‘A river is a natural landscape element where due to gravity-driven flow, water connects the river’s highest point with the lowest one.’
Even though this definition sounds complicated, it is not difficult to imagine such a structure.
But the simplest and the shortest definition I have ever heard was that of a student’s response to an exam question, “What is a river?” One of my students replied, “A river is an area of flowing water whose length is greater than its width.” This short and simple response covered all the concepts necessary to imagine this landscape element. By considering this definition from the lens of how water systems actually work, we can see how this natural element presents an immense potential for use. All this is possible due to the energy produced by gravity-driven water flow, commonly known as ‘the water current’. The greater the current velocity, the higher the energy that may be harvested from the river.
But utilizing high-speed water currents is not always profitable. If it was, rushing mountain streams would have been massively used for this purpose. What matters is also the amount of water, or the ‘flow discharge’. Therefore, humans more often use the energy of larger rivers, rather than small mountain streams.
Rivers constantly generate energy. Hence, for millennia, humans have used rivers as inland waterways for carrying goods on vessels, and for transporting goods straight to the water surface, e.g. by timber floating. Lower water tables ensured that water is transferred via aqueducts to rich mineral grounds. Here, the extra amount of water ensures a good crop. In the past, such practices were implemented in areas adjacent to the Nile, the Tigris-Euphrates river system, and more recently, in the Volga basin in Russia. Finally, electric energy harvested from the water current has been used for centuries to power structures and devices that facilitate the production of various goods, such as watermills, fishponds, forges, and today, modern hydroelectric power stations.
Without doubt, the river current is one of the cleanest unconventional energy sources. Given current declarations and actions taken by key energy production units, and the fact that coal is the largest energy source worldwide, it seems unlikely that other unconventional energy sources might be used more widely than coal in global energy production.
Contrary to other unconventional energy sources, such as solar and wind power stations and biogas plants, water is a constant resource whose power depends on the aforementioned water flow. The more water there is in the riverbed, the greater the flow. To keep the water at a level sufficient enough to fulfill power requirements, humans apply water lifting methods and create dams in riverbeds. Falling from a certain height at high speed, water strikes the turbines and propels them. Then the energy produced by the generator flows into a power network.
The energy harvested from shifting river current speed is a crucial aspect of the economy.
The question is whether environmental losses caused by the harvesting of this pro-ecological energy can be offset by the profits. Given all this, shouldn’t this energy harvesting practice not stir controversy? It appears, it does. River ecologists believe that any changes to the riverbed, such as river damming, leads to a transformation in the habitats of plants and animals. This, in my opinion, is not even the most detrimental consequence of all. A river is a type of an ecological corridor where active and passive organisms swim or drift in search for food, and seasonal or reproductive habitats. Organisms like fish and tiny invertebrates cannot migrate when dams are constructed. One of the greatest and most well-known impacts of dams is on the population of migratory fish.
Migratory fish travel from seawater to freshwater, or the other way around, for spawning (release of sperm and eggs into the water for reproduction). Among these, we can distinguish anadromous and catadromous fish. Anadromous (from ana – ‘up’ and dromos – ‘running’ in Greek) fish, such as salmonids, migrate from the sea to shallow rivers and streams for spawning. Whereas catadromous (from cata – ‘down’ and dromos – ‘running’ in Greek) fish, such as the eel, migrate from freshwater to seawater for spawning. Anadromous fish face the most difficulties in their spawning migrations. Dams pose a grave danger to these fish, because if they cannot swim upstream to their spawning grounds, they will not be able to reproduce. The fish will not have the chance to propagate the species, and in nature, this leads to the weakening of one link of the food chain. This creates irreversible alterations in the entire ecosystem.
The situation of migratory fish, especially anadromous fish, wherever river dams have been constructed is alarming. In numerous countries, the population of these fish is critically endangered, and their existence depends solely on human activity. Poorly constructed dams that do not allow for fish migration to spawning grounds are the main cause of this
situation. The survival of the species in its environment primarily depends on whether they reproduce in the natural habitat. Today, in numerous countries, the existence of anadromous fish depends on anthropic activity because humans literally obtain the fish by artificial spawning. The situation of the eel is far less dramatic because the species cannot be produced by artificial spawning.
Today, it is crucial for dams to be equipped with fishpasses that allow fish to successfully reach the upstream to spawn. A fishpass functions like a corridor that allows fish to bypass a river dam. Currently, regulations in several developed countries prevent the construction of impoundments for energy harvesting without a fishpass in riverbeds with migration. Fishpasses are not a new solution and have been incorporated into dam construction over the last few decades. Nevertheless, it should be noted that these passes do not guarantee that all fish migrating upstream reach their destination.
Some consider dam reservoirs to positively impact rivers. This is true on one hand, because river dams may increase water retention. However, this also means that a larger quantity of water evaporates than it reaches downstream. Sure, dam reservoirs allow for the river to be used for energy harvesting. But without a doubt, they negatively affect the river’s natural state. Not only do they present migration obstacles, but also increase the amount of suspension in the water. Sediments of drifting organic matter accumulate in dam reservoirs and annually increase in amount. Consequently, dead organic matter releases biogenic compounds that change the trophic state of water. If river damming was a beneficial process, then nature would have already created a mechanism allowing for creation of such conditions.
Water retention in dams and reservoirs is not even the slightest bit as effective as retention in soil or marshlands. In addition, the costs of constructing enormous structures for this purpose are remarkably high. Nevertheless, efficient water retention in soil is not possible today due to extensive drainage and construction on land. We can achieve water retention for navigability by restoring the natural state of the riverbeds (renaturalization). Straightening and deepening of channels, and regulation of catchment areas pose further problems for rivers.
Such maintenance practices are performed either to reduce flood risks or to improve transport conditions. But in reality, they achieve the opposite. Certain maintenance practices that change the natural state of rivers directly or indirectly impact previous renaturalization efforts. We could say that these contrary practices are performed in the same areas, which seems irrational. First, vast sums are invested into naturalization, and then considerable financial resources are invested in destroying it.
The potential of the rivers should be utilised. However, this should not be done everywhere and at all times, and especially not using the means that depend on human convenience. Nature is not our partner. It is us, humans, who are part of nature and not the other way around. Even though human brains are more developed than those of other animals, this does not give us the right to make decisions for them. And most certainly humans should not make decisions in the name of natural processes that take place in well-functioning ecosystems. It is as if someone tried to make healthy humans happy by imposing on them unnecessary experimental treatments. While humans can refuse such treatment, animals cannot. Of course, public consultations and talks with objectors of various investment projects are being held. And at some point, both parties of the dispute reach a consensus through compromise. But at the end of the day, even those parties are deciding for nature. But this is merely a compromise between both parties of the dispute, and not the investment supporters or the natural state of things. Nature never agrees to compromise with humans. At the very most, nature compromises with itself.
Even the slightest alterations to the natural environment are still alterations. If an alteration changes the river, nature, as the unconsulted party, will surely show its strength. Currently, we are witnessing the revenge of rivers. Draining and land melioration leads to low levels of water in rivers during the year, and sharp rises during periods of rainfall. Regulation, straightening, and laying concrete in numerous sections of rivers increase the speed of water currents. This leads to the destruction of existing structures, such as bridges at narrower parts of the river. Talk about digging your own grave.
But probably the worst thing is that supporters of such negative undertakings try their best to fool the world of their actions’ deadly consequences on nature.. According to numerous articles quoted by the supporters of river transformations, barges and dams increase biodiversity. Even if this is true, it is still a fraudulent manipulation. This is because typical riverine species are replaced with more ubiquist species, i.e. species that tolerate transformation. This is artificial manipulation.
Any experienced aquatic ecologist or aquatic environmental engineer can easily make changes that will lead to an increase in biodiversity. Even a vehicle tire left at the bottom of a stream has an impact on the number of animal species found in that section. It is plain and simple. The bigger the number of habitats and niches, the more the species present. A tire is an example of such a niche. Pondings, meanders, overdeepenings, and rapids caused by renaturalization are other examples of niches.
Naturally, climate change significantly affects rivers. Our role is to convince people that humans also have an impact on these changes. However, current climate and energy policies make speaking to laypersons challenging. Even if we succeed in convincing a large number of people, the majority remain skeptical about this issue.
We should ask the question whether humans are allowed to change nature entirely, and just like certain animal species, can they freely and consciously, or maybe even unintentionally, modify its current state. The beaver is a species that changes and adapts the environment to its needs. Humans are also a part of nature, and evolution gave us the abilities and skills to completely dominate other species and landscape elements. However, in the process of evolution, we also developed reasoning and questioning minds that have the ability to innovate for non-survival purposes. In the light of the current anthropic changes in the environment, the command to ‘subdue the Earth’ is no longer valid for at least a 100 years, or maybe even abused. It would seem that the Earth will not subdue any more.
It is necessary to conduct thorough studies to analyse environmental conditions, prior to the construction of hydroelectric power stations and the deepening of riverbeds to develop inland navigation. This would allow us to provide solutions that minimize human impact on the natural environment. It would seem that this clean, pro-ecological river energy would reduce greenhouse gas emissions, but without doubt, it would also decrease the environmental value of river ecosystems. It is crucial that scientists, administrative staff, business representatives, and ecologists agree that humans have a negative impact on rivers. Even though reaching a compromise poses a challenge, there is little doubt that we have no option but to achieve this. If making up for the damage we’ve caused is too cumbersome, well, cry me a river.