climate change (CC) is often regarded as a threat to inland waterway transport (IWT). In press releases CC is often related to images of shrinking rivers with significantly extended low flow situations. On the other hand, information about future climate change is known to be uncertain. This combination represents an obstacle for decisions in long term planning of logistic chains that include IWT.
Improved information on observed and future river flow, stream velocities and water levels help to guide users and managers of IWT in optimising their system and processes, thus improving the competitiveness of the inland navigation sector in the overall transport market.
The SWICCA portal has proven to be a good choice when a quick look on pan-European indicators of water-related CC impacts is needed. It adds significantly to available services that often focus on climate variables only. The easy access to high-resolution time-series data for selected points allows quick integration of results from pan-European studies into regional scale assessments, thereby linking EU- and national research activities.
CC Impact on IWT on the River Rhine: With respect to CC impacts on navigation on the middle River Rhine area, the change signals of load factors calculated in SWICCA re-confirmed results from national German research activities. While the projections show no clear change in the next decades, significant effects on the infrastructure can’t be ruled out for the end of the 21st century. Reduced load factors are simulated regardless of the scenario applied. Several adaptation options exist to limit the adverse effects of CC (organisation, investment). In SWICCA, a selection of adjustments in the design of ships was evaluated.
Improved information on observed and future stream velocities and water levels help to guide users and managers of inland water way transport in optimising their system and processes, thus improving the competativeness of the inland navigation sector in the overall transport market.
Thanks to SWICCA and other portals and services, BfG and CCNR are aware of the plentiful new CC information that has been developed in the aftermath of CMIP5, EU-CORDEX, and IPCC-AR5. The new data and findings are currently being collected, structured, compared, evaluated, and finally integrated in reports for the relevant authorities and the transport sector on a national and international level.
In the years 2018 and 2019 CCNR is re-evaluating the current knowledge about CC impacts on navigation and explores together with its members to what extent new conclusions have to be drawn for the IWT sector. The results from SWICCA are adding to the pool of information.
The Rhine River is the most important inland waterway in Europe. It is a backbone of the Rhine-Alpine and Rhine-Danubian corridors of the trans-European transport network (TEN-T). The middle Rhine is a bottleneck for inland waterway transport on these corridors. Thus monitoring this area is of utmost importance and adaptation measures in this area are supposed to have an effect along the international transport routes from the Netherlands to the Alps, and to the Danube.
Various adaptation options have been indentified to make inland waterway transport more robust against changing flow conditions. These refer to ship technology and operation, logistic chains and the waterway management. Implementation of these measures is costy and takes several decades. Given the current climate change information (change signals and spread related to IPCC AR4), CCNR sees no need for immediate action. The information gathered by the SWICCA case study will be used to re-evaluate the situation with updated climate change knowledge.
With its strong expertise in the field of navigation, the CCNR is used to acquire observed water level data at gauging stations and to translate these into relevant information for the transport sector (e.g. load factors). Consultancy is required when it comes to simulations of future flow regimes that need to be translated into local discharge values, water levels, flow velocities, and finally into information for the transport sector.
Key issues of the client are the large volume of original climate model data, the level of uncertainty associated with these data as well as a lack of modelling capabilities to produce local data. BfG established a modelling and evaluation framework to fill this gap and to support the navigation sector. This framework was discussed with CCNR and other navigation experts (waterway managers, ship technical engineers, ship operators and logistic operators) during many workshops in a major national reseach programme (KLIWAS) as well as in an EU-FP7 project (ECCONET).
The framework includes the evaluation, selection and bias correction of climate model outputs, hydrological and hydrodynamical modelling, and finally a model of the Rhine fleet. At the end it provides information characterising the climate impact on navigation in units well understood by the client: water levels, load factors, transport costs.
The results are communicated to the client through (quasi) annual meetings at the CCNR in Strasbourg. These meetings are motivated by CCNR when specific information is required by one of the thematic boards (e.g. on economy, infrastructure) or by BfG when new scenario information becomes available (e.g. CMIP3-ENSEMBLES through KLIWAS, CMIP5-EUCORDEX through SWICCA). The dialogue of CCNR and BfG on CC is already running since almost ten years. In SWICCA it contiuned via phone and personal meetings.
Data from SWICCA, together with data from other ressources need to be combined to gain an overview of the current state of knowledge on CC impacts. In addition to climate change, seasonal predictions are of high interest for CCNR.
Three main issues can be adressed by pan-European indicators:
a) Transport limitations due to low flow: Waterways are often maintained in such a way that certain water levels are not undershoot more than a defined number of days per year on average. This management target determines the amount of goods that can be transported on each river segment. In Germany, which includes much of the most important inland waterwayw of Europe (i.e. the Rhine river), a number of 20 days per year is the management target. Technically, this number corresponds to the 95th percentile of the flow duration curve of the reference period 1961-1990. Changes of this number determined between reference conditions and future projected conditions have shown to be a well comprehensible indicator for transport limitations due to low flow.
b) Transport limitations due to high flow: High flow can lead to restriction or suspension of navigation. The level of restriction is officially regulated and depends on the local water level. For the River Rhine, three high water levels were defined with respect to selected gauges. The first, lower threshold (HSW-I) stops selected ship types and limits the speed of the remaining ships. It also concentrates traffic in the centre of the fairway to reduce wave stress on the lateral infrastructure. The second, higher threshold (HSW-II) leads to stoppage of navigation (with few exceptions). In addition to the protection of the infrastructure the security of navigation is a motivation here. High flow velocities associated with discharges above HSW-II reduce the manoeuvrability of the vessels travelling downstream. A third threshold (HSW-III) leads to a general stoppage of navigation. At several gauges on the middle Rhine, the discharges associated with the thresshold HSW-I are close to the 3rd to 5th percentile of the flow duration curve of the reference period 1961-1990. Here, we use the number of days with discharges above the 5th percentile of the period 1961-1990 as an indicator. The exact degree of limitation would, however, depend on the local conditions of a river stretch.
c) Transport limitations due to river icing: The exact relevance of river and canal ice for navigation depends on the characteristics of the respective river stretch or canal. The lower air temperature and the lower the flow velocity in a river stretch, the higher the disposition for icing. River ice is mentioned in various places in the official regulations and can constrain or even stop navigation. Even when navigation is allowed according to the official rules, river ice has the potential to damage the underwater part of ships and thus requires attention by the ship operator who sails on his own risk. Thus, in addition to the days with official suspension, there are several days when navigation is affected by river ice. The sum of temperatures below 0°C between November and March is usually applied as a proxy for the strength of a winter season associated with the disposition for ice formation on standing water bodies. Here we use this proxy to indicate changes in the disposition for ice formation. Note, however, that this indicator is much better suited for canals, which have very low flow velocity, than for free flowing rivers.
Based on Pan-European data, indicators will be provided showing climate change effects on the fleet sailing currently on the Rhine River. These effects will be expressed in transport costs.
Step 1: Hydrology in future climate Extract runoff data generated with pan-Euopean hydrological models for a defined set of gauges along the Rhine River.
Step 2: Hydrodynamics Calculate change of water levels and flow velocities with a hydrodynamic model of the Rhine River (local DEM) using the runoff data as input.
Step 3: Local climate-impact indicators Derive local climate-impact indicators from (number of days above/below high/low water level thresholds "GlW" and "HSW").
Step 4: Cost effects (current fleet) Evaluate cost effects based on specific hydrodynamic properties of current vessel types (weight, propulsion, operation etc.).
Step 5: Cost effects (innovative fleet) Evaluate cost effects based on specific hydrodynamic properties of innovative vessel types (adapted weight, propulsion, operation etc.).
In general SWICCA offers a variety of relevant information for the water sector. Its functionality is developed further than that of many other service portals. As a next step of development, we suggested constructing sector specific views in the portal allowing filtering of the most relevant information if desired. Only few people are interested in floods, droughts, water quality, and socio-economy at the same time. Furthermore, we suggest making the mapping service OCG more compliant.
Download: We used daily data on river flow from the SWICCA portal (step 1). Retrieval was unproblematic for some individual gauging stations. Redoing the download for a larger batch of gauging stations (which was originally planned for hydrodynamic modelling in step 2) would be a bit annoying with the current user interface.
Data quality: The downloaded data yielded large biases, and some implausible values including initialisation artefacts (Step 1). These had to be removed before further processing. Moreover, it is not clear, if the IMPACT2C data pool underlying SWICCA account for the changes in the EU-CORDEX data pool that came after the end of IMPACT2C. To our knowledge, some RCM runs were withdrawn and replaced later for different reasons.
Processing: Steps 2 to 5 were done with data and tools at BfG. The load factor is an indicator also used in the regular "market observations" of CCNR. While the application of the pre-existing tools (mostly R-scripts) to the SWICCA data was technically unproblematic, the interpretation of the data is hampered by the quality issues mentioned above.
Before SWICCA, adaptation options/needs of the inland navigation sector were evaluated with the same processing chain, but with climate projections mainly from the CMIP3/ENSEMBLES data pools. Climate data processing and "fast track information" (change signals of essential climate variabiles, indicators) had to be produced by BfG and partners. Now, it seems like those information could be easiliy retrieved from C3S based on the latest generation of climate projections CMIP5/EU-CORDEX. This makes it much easier to re-evaluate the necessitiy of adaptation.
"The CCNR affirms the strategic goal to take the necessary adaptation works for the waterway Rhine and the logistic chains of inland navigation on the River Rhine that allow reliable and economic transport performance, thereby contributing to the preservation of important industrial locations."
"The CCNR tasks its Committee on Infrastructure and Environment to continuously monitor the topic 'Climate Change' and to revise the existing report on 'Climate Change and Navigation on the Rhine' by 2020 et the latest."
SWICCA adds to the work of the comittees mentioned here.
For the next decades (until 2050), no clear changes are obvious. Consequently, adaptation needs are limited for that period. Despite of that, some situations observed in the recent past have lead to the conclusion, that the demands of the logistic sector already need attention today. In order to ensure and optimize the reliability of IWT, two strategic targets emerge: (a) The optimisation of the fleet composition to varying flow conditions, and (b) better integration of IWT in concepts of transport co-modality (use or combination of different traffic carriers). After 2050 "The impact will be seen in a growing importance of high water and low water periods. Various measures can be envisioned for limiting the negative effects of this change on navigation on the River Rhine. The conditions for implementing these measures still need to be worked out in more detail."
Climate Change and Rhine Navigation from Central Commission for Navigation of the Rhine
Dr. Enno Nilson
Department Waterbalance, Forecasting and Predictions (M2)
Federal Institute Of Hydrology
Am Mainzer Tor 1
Phone: +49 (0)261 1306 5325
Relevant EU policy
Purveyor: Dr. Enno Nilson
Department Waterbalance, Forecasting and Predictions (M2)
Federal Institute Of Hydrology
Value added by Copernicus Climate Change Service: