Low-Flow in 2018 Content Outline 3 Chronology … 4 Impacts of the 2018 low-flow 8 Lowest water level in recent years? New record? 13 Editor: Lower water levels do not always mean lower Federal Institute of Hydrology Am Mainzer Tor 1 • P.O. Box 20 02 53 water volumes 14 56002 Koblenz • Germany Mitigate effects by means of information: Tel.: +49 261 1306-0 • Fax: +49 261 1306-5302 the role of BfG 16 E-Mail: [email protected] • Internet: http://www.bafg.de Low-flow 2018 – a harbinger? 18 Effective: February 2019 DOI: 10.5675/BfG-Niedrigwasserbroschuere_2018 Water level – press reviews 21 Outline
The year 2018 was marked by In many places, water levels at also impacted on the industry: persistent drought. In its wake, the gauging stations reached due to the high water temperatu- riverine water levels sank historically low levels. Runoff res in rivers, the discharge of dramatically in the course of the was also extremely low, but warm water into the rivers had year. After a humid winter with without breaking any records. to be limited. In addition to the large amounts of snow in the The runoff of the extreme low water quantities, notably Alps, average monthly rainfall year 2003 was reached or even high water temperatures and the had not been reached since undercut. In terms of the major inherent deterioration of water March 2018. From April onwards, federal waterways, the rivers quality gave rise to concern. The rainfall in Germany accounted Weser and Elbe were particularly summer heatwave of 2018 also for only about half the long-term affected: their water levels fell affected the riverine biology, mean. As a result, riverine water below the navigation-relevant entailing i.a. the blue-green levels first sank in the North and low level in 80 % resp. 90 % of algae bloom in the Moselle river East of Germany, and later on in all days between June and as well as major heat stress for the South and West. In the December 2018. numerous species of fish and Middle and Upper Rhine, snow invertebrates. It was not before and glacier melt water delayed a Notably the low water level of early December, that an improve- decrease of the water levels. the Rhine, causing lower cargo ment of the low-flow situation Therefore, low stages impeding tonnages on inland vessels, and came into sight. Information on navigation were not reached hence supply bottlenecks, had current water levels and multi- until mid-November. economic impacts. Low-flow day forecasts in all federal
3 waterways notably helped the cause a more frequent occur- boatmen and the logisticians to rence of such low-flow periods. determine or adapt the maxi- Towards the end of the century, mum cargo capacity or to find it is expected that earlier and alternative solutions. reduced snowmelt as well as absent glacier melt will pose Studies implemented by BfG new challenges to the manage- show that climate change may ment of the federal waterways.
Chronology
Overall, 2018 was marked and West of Germany. Persis- by low rainfall. In particular tent drought increasingly from June onwards, major impeded inland navigation in precipitation deficits were the course of the year. Smaller recorded. As a result, riverine amounts of rainfall failed to water levels decreased. The bring lasting relief. From late watercourses in the North and summer, progressive drought East were affected first, follo- caused new historical all-time wed by the rivers in the South lows.
4 June July August
+ 2,0° + 2,3° + 2,4°
– 40 % – 52 % – 45 %
As of: 29.06.2018 As of: 26.07.2018 As of: 31.08.2018
September October November
+ 2,6° + 1,5° + 0,8°
– 36 % – 55 % – 70 %
As of: 27.09.2018 As of: 25.10.2018 As of: 29.11.2018 precipitation anomaly [%] Mean water level Low water level High water level No current water level 1 25 50 75 100 125 Fig. 1: Water levels, deviations of monthly rainfall totals and mean monthly temperatures from the long-term average (1981–2010). Data: PegelOnline (WSV / Federal Waterways and Shipping Administration) and Deutscher Wetterdienst (DWD/German Meteorological Service)
5 June July August September October November 650 1 2 3 4 5 600 550 500 450 Upper Rhine/Maxau 41% days June – Nov below GIW* 400 350 300
500 450 400 350 Lower Rhine/Duisburg-Ruhrort 300 67% days June – Nov below GIW* 250 200 150
400
350 300 Danube/Hofkirchen 67% days June – Nov below RNW* 250
200
160 Water levels in cm at gauging station Water 140
120 Weser/Vlotho 83% days June – Nov below GIW*
100
100 90 80 93% days June – Nov below GIW* 70 Elbe/Magdeburg 60 50
Fig. 2: Temporal development of water levels (solid line) of selected rivers and the pertaining gauge-specific low-flow reference value (dashed line). Provisional data. Data WSV, graph BfG
* GlW (equivalent water level) and RNW (regulation low-flow) are river-specific reference values. They are of major importance as reference values for the maintenance of free-flowing waterways and for navigation, especially during low-flow. If the water level falls below these reference values, the ships’ potential draught and hence cargo capacity decreases, depending on the type of ship.
6 1 Mild and rainy autumn and winter seasons in 2017 were followed 4 The very dry weather in by a warm and dry spring in 2018. The months from March to October clearly escalated the June 2018 were continuously too dry and mild all over Germany. situation: historically lowest levels were reached at some At the beginning of the year, the rivers still carried larger amounts gauging stations. The Upper of snowmelt. A low-flow situation soon occurred on the rivers Rhine’s water level constantly Elbe and Oder, as rainfall in these regions had been below average dropped below the reference since 2014 and natural reservoirs were depleting fast. Therefore, value GIW that is crucial for the Elbe’s water level reached a low that impeded navigation navigation. already in June.
5 After short rainfalls, briefly 2 The outstandingly warm and dry weather persisted in July and easing the situation on Middle August. Regional, short rainstorms brought no relief. Riverine water Rhine and Danube, the sixth levels continued to drop on a large scale: On Weser, Danube and driest November since 1901 Lower Rhine they dropped below the river-specific reference values. caused another decline of the Merely the partly impounded Upper Rhine and the Middle Rhine water levels. It was not before initially maintained an adequate water level. early December that rising water levels were recorded again. Persistent rainfall must now fill 3 Rainfall, primarily in Southern Germany, slightly improved the empty groundwater and soil the low-flow situation, especially on Danube and Upper Rhine. water storage, before more stable Water levels on Elbe, Weser and Lower Rhine remained low. water levels can be expected.
7 The impacts of the 2018 low-flow
Deteriorated water quality and discharges, e.g. from to rise to the second highest Low discharge impacts in sewage treatment plants and temperature values after the different ways on the water industry, are less diluted. The 2003 heat wave. A water quality in federal waterways: above-average air temperatures temperature of 25°C is a critical i.a. algae growth is stimulated caused the water temperatures value for many of the fish and invertebrate species living in
Discharge /s the Rhine. 3 Turbidity In 2018, this value was exceeded urbidity E/F urbidity
Discharge m in the Rhine near Koblenz on 31 consecutive days (fig. 3); this is un ul Aug Sep Oct Nov normally only true for 9 days in a year. 17 respectively 16 days ritical water te perature above 25°C were measured in the Elbe and Oder rivers, setting
ritical oxygen concentration a new record value for the last Oxygen mg/l Oxygen 20 years. In the Rhine and Temperature temperature C Water further federal waterways, un ul Aug Sep Oct Nov Lorem ipsum Fig. 3: Temporal development of discharge (blue), turbidity (grey), oxygen content (green) however, oxygen values (blue) and temperature (red), on a daily basis during low-flow period June – December 2018. remained clearly above the Discharge from Kaub gauging station, data WSV (Federal Waterways and Shipping Ad- ministration). Remaining values from the Rhine at Koblenz: data BfG, graph BfG critical level for fishof 4 mg/l.
8 Inland vessel on the Rhine carrying containers. Photo by Dr. Sebastian Kofalk, BfG
During a short period, however, critical values (up to 3.5 mg/l) Restrictions to inland were recorded on the rivers Oder, Lower Havel and tidal Elbe. navigation The summer low-flow on the Rhine and Moselle rivers featured a Due to low flow, inland vessels special phenomenon, i.e. the occurrence of algae blooms. These were unable to utilize their full algae caused an increased turbidity of the Rhine water in August. loading capacity and had to Usually, high turbidity values occur when discharge, and hence travel with low cargo volumes. sediment transport, are higher. In August alone, freight figures dropped by 21 %1. Hence, many In the Moselle river, a blue algae bloom lasting more than two ports (e.g. Mannheim –42 %) months caused restrictions for water sports, as these organisms may suffered losses from reduced present a risk to health. handling2.
9 Large-scale power station at Mannheim. Photo: Immanuel Giel, CC BY 3.0
According to the Federal Waterways and Shipping Administration amounted to almost 1 million €. (WSV)3, clearly less cargo was shipped in the locks at Iffezheim In some instances, ferry services (–23.6 %), on the Wesel-Datteln Canal (–24.9 %) and on the Main on Rhine and Elbe had to cease river (Kostheim lock –21.8 %) than in the previous year. operation or dispense with Moreover, less cargo vessels were channelled (13.8 %, 12 % and heavy goods transports, and 20.6 %). A first assessment by the Kiel Institute for the World implement structural measures Economy (IfW) on the impacts of low-flow resulted in a reduction and dredging work4. of the German production rate of growth by 0.5 percentage points in the 3rd and 4th quarter 20181. Drastic declines affected excursion ships and ferry operators. According to first estimations for this field of business, the loss – just for the Middle Rhine section –
10 Oil storage tanks at the port of Hamburg. Photo: Dirtsc, CC BY 3.0
Supply bottlenecks/ (e.g. BASF TDI production5) released. Moreover, several Energy industry were particularly affected. power stations along the Rhine The significance of the federal had to cut back their power waterways for the industry BASF in Ludwigshafen incurred generation. Affected were became apparent once again. a loss of 250 million € 6 caused i.a. the nuclear power plant Due to supply bottlenecks, by the low-flow situation. Philippsburg and the coal-fired several industrial plants had to General fuel supply was also power stations Bergkamen, downscale production or restricted. Fuel prices at the Walsum, Mannheim, and temporarily cease production petrol stations were skyrocketing Rheinhafen steam power plant, altogether. The industrial sites and parts of the federal strategic due to supply bottlenecks and upstream of the Middle Rhine energy reserves had to be increased water temperatures7.
11 Tourism/Education The impacts of low-flow on tourism were ambivalent: cruise ships and excursion boats had to cease operations temporarily and organise bus transport instead. On the other hand, the water level record lows resulted in a kind of “low-flow tourism“. For several week-ends, the Mäuseturm near Bingen, for instance, could only be reached on foot by visitors. In contrast, the school on the Rhine island Nonnenwerth had to be relocated on shore due to the low-flow induced cessation of the ferry service.
The Mäuseturm near Bingen listed a record number of visitors in the summer of 2018. Photo: Dr. Klaus Wendling, Ministry for the Environment, Energy, Food and Forests, Rhineland-Palatinate
12 Lowest water level in recent years? New record?
Depending on the location, new record lows were reached at the In 2018, extremely low discharge gauging stations (in fig. 4, left-hand scale per river). Examples was measured indeed, but no include the Elbe at Magdeburg or the Rhine at Cologne (no records were broken. The illustration). However, these records have little validity, as the illustration shows record values riverbed may vary markedly over the decades. The more objective for water level and discharge value for statements on low-flow is the water volume discharged for the ice-free months from (in fig. 4 right-hand scale). May to November 2018.
pper Rhine/Maxau Weser/ lotho Elbe/Magdeburg Danube/Hof irchen
26 11 2018 1971 1911 1964 1976 1930, 2004, 2009 23 08 2018 310 480 19 09 2018 1921 1935 1998 1911 1906 2003 180
130 1959, 2003 36 1964 1962 1904 1935 65 95 1962 1985 240 1962 1907 460 1949 1949 1952 300 1934 1934 1972 1962 1952 1959 1921 2016 1949 1949 34 440 1934 23 10 2018 120 230 1972, 26 11 2018 1947 60 1921
1972 175 290 1959
2003 90 2015
1900 420
1976 32 1934 1964
1964 1911 1998 220 55 280 1959 110 400 23 10 2018 1921 30 1934 170
1906 1959 85
380 2015 270 1947 23 08 2018 210 50 100
28 1934 360
260 1904 1947 1947 1991 1911 19 09 2018 2003 200 1947 water level [cm above PG] discharge [m /s] water level [cm above PG] discharge [m /s] water level [cm above PG] discharge [m /s] water level [cm above PG] discharge [m /s] PG: zero point gauge
Fig. 4: Comparison of record water levels at the gauge (above zero point of gauge (PNP)) with record levels during ice-free months in selected rivers, since records began (blue: values and data 2018). Provisional data. Data WSV, graph BfG
13 Lower water levels do not always mean lower water volumes
How can one explain the mainly the traversed river cross discharge, but a lower water differences in the record values section and the flow velocity. level is thus reached at the between levels and discharge? In the example shown in the gauging station. Such modifica- A low water level does not graph, the currently traversed tions of riverbeds can be necessarily mean low discharge, river cross section (red frame) observed in all German rivers. as the riverbed may have is deeper than in the former At the Vlotho/Weser gauging changed in the meantime. state (grey frame), because the station (see fig. 4), the record Relevant parameters for riverbed has deepened. With low was measured in 1991, determining the discharge are equal flow velocity, the same although discharge was higher than the record value of 1911. The riverbed has deepened accordingly. In order to be able to measure
Mean discharge correct discharge values, Lo flo old the ratio between water level
Lo flo 2018 and discharge is constantly analysed by the WSV and the Old riverbed calculations of the water Current riverbed volumes based on the level (water level-discharge-ratios) Fig. 5: Diagram of the effect of sole erosion on the water level recorded by a gauging station. are adapted accordingly.
14 Photo: Dr. Sebastian Kofalk, BfG
15 Mitigating effects by means of information: the role of BfG
Daring to take a (multifari- Water level measurements and data (fig. 6) featuring a large ous) glimpse into the future traffic-related forecasts for the number of single forecasts are Real-time monitoring of water federal waterways are published entered into a hydrological model levels and their prediction are via the WSV’s platforms PEGEL- to determine the discharge essential to allow optimum ONLINE and ELWIS (Electronic volume. In a hydrological model, handling of low-flow conditions Waterways Information Service). these are converted into water and acting anticipatorily. This The BfG develops and maintains levels and eventually optimized information notably enables forecasting systems that are and interpreted by means of optimizing the cargo volume of adapted to the relevant waterway statistical models. This multitude vessels and hence of transport and operates them jointly with of methods and models is neces- routes and dates. Moreover, WSV to continuously provide sary in order to minimize and they allow longer-term planning daily updated information. communicate the varying uncer- of transport capacity as well as The BfG’s diverse forecasting tainties in the various prediction optimization of warehousing for products are based on complex horizons. While indicating the loading trade. Eventually, model chains using extensive absolute values (including this real-time information can real-time data. Furthermore, the uncertainty range) is possible for be used to support planning in BfG regularly publishes low-flow short to medium-term forecasts, a waterways management, using reports during low-flow periods. prototypical 6-weeks-forecast is river water for industrial implemented in five categories processes or for drinking water To develop the forecasts, measured (from “lower” to “higher” than in production. data as well as weather model the long-term mean).
16 Meteorological forecasts Models Water level and discharge forecasts
a. Deterministic short to medium-term forecasts APRA-SIM Hydrological Kaub gauging station Water level forecast as of 12.12.2018 (20 Single forecasts) models
ECMWF/DWD (51 Single forecasts) Hydraulic models
Measured data measurement (raw data) forecast (0–2 days) estimation (2–4 days)
Meteorological and hydrological Statistical models measured data b. Probabilistic 10-days-forecast c. categorized 6-weeks-forecast (experimental, remains an ongoing subject of research and development) Probabilistic forecast – Kaub gauging station
0 % 6 % 14 % 4 % 20 % 22 % 35 % 47 % 6 % 25 % 2 % 100 % 0 % 29 % 43 % 2 % 45 % level [cm] Water
measured 29.11.18–05.12.18 06.12.18–12.12.18 13.12.18–19.12.18 20.12.18–26.12.18 values Probability of undercutting water level
6 % 10 % 10 % Longterm expected value 12 % 0 % 29 % 8 % 29 % slightly lower low
49 % 47 % normal high Fig. 6: Flowchart of prediction method used by BfG to 27.12.18–02.01.19 03.01.19–09.01.19 slightly higher generate three different forecast products.
17 Low-flow 2018 – a harbinger?
Are we feeling the effects of stream. It must therefore be Beyond these general conclu- climate change or is it a assumed that such periods of sions, the BfG has already normal weather pattern? drought may occur more implemented extensive and There have always been low- frequently along with rising detailed studies on the impacts flow periods. In Germany, they temperatures in the wake of of climate change on the occurred more frequently in the climate change. federal waterways. first half of the 20th century Within the scope of the inter- (e.g. 1921, 1947). They are the In the process, the negative agency departmental research result of a normal Central impacts on runoff might even programme KLIWAS European weather pattern. Such increase: notably the rivers (www.kliwas.de) by the Federal low rainfall as in 2018 is Rhine and Danube benefitted Ministry of Transport and caused by so-called atmospheric from above-average water Digital Infrastructure, the blocking situations. During the volumes from snow and glacier potential low-flow trends in the latter, a central high fails to be melt in 2018. 21st century have been ascertai- displaced by low-pressure By the end of the century, both ned. areas. This may be caused by a shares in the total water volume weakening of the jet stream. discharged will be, as a rule, Figure 7 illustrates the long- The rising temperatures that substantially lower than presently term increase in days with have been observed for decades and will then be especially values falling below a low-flow and the melting of the polar ice lacking during the autumnal dry specific value (Q95) using the cause a decrease of the jet period. example of the Middle Rhine
18 60
50
40
30
20
10
0 Total of days falling below low-flow specific values 1961 1990 2021 2050 2071 2100
AOGCM/ CM-dry AOGCM/ CM-humid ensemble mean Fig. 7: Projected number of days falling below low-flow specific values of the 95 % percentile (Q95) of the daily mean of runoff at the Kaub gauging station for the ensemble mean (grey bar) as well as dry (green) and a humid (blue) projection compared to the reference period 1961–1990. gauging station Kaub. For three scenarios. The question how the timescales it depicts the mean probability for the occurrence of value as well as the upper and low-flow events will change in lower limit of a range resulting future is subject to current from the use of varied climate research.
19 German Strategy for Adaptation to Climate Change scope of the German Strategy (DAS) – Basic service as a tool for handling future challenges for Adaptation to Climate Against the background of a changing climate with more frequent Change (DAS), that does not extreme events, the challenges facing users and managers of merely provide figures on water federal waterways become greater and increasingly socially levels, but a multitude of relevant. An improved and more comprehensive data basis for information for users, riparians decision-making is vital for potential adaptation. Therefore, the and managers of federal water- development of a basic service “climate and water” within the ways, is of vital importance.
Photo: Dr. Sebastian Kofalk, BfG
20 Water level – press reviews
Many people are closely linked to their home waters. The 2018 low-flow had diverse, partially extensive impacts on people’s daily lives. Therefore, the impacts of the persistent drought period in 2018 received major media attention. Using the BfG’s public relations work as an example, the following illustration shows the press response during the low-flow period.
30 440 BfG expert: BASF: “damming the Rhine” “extreme event” “Glacier melt will be lacking” 25 420 Heat stress “Tomatoes and melons
for fish growing in the Rhine” 400 20 380 15 GLW, Maxau 360 “Fuel prices are on the rise” 10 340 Water level Maxau “Rhine levels are rising once more” 5 320 [cm above zero point of gauge ] Number of digital press references
0 300
Wee 29 Wee 30 Wee 31 Wee 32 Wee 33 Wee 34 Wee 35 Wee 36 Wee 37 Wee 38 Wee 39 Wee 40 Wee 41 Wee 42 Wee 43 Wee 44 Wee 45 Wee 46 Wee 47 Wee 48 Wee 49
Fig. 8: Number of digital press references stating BfG in 2018 as compared to water Low flow issue temperatures and water levels at Kaub on the Rhine. Water temperature issue Various issues in the press were added, marked in blue and in italics, as „timer markers” and explanatory approaches. Water level Maxau
21 Literature:
1. Ademmer, M., J. Boysen-Hogrefe, S.Fiedler, D.Groll, N .Jannsen, S.Kooths und G. Potjagailo (2018). Aufschwung stößt an Grenzen–Belebung nur temporär. Kieler Konjunkturberichte 50(2018|Q4). Institut für Weltwirtschaft, Kiel (Kasten 1: 15–18)
2. Binnenschifffahrt online, 14.11.18: Niedrigwasser lässt Umschlag in Mannheim absacken, unter: https://binnenschifffahrt-online.de/2018/11/haefen-wasserstrassen/5277/niedrigwasser-laesst- umschlag-in-mannheim-absacken/
3. Wasserstraßen- und Schifffahrtsverwaltung des Bundes, Jahresbilanz 2018 für den Rhein vorgelegt. Pressemitteilung, 05.12.2019
4. Deutscher Fährverband, mdl. Aussage Michael Maul, Vorstandsvorsitzender, 14.12.18
5. Reuters Nachrichten, 26.11.2018: BASF stellt TDI-Produktion im Ludwigshafen wegen Niedrigwasser ein, unter: https://de.reuters.com/article/deutschland-basf-idDEKCN1NV1L0
6. SWR Aktuell, 8.12.2018: BASF macht Millionenverluste durch Niedrigwasser, unter: https://www.swr.de/swraktuell/rheinland-pfalz/ludwigshafen/Ludwigshafen-BASF-mit-riesigem- Schaden-durch-Niedrigwasser,meldung-21360.html
7. ZDF, Frontal21, Sendung vom 27.11.2018: Manuskript: Deutschland auf dem Trockenen – Wie der Klimawandel unser Land trifft, unter https://www.zdf.de/assets/manuskript-deutschland-auf-dem- trockenen-100~original
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Federal Institute of Hydrology Am Mainzer Tor 1 • P.O. Box 20 02 53 56002 Koblenz • Germany
Tel.: +49 261 1306-0 • Fax:+49 261 1306-5302 E-Mail: [email protected] • Internet: http://www.bafg.de
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