This is a recounting of the re-wilding of a portion of the Fulda River valley in the city of Fulda, Germany. We have been to Fulda in the past. See the post on Chrysanthemums. The city of Fulda is geographically, historically, culturally, and politically important. At one time it was the most important place on earth. During the height of the Cold War tens of thousands of NATO and Warsaw pact troops faced each other with troops, tanks, canons, and nuclear weaponry ready to engage in what would have been the start of WW III. That was in the valley nearby area called the Fulda gap. We have learned a lot from the experiences of Fulda and today we have a lesson of a different nature. It is a lesson of peace, beauty, and imagination. It is a lesson of water and land conservation. It is the bio-diversification and restoration of a portion of the swamps and river of the valley. It is the creation of a garden park and habitat for wildlife. It reflects cooperation rather than confrontation.
The feature image is an abandoned rail-line learning to the Fulda Gap
The Fulda River is one of the headwaters of the Weser River. It flows northwestward through central Germany for about 224 Km. (Fig 1.) The Fulda River is an important recreation area for the city of Fulda. It has been engineered several times over the past years, however, there has been a water area with a persistent overgrowth of cyano/alginate bloom in two accidently created retention ponds. Historically this area was a meadow and an open pit mine which had a clay base suitable for making masonry bricks. The open pit mine was not remediated, it simply filled with ground water. The meadow is in a depression which was also infiltrated by ground water forming a second pond. (Fig 2, Ponds adjacent to but not fed by the Fulda River) ground water supplying the lakes is a runoff from the nearby farmland. It is rich in organics with high concentrations of potassium, nitrogen, phosphorus, and chlorophyll. The retention ponds are fed by groundwater and without flow were stagnant. A growth of algae covered the surface of the ponds thereby depleted the oxygen content of the water (Fig 5). It was toxic to the fish and other plants. In the summer months with much less precipitation, algae growth increased and oxygen percentage was very low. Fish in the ponds died. The only surviving result was an ugly mass of blue-green algae.
Fig 1. Map of the central area of Germany with the country map as an insert and the Fulda river indicated in red in the larger portion of the image
The city hosted the Landesgartenschau from April through October 2023. This was an important regional horticultural show for the State of Hessen, Germany. Prior to the show the mess in this area needed to be resolved. It would seem reasonable to solve the polluted water problem by simply circulating the fresh water of the Fulda River through the two ponds and thereby improving the water supply. This well intended effort would have had terrible consequences. With testing and surveying and due consideration of alternatives, a more effective management was employed. The testing found that the water of the retention ponds had an assay of mineral and organic compounds equivalent to the neighboring farmland ground water. The surrounding farmland has been treated with animal manure and fertilizers and has the remnants of decayed vegetation. The river was very different. The Fulda River water is high in phosphates and low in other nutrients because it originates in the Rhön region mountains. Introduction of the pond water would have contaminated the downstream river.
Fig 3. Schematic of reengineered combined ponds
The derived solution to the problem of the stagnant ponds was ingenious. It included connecting the two ponds, installing a multi-port hydraulic line (Fig 3) through the length of the resulting lake and connected to a pump to recirculate the water and placing pond overflow gutters. These two methods direct the flow through a large stone/gravel pack over the southern banks to filter and re-oxygenation the water. (Fig 4)The surface algae is filtered and removed from the lakes and placed into a land fill area. The two water types are not comingled and soon the pond was clean, safe, and suitable for swimming (Fig 6). Separated from the pond, the undisturbed river flood plane is not toxic and native German beavers have been reintroduced into the river wilderness to facilitate the control of the vegetation.
Fig 5. Pre-remediation ponds overgrown with algae
The horticultural show was a wonderful display of crops, gardens, and my favorites which are the flowers and the wilderness. Here are some examples.
The lesson for Florida to be learned from the Fulda River water management is this.
- Research and think before acting.
- Combining community stagnant retention pond water with river water must one done with careful thought and planning.
- Reducing the nutrient value of the pond water by removing the pond plants and algae is effective.
- Aeration of water by the natural process of tumbling-through-stone is an effective re-oxygenation method.
- Use of wiers, gutters and pumps is sometimes necessary to facilitate the process.
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#Fulda #hydrology #Fulda Gap