Goals and Management of the Ruhr Reservoir System Since the Beginning of Our Century
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Scientific Procedures Applied to the Planning, Design and Management of Water Resources Systems (Proceedings of the Hamburg Symposium, August 1983). IAHSPubi. no. 147. Goals and management of the Ruhr reservoir system since the beginning of our century F, W, RENZ Ruhr Reservoir Association, Kronprinzenstrasse 37, D-4 300 Essen 1, FR Germany ABSTRACT In the last 85 years a system of reservoirs has provided augmentational low flows in the Ruhr drainage area. The necessary discharge of the reservoirs compared with the water losses of the basin (i.e. the amount of water pumped over the watershed into adjacent areas for public water supply and the losses due to evaporation within the Ruhr basin) gives the gross efficiency rating of the reservoir system with respect to the goals of water management. The periods when parts of the reservoir system are not fully available for water manage ment are presented as a duration curve. Moreover the predicted water demand in the Ruhr area is compared with the measured amount. Today, the time which is needed to introduce a new reservoir within the system is longer than the period of time for which reliable forecasts of water demand are possible. Objectifs et aménagement du système de réservoirs de la Ruhr depuis le début de notre siècle RESUME Au cours des 85 dernières années, un système de réservoirs a été réalisé sur le bassin versant de la Ruhr en vue d'augmenter le débit de basses eaux. Le débit sortant exigé des réservoirs comparé aux pertes en eau du bassin (c'est à dire le volume d'eau pompée dans le bassin vers les zones voisines pour la fourniture d'eau au public et les pertes par evaporation dans le bassin de la Ruhr) conduit au calcul de l'efficacité globale du système de réservoirs par rapport aux objectifs de l'aménagement des eaux. Les périodes de temps au cours desquelles certaines parties du système de réservoirs ne sont pas disponibles pour l'exploitation des eaux sont présentées comme courbe de durée. En outre la demande prévue en eau est comparée avec la dernière valeur mesurée du volume d'eau qui a été utilisée. Actuellement le temps nécessaire pour aménager un nouveau réservoir dans le système est plus long que la période de temps pour laquelle il est possible de donner une prévision valable de la demande en eau. I PRODUCTION The subject of this paper is the water management system in a highly industrialized area in the Federal Republic of Germany (FRG). In the last decades of the nineteenth century coal mines and steel 637 638 F.W.Renz production developed in a formerly rural area. In 1899, steel production in this district was 4.6 times higher than in 1880. In 1899, only in the USA and England was more coal produced than by the Ruhr mines. In the first years of our century, the first steps towards today's water-management system were taken. Only five years after the foundation of the Ruhr Reservoirs Association in 1899, four reservoirs were completed for low-water augmentation of the River Ruhr (Renz, 1980). The water works pump the necessary water from the Ruhr into adjacent areas. Nowadays about 5 million people are supplied with water from the Ruhr. These 5 million people comprise about 8% of the total population of the FRG and are living in only 2% of its territory. The area is today, as well as 80 years ago, an area of heavy industry. Sixty percent of the coal, 40% of the steel, and 17% of the energy of the FRG are produced here; chemical, glass and car production are also to be found. Moreover an important part of the German brewery capacity is located here. Only a small amount of light industry exists (Londong, 1978). In this highly industrialized area called "Ruhr Revier" an amount of water equal to 75% of the mean annual rainfall is needed to supply the population and industry. Therefore it is necessary to pump water of good quality from other drainage basins into this district . For more than eighty years this water has been mainly drawn from the River Ruhr. Today a complex water management system exists, which comprises several subsystems, e.g. cooling water for energy production is today taken from the River Lippe in the north of the area and from shipping canals; during critical dry periods water is also pumped from the mouth of the River Ruhr; part of the demand for water of good quality is nowadays supplied by groundwater, which is pumped from the north into the district of high population density. Until now the water of the River Ruhr has been the basis for supplies for both domestic and industrial consumption. NATURAL RUNOFF AND WATER DEMAND 2 The mainly forested drainage basin of the Ruhr (4488 km") is hilly and a part of the so-called "Rheinisches Schiefergebirge" (Rhenish Slate Mountains). This type of rock is not very suitable for infiltration and storage of groundwater. The aquifers are mainly restricted to river valleys with layers of sand and gravel over an impermeable formation. The runoff of the Ruhr can decrease to 3—1 3—1 3.5 m s during extreme low-flow periods and increase to 2000 m s during floods. The average runoff for the period 1927/1981 is 78.3 m3s_1 or 2450 m3xl06year_1. The extent of human influence on the water cycle on the Ruhr is indicated by a comparison of the 3 P observed lowest annual runoff of 1316.6 m xlO" in 1964 to the 3 6 — 1 average water abstraction of 900 to 1400 m xlO-year In contrast to some other districts in Germany, e.g. the water supply system of the Harz reservoirs, the water for public water supply in the Ruhr district is not taken directly from the reservoirs by pipelines, but indirectly transported by the River Ruhr to the water works. The water discharged from reservoirs is used for a Management of the Ruhr reservoir system 639 variety of purposes (cooling, energy production etc.). The main water works are located in the lower and medium reach of the Ruhr (Imhoff & Mantwill, 1980). Except for dry periods the water demand can be covered by the natural runoff of the drainage basin. In dry periods the minimum runoff in the River Ruhr, which is necessary for the water works, is guaranteed by water discharged from the reservoirs of the Ruhr Reservoirs Association (Maniak & Renz, 1978) . This means that in the Ruhr system the reservoirs are required only during periods of low flow. This reduces the necessary storage capacity. The supply district of the water works along the river is not restricted to the drainage basin of the Ruhr. It includes adjacent areas (Fig.l) (i.e. the drainage basins of the rivers Emscher, Lippe, and Wupper). Ruhr water which is pumped for domestic and industrial supplies in these adjacent areas or lost by evaporation from the supply system in the drainage basin of the Ruhr is termed "water losses" in this text. These water losses of 320 to 420 m3xl06year_1 or about 30% of minimum annual runoff are the crucial point for the formulation of the goals of water management in the Ruhr basin. THE DUTIES OF THE RUHR RESERVOIRS ASSOCIATION The water works along the Ruhr require a minimal water quantity and quality in the river. The water quality of the River Ruhr and its :/*>*' (W e« ,\to«* ^ , Wf ol°*vAe° pve» ' IDORTMUNn, I ESSEN . ^J> Sorpe A Gauge with long-distance trans- r mitterused for the daily management of the system -Watershed of the Ruhr drainage basin ^***v impounded Lakes •^ Reservoirs /rT Wate r pumped to adjacent areas ESSEN, DORTMUND = towns Rhine.Ruhr, Lenne.Volme = rivers FIG.l Water management system in the Ruhr drainage basin, 640 F.W.Renz tributaries is guaranteed by the Ruhr River Association (Ruhrverband, founded 1913) and the water quantity by the Ruhr Reservoirs Association (Ruhrtalsperrenverein, founded 1899). The organization and the financing of these two associations, operating in the natural drainage basin of River Ruhr, were formulated by two special laws of 1913 (RTG 1913, Imhoff, 1977). In the adjacent drainage basins other authorities were founded in order to resolve special water management problems (Imhoff, 1974; Londong, 1978). The special law for the Ruhr Reservoirs Association ("Ruhrtalsper- rengesetz") guarantees that the existing ecological system will not be changed by water abstractions for population and industry. The law requires an augmentation of low flows smaller than 4.5 1 s— 1k m 2 during dry periods by water from reservoirs of the association (Bower et al., 1981). Today a total storage capacity of 471.1 m x 10 exists from which only an effective storage capacity of about 410 m x 10 (cf. Table 1) can be used for replenishing natural runoff, i.e. a storage capacity nearly corresponding to the average annual amount of water TABLE 1 Data from the large reservoirs in the Ruhr drainage basin Moehne Henne Sorpe Bigge Verse Total Gross storage capacity (m3 x 106 ) 134.134.5 .5 38. .4 70. .0 171. .7 32. .8 447. .4 Dead storage capacity (mi x 10°) 6. .7 2. .0 3. 5 7. .5 2. .0 21 .7 Net storage capacity (m x 10 ) 127. .8 36. .4 66. .5 164. .2 30. .8 425. .7 Drinking water (m3 x 10s) - - 0. .5 4. .0 12. 3 16. .8 Effective storage capacity (m3 x 106 ) 127. .8 36. .4 66. .0 160. .2 18. .5 408 .9 Mean annual inflow (m3 x 10e) 204.