Interaction between dams and valves

The Schwarzenbach Dam in the northern Black Forest has been in operation since 1926. (Source: Wikimedia/Dpesek)

Industrial valves and dams form a significant symbiosis in the context of contemporary water supply and power generation. Smooth coordination between these two elements is essential to effectively use water resources while ensuring safety and control over these vital resources.

Dams are basically artificial reservoirs capable of storing and releasing large quantities of water in a controlled manner. They serve a variety of purposes, such as providing drinking water, irrigating agricultural land and generating hydropower. The heart of every dam consists of technical components such as sluices, valves and throttling devices that function as industrial valves. Butterfly valves and control valves enable the flow of water into the dam to be controlled and ensure that flooding does not occur in the river sections downstream of the dam.

The overall concept of cooperation between industrial valves and dams illustrates how modern infrastructures use complex systems to sustainably manage natural resources and generate energy. This harmonious cooperation guarantees not only a reliable water supply and energy generation, but also protection against natural disasters and the sustainable use of water resources.

Dams can be opened to reduce the risk of flooding. (Source: Landestalsperrenverwaltung Sachsen)

One dam per 1,000 square kilometres

In Germany, there are a total of 371 large dams according to the established definition. These dams are characterised by dam structures whose height from the deepest foundation base to the top of the structure is more than 15 metres and/or whose storage reservoirs have a total volume of more than 1 million cubic metres. Alternatively, this information can be found in the World Register of Dams, provided by the International Commission on Large Dams (ICOLD). It should be noted, however, that internationally we speak of large dams when their total volume exceeds 3 million cubic metres. In relation to the total area of Germany, this means that on average there is one dam per 1,000 square kilometres.

Of the aforementioned 371 large dams in Germany, 231 serve different purposes. They fulfil multi-purpose uses, including flood protection, hydroelectric power generation, irrigation of agricultural land, support for the fishing industry, provision of water for artificial and natural navigation routes, tourism, raw material and drinking water extraction, and provision of service and/or cooling water. In addition, they are becoming increasingly important in raising the water level of rivers and streams during dry periods to combat low water.

The floods in North Rhine-Westphalia and Rhineland-Palatinate caused billions in damage in 2021. (Source: AdobeStock/Christian)

Many dams are multi-purpose facilities

Dams have important functions related to flood protection, water supply and maintaining adequate water levels in rivers and streams during dry periods. The changes in Germany's hydrological conditions due to climate change mean that the challenges of extreme weather events, such as heavy precipitation and flooding in our rivers, but also the effects of drought and drought, lowered groundwater levels and falling water levels in standing water bodies must be faced. Without dams, the flow of water would already have dried up on many watercourses this year.

However, a look back at 2021 shows that most of the dams in the federal states of North Rhine-Westphalia and Rhineland-Palatinate, which were particularly hard hit by floods, were generally designed as multi-purpose facilities. Historically, their main purpose was to supply raw water. In practical terms, hindsight has shown that each of these plants, operated by different operators in the flood region, contributed significantly to mitigating the consequences of the floods without neglecting the continuous supply task. The effects of this natural disaster would otherwise have been many times more severe.

The catastrophic floods in Rhineland-Palatinate and North Rhine-Westphalia can teach us something. It showed two types of destructive floods: On the one hand, unregulated rivers and sometimes inconspicuous streams swelled into raging floods from one moment to the next. On the other hand, dams on regulated rivers experienced an “overflow”, i.e. the inflow was temporarily equal to the outflow, and this was not arbitrary but forced. In this case, obviously not enough reservoir space had been created in the days before to be able to fulfil the main purpose of the dams, flood protection.

At the Pirk dam in the Vogtland district of Saxony, the historic valves were replaced with new annular piston valves this year. (Source: Landestalsperrenverwaltung Sachsen)

In the two affected federal states and in the water associations that operate the dams, there is a desire to learn, and the process of coming to terms with the situation has been initiated. But it does not give the impression that they want to learn everything: the second type of flood, the dam issue, is only approached with very pointed fingers. The excuses are: Almost everything went well.

It is conspicuous that the actors stop at a small-scale and isolated investigation approach. However, the question of how to regulate dams under the conditions of climate change - i.e. under completely changed weather conditions - in such a way that they are able to guarantee flood protection in the future as well, must be addressed on a much larger scale if it is to be fruitful. New large-scale weather situations of the “Central European depression” type can lead to stationary permanent precipitation that affects an entire river basin. Such a major depression currently occurs in this country on an average of nine to 15 days a year - and can hardly be predicted with local precision five days in advance.

The dam operators, for their part, rightly point out that they are only able to create sufficient reservoir space with a five-day lead time - given the usually high filling levels of the dams in summer. This is a real dilemma; and novel. According to the German Meteorological Service (DWD), by the year 2100 large-scale weather conditions that pose a flood risk will occur about 20 percent more frequently than before. No progress will be made here without a joint working group of DWD, dam operators and supervisory authorities. The DWD has set up a working group on forecasting suitable for dams, but against all the principles of wise science, its questions are withheld from public discussion by confidentiality.

High risk for regions around the low mountain range

However, the issue of how to manage dams under the conditions of climate change does not only concern the Wupperverband or the federal states of North Rhine-Westphalia and Rhineland-Palatinate. There are more than 370 dams in Germany - the majority of which will have to adapt to the consequences of climate change. The low mountain ranges will be particularly affected by persistent extreme precipitation.

The districts that will have to expect the most extreme precipitation in the future stretch like a ribbon from southern North Rhine-Westphalia, from parts of Rhineland-Palatinate across Hesse and southern Thuringia down to the east and centre of Bavaria. This is what a study by the Hamburg Climate Service Center (CSC) predicts, prepared in 2015 for the German Insurance Association. The topic of “adapting dam management to climate change” affects at least five federal states. In fact, however, the state government of North Rhine-Westphalia announces that it will only review “the existing management concepts for dams” “on the basis of the findings from the 2021 flood”. And that too only in “discussions with the affected water associations”.

Will the dam supervisors of the other federal states do the same and will the wheel thus be reinvented at least five times in the best case? The business of dam operators is necessarily monopolistic. That is why it is subject to state supervision. Up to now, this supervision has been extremely sparsely staffed, as the progress report from NRW also documents. For a long time, the lack of personnel was not a problem - until climate change now upsets the weather patterns and thus also upsets the established business model of the dam operators.

As long as this insight does not take hold among the regulators in the various federal states, the dam operators can continue as before. They have a considerable economic interest in maintaining the status quo.