Introduction
Water resources management refers to humans manipulating the water environment to serve their distinct values and needs. It involves practices that ensure efficiency, equitability, and sustainability. Ideally, successful water resources management should be able to achieve water security. This is the access to an acceptable quantity and quality of water for health, livelihoods, ecosystems, and production with acceptable levels of water-related risks to people, the environment, and economies (Grey and Sadoff, 2007).
Since the 17th century, water resources have been continuously exploited to serve society's agricultural, cultural, religious, and developmental needs. In the first level of civilization, development was based around water resources and river basins such as the Nile, Euphrates, and Indus. Societies that were leaders in water management at the time became very powerful (Mitchen, 2012). In the industrial revolution, water was a very important resource as a factor of production and urbanization, particularly in Europe (Barbier, 2019). More than ever, water was displaced in ways that had never been seen before. As such, there were bigger developments in water resources exploitation. Further development was taken up by the United States, with the introduction of huge reservoir to store water. At the time, solving the challenge of water access was seen as an engineering matter giving rise to huge dams (Barbier, 2019).
Dams are manmade water reservoirs constructed in rivers for multiple purposes. These include electricity generation, irrigation, flood control, and recreational purposes. Essentially, dams have two main functions. To store water to compensate for river flow fluctuations and raise the water level upstream to divert water (Silva,1991). To some, the importance of dams is colossal, while to others, dams are a hazard to societies. In this light, the need for more or fewer dams is debatable, and a position can only be taken by evaluating the impacts of specific dams on society. While considering these impacts, it is only then that the reader can conclude whether we need more or fewer dams within our ecosystems.
Impacts of dams on societies and the environment
Without a doubt, dams have their share of challenges but also have certain positive impacts on human societies.
First, one of the main environmental functions dams may serve is flood control. Unfortunately, there is evidence to note that dams have increased the magnitude of flooding at certain times, leading to catastrophic results. Moreover, the seemingly positive impact, including power generation and water supply, can be provided through alternative means that have a less grave impact on societies and the environment. For example, enhanced natural flood management can provide a better and more sustainable way to manage floods. On the other hand, solar energy, geothermal, and wind are readily available sources that can be developed as an alternative to hydropower.
Second, dams have a serious impact on societies and the environment. Like agriculture, dams disrupt freshwater systems from the pristine states (Moss, 2008). At their conceptualization and planning stage, proponents of dams usually will have laid down the benefits of their investment to societies. However, these benefits are usually based on superficial analysis that concrete evidence cannot support. For example, if one takes the number of farmers to benefit from irrigation, this benefit is usually achieved by counting the number of farmers within the coverage area. However, most dam construction phases rarely consider all farmers since the construction and irrigation phases are distinctly separate. In most cases, only farmers who have huge properties benefit.
On the other hand, the core function of the dams is critical to consider. In Kenya, for example, the core function of some of the biggest dams, e.g., Masinga dam, is electricity generation. As such, priority is only given to that function in most cases, with other expected benefits such as water supply and irrigation being secondary.
Third, as far as the human impact of dams are concerned, dams have displaced millions of people. According to the World Commission on Dams, large dams have forced 40-80 million people from their land in the past six decades. Those that remain and live downstream of dams have suffered from the hydrological changes that dams create on the hydrological cycle within the ecosystems. Dams control the stream flow of water in areas where they are constructed. Essentially, dams and reservoirs are the leading contributors to the loss of river connectivity. Only about 23% free flowing rivers flow uninterrupted to the ocean (Grill et al., 2019).
On the one hand, they change the instream processes by affecting the hydraulic channel process. This is the water, heat, sediments, and solute movement within the river channel. By affecting the movement of water by either reducing the movement or increasing their movement, they can increase evaporation. Further, creating stagnant conditions downstream due to reduced water levels can increase evaporation. This atmospheric process of the hydrological cycle increases the atmosphere's moisture, increasing the precipitation level.
Fourth, dams negatively affect the water quality, rapidly affecting aquatic ecosystems. Increased sedimentation in dams creates more suspended particles that absorb solar energy and warm, turbid waters. As a result, in increased water temperature, there is less dissolved oxygen and light, decreasing photosynthesis. On the other hand, particles settling on the bottom suffocate fish eggs. These sediments also increase the cost of water treatment in the drinking water supply.
Fifth, the construction of dams alters the landscape giving rise to seismic activities, altering the streambanks, and extending the shorelines. The dam's construction process involves using heavy machines and fracturing rocks. As a result, this affects the geomorphology of the landscape in some cases leading to low-magnitude earthquakes. Triggering of earthquakes by dams has been done since the 1960s. Globally, at least 100 cases scientists believe have been triggered by dams (Gupta, 2002). For example, the construction of Zipingpu Dam is believed to have caused the Sichuan earthquake in Southwest China in 2008.
Finally, dams have a negative impact on the aquatic flora and fauna. As a result of increased temperature due to sediment particles, photosynthesis activities slowly reduce the biodiversity of plants in dams. Further, since many aquatic animals depend on plants for food, they either migrate or die. Water temperature, such as fish reproductive cycles, is fundamental in the biotic process. For example, Salmon production is highest between 5-20 degrees. Above or below this temperature creates a danger zone (King and Pankhurst, 2007). On the other hand, temperature also influences instream chemical reactions in lakes and reservoirs. For example, low flow below dams in 2002 killed thousands of salmon fish in Klamath.
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