By Jan Seibert and Ilja van Meerveld
Water is a vital part of our lives, and everyone interacts with water in some way. This makes it easy for people to relate to water and hold opinions on it. However, members of the public, including politicians, hold many misconceptions about water and hydrological processes. These tend to persist in society despite progress in our scientific understanding. Especially among decision-makers, these misconceptions can lead to unrealistic expectations regarding water management and suboptimal decision-making.
Some misconceptions can be attributed to the repeated exposure to simplistic depictions of the water cycle, in children's books and even hydrology textbooks. People often imagine the water cycle as one cycle, with evaporation happening (mainly) over the oceans, as is shown in many schoolbooks. As a result, they do not realize the importance of evaporation over land, let alone that for many land areas, it is the largest flux. Furthermore, they may not realize that there are "water cycles" at different scales. Understanding the complexity of the water cycles is important because water issues are interconnected; land-use change in one region may, for instance, affect evaporation and precipitation in neighboring regions. Textbook diagrams of the water cycle frequently overlook major human impacts like dams, irrigation, groundwater extraction, pollution, and changes in land use (Abbott et al., 2019). Again, this may lead to a misunderstanding of the impact of these activities on groundwater levels or downstream streamflow.
Other misconceptions are based on people's own observations and inferences. People observe that streamflow increases in response to rainfall and therefore conclude that the water in the stream is the rainfall itself (i.e., correlation instead of causation). However, isotope tracer studies have shown that in most studied cases, "old" water (i.e., water that was already in a catchment before a rainfall event) is the main source of water in streamflow, even during high-flow events (Buttle, 1994; Klaus and McDonnell, 2013). The large portion of old water in streamflow, the importance of underground flow pathways, and general long residence and transit time are important to recognize because the effects of improved land management or pollution control may appear only after a long delay. Understanding the importance of this delay helps set realistic expectations and monitoring horizons until when impacts of new policies might become visible.
A third group of misconceptions may be based on notions about what is "good". A widely held misconception is related to the role of forests in water resources, particularly as a source for streamflow during dry conditions (Calder, 2007; van Meerveld and Seibert, 2025). Forests are often seen as "good" in themselves and, therefore, beneficial for streamflow. This often leads to the expectation that afforestation and reforestation will lead to increased streamflow during dry conditions. The reality, however, is more complex. In most cases, increasing the forested area in a watershed will actually lead to decreased flows as evaporation from forests is generally higher than for other vegetation. This is due to the higher interception losses, i.e., precipitation being held on the trees and returned to the atmosphere by evaporation, and because of the higher transpiration losses of forests than for shrubs, crops, or grasslands. The background to this misconception might be the basic idea that forests are "good" for the environment (which is certainly the case for many aspects) and, thus, are good for everything (Calder, 2007). Alternatively, it may be based on observations that forests are often cooler than surrounding areas, forest soil may feel wetter, or the occurrence of clouds above mountain forests. Misconceptions regarding the role of forests in providing streamflow are problematic when these guide land management decisions or payments for ecosystem services, and the proposed benefits are not delivered. They are also especially damaging when dry season flows decrease (or streams even dry up) and impact people's access to water and their livelihoods.
The three examples above highlight specific water-related misconceptions. Such misconceptions can be based on repeated exposure to simplistic depictions (e.g., the water cycle), naïve interpretations of one's own observations (e.g., the origin of stream water), and predetermined ideas on what is "good". While all such misconceptions are understandable, they are problematic when they lead to water management decisions that are not based on scientific knowledge (Calder, 2007). In some cases, "good" decisions may still be made, but for the wrong reasons (i.e., reforestation based on the promise of increased streamflow during the dry period may bring many benefits, such as improvements in water quality, biodiversity, or carbon storage). However, such decisions may lead to unrealistic expectations and harm environmental decisions in the long term.
Misconceptions are very persistent and are difficult to change. Only if one is aware of the misconception is it possible to explicitly address the misconception. This requires that scientists carefully listen to non-scientists, particularly policymakers, to identify any misconceptions they may have. Sometimes, there is overcompensation once people are made aware of the initial misconceptions. This can lead to another, but opposite, misconception. For instance, one might switch from ignoring the effect of evaporation from land surfaces to overestimating the effect of changes in evaporation on precipitation because of land-use change. One can sometimes see statements on the increased evaporation of forests as being good because it will increase precipitation downwind. While this can be the case, inefficient irrigation would also increase air humidity and lead to increased precipitation downwind. However, most people do not view inefficient irrigation in a positive light.
Beyond the general demand for scientific literacy, hydrologists and the media are called upon to address water-related misconceptions. The media is important, but unfortunately, headlines often oversimplify findings to attract attention and, in doing so, contribute to or reinforce existing misconceptions. Hydrologists need to explain the complexity of hydrological processes in clear and understandable terms. Therefore, it is important to work with science communicators to provide simple, but not simplistic, explanations and the implications for various policy options.
PS: We assume there are more examples than those we are aware of on how water-related misunderstandings have led to suboptimal or even bad decisions and outcomes. Therefore, we invite readers to provide such examples in their responses.
References
Abbott, B.W., Bishop, K., Zarnetske, J.P. et al. (2019) Human domination of the global water cycle absent from depictions and perceptions. Nat. Geosci. 12, 533–540). https://doi.org/10.1038/s41561-019-0374-y
Buttle, J. M. (1994). Isotope hydrograph separations and rapid delivery of pre-event water from drainage basins. Progress in Physical Geography: Earth and Environment, 18(1), 16-41. https://doi.org/10.1177/030913339401800102
Calder, I.R. (2007) Forests and water--Ensuring forest benefits outweigh water costs. Forest Ecology and Management 251, 110-120.
Klaus, J., McDonnell, J.J. (2013) Hydrograph separation using stable isotopes: Review and evaluation. Journal of Hydrology 505, 47-64.
van Meerveld, I., & Seibert, J. (2025). Reforestation effects on low flows: Review of public perceptions and scientific evidence. WIREs Water, 12(1), e1760. https://doi.org/10.1002/wat2.1760