Are we running out of clean drinking water? On the challenges of managing water for human consumption in the face of climate changes.
Progressing climate changes will have a significant impact on the availability and quality of water resources, including water for human consumption. As a result of changes in the hydrological cycle (or hydrosocial cycle, according to the most current theories in the water resource management literature1) extreme natural events, such as acute droughts and violent downpours, can be observed today in Poland. They affect not only the amount, but also the quality of potable water derived from rivers, lakes and groundwater. As the direction of these changes is highly unpredictable, water resources management, including potable water, is and will be a difficult challenge requiring a complex and multifaceted approach. At the same time, adequate preparation of water resources for human consumption for the coming climate change requires particular attention, given the catastrophic effects these changes may have on the health security of the population.
A thorough analysis of the climate change effects on water resources for human consumption is difficult due to other negative human activities which equally impact water resources. The overuse of pesticides, deforestation, the ever increasing concrete expanse of cities - these activities magnify the effect of climate changes on the quality and quantity of potable water. Therefore, in order to fully understand occurring phenomena and to adjust appropriate methods of adaptation, it is necessary that these activities should be taken under consideration.
Understanding the impact of climate changes, including unpredictability of atmospheric precipitation on availability and quality of water for human consumption, is essential from the perspective of the water and sewage system sectors, which provide potable water, as well as the government, which is responsible for forming policies in this area. Minimising the effects of extreme natural events will require renewal of the water and sewage infrastructure, and consequently a number of capital expenditures. What is more, the way water resources are managed, and the legal arrangements need to be periodically reviewed and revised in the context of changing conditions. Progressive climate change may impede the progress achieved in environmental protection through the implementation of the Water Framework Directive or other water directives and sustaining it at an adequate level will require additional measures, including legal action. Therefore, it is of great importance to diagnose and understand the processes taking place, their impact on drinking water, and to apply an appropriate approach to adaptation and management of water resources.
When we consider the effects of climate change, we mainly analyse the average rise in temperature and its negative impact on the environment. It also has an impact on drinking water supplies - changes in ambient temperature affect both the quality and quantity of water available, including that for human consumption. While temperature directly affects water levels in reservoirs, its indirect effect is to change the biological and chemical parameters of the water. In warmer water: chemical reactions are accelerated, the content of dissolved substances increases, while the concentration of dissolved gases, including oxygen, decreases. It is worth noting that for this element, a 3oC increase in water temperature means a 10% decrease in its saturated concentration in water. To illustrate, according to the IPCC2 scenarios, we can expect a temperature increase between 1.8 and 4.0oC above pre-industrial levels as a result of climate change. In practice, this means not only a reduction in oxygen levels, but also changes in the chemical reactions taking place in the water and alterations in the microorganisms present into predominantly anaerobes.
Changes in temperature will particularly affect the quality of water derived from lakes. In these reservoirs, water mixing will be modified in response to rising temperatures, whereby warming water from the surface is mixed with cooler water from deeper layers, along with chemicals released from the sediment and the ones contained deeper. As a result, lakes that were previously used as a source of drinking water may deteriorate3. Shallower reservoirs, where the process of water mixing occurs more rapidly, are particularly susceptible. To illustrate the problem, it is worth adding that in Poland rivers and lakes constitute approximately 30% of water sources for human consumption, while in the case of the Małopolska and Silesia regions such surface intakes constitute the primary source of drinking water.
Although rising temperatures will undoubtedly affect drinking water supplies, the greatest impact on water quality and availability will be exerted by extreme natural phenomena that have been observed in Poland for some time, such as alternating prolonged droughts and torrential downpours resulting in flash floods. As can be seen in Figure 1, in 2020 alone, for three months (April to June), some areas of the country experienced a lack of precipitation (April), followed in short order by a high risk of surges, above the maximum daily precipitation totals (June). Prolonged precipitation deprivation not only lowers surface and ground water levels, but also adversely affects water quality by increasing harmful substances in reservoirs, watercourses and groundwater. The concentration of heavy metals, pesticides and other chemicals in water increases with decreasing water levels. This is important given the potentially catastrophic health effects of such increased concentrations, particularly in areas where the population draws untreated drinking water from deep wells4.
Wersje A (lewo) i B (prawo)
Rys. 1. The probabilities of exceeding the maximum daily rainfall totals in 2020 A. in April B. in June. During the three-month period there was a wide variation in the likelihood of heavy rainfall, from a drastic lack of rainfall to a risk of surge5.
Similarly, agricultural areas are at risk from the negative effects of flash floods exacerbated by the preceding lack of precipitation. During dry summers nitrogen from artificial fertilisers accumulates in the soil. With the first heavy downpour it is washed away in large quantities into a nearby river or lake where it can not only lead to chemical pollution but can also be a major cause of cyanobacteria blooms in reservoirs. These microorganisms secrete toxins that are harmful to health, making the water in which they are found unfit for human consumption without proper treatment. In addition, heavy rains affect the rate of runoff in rivers, slowing down the sedimentation of heavy substances and the absorption of pollutants by river vegetation8. Understanding this process is vital in view of climate scenarios predicting an increase in annual river flow in northern and central Europe as climate change continues9.
A sudden downpour can also result in water contamination by pathogens of human or animal origin. In the case of combined sewers, which carry both sewage and rainwater, too much rainfall inflow can cause the system to overflow and discharge into the river along with the pathogens contained in the faeces. In the United States alone, it is estimated that half of the outbreaks of water-borne diseases occurred after a period of heavy and violent rains10.
Due to the complexity of climate change impacts on the quality and availability of water for human consumption, it is necessary to take a holistic, multi-faceted approach to water resources management, both from the intake and consumption side of drinking water. The methods introduced should take into account both the horizontal scale (between water use by different sectors and nature) and the vertical scale (involving planning from central authorities to local users).
In legislative terms, the European Union has taken a number of initiatives to ensure integrated management of water resources. One of the most important documents addressing the holistic approach to water quality protection is the Water Framework Directive (Directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000 establishing a framework for Community action in the field of water policy). Last year's amendment to the Drinking Water Directive (Directive 2020/2184 of the European Parliament and of the Council of 16 December 2020 on the quality of water intended for human consumption) also provides for multifaceted surveillance and prevention of water pollution, e.g. by introducing risk assessment from the source to the consumer's tap, or by creating a watch list for newly emerging substances such as pharmaceuticals and microplastics. Member States, including Poland, have two years from the entry into force of the directive, i.e. by January 2023, to transpose these changes into law. In the future it will be necessary to extend these legal acts to include issues relating to other sectors and water users because with the increasing scarcity of clean drinking water not only will the costs of treating it increase, so will the competitiveness of its demand and use.
The next step towards achieving multi-faceted protection of the quality and quantity of drinking water is the introduction of modern technologies that allow cities and the countryside to be designed in such a way as to level the pollution of watercourses, reservoirs and groundwater and to increase retention. One such engineering innovation, gaining increasing popularity in Australia, the US and the UK, among others, are sustainable urban drainage systems. These allow a series of retention and treatment facilities to be designed into a city's spatial plan, using natural and artificial features of nature such as urban wetlands or roof gardens. Part of a sustainable urban drainage system can also be car parks covered with a porous surface, allowing rainwater to be retained and gradually purified as it percolates into subsequent soil layers, or an artificial system for removing pollutants. Although such systems can be constructed from individual elements, they achieve their best effect in protecting against e.g. torrential downpours as combined structures built into the landscape of an entire town or housing estate. Such a sophisticated system has, for example, been built into the urban neighbourhood space of the Lynbrook Estate, Melbourne, Australia where over time a 60% reduction in phosphorus runoff during regular rainfall has been recorded, compared to the state before the system was installed11.
The occurrence of extreme events adversely affects the condition and treatment capacity of water and sewerage infrastructure. As new types of pollutants appear and concentrations of chemical substances and microbiological parameters increase, it will be necessary to adapt the technology. An outdated sewerage system will have to face more rainfall, which can lead, for example, to the aforementioned contamination of water with pathogens and the spread of water-borne diseases (Figure 2). If no action is taken to reduce leakage from pipes water will be wasted, which will have a negative impact on the amount of drinking water available. Adapting the water and sewage sector will require a number of costly investments allowing for, among other things, the renewal of infrastructure and the introduction of a health and safety risk analysis that takes into account the risk of natural disasters and extreme events and the need to protect drinking water from source to tap. Moreover, it is necessary to plan the investments properly and with consideration of the local conditions; due to the different resistances of various systems and water treatment methods, with some sewerage systems being very resistant to drought effects but failing during heavy downpours12.
Rys. 2. Diagram of the climate change impact (through temperature fluctuations and precipitation unpredictability) on the quality of drinking water derived from rivers and lakes and supplied to consumers by water and sewage companies, considering the impact on public health security7
Support for such costly and priority investments is provided for in the European Union's Multiannual Financial Framework 2021-2027. The basis for receiving funding is the preparation of a national investment plan. To this end, the Ministry of Infrastructure is implementing a project entitled: “Development of an investment programme for improving the quality and reducing the loss of water for human consumption", financed by European funds under the Operational Programme Infrastructure and Environment 2014-2020. Based on this document, water and sewage companies will be able to apply for funds from the European Union, which will facilitate the sector's adaptation to climate change.
Author: Sylwia Łyskawka, Ministry of Infrastructure
References:
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