Danube-Main crossing

from Wikipedia, the free encyclopedia

With the Danube-Main crossing , the water management authorities of the Free State of Bavaria channel water from the Danube river system into the Regnitz and Main river in Franconia , which is threatened by temporary drought . The water crosses the main European watershed in the northern foreland of the Franconian Jura and the entire Franconian Jura traversed by the sheath .

Overview

The transition includes two independent systems that were created with considerable effort in terms of hydraulic engineering. At the upper Altmühl , floods have been diverted into the Altmühlsee since 1999 , from where it passes through a tunnel into the Brombachsee , which is already lower on the other side of the watershed . It is stored here and, if necessary, released into the Regnitz via several other rivers. The electrical energy-powered canal crossing through the Main-Danube Canal accounts for a much larger share . Since 1994, water has been pumped from the Danube into the top of the canal via pumps at the five locks on the southern ramp of the canal , from where it flows downwards over another barrage into the Rothsee , where the water is stored and, if necessary, in two different ways is also delivered to the Regnitz. In the long term, an average annual transfer through the entire system of 150 million m³ of water is expected, 5/6 of which via the Main-Danube Canal.

The system of the Danube-Main crossing includes a total of three lakes, of which the Altmühlsee with ring dam and two dams with Brombach and Rothsee, which because of their pre-dams comprise five dams, three hydropower plants at the dams and the Hilpoltstein lock, the canal routes to Altmühlsee and from there to the Brombachsee and 27 further weirs on watercourses, some of which have been developed for higher water flow. In addition, there are parts and facilities of the Main-Danube Canal that also serve other purposes: the canal itself between the connection to the Danube and the outlet into the Schwarzach along with inlet and outlet structures and the pumping stations of the southern ramp. The cost of setting up the system, the detailed planning of which was started in 1971 by the Nuremberg New Dam Construction Office, which existed until 2000, amounted to around 450 million euros.

The operator of the transition is the Ansbach water management office, which maintains an operations management in Schlungenhof am Altmühlsee and has also set up an information center in the Mandlesmühle directly at the outlet of the Großer Brombachsee .

In addition to the water management functions, the lakes with a total of 20 km² of water and 80 km of public roads are also used for local recreation . 540 hectares of lake and bank areas are under nature protection .

While in the name Rhine-Main-Danube Canal, the rivers in the word of the geographical arrangement on the two available modes corresponding map, the term Danube-Main Reconciliation reflects the direction of flow of the pumped from the Danube toward Main resist trickling water.

aims

Without the addition, the Regnitz can carry less than 10 m³ / s of water at the Hüttendorf gauge when it is dry . This brought considerable restrictions on use and ecological dangers. B. for the removal of bank filtrate for irrigation of the Central Franconian vegetable growing area , which was only possible with the transition, or through the use of cooling water u. a. through the energy industry . The aim is therefore to increase the low water discharge of the Regnitz at the Hüttendorf gauge to 27 m³ / s in summer and to 22 m³ / s in winter. In addition, high water in the upper Altmühl near Ornbau is diverted into the transfer system, which is intended to protect the Altmühltal below from flooding.

Brombach transition

Heights [m above sea level NN] Altmuehlsee Little
Brombachsee		 Great
Brombachsee
Highest congestion destination 416.00 411.50 411.40
Flood target 415.50 - 410.50
Summer traffic jam destination 415.00 410.60 407.50
Winter traffic jam destination 414.50 410.60 406.50
Lowering target - - 403.50
Exceptional lowering target 413.50 409.00 -

In the event of flooding in the Altmühl, excess water at Ornbau is fed into the 5 km long Altmühl feeder to the Altmühlsee. Because of the very flat Altmühltal in this area, the lake floor is at the same height as the surrounding area. The 4.5 km² large lake is surrounded by a 12.5 km long circular dam, very shallow with an average water depth of 2.5 m and the inlet has to branch off from the river well above the lake in order to be able to reach the necessary storage target. At low tide, water can also be released back into the Altmühl from the lake, but as a rule it is initially transferred from the Altmühlsee through the 8.7 km long Altmühlüberleiter , which crosses under the watershed in a tunnel for 2.7 km the Kleiner Brombachsee and from there into the immediately adjacent Großer Brombachsee. The transfer bridge has a maximum capacity of 70 m³ / s and last uses the former bed of the Brombach . The water level of the small Brombach lake is, like that of the large flow through the second Igelsbach fed Igelsbach lake , held by a feedforward Perren dam largely constant. The Große Brombachsee, dammed up by the main dam, serves as a reservoir and the water level can fluctuate by up to seven meters in regular operation depending on the irregular inflow and outflow. If the water flow in the Regnitz is insufficient, water from the Brombachsee can be discharged into the lower reaches of the Brombach in excess of the minimum amount. This is done via a power plant with a design output of 630 kilowatts (two through-flow turbines with 315 kW each). This amount of water flows into the Main via Swabian Rezat , Rednitz and Regnitz .

In the years 1995–2013, an average of 27.9 million m³ of water was passed over the watershed in this way, after the end of the damming, an average of 26.5 million m³ was passed over and 28.7 million m³ out of the water between 1999–2013 Brombachsee surrendered, with 11 million m³ additional inflow from the catchment area of ​​the Brombach expected.

Channel transition

Height and length profile of the Main-Danube Canal. The channel transition is from the right in the schematic representation.

At the locks on the southern ramp of the Main-Danube Canal - Kelheim, Riedenburg, Dietfurt, Berching and Bachhausen - pumping stations with a delivery rate of 35 m³ / s are installed, which serve both to supply the canal with water and to transfer it. A maximum of 21 m³ / s is provided for the transfer, which is pumped into the apex of the sewer during low tariff periods . Thereby, 67.8 m from the Danube and 51 m from the lower Altmühl, which is identical to the canal below the Dietfurt lock, but usually does not have enough water. This water then flows through a power plant with 3 megawatts of electrical output at the Hilpoltstein lock with a drop height of 24.67 m  . At the Eckersmühlen lock, it is channeled from the upper water into the immediately adjacent Rothsee, a reservoir created in the valley of the Kleine Roth . Since the inflow can be controlled in large areas here - with the exception of low water levels in the Danube - the Rothsee is much smaller than the Brombachsee.

Heights [m above sea level NN] Danube near
Kelheim		 ...
Riedenburg
(Altmühl) attitude		 ... Hilpoltstein apex
posture
 Attitude
Eckers-
mills		 Rothsee Entertainment
spaces
stetten
Highest congestion destination - - - - 375.26 -
Summer congestion destination
Winter congestion destination 		338.2 355.0 406.0 381.3 374.20
373.70 		356.7
Lowering target - - - - 367.20 -

The water discharge from the Rothsee of a maximum of 15 m³ / s takes place partly in the lower reaches of the Kleine Roth, from where the water flows over Roth , Rednitz and Regnitz in turn to the Main , partly into the underwater of the canal lock, where it flows through another barrage the Schwarzach is diverted, which also flows into the Rednitz.

In the years 1994–2013 an average of 97 million m³ of water was transferred into the Rothsee annually, the natural inflow of the Kleine Roth amounts to approx. 9.3 million m³, 107 million m³ were released. The water level in the main dam can fluctuate by up to seven meters, in the pre-dam fed by the Kleine Roth it is largely constant. In the case of low and medium discharges, the water is discharged via the two turbines of the associated power plant, which are designed for a flow rate of 1.0 m³ / s and 5.0 m³ / s, with a total of 750 kW with a 14.4 m head, and a further 9.0 m³ / s can be diverted past the power plant. The average annual electricity generation by hydropower is 2.7 million  kWh , which means that a further part of the pump energy used is recovered.

literature

  • Robert Karl, Thomas Liepold, Gregor Overhoff: Water for Franconia . The transition. Ed .: Bavarian State Ministry for State Development and Environmental Issues (=  Water Management in Bavaria . No. 34 ). 2000, ISBN 3-910088-60-0 .
  • Brochure "Transition Danube-Main" , as of June 2014

Individual evidence

  1. ↑ a b Bavarian State Office for the Environment: flood news service
  2. ↑ Description of the Brombachsee power plant on the website of Landeskraftwerke Bayern , accessed on June 1, 2013
  3. ↑ a b Wasserwirtschaftsamt Ansbach: Overall balance of the transition (PDF; 15 kB)
  4. ^ Description of the Hilpoltstein power plant on the website of Landeskraftwerke Bayern , accessed on June 1, 2013
  5. ↑ Nuremberg Waterways and Shipping Office: Height map of the Main-Danube Canal
  6. ↑ Description of the Rothsee power plant 1. Landeskraftwerke Bayern, accessed on August 9, 2015 .
  7. ↑ Description of the Rothsee power plant 2. Landeskraftwerke Bayern, accessed on August 9, 2015 .

Web links