Inland Navigation (Rhine River)

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.

Read recent progress here!

Vessel on the Rhine River south of Koblenz (Middle Rhine area) during a low flow situation in 2015.

Vessel on the Rhine River south of Koblenz (Middle Rhine area) during a low flow situation in 2015.

Case Study Description
Data Description
Reference information

Water-management issue to be addressed

In Europe, the Rhine River is the most important inland waterway. Ship operators and industries along the river are dependent on reliable transport conditions. As the Rhine River is a free flowing river over most of its course, the reliability is in part dependent on meteorological conditions in the river catchment.

Flow conditions determine the cost of transport for the shipper via stream velocities (affecting propulsion) and water levels (affecting load factor). Especially during long lasting low flow situations the river bourne transport mode loses economical advantages.

Decision support to client

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.

Temporal and spatial Scale

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.

Knowledge Brokering

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).

Climate  Impact Indicators

Pan-European Indicators

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.

Local indicators

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.

Pan-European data to local scale


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.).

Lessons learnt

With the service, fundamental climate change indicators and data become easily accessible.

Bridging the gap between pan-european data and indicators and the local scale applications remains one of the key challenges. Output from large scale hydrological models, which are used  as boundary conditions here, show considerable mismatches biases/errors on a regional/local scale. With regard to climate models, this is usally handled by bias correction thereby modifying/destroying interdependencies between different variables. Likewise, hydrological model outputs cannot be corrected because data are autocorrelated over weeks and months and could lose important temporal characteristics through statistical correction.

Importance and Relevance of Adaptation

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.

Pros and Cons or Cost-Benefit analysis of climate adaptation

Studies carried out within the German KLIWAS research programms showd an increase of overall transport costs on the Rhine River by approximately 10% compared to today assuming (1) a pessimistic development of flow conditions (more low flow situations), (2) the present day composition of the fleet sailing on the Rhine River, and (3) an averagy amount of goods transported (example of year 2000). Using a selected (though not exhaustive) set of adaptation options (ship technology, waterway management), the adverse effects could be cut by half.

Policy aspects 

Uncertainty guidance is important for policy makers. The complete climate knowledge (including uncertainty) has to be transferred to them in a comprehensive way. A preselection of climate scenarios (e.g. chosing only the most dramatic ones) can motivate wrong decisions.


Dr. Enno Nilson
Department Waterbalance, Forecasting and Predictions (M2)
Federal Institute Of Hydrology
Am Mainzer Tor 1
D-56068 Koblenz
Phone: +49 (0)261 1306 5325
Email: nilson‹at›



Relevant EU policy


Purveyor: Dr. Enno Nilson
Department Waterbalance, Forecasting and Predictions (M2)
Federal Institute Of Hydrology
Email: nilson‹at›

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