Water scarcity and climate change led to changes in water management, especially in urban areas. RainWater Harvesting (RWH) is a promising technique that allows the collection and reuse of rainwater, as well as protecting sewage systems from overload. This article reviews the current state of RWH in Europe, including advantages, implementation, potential efficiency, usage requirements, quality, and treatment processes. The main findings include the importance of RWH as a sustainable water management technique, the historical background and renewed interest in RWH systems in recent years, the positive impact of RWH on reducing energy consumption and greenhouse gas emissions, the versatility of rainwater usage, and the potential cost savings and benefits in various regions. RWH systems are gaining popularity in Europe, particularly in Germany, Austria, and Switzerland. Climate change and precipitation patterns affect rainwater availability and quality. RWH can be used for various purposes, including drinking, but requires proper purification for health safety. It is also being implemented in new locations like airports and large buildings. RWH systems have a high potential to overcome undesired results of climate change. Among that, numerous aspects still need to be considered in the future that allow the application of RWH systems on a larger scale.

The use of rainwater for washing clothes is determined by its amount, composition and quality of washing. Raw rainwater is soft and free of pollution. The collected rainwater already contains pollution present in the atmosphere and washed away from roofs and other surfaces. It can also change its quality when stored in tanks. Washing clothes does not require drinking quality water but just clean, safe water that guarantees effective removal of dirt from fabrics. The study determined the physicochemical and microbiological changes of rainwater characteristics during retention. Rainwater was collected in a standard underground tank for 30 days and water analyses were conducted every 10 days. The possibility of tap water replacement in the household with collected rainwater for ecological clothes washing has been assessed.

In water management, climate changes require adaptation, protection of existing resources and the search for alternative water sources. Rainwater harvesting (RWH) is increasingly becoming an alternative water source, applicable for many directions of its use. The aim of the research was to analyse the influence of long-term climate change on the potential for rainwater harvesting in households in Central Europe in Poland. The analysis of long-term climate changes impact on the household rainwater harvesting potential was conducted for the 50-year period for 19 cities in Poland. The water balance model was operated in a day-step mode, and the research was carried out in four “time scales approach”. For the purpose of all analyses, a standard weekly water demand profile was developed. It includes the daily sub-profiles for every working day and weekend, covering the washing and toilet flushing needs for a 4-person household. In order to evaluate the long-term changes in residential harvesting in Poland, a hypothetical residential RWH was investigated in 19 locations and rainfall conditions. To illustrate the time-spatial variation of annual rainfall amounts in the analyzed period, the heat map was prepared as the pre-simulation stage. Results show that the design of RWH systems should be based on archival data and take into account the many years of rainfall changes. This will improve performance and secure benefits for the users of this system.

Rainwater harvesting (RWH) for domestic uses is widely regarded as an economic and ecological solution in water conservation and storm management programs. This paper aims at evaluating long-term trends in 20-day cumulative rainfall periods per year in Poland, for assessing its impact on the design and operation conditions for RWH systems and resource availability. The time-series employed corresponds to a set of 50-year long time-series of rainfall (from 1970 to 2019) recorded at 19 synoptic meteorological stations scattered across Poland, one of the European countries with the lowest water availability index. The methods employed for assessing trends were the Mann–Kendall test (M–K) and the Sen’s slope estimator. Most of the datasets exhibit stationary behaviour during the 50-year long period, however, statistically significant downward trends were detected for precipitations in Wrocław and Opole. The findings of this study are valuable assets for integrated water management and sustainable planning in Poland.

Heating and cooling sectors contribute to approximately 50% of energy consumption in the European Union. Considering the fact that heating is mostly based on fossil fuels, it is then evident that its decarbonization is one of the crucial tasks for achieving climate change prevention goals. At the same time, electricity sectors across the globe are undergoing a rapid transformation in order to accommodate the growing capacities of non-dispatchable solar and wind generators. One of the proposed solutions to achieve heating sector decarbonization and non-dispatchable generators power system integration is sector coupling, where heat pumps are perceived as a perfect fit. Air source heat pumps enable a rapid improvement in local air quality by replacing conventional heating sources, but at the same time, they put additional stress on the power system. The emissions associated with heat pump operation are a combination of power system energy mix, weather conditions and heat pump technology. Taking the above into consideration, this paper presents an approach to estimate which of the mentioned factors has the highest impact on heat pump emissions. Due to low air quality during the heating season, undergoing a power system transformation (with a relatively low share of renewables) in a case study located in Poland is considered. The results of the conducted analysis revealed that for a scenario where an air-to-water (A/W) heat pump is supposed to cover space and domestic hot water load, its CO₂ emissions are shaped by country-specific energy mix (55.2%), heat pump technology (coefficient of performance) (33.9%) and, to a lesser extent, by changing climate (10.9%). The outcome of this paper can be used by policy makers in designing decarbonization strategies and funding distribution.