Hydrology for the WaterManagement of Large Biver Basins (Proceedings of the Vienna Symposium, August 1991). IAHS Publ. no. 201,1991.

CO-OPERATION IN HYDROLOGY OF THE BASIN COUNTRIES

K. HOFIUS Bundesanstalt filer Gewaesserhmde, IHP/OHP-Sekretariat, Postfach 309 D-S4O0 Koblenz, Federal Republic of

ABSTRACT Since 1970 the Rhine basin countries, i.e. Austria, , Federal Republic of Germany, France, Luxemburg and the Netherlands, are co-operating under the International Hydrological Decade and the International Hydrological Pro­ gramme. The type and the results of that co-operation are dis­ cussed. The first part of the paper deals with the administrative possibilities of implementing the co-operation of several states bordering a large river basin. It is important that the programmes to be set up are not too comprehensive so that they lead to results within a reasonable time. Particular problems arise in integrating the results at the borders. Isolines, for instance, do not agree with one another etc. Through the co-operation of the Rhine basin coun­ tries experience has been gained, which may be of use for other states in their co-operation for large river basins. The results of the work achieved so far by the International Commission for the Hydrology of the Rhine Basin established in 1970 are presented. In the second part of the paper the most striking hydrological charac­ teristics of the flow regime of the Rhine are presented.

ORGANIZATION OF THE CO-OPERATION

The International Hydrological Decade (IHD), which was launched in 1965 by UNESCO, had as one of its objectives the stimulation of regional co-operation in the field of hydrology. Representatives from the Rhine basin countries, i.e. Austria, Switzerland, the Federal Republic of Germany, France, Luxemburg and the Netherlands, established the International Commission for the Hydrology of the Rhine basin in 1970. The Commission maintains a permanent secretariat in the Netherlands; the chairmanship of the Commission rotates every three years. The first important decision taken by the Commission was to concentrate on quantitative hydrological data. Subjects such as navigation and pollution loads were intentionally omitted, because these subjects were handled by other commis­ sions, such as the Central Rhine Navigation Commission and the International Commission for the Protection of the Rhine against Pollution (ICPR). The Commission's objective was to make a study of hydrological phenom­ ena in the Rhine basin, aimed mainly at making an inventory of data and improving methods of forecasting.

25 KHofius 26

It was decided to publish such an inventory in the form of a monograph on the Rhine basin. After many years of intensive co-operation between hydrologists, meteorologists and geographers from the CHR member countries, the monograph was published in 1978. It consists of three parts: a textbook, a section with tables and an atlas containing maps and figures. The textbook describes the geography and geology of the Rhine basin and its climate, hydrography and hydrometry, discharge, meteorological and hydrological conditions during some wet and dry periods, and the application of hydrological forecasting models. In the tables section, a large quantity of information concerning gauging stations, precipitation gauges, discharges, evaporation etc. is listed. The atlas contains 67 maps and figures, presenting information on subjects such as morphology; geography; geology; pedology; geohydrology; land use; average precipitation depths and numerous hydrological characteristics, such as longitudinal profiles and cross sections of the Rhine and a large number of its tributaries; discharge-duration curves and hydrographs for water level and discharge. Upon completion of the monograph, the Commission began work on a new research programme with the following topics: (a) A study on standardization and processing of hydrological data of the Rhine basin. A working group was established to harmonize measurements and data-processing. In 1986 this working group prepared a report on the calculation of high- and low-discharge probabilities in the Rhine basin (report 1-4), describing the calculation methods used in the member countries of the Commission and presenting a survey of the distribution functions applied. In the same year the working group, as a result of German-Dutch co-operation, prepared a report on discharge measurements in the German-Dutch border area (report 1-5), clarifying the differences that have existed for several decades between the discharge rate figures of the Rhine on the German and on the Dutch side of the border. The report also contains recommendations for improving the existing situation. Another report of this working group discusses the calibration of current meters (report 1-6). It contains the results of an intercalibration experiment which had been implemented to determine the influence of the calibration of current meters on the accuracy of discharge measurements. On the basis of the calibration results, sources of inaccuracy in calibration are analyzed and recommendations are made for reducing such inaccuracies. (b) A study on how to improve hydrological forecasts by means of a regular exchange of information. A working group named "Forecasts" was established to carry out such a study. As the first result of its work, a report on objective, quantitative precipitation forecasts in the Rhine basin was prepared in 1982 (report 1-1). A report describing the water level and discharge forecasting models used in the Rhine basin was published in 1988 (report 1-7). (c) A survey of hydrological research basins and representative basins in order to attain a more adequate exchange of results and a better harmonization of studies. As a result of these activities, a catalogue was published in 1985, in which all existing and some former hydrological research basins in the 27 Co-operation in hydrology of the Rhine countries

Rhine area are described (report 1-3). (d) Description of the extreme hydrological periods in 1976, 1983, 1988, in order to gain a clearer insight into the hydrological phenomena of such periods. The report on the 1988 flood also contains an analysis of the relation between the discharge and the waterquality, including the sediment transport. (e) An update of the information that was published in the tables section of the monograph. The Commission intends to publish a survey for every decade; the first survey, for the period 1971-1980, is in preparation. (f) Study of the changes in discharges caused by anthropogenic influences. This study is being prepared by a working group which will first make an inventory of the engineering works that have been carried out in the Rhine basin since about 1800. Subsequently, the influences of these works on discharges will be examined. (g) Research into travel and residence times in the Rhine. The disaster which occurred in 1986 at the Sandoz chemical plant in has accelerated this study. A joint working group of the Commission and ICPR has developed a forecasting model for travel times of pollutant waves (report II-2). A further improvement of the model, including tracer experiments, is being worked on (see paper by Broer in these proceedings).

Other items on the CHR research programme are: Relationship between forest damage and the hydrological regime of the Rhine Digitization of maps Effects of climatic changes on the Rhine basin and development of a discharge model which covers the complete Rhine basin Sediment transport Hydrological distribution functions Cost-benefit analysis of surface-water gauging networks.

Reports resulting from studies of working groups and rapporteurs appear in the CHR series I. The Commission also offers the opportunity to individual authors to publish hydrological studies (provided they are relevant to the Rhine basin) in a second series of CHR publications. The author however remains responsible for the content of these reports. A list of all CHR publications is given at the end of this paper. In general, all CHR publications are bilingual (French and German) with a summary (and sometimes recommendations) in Dutch and English. Water resource departments normally have no time for a coordinated elaboration of hydrological fundamentals of the entire catchment basin. However, there are many important questions going beyond the events of the day, which require a thorough analysis of the hydrological properties of a river basin. How else could one give answers to questions such as the influence of dying forest on streamflow conditions, the influence of climate changes on runoff etc. Again and again it is found that scientific results from studies carried out in the framework of the CHR are suddenly urgently needed for practical pur­ poses. This can be illustrated by an example: In the early eighties the CHR started to examine flow velocities. During and after the Sandoz pollution disaster K. Hoflus 28 in 1986, the relevant results of this study were of high topicality and very much in demand for the construction of an alarmmodel. The co-operation of the Rhine basin countries shows that the programmes to be set up should not be too comprehensive so that they lead to results within a reasonable time. Summing up, it can be stated that the co-operation of the Rhine basin countries - and this applies equally to the Danube countries (see relevant contribution in the present publication) - fulfils an important function which cannot be fulfilled by the national water resource departments alone.

HYDROLOGY OF THE RHINE BASIN

Introduction

The catchment area of the Rhine (Fig. 1) of some 185 000 km2 is relatively small as compared to the catchments of the other major European rivers, yet the Rhine is one of the most important and most voluminous rivers in . The water flow is steady and so it has become one of the busiest navigable waterways in the world. It is a river that links the Alps with the North Sea. Its catchment area is partly in the Alps and the alpine foothills, partly in the Central Uplands, and partly in the lowlands. The total length of the river is 1 320 km. The principal tributaries of the Rhine and their respective catchment areas are the (28 100 km2), (27 200 km2), (17 800 km2) and (14 000 km2). Except for a few parts of the Alps the Rhine basin is used for agriculture and forestry, with varying degrees of intensity. The Rhine basin is densely populated, about 50 million people live in the area with highly-developed land use by commerce, industry and agriculture is combined with a sound infrastructure and favourable temperatures. The Rhine basin is situated in the west-wind belt of the northern hemi­ sphere. Within this belt, moist Atlantic low pressure systems move over the Rhine basin from the south-west, west and north-west. However, their influence on the climate and weather varies considerably within the Rhine basin depending on altitude and distance from the sea. The frequency and the effects of the westerly weather conditions decrease steadily from the Rhine estuary towards the region of its sources, whereas high pressure conditions increase towards the south. The water levels of the Rhine have been continuously observed for some 240 years. Most of the water gauges were installed during the first half of the 19th century. During the 20th century, and particularly after World War II, more and more recording gauges have been installed and their data have been used for various purposes: flood forecasting, navigation, riverbed investigations, the transport of sediments and pebbles, water supplies, investigations of water quality, and the colonisation of the water by plants and animals. 29 Co-operation in hydrology of the Rhine countries

JEDERLAND*- BUNDESREPUBLIK

DEUTSCHLAND

TTpPe

BELGIE ^

(l*v >\V

Kinzig

OSTFRREICH

ITALIA O 25 50 75 100 125 ktr

Fig. 1. Catchment area of the Rhine basin. KHofius 30

Discharge Characteristics

Discharge is influenced by a number of individual factors which are subject to considerable variation within the Rhine basin. In general terms it is true that the further downstream one goes the more steady the discharge becomes because all the different influences cancel each other out. The alpine catchment area of the Rhine has an area of more than 16 000 km2. The highest parts of this region are drained by the Aare and its tributaries, the Reuss and Limrnat. The peculiar feature of the Aare basin is its large number of lakes. The alpine catchment area of the Rhine includes an unstable area of glaciers that has varied from 663 km2 in 1876 (Siegfried Atlas) to 548 km2 in 1934 (Landeskarte der Schweiz, Mercanton, 1958), to some 460 km2 in 1973. These three figures indicate that nowadays some 1.3% of the catchment area of the Rhine up to Basel has been or is glaciated. The percentage area of the lakes is even higher. The surface area of the 16 largest lakes is 1,219 km2, with taking up 542 km2 of this. Snow, glaciers and lakes all have an effect on the discharge. One of the effects of lakes is that they curb the high water levels and augment the low water levels. Table 1 shows the lowest (LQ), mean (MQ) and highest (HQ) discharge rates at selected water gauges in the alpine catchment area of the Rhine for the years 1951-1970, and also the ratio of LQ:MQ:HQ. Comparison of these figures permits assessment as to how steady or unsteady the discharge is. In fact, the discharge rates of the Vorder Rhine and Hinter Rhine are very unsteady. The high discharge peaks from this sampling period are more than 1,000 times the lowest recorded values (the water gauges at Disentis and Hinter Rhine). Also the ratio of the lowest to the mean discharge rate is, at 1:32 or 1:34, very high. As the catchment area increases in size, so these differences become less marked. At the Schmitter water gauge on the Rhine above Lake Constance the ratios are 1:4:40. It is only when Lake Constance has been crossed that there is any decisive change in the discharge ratios. At the Rheinklingen water gauge the ratio is 1:3:8. This clearly shows the levelling influence of Lake Constance. With the influence of the left bank tributaries and Toss, which, without the influence of any lakes, have an extremely unsteady discharge regime, the discharge ratio of the High Rhine becomes slightly more unsteady. The discharge pattern of the Aare (Table 1, Stilli) and its tributaries is due above all to the presence of the lakes. With a relatively small increase in their water surface they are able to store a considerable volume of discharge. They therefore act as reservoirs at times of high water, and have a levelling effect on the highly fluctuating discharge rate in the high mountain region. In addition to this, almost all the lakes can be regulated so that there can be a direct influence of man on the natural rate of discharge. The water gauge at Basel records the discharge of the entire catchment area of the . As Lake Constance and the lakes in the catchment area of the Aare have a levelling effect, the ratio of 1:4:12 at Basel is relatively steady. Table 2 summarises some of the monthly discharge rates in the Alpine Rhine basin. The melting of the glaciers, together with the precipitation which 31 Co-operation in hydrology of the Rhine countries

Table 1. Lowest, mean and highest discharge rates and the LQ:MQ:HQ at selected water gauges in the Rhine basin up to Basel for the years 1951 ... 1970.

Gauge, elevation above m3.s-' ratio msl LQ MQ HQ LQ MQ Receiving stream m

Disentis, 1066 m Vorder Rhine 0.16 5.1 170 1 32 1063 Hintherrhein, 1581 m Hinter Rhine 0.1 3,44 115 1 34 1 150 Schmitter, 400 m Rhine 64.5 233 2600 1 4 40 Stilli, 319 m Aare 138 557 2 050 1 4 15 Basel, 24 m Rhine 319 1079 3 890 1 4 12

attains its maximum level during the summer months, results in the highest discharge rates being recorded in June (maximum), July and August. The low water period is not so consistent and the mean low water levels (MLQ) are not always recorded in the same month: in February they are observed at the Hinter Rhine water gauge, in January at the Rheinklingen water gauge, and in Novem­ ber at the Stilli and Basel water gauges. Catchment areas that have their maxi­ mum discharge in the summer and their minimum discharge in the winter are, following Pardé, termed glacial discharge regimes. At Basel the Rhine loses the predominantly alpine character of its catch­ ment area. It flows through the rift valley between Basel and Bingen, and this section is called the . This is a large region of 63 000 km2 and drains the Central Upland areas. The hydrological regime of the running water in this region is fundamen­ tally different from that in the high mountains. The maximum discharge in winter and spring and the minimum in the summer months (see Table 3). Although precipitation amounts in the Upper Rhine basin and the periph­ eral uplands generally reach their maximum during the summer months, the maximum discharge, as mentioned above, is recorded during the winter. A discharge regime that is characterised by the retention of snow and the distribu­ tion of precipitation is termed either a nivo-pluvial or a pluvio-nival regime according to which of these two factors predominates. At Basel the mean water flow of the Rhine is 1 079 irf.s"1; at the Maxau gauge this has increased by 231 m3.s"' to 1 310 m3.s"'. Downstream of the Rhine/Neckar confluence the mean discharge increases to 1 440 m3.s_1 at the Worms gauge (see Table 3). At the Mainz gauge, downstream of the confluence of the Main and the , as mean annual discharge is 1 620 m3.s4 measured. At Basel the Rhine drains of almost 36 000 km? and at Mainz an area of 98 500 km2. Although the catchment area increases 2.7 times between Basel and Mainz, the mean annual discharge between these two points only increases 1.5 times. K. Hofius 32

Table 2. Mean monthly rates and mean annual rate of discharge at selected water gauges in the Alpine Rhine basin for the period 1951 ... 1970 in nf.s'1.

Gauge Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year river/basin size km1

Hintherhein, HinterRhine 0.43 0.32 0.39 1.33 4.93 8.94 8.52 7.40 4.89 2.07 1.17 0.62 3.43 Rheinklingen, Rhine 221 227 245 312 442 582 606 515 447 342 272 239 372 Stilli, Aare 415 468 495 598 753 834 799 712 557 424 395 396 557 Basel, Rhine 802 883 927 10871336 1512 1512 1340 1092 849 778 780 1079

Table 3. Mean monthly rates and mean annual rate of discharge at selected water gauges in the Alpine Rhine basin for the period 1951 ... 1970 in nf.s'1.

Gauge Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year river/basin size km2

Maxau, Rhine 1110 1210 1230 13601550 1730 1680 1490 12601020 10001070 1310 Worms, Rhine 1310 1450 1460 15301640 1800 1740 1540 13201100 10901230 1440 Mainz, Rhine 1570 1740 1760 18001820 1930 1860 1650 14301220 12201470 1620

This means that in the alpine catchment area runoff rates of the land surfaces are almost double the runoff rates of surfaces of the same size in the Central Uplands, and this in turn is reflected in the gradual decrease of the specific yields at the Rhine gauges: Basel 30.9 l.s'.km"2, Marlen 26.8 l.s'.km"2, Maxau 26.0 l.s.-'km"2, Worms 20.9 l.s'.km"2, and Mainz 16.4 l.s'.km2. Study of the mean discharge rates recorded through the year at the Rhine gauges also shows the dominating influence of the alpine catchment area. Although the water gauges on the tributaries downstream of Basel record the highest water levels in wintertime or early in spring, the water gauge on the Rhine at Mainz always records the highest discharge in June, whilst in October and November the lowest discharge rates are recorded. The ratio between the mean low water and high water discharges decreases steadily: at the Basel gauge the ratio of MLQ: MQ is 1:1.94, at Maxau 1:1.73, at Worms 1:1.65, and at Mainz 1:1.58. Between Bingen and the Rhine/ confluence the Rhine basin increases by only 800 km2. There are no large tributaries along this section, hence the 33 Co-operation in hydrology of the Rhine countries

Rhine has almost the same features at the Kaub gauge (see Table 4) as at the Mainz gauge (see Table 3). Downstream of the Rhine/Lahn confluence and of the most voluminous tributary, the Moselle, the Rhine takes on other characteristics, as is demon­ strated at the Andernach gauge. At this point (see Table 4) the maximum discharge is 2,520 m3.s"' which is recorded in February, whilst the lowest dis­ charge rate is recorded in autumn (September, October, November). Spring and summer discharge rates are still considerable, with a MLQ: MHQ ratio of 1:1.73. The discharge rate of the Rhine is now significantly influenced by the discharge rates of the Moselle, which in winter contribute to about 1/4 and in summer about 1/8 of the total discharge of the Rhine. Downstream of the Rhine/Moselle confluence, the Rhine shows the combined discharge characteris­ tics of die glacial, nival and pluvial regimes. This means an extremely steady water flow throughout the year. Rivers which are influenced by a number of different but compensatory factors have, according to Pardé, a complex discharge regime. That discharge regime is characteristic for the Rhine down to its mouth.

Table 4. Mean monthly rates and mean annual rate of discharge at selected water gauges in the entire basin, in rrf.s'1 over a period of many years.

Gauge Jan Feb Mar Apr May Jim Jul Aug Sep Oct Nov Dec Year river/basin size km1

Cochem, Mosel 562 573 445 364 252 176 144 135 144 178 307 514 315 Kaub, Rhine 1670 1830 1840 18701980 1980 1900 1680 14601250 12801570 1670 Andernach, Rhine 2350 2520 2380 23002160 2160 2060 1830 16301460 16302200 2060 DUsseldorf, Rhine 2600 2750 2610 2530 2320 2320 2230 1980 17901640 18002440 2250

Anthropogenic influences

The demands that man makes on a large river and its immediate surroundings are very diverse. They include shipping, water supply, energy production, sewage disposal, recreation, special areas for the development of housing and trade and construction of roads and railways. In previous centuries, high water and flooding over wide areas, particularly in the Upper and basins, forced man into a continuous defensive activity which has led to developments in almost all the watercourses during the last 180 years. The main aim of these developments has been protection against floods and of the interests of shipping. The measures taken have involved strengthening and straightening of river courses, the building of dikes to prevent flooding, works to develop and stabilise the shipping channels and the construction of weirs and reservoirs. K. Hofius 34

These measures have, as intended, effected in draining off peak flows more quickly and keeping the Rhine open as a shipping route throughout the year. Naturally such modifications, which were necessary and ecologically justifiable at the time, have not been without effect. Erosion in the riverbed occurred especial­ ly in the southern part of the Upper Rhine, with the result that the Rhine bed soon became several metres deeper. This in turn led to a lowering of the water table which in certain regions is now below the level at which it can be reached by the vegetation. During the present century, reconstruction measures have been undertaken with the Grand Canal of Alsace, the straightening of meanders, and projects to modify the river course between Basel and Neuburgweier. These have all been aimed at improving the Rhine as a shipping route, managing the quantity of water, and generating energy. Each new project has initiated further erosion of the riverbed, and to prevent this, work has continuously been undertaken on the more northern sections of the Upper Rhine to construct weirs, insofar as erosion of the riverbed cannot be halted by any other means. The modifications carried out by man in the Upper Rhine have been the most extensive that have been made in the entire catchment area of the Rhine and the most significant in their consequences. The measures taken in the Swiss area must, even from an ecological point- of-view, be judged as mainly positive. The so-called first and second adjustments to the Jura rivers directed various rivers into lakes and produced a marked reduction in high water levels and an augmentation of low water levels. As a protection against flooding and silting-up, the Rhine upstream of Lake Constance has been modified by canals and by straightening of the riverbed involving the construction of channels and dikes. Twelve hydroelectric power stations have been built on the High Rhine; further twelve locks had to be built in order to convert it into a navigable waterway. In the upland section of the Middle Rhine, a navigable channel was constructed but this did not alter the discharge behaviour. In the German part of the Lower Rhine measures to stabilise the navigable channel and the construction of dikes began in the 18th century. Till then this section of the Rhine, like the Upper Rhine, had been flowing through an alluvial plain up to 8 km in width and with a bed that frequently changed its course during low flow periods. In the Netherlands very extensive modifications have been made to the various branches of the Rhine delta with the aim of protecting the land against floods, improving the navigable channels, and providing drinking and other water as required. The sluices constructed at Volkerak and Haringvliet in the coastal region are measures against storm tides and the intrusion of salt water into the estuarine region. In many of the Rhine's tributaries developments have taken place also for reasons of flood protection and, in the case of the Neckar, Main, Lahn and , also to make navigation possible. It is not only the direct modifications of the flowing waters that have contributed to changes in the pattern of discharge. Intensified agricultural land use and surface sealing of extensive regions of the catchment area of the Rhine through settlements, industry and roads have all had some influence on individual 35 Co-operation in hydrology of the Rhine countries parameters of the water balance. It would be possible to quantify the effects of individual activities in parts of the area, but no attempt has yet been made to do this for larger parts of the catchment area because of the enormous complexities of such a task.

ACKNOWLEDGEMENT The secretariat of the CHR is gratefully acknowledged for providing the basis for the first part of this paper.

CHR PUBLICATIONS

CHR/KHR (1978) Dos Rheingebiet, Hydrologische Monographie. Le bassin du Rhin. Monographie Hydrologique. Staatsuitgeverij Den Haag. ISBN 9-1201-775-0. CHR/KHR (1990) Das Hochwasser 1988 im Rheingebiet/La crue de 1988 dans le bassin du Rhin. ISBN 90-7098-011-8. Buck, W., Kipgen, R., Madet J.W. van der, Montmollin, F. de, Zettl, H., Zumstein, J.F. (1986) Berechnung von Hoch- und Niedrigwasserwahrscheinlichkeit im Rheingebiet/Estimation des probabilités de crues et d'étiages dans le bassin du Rhin. ISBN 90-7098-003-7. Engel, H., Schreiber H., Spreafico, M., Teuber W., Zumstein, J.F. (1990) Abfluj3ermittlung im Rheingebiet im Bereich der Landesgrenzen/Détermination des débits dans les régions frontalières du bassin du Rhin. ISBN 90-7098-001-x. Gerhard, H., Made, J.W. van der, Reiff, J. Vrees, L.P.M. de (1983) Die Trocken- und Niedrig wasserperiode 1976. (2. Auflage 1985)/La sécheresse et les basses eaux de 1976 (2 ème édition, 1985). ISBN 90-7098-001-0. Grebner, D. (1982) Objektive quantitative Niederschlagsvorhersagen im Rheingebiet. Stand 1982 (nicht mehr lieferbar)/Prévisions objectives et quantitatives des précipitations dans le bassin du Rhin. Etat de la question en 1982 (édition épuisée). Griffioen, P.S. (1989) Alarmmodell fur den Rhein/Modele d'alerte pour le Rhin. ISBN 90-7098-007-x. Hofius, K. (1985) Hydrologische Untersuchungsgebiete im Rheingebiet/Bassins de recherches hydrologiques dans le bassin du Rhin. ISBN 90-7098-002-9. Made, J.W. van der (1982) Quantitative Analyse der Abflusse (nicht mehr lieferbar)/Analyse quantitative des débits (édition épuisée). Mendel, H.G.(1988) Beschreibung hydrologischer Vorhersagemodelle im Rheineinzugsebiet/ Description de modèles de prévision hydrologiques dans le bassin du Rhin. ISBN 90-7098- 006-1. Schroder, U. (1990) Die Hochwasser an Rhein und Mosel im April und Mai 1983/Les crues sur les bassins du Rhin et de la Moselle en avril et mai 1983. ISBN 90-7098-009-6. Sprokkereef, E (1989) Verzeichnis der fttr internationale Organisationen wichtigen MeQstellen im Rheingebiet/Tableau de stations de mesure importantes pour les organismes internationaux dans le bassin du Rhin. Katalog/Catalogue 1. ISBN 90-7098-008- 8. Teuber, W., Veraart A.J. (1986) Abnu/3ermittlung am Rhein im deutsch-niederlândischen Grenzber eich/La détermination des débits du Rhin dans la région frontalière germano-hollandaise. ISBN 90-7098-0045. Teuber, W. (1987) Einflu/3 der Kalibrierung hydrometrischer Me/?flugel auf die Unsicherheit der Abflu/3ermittlung. Ergebnisse eines Ringversuchs/Influence de l'étalonnage des moulinets hydrométriques sur l'incertitude des déterminations de débits. Résultats d'une étude compara­ tive. ISBN 90-7098-005-3.