Rainwater capture and management – from concept to implementation

zagospodarowanie deszczówki

One of our readers, Mr. Franciszek from Kędzierzyn-Koźle, boasted in the pages of Water Matters about the implementation of his own water-saving system and how he manages rainwater. He implemented a water retention system on the property for his own use and provided us with a detailed description of the solution along with a cost-benefit analysis.

We are pleased to take the opportunity to share this initiative and publish Mr. Francis’ letter. All the more so because it is not a textbook, potential solution, but a realized author’s project that works and brings a tangible financial return. Below is a letter from Mr. Francis.

Why and what for?

Drinking water is a good that will not always be guaranteed in abundance.

Deep-sea water, which is the raw material of drinking water, must be conserved. Its resources are replenished slowly, and rainwater flowing directly into the general drainage system becomes a once and for all lost and wasted valuable resource (soft water).

Poland is one of the few countries in Europe where there is no widespread legal obligation to pay a fee for lost retention (no intake and insufficient or no rainwater management on the property).

The introduction of mandatory rainwater harvesting, following the example of Western countries, will support the national expansion (without budgetary resources) of the water retention system. The opportunity to improve retention and reduce pressure on drinking water consumption should be recognized by the country’s authorities. The massive and dispersed solution will slow down rainwater runoff into local watercourses and then into the Oder, Vistula and Baltic, from where it returns as rain. Therefore, it is necessary to move away from disposing of water according to the “cloud to pipe” principle, and to bet on managing rainwater where it falls, which in 2009. I realized and still use today.

Stated state

The building is supplied with tap water and rainwater and snowmelt. Rainwater flowing from the roof is stored in a masonry underground tank (V = 7m3), which until 2008. was a septic tank, and since the city’s sanitary sewer system, built under the ISPy, has been a rainwater tank. After adaptation (cleaning, disinfection, construction of a suction and pumping system) in 2009. is an excellent reservoir of rainwater. Adaptation of the reservoir significantly reduced the cost of the project. Rainwater is used for purposes for which consumptive quality is not required, such as flushing toilet waste, watering the garden, etc.

The use of rainwater is included in the settlement with the water utility. In agreement with MWiK, I installed a water meter that measures the share of rainwater in the total consumption in the toilet, and based on its readings, I pay the appropriate wastewater fee. In addition, MWiK, prior to commissioning my installation, investigated its connection to the city installation. The installation was also checked to see if it had an anti-corrosion valve.

Wodne Sprawy 21 2023 2
Rainwater capture and management - from concept to implementation 1
Wodne Sprawy 21 2023 1
Rainwater capture and management - from concept to implementation 2


Analysis of water use

In the 2009-2022 period, water consumption was 1536m3, of which there were 539m3 of water from rainfall, accounting for 35 percent. overall. Rainwater management is not only an ecological solution, but also an economical one.

image 2
Fig. 1. Percentage of rainwater consumption
image 14
Fig. 2. Water consumption [m3/year].
image 11
Fig. 3. Water purchase costs [1zł/rok]
image 12
Fig. 4. Incremental profit and water purchase costs [zł]
image 10
Fig. 5. The cost of purchasing drinking water [zł/rok]
image 9
Fig. 6. Gross unit price of water purchase from MWiK in Kędzierzyn-Koźle [PLN/m3].

In this context, public awareness and financial coercion – a fee for lack of retention – will force the use of a widely available and valuable gift of nature that is available free of charge.

image 13
Fig. 7. Water consumption for domestic use [m3/month].

Further investments

“Forced” expansion of rainwater and snowmelt intake capacity (in August 2019).
The structure of rainfall (frequency and abundance) in 2009-2016 allowed undisturbed use of rainwater resources collected based on the roof area of the house (110m2) and a tank of 7m3. As of 2017. periodic irregularities in rainwater collection have begun to appear. The rains have become torrential and short-lived, and their frequency has decreased compared to the period when I started rainwater management.

The above observation corresponds with predictions that a warming climate will have a negative impact on the water cycle in the ecosystem. In August 2019. I decided to enlarge the area used to collect rainwater . For this purpose, I used a residential street that borders my property.

This solution will if not rule out then reduce the storage shortages I noted in 2018 and especially in the spring of 2019. At this point, the reconstruction has eliminated periodic shortages of rainwater in the reservoir, and I hope that the limitations occurring in 2018 and 2019 in meeting needs, especially garden needs, will no longer occur. The abundant rainfall, which fills the reservoir 100 percent, ensures the use of rainwater for a rain-free period lasting at least two months.

Wodne Sprawy 21 2023 3
Rainwater capture and management - from concept to implementation 3


Mr. Francis’ appeal for rainwater management

Water covers 70 percent. our planet and it is easy to assume that there will always be an abundance of it. However, fresh water accounts for only 3 percent. of the total stock, of which 2/3 are stored in glaciers or other unreachable places. As a result, some 1.1 billion people worldwide lack access to clean water, and a total of 2.7 billion experience water shortages for at least one month a year. According to UN estimates, access to clean and safe drinking water could decline by as much as 40 percent over the next decade, and by 2050 more than half of the world’s population will be at risk of water scarcity.

The economical management and stewardship of water resources, especially rainwater, is a challenge for now.

Individual solutions, such as those implemented and then described in a letter to us by Mr. Francis, are important. Small investments, seemingly insignificant on a global scale, provide the basis for developing retention on a larger scale. Mr. Francis, thank you and please register on the retention map.

Map information as of October 16, 2023. indicate that we have reached the level of 76,249 m3 of retained water. This is more than the recent investments of the waterworks in Wroclaw, where four retention reservoirs with a total capacity of 60,000 m were built at a cost of PLN 80 million.3. And not much less than a similar facility in Warsaw, built at a cost of 91 million zlotys and able to accommodate 80,000 m.3.

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