Dams and reservoirs paradoxically increase water scarcity

The construction of dams and reservoirs is one of the most common approaches to combat drought. The goal is simple: tanks store water during a period of water supply and stabilize its level in a dry season. So they can balance the access of water, thereby reducing the deficit.

An international team of drought scientists reports that many dams and reservoirs can paradoxically contribute to the shortage of water, which they, on the contrary, are intended to solve. A study published in Nature Sustainability.

A group of scientists led by Prof. Giuliano Di Baldassarre from Uppsala University (Sweden) showed that increasing storage capacity in the long run can lead to unintended effects and, paradoxically, increase water shortages. The authors argue that the expansion or planning of reservoirs should take into account two contradictory phenomena: the supply and demand cycle and reservoir effect.

The supply and demand cycle describes cases where an increase in water supply leads to an increase in demand for water, which can quickly compensate for the initial benefits of creating reservoirs. These cycles can be viewed as the Jevons paradox: since more water is available, its consumption increases, which creates a vicious circle. New water shortages are being eliminated by further expanding storage and reservoirs to increase water consumption until the next shortage.

The reservoir effect, on the other hand, describes cases where excessive reliance on reservoirs increases the potential damage caused by drought. Expansion of reservoirs often reduces incentives to be ready to respond quickly in emergency cases, thereby increasing the negative effects of water shortages. Moreover, long periods of abundant water supply, supported by reservoirs, can lead to greater dependence on water resources, which, in turn, increases social vulnerability and economic damage, when in the end the deficit does occur.

New research has political implications. The authors argue that current attempts to increase water supply to meet the growing demand for water are irrational. Instead, they offer less reliance on large water infrastructure, such as dams and reservoirs, and work to conserve water resources.

In other words, scientists are proposing to deal with drought and water scarcity by reducing water consumption, rather than increasing water supply. However, despite the fact that many water experts agree with this recommendation, dams and reservoirs continue to be built in many countries.