Approved 16.9.2023 – No editing after that.

This design was started in June 2021 as “Water and Making Ponds”. After reviewing it in June 2023 I decided that the design is too big and should be divided in smaller bits that are easier to manage. The largest part of the design is the Ponds at Iso-orvokkiniitty (this design). Other designs evolving from the original could be “Household water system at Iso-orvokkiniitty, “Plants for the Ponds” and “The Technical Wetland”. Those will be mentioned here only as much as they are necessary to understand the Ponds design. The original full design as presented in October 2022 is here.

ABSTRACT:

Content

• The Design Framework
• Vision connected to the three Ethical Principles of Permaculture
• The vision
• Needs: Water for Cultivation
• Observe
  • Water sources for cultivation (summer 2021)
  • Drainage
  • Borders, limitations, resources
• Evaluate
  • Challenges in water for Cultivation
  • PMI: water for cultivation
• Guiding principles
  • Scale of permanence
  • Planetary boundaries
• • Ponds: Sources of information
  • • The main takeaways from “How to build a natural swimming pool”
  • • The main takeaways from the “Million Ponds Project”
• Design
  • Placement of ponds
  • PMI of ponds and elements
  • Defining targets for excavation
• Implementation: Excavation
  • Garden pond
  • Clean water pond
  • Eutrophic pond
  • Big pond
• Budget
• Implementation Backlog
• Maintenance
• Evaluation
  • Pond excavations
  • Evaporation and leakage in the Big Pond
  • Water quality in the Big Pond
  • The other ponds
  • Water analysis
  • Reflecting on Vision and Needs
  • Using Permaculture Design Principles
  • Yeoman’s Scale of Permanence
  • Planetary Boundaries
  • What tools were used
• Tweaks

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The Design Framework

I am using a version of OBREDIM, called VOBREDIMET.

OBREDIM is an intentional design process especially used in Permaculture design. It is one of the design processes suggested by the UK Permaculture Association within their Diploma in Applied Permaculture, besides SADIMET, CEAP, SWOC and PASTE. The process is described in Aranya’s book “Permaculture Design”[x]. The process is well documented in the Fench speaking Ekopedia.[3], which besides Obredim also describe alternative versions.

• Vision is what guides the designer by telling why the design is made, for what needs.
• Observe: Gathering all relevant information in order to be able to design. This could be zone and sector -analysis or information coming from other relevant input methods.
• Boundaries: Setting the limits and expectations.
• Resources: Describing what resources are at hand and can be used. This could involve abstract values like time and money but also non-abstract gods like trees, soil and water.
• Evaluation: During the evaluation step the accquired knowledge from the previous steps is checked. Guiding principles are selected.
• Design: The actual design step. Herin the Permaculture ethics and principles are applied to the subject given.
• Implement: With a finished design the implementation step can happen. The design gets executed.
• Maintain: Making sure that the implemented design is kept running.
• Evaluation: to see what works, what does not and what to improve
• Tweak, improve on the design

OBREDIMET

OBSERVE, EVALUATE, DESIGN, IMPLEMENT, MAINTAIN, EVALUATE, TWEAK

The reason to choose VOBREDIMET is that it includes quite detailed design steps which can be helpful in a Land-based design. Starting with Vision is to me the key to a successful design and gives a benchmark for the final evaluation. Evaluate and Tweak in the end of the process is a reality – no design will get it 100% right.

Vision connected to the three Ethical Principles of Permaculture

Let’s lay the foundation first and describe the Vision and how the Permaculture 3 ethical principles come to play:

• EARTH CARE:
  • The water system should rely on local resources in terms of water sources, energy and material.
  • There should be no or minimal outputs from the system in terms of waste water or nutrient leaching (Biogeochemical cycles).
  • The system should support wildlife and biodiversity on Iso-orvokkiniitty.
• PEOPLE CARE:
  • The ponds should provide us with sufficient water for our cultivations.
  • The main pond should be large enough and water quality good enough that it is possible to swim (from sauna / for children)
• FAIR SHARE:
  • The system should enhance a beautiful landscape and provide recreation for us and visitors.
  • The design and experience is shared with others for inspiration.
  • The water system and ponds will support nature and be there for the enjoyment and benefit of future generations

The Vision

Here I link together the Vision with the Permaculture Design Principles (David Holmgren)

Vision / Need	Principles and Considerations
– The system should provide us with sufficient water for cultivations.	– The ponds will be used for irrigation and recreation. INTEGRATE RATHER THAN SEGREGATE OBTAIN A YIELD
– The main pond should be large enough and water quality good enough that it is possible to swim (from sauna / for children)	– A low carbon system with limited Phosphorus will be attempted in order to keep the water clean and clear. INTEGRATE RATHER THAN SEGREGATE
– The system should enhance a beautiful landscape and provide recreation for us and visitors.	– A deck will be installed at the big pond and an area of sand/gravel for accessibility. A water “flow form” system will be installed both for visual appeal and to increase oxygen levels in the pond water. USE EDGES AND VALUE THE MARGINAL
The water system should rely on local resources in terms of water sources, energy and material.	Water enters the system as rain, surface water or along the ditches. CATCH AND STORE ENERGY Water enters the system gravitationally and leaves the system gravitationally or by evaporation. CATCH AND STORE ENERGY, DESIGN FROM PATTERNS TO DETAILS Water is moved within the system with solar/wind power (or by carrying it) USE AND VALUE RENEWABLE RESOURCES AND SERVICES Excavators must be used for digging. Therefore fossil fuels are used for earth works CATCH AND STORE ENERGY Our fields are heavy clay and therefore ponds can be dug without using any lining (plastic) to close the ponds. USE EDGES AND VALUE THE MARGINAL PRODUCE NO WASTE
There should be no outputs from the system in terms of waste water or nutrient leaching (Biogeochemical cycles).	Nutrients are not added in the ponds, but water vegetation is planted so the pond should bind entering nutrients. Vegetation can be harvested from the pond and used f.ex. in compost or food. OBTAIN A YIELD PRODUCE NO WASTE USE AND VALUE RENEWABLE RESOURCES The big pond overflows through a height adjustable well from the surface so mud does not leave the system. PRODUCE NO WASTE
The system should support wildlife and biodiversity on Iso-orvokkiniitty.	A high degree of biodiversity will be developed in and around the pond both by planting and naturally. APPLY SELF-REGULATION AND ACCEPT FEEDBACK USE SMALL AND SLOW SOLUTIONS USE AND VALUE DIVERSITY
The design and experience is shared with others for inspiration.	This design is shared on our website (here).

Needs: Water for cultivation

• Greenhouse. The greenhouse totally depends on water from outside.
• Garden: especially any new plantings and annuals:
• Seedlings in the spring:
• Forest garden plantings at least in the year of planting and following year.
• Mushroom cultivation: For shiitake force-fruiting cold fresh water from the well is needed.

Water demand is difficult to estimate and the need will evolve as our cultivation systems evolve. Some estimates can be taken from “Maankuivatuksen ja kastelun suunnittelu” (Planning drying and irrigation of land)(1). Some key numbers taken from the guide:

• A grass field uses 3-6 mm water per day.
• Potatoes use 1,5 mm to 4,5 mm per day depending on development stage.
• Also fruit trees need more water towards the end of the season and early season dryness can decrease shooting and increase blooming in the following year.
• Cultivated berries (strawberry, raspberry, currants, gooseberry) each have different preferences in terms of water availability during the season.
  • Raspberry and currants have a high water demand for making big berries. Autumn dryness can decrease shooting for following year
  • Strawberries require a lot of water during blooming. Dryness after harvest can increase blooming the following year.
  • Raspberry can suffer in the winter if soil is wet after mid-August.
• In a Spray irrigation system the aim is to irrigate as much as the soil can take at once. That means 20-35 mm depending on soil type.
• Potato and garden cultivation (including fruit trees and berries) water need for irrigation can be up to 1500-2000 m3/ha or up to 200 mm during the growing season.
• When planning a storage dam for irrigation water one can calculate 1000 m3/ha collected water during the winter and spring.

As a conclusion, if we presume 1 ha cultivated and forest garden area we need up to 2000 m3 of usable stored water to be able to irrigate optimally in almost all conditions (except extreme draught). That would mean 1000 m2 pond area with 2m average depth. Or 2000 m2 with 1m average depth. If we allow only max 20% usage of the pond volumes – due to recreational and ecological purposes of the ponds – it means that we need 5000 to 10000 m2; i.e. 0,5 to 1 ha pond area. It is clear that this is not realistic so we need to decide which parts of our cultivations we need to be able to irrigate.

Our more intensively cultivated garden area in Zones 1 and 2 is approximately 1000 m2 (0,1 ha) which means we need 200 m3 of usable water and 500-1000 m2 pond area containing approximately 1000 m3 of water (20% usage).

Observe

I have covered some of the survey part already in the previous articles. In 60 DEGREES NORTH, 23 EAST I included climate data from which I show the rainfall and evaporation graphs also here. The main points:

• Rainfall per year is 700-750 mm of which 380 mm during the growing period.
• Precipitation is 300-400 mm higher than evaporation so on annual level there is a huge oversupply of water.
• Nevertheless late spring and early summer draught is typical when rainfall is low and evaporation high. This period is critical for cultivation.

Water sources for cultivation (summer 2021):

• We think well use should be minimised for other than household purposes. However we have had to use it for watering purposes to some extent.
  • My estimation is that we use 70 m3 of household water per year. On top of that we have used water for watering the garden and for mushroom cultivation without any problems. So we could just presume that we can safely double water usage during the growing season, using 30 m3 of water to other than household use.
• Collection from roofs of buildings. We have 1000 liter IBC tanks on 2 south corners of our house and 1 more could be put in the NW corner. We can place more tanks on the upper side of the garden where we can gravitationally move water from the tanks at the house. The roof area of our house is appr. 180 m2 which means theoretically collecting 1800 litres of water for each 10 mm of rain. So we need 30 mm of rain to fill 5 IBC tanks. We can add water collection also to the storage building and sauna adding some 80 m2. The tanks will be full in the spring but after that their usefulness depends on collecting rainwater during the growing season: theoretically 13m3 in June and 20m3 in July.
• Ditches around the fields. The ditches are full of water in early spring when snow has melted. However they will dry out at some point in June depending on rains. I have used the ditches to water nut tree seedlings on the fields after planting them and early summer as the ditches are the closest place with water.
• Circulation of water
  • Willow waste water system. The willow waste water system has been in use since 2018. In the first years the willows were still quite small and have not had the capacity to evaporate all the water entering the willow system but now the willows seem to use all the water.
    • Most of the 70 m3 household water ends up as waste water.
  • Water used in shiitake force-fruiting: In 2017 and 2018 and 2022 I tested the production capacity of our shiitake logs by regularly force fruiting them. Fresh well water was hosed up to the forest and after being used it was hosed gravitationally back into an IBC tank for use in the garden.
    • We used two 380 litre tubes. We change the water once a week. So 2,4 m3 water per month during the season (3 months = 7 m3)
    • Force fruiting was continued in 2022 when we had wwoofers to do it.
  • Water from the hot water tub: Our greenhouse and kitchen garden are lower than the hot tub at the sauna which will enable us to hose the water gravitationally to the garden and greenhouse.
    • 1,5 m3 per week = 18 m3 during June-July-August.
  • Water from sauna is also collected and used for irrigation in the summer period.
• Ponds (not existing yet in summer 2021)

Drainage

Water runs through the site from east to west. The main visible water flows are the ditches coming from east /the forest and south-east. All the water flows must go to the other side of Varkalahdentie through a road pipe in the west corner of the site (PA7). The height of the pipe determines the water level on the site. Therefore water levels stay quite high on the lower parts of the site (PA7). The field itself has subsoil drainage which was installed presumably in the 1980’s. We don’t have the drainage map but drainage is from east to west. The ditches on the NE side have not been cleared for decades and probably the drainage is clogged so even the more elevated parts of the field on the east side of the field are wet due to groundwater from the forest slope coming to the surface. (PA = Planning Area; see Evaluation and site analysis: Planning Areas.

Borders, limitations

Summing up the most important borders and limitations:

• The physical borders of the property have been described in previous articles, mainly: Iso-orvokkiniitty: the site
• Early summer draught in June, July
• Waste water legislation and principles: waste water should not leave the property (and we don’t want it to)
• Lack of water for irrigation.

Resources:

• In an annual perspective there is sufficient rain water.
• We have dug a traditional well that has good water supply for household and even other uses.
• We have plenty of solar electricity in the summer for moving water with pumps.
• Water collection from roofs.
• Ditches bringing clean water from outside our property.
• Possibility to locate ponds on the field in places where there already is water or where water flows.
• Possibility to invest in the form of hiring an excavator or other necessary costs.
• Limited time.

Evaluate

Challenges in water for Cultivation

Challenges on the cultivation side are both practical and theoretical. The obvious practical problems we experience during the summer are lack of water for irrigation and supplying the water where it is needed. Theoretical problems relate to estimating the actual and needed water flows. All the numbers given earlier (and in graph) are crude estimates albeit they are all based on something and thereby give a much better starting point for a design than “nothing”. Years differ widely (rain, temperature, wind) from each other affecting both supply and demand of water. And when supply is low typically demand is high.

The graph above shows that we could potentially cover half of the 200 m3 water demand in our garden cultivation (Zone 1 and 2) with water from the well and roof collection including circulated water (excluding the willow system). To supply the other half we need to store water from the winter and spring and for that we need ponds. The capacity of the ponds should be 200 m3 usable water of which half would be used in the intensive cultivation. This requires 1000 m3 pond volume (20%). This is the same number as I arrived to in Needs.

The water that is available from the willow waste water system can not be used in the intensive cultivation due to hygienic risks so it would be used for watering trees in the forest garden. The forest garden could be also watered from the ponds, but overall the forest garden would have to be maintained largely without irrigation.

PMI: water for cultivation

Element	Plus	Minus	Interesting
Well	– clean water – sufficient for household	– limited for cultivation	– estimated 30m3 water can be used for cultivation
Sauna & Hot tub	– needs clean water	– water needs to be changed every time (we don’t treat it chemically)	– water can be reused for irrigation
Water collection from roofs	– water can be collected gravitationally into tanks and from tanks to garden	– aestetics of water collections systems	– 260 m2 of roof surface results in 33m3 of water in June-July
Ditches	– Water close to forest garden	– Ditches dry in the summer
Ponds	– Can be used for water storage – can be used for recreation / swimming	– water level will be lower in summer limiting usable capacity – water must be pumped for irrigation	– the biggest potential for water storage
Plants in ponds	– plants enable keeping water clean – aestethics	– plants take up to 65% of pond surface – probably necessary to weed too competitive plants	– biodiversity – some edible plants – weeding results in compostable material

Guiding principles

I have already used the Permaculture Ethical Principles and David Holmgren’s Design Principles in formulating the Vision. Here I will also look at Yeoman’s Scale of Permanence and Rockström et al’s Planetary Boundaries. See “My Permaculture Design Pathway” for more info about both.

For more specific information about building ponds I am looking at mainly 2 sources: “How to Build a Natural Swimming Pool” and “Million Ponds Project” (see below for details).

Yeoman’s Scale of Permanence

Can we and will we affect the different levels of the permanence? Here I am using a modified scale of permanence based on what I wrote in “My Permaculture Design Pathway” where Soil has been upped to 6. position above Structures and Subdivisions. This I justify by the difficulty and energy input required by changing soil.

1. Climate: We will invest fossil fuels (carbon emissions) in the design mainly in the excavation works and some plastic pipes. Can we compensate that (or more) with carbon sequestration in vegetation in and around the ponds?
2. Landshape: Definitely we affect landshape with digging ponds and ditches and making some mounds. However it is hardly visible from a distance, f.ex. from Varkalahdentie road that passes our property.
3. Water Supply: Water supply is the main focus of this design. We are catching water that runs through our site.
4. Roads/Access: We need to prepare paths around the ponds and small bridges over the ditches.
5. Trees: Trees will be planted around the ponds.
6. Soil: The banks around the ponds are the heavy clay from the excavation. Building a topsoil will partly be achieved with time and deep rooted plants and leguminous plants (clovers etc), partly with bringing new topsoil to the spots where we want to see faster results from planting plants.
7. Structures: Bridges, the deck, the TWL, the Flowform
8. Subdivision Fences: Not planned for the moment.

Planetary Boundaries

Earth-system process	What can we do?
1. Climate change	See 1. in Yeoman’s.
2. Biodiversity loss	One of the main targets of the Water & Ponds design is enhancing biodiversity
3. Biogeochemical	Plants use N and P from the water flowing through the system thereby decreasing the amounts of nutrients that get in the watershed. We might cause erosion due to excavation works.
4. Ocean acidification	C-limitation strategy in the ponds
5. Land use	We are transforming field into ponds and increasing diversity of land use.
6. Freshwater	We are using fresh water for household and cultivation. Freshwater itself is not a critical limiting factor in our conditions.
7. Ozone depletion	no effect presumed
8. Atmospheric aerosols	no efect presumed
9. Chemical pollution	We avoid all chemical pollution.

Ponds: Sources of information

For designing ponds I am referring mainly to two sources of information:

1. Wolfram Kircher, Andreas Thon: How to Build a Natural Swimming Pool. The complete guide to healthy swimming at home. 2019. filbert press. [NSP] (the book was recommended to me by Joel Tefke.) The ideas in this book are reviewed f.ex. in Lowimpact.org.
2. “Million Ponds Project” in the UK: https://freshwaterhabitats.org.uk/projects/million-ponds/ [MPP]

The two are to some extent contradictory to each other as they have different targets.

“The German Landscaping and Landscape Development Research Society has published standards for private natural pools (FLL 2006): A natural pool is a pool system designed especially for swimming. It is sealed against the subsoil and comprises the swimming area and the regenerative area, and it has defined requirements in terms of water quality. The water is cleaned biologically and possibly also physically or physically/chemically.” NSP p.9

” The Million Ponds Project aims to make clean water, unpolluted, ponds for endangered freshwater plants and animals!” MPP

We wish to do both and therefor take elements from both.

The main takeaways from “How to Build a Natural Swimming Pool”

• The book presumes plastic lining of the pools.
• There are 3 or 4 key desired characteristics of a natural pool
  • clear water
  • no string algae or other undesirable weeds
  • free from pathogens
  • surrounded by lush healthy vegetation
• Natural pond water is clean due to
  • self regulating plankton
  • biofilm (micro-organisms on all underwater surfaces)
  • plants and associated mycoritzal fungi
• Clear water is achieved by limiting algae in the water which can be achieved by reducing nutrients in water and when possible shading (p24).
• A well designed pond does not require equipment for oxygen enrichment. Underwater plants guarantee sufficient oxygen saturation (p27).
• Carbon is present in water as dissolved organic carbon (DOC) or dissolved inorganic carbon (DIC).
  • DIC is in the form of CO2, HCO3(-) or CO3(2-)
  • CO2 is present in significant amounts in water only if pH is below 7.
  • Aquatic plants are categorised in 3 groups according to their C-assimilation: (p28)
    • Fontinelis type plants mainly take up CO2
    • Elodea type can use also HCO3(-)
    • Scenedesmus type green algae prefers HCO3(-)
• In most natural pools nitrogen might be a limiting factor for plant growth and therefore urea is often added (p31)
• The overall nutrition level of a water body is defined as its Trophic level (p32)
• There are 2 possible strategies for achieving clear water in a pond (p34):
  • Most natural pools are oligotrophic or moderately mesotrophic so algal bloom is not a problem. The main objective is to eliminate string algae.
  • Minimising dissolved phosphorus
    • a high concentration of oxygen and pH8 cause P sedimentation
    • P can be eliminated from the pond by removing mud from the pond bottom
    • iron hydroxide filters can effectively fix P
  • Minimising absorbable carbon
    • pH below 7 effects a reduction of DIC for aquatic plants
    • low hardness of water reduces available hydrogen carbonate HCO3 thereby limiting Elodea and Scenedesmus type plants.
    • Water hardness can be reduced with peat due to release of humin acid and fulvic acids but results also in lower visibility and brownish colour.
    • In cool climates with soft water C-limitatioin can be the natural choice. (p37)
• Filter systems relevant for natural pools (p45):
  • Hydrobotanical systems with plants (HBS) (Plant lists offered in the book)
  • Technical wetlands (TWL) (Plant lists offered)
  • Biofilm accumulating substrate filters (BSF) (mainly relevant in P-limitation systems)
• Basic models of Natural Swimming Pools (p82):
  • Standing bodies of water without technical installations (HBS)
    • ≥65% densely planted area
  • Bodies of water with slow surface flow (HBS)
    • ≥50% densely planted area
  • Bodies of running water with technical wetland filtration (HBS+TWL)
  • Bodies of running water with Biofilm-accumulating Substrate filter (BSF)
• The book contains extensive plant lists, planting advice etc that are highly relevant, but I will not reference them here in detail.
• Fish are not recommended

Main thoughts and conclusions from “How to Build a Natural Swimming Pool” for our pond design:

• We will target minimising absorbable carbon
• We will design a HSB system where a TWL can be added.
• We will not use plastic lining, in principle and because it is not necessary in the heavy clay soil we have.

The main takeaways from the “Million Ponds Project” (2)

• The best way to protect pond wildlife today is to create waterbodies that mimic the clean wild ponds common in the past. The main requirement is clean, unpolluted water.
• Recipe for a clean water pond
  • Find a place with a clean water source. To do this:
    • make sure the pond has natural surrounds.
    • avoid linking the pond to stream or ditch inflows.
    • don’t add topsoil in or around the pond. The ideal substrates for the base and banks of a clean water pond are those that are naturally nutrient-poor, like bare clay or sand.
  • Leave the pond to colonise naturally – don’t stock it with plants, fish or other animals.
  • Make sure the pond will have few impacts during its lifetime: no frequent disturbance from dogs or duck feeding.
• If possible make several ponds.
• Also ponds that only temporarily have water are beneficial for biodiversity.
• Fish are not recommended

Main thoughts and conclusions from the “Million Ponds Project”:

• We presume that in our area even the ditch inflow water is clean. This must be confirmed with water analysis.
• The ponds and the pond banks are pure heavy clay. Some of the original topsoil could however remain in contact with the pond water.
• The ponds will be predominantly colonised naturally but some plants will be planted and seeded.
• We will not stock the ponds with fish or crabs.
• If we eventually have ducks they should have access to only one of the smaller ponds.

Design

Placement of ponds

Pond	Where	Why	Water source	Water output
Garden pond	on forest edge between house and greenhouse PA3	We wanted a pond for collecting water from the roofs to supply the garden and greenhouse and provide aesthetics in the garden.	– ditch on edge of forest/field – house drainage and roof (overflow from IBC tanks)	– use in garden – greenhouse – overflow by surface ditch to Big pond
Clean water pond	at high end of field PA8	The upper part of the field is naturally wet. The pond can collect water and improve drainage.	– groundwater, rain and surface water from surrounding (no incoming ditch) – the location was originally wet, probably groundwater pushing into the field from the forest (border of lighter soil and heavier clay)	– use in winery – overflow to Big pond
Eutrophic pond	at low point below sauna PA4	A natural low point.	– surface water & rain, overflow from sauna, tub	– use in forest garden – overflow to ditch in north
Big pond	at low point of field PA7	The lowest point in the field is naturally wet. Space for a big pond as main water storage and recreational use.	– main ditch entering the site from SW redirected into pond – subsurface drainage from field (PA7, PA8) – ditch from Clean pond – surface water and rain	– use in forest garden and garden – overflow back to main ditch

PMI of ponds and elements

Element	Positives	Negatives	Interesting
Garden pond	– close to garden and greenhouse	– needs a ditch through the garden for overflow – somewhat lighter clay soil and previous excavation for water pipe means that the pond could leak	– should help to dry the upper part of the garden which is very wet in spring due to broken subsurface drainage.
Clean water pond	– the area is wet already so groundwater, surface water and rain should suffice to fill the pond. – overflow can feed the Big pond.		it’s a clean water pond according to “Million Ponds” definition (no ditches running in)
Eutrophic pond	– location below sauna	the overflow ditch has to pass the willow system.	this pond will have higher nutrient level due to sauna and tub.
Big pond	– space for a big pond in the lower part of the field in PA7 which is already wet	– massive excavation work – large area around the pond will be bare clay after the excavation work	– a mound on the field (soil from building sight) can become an island – using hydro botanical system (HBS) and if needed technical wetland (TWL) can become a natural swimming pool – space for 25 m long deep area for swimming – large reservoir for irrigation
All ponds	– heavy clay soil means no plastic lining of the pond is necessary		– water available for irrigation at different parts of the site. – Increase in biodiversity
Main ditch from SW	– enables filling the Big pond effectively – Big pond water flows keeping it cleaner – ditch originates from forest area	– part of the ditch watershed is affected by the Karjalohja main road	– water quality must be analysed for nutrients, pH, water softness and microbiology – a sedimenting pond can be dug before ditch flows into big pond to catch solids
Ditch from Clean pond to Big pond	– will at the same time dry the wet area SW of garden		shallow ditch will increase biodiversity

Defining targets for excavation

Garden pond

• water for garden and greenhouse
• reservoir for winter rain water from roofs
• space for planting wetland and water plants (aestethics, biodiversity)
• dry upper part of garden by guiding water from the forest edge into the pond (instead of flowing into the garden)
• shallow ditch for overflow towards the road and on roadside towards Big pond

Clean water pond

• water for vineyard and forest garden
• reservoir for winter water
• no incoming ditch: keeps water as clean as possible
• space for planting wetland and water plants (aestethics, biodiversity)
• use the pile of rocks lying close to the planned pond to create a rock habitat on the warmer north side of the pond
• leave the south and west side of the pond open (no trees)
• meandering shallow ditch for overflow towards the Big pond

Eutrophic pond

• water for berry bushes and fruit trees along the road
• reservoir for winter water
• collect water from uphill and sauna
• potential for emptying water from Willow system if necessary (and space in the pond)
• explore characteristics of a higher nutrient level pond
• space for planting wetland and water plants (aestethics, biodiversity)
• separated from Big pond with tree and bush planting area and road
• overflow past the willow system towards the ditch in the north in shallow ditch with vegetation

Big pond

• the main water reservoir
• filled with water from the main ditch and overflow back to the same
• lift the pond with banks using clay from the excavation. target is that water level is approximately at original field level.
• avoid straight lines in the banks and ditches / increase edges
• incoming ditch must start at 1 metre higher (in terms of contour)so that targeted water level can be reached
• incoming ditches (main ditch from SW and 2nd ditch from the Clean pond) enter a smaller sedimentation pond first before water flows into Big pond
• overflow must be from surface so that mud and nutrients don’t flow downstream
• enough space and deepness for swimming
• follow Natural swimming pool design principles
• 1/3 of pond is over 2m deep for swimming and open water
• 2/3 shallower area for planting the hydro botanical system (HBS) for keeping water clean
• add gravel on south bank for access into the pool for swimmers and kids
• install poles in the pond for building a deck

Implementation: excavation

So far we have used MR who is also the organic farmer leasing our fields for doing the excavation works at our site. He and his sone PR are the only ones locally who have 16 ton excavators that are needed for the Big pond excavation. However as these guys are also farmers and doing contract work for other farmers during the summer they are really busy. Therefore we decided to do the small ponds without them with a rented smaller excavator. A friend of ours with experience with landscaping gardens promised to dig the Garden pond for us over a weekend. Everything didn’t go to plan however as the rented excavator broke down and he managed only to start the work. The following weekend we hired an other man with some experience to do the the digging. I dug the Clean pond and the Sauna pond myself. Previously I had limited experience with a small 3 ton excavator. The rented excavator was an 8 ton Volvo.

Garden pond

The Garden pond

• dimensions are 7,3m x 4,1m
• surface area when full 24 m2
• estimated average depth 50 cm
• estimated volume when full 12 m3

Clean water pond

The Clean water pond

• dimensions are 9,5 x 5,7
• surface area when full 43 m2
• estimated average depth 70 cm
• estimated volume when full 30 m3

Eutrophic pond

The Eutrophic pond

• dimensions are 7,5m x 5m
• surface area when full 29 m2
• estimated average depth 70 cm
• estimated volume when full 21 m3

Big pond

The Big pond

• dimensions are 50m x 31m
• surface area when full 1200 m2
• estimated average depth 100 cm
• estimated volume when full 1200 m3

The total surface area of the ponds is appr. 1330 m2 and volume when full 1300 m3. So it fulfill the estimated 1000 m3 pond volume. Additionally in the 3 small ponds there is 63 m3 water volume when full. So the big pond is by far the most important water reservoir.

Now the ponds are dug. Next step is to design the plants but that will be a separate design.

D

Map no	Explanation
A.*	Incoming water from ditch. Main source of water but dries out in mid June.
B.*	Ditch from Clearwater pond. Generally dry in the summer.
C. *	Ditch from Garden pond. Generally dry in the summer.
D. *	Outflow into original ditch. No outflow after early June / midsummer.
1.*	Island in the pond. Natural vegetation + earlier seeded meadow plants.
2.**	Mound, Flowform steps.
3.**	Technical wetland to enhance water pureness. (Separate Design)
4.**	Perennials
5.	Low-growing coniferous trees and bushes.
6.**	High growing coniferous trees.
7.	Perennials.
8.*	Pond zones 2, 3 and 4: wetland, swampy and shallow water
9.	Pond zone 5: floating or submerged plants
10.*	Gravel road to “beach”
11.	Deck on the pond for recreation.
12.**	Path around pond made of bark mulch
13.**	Mowed path
14.	Bridge over ditch
15.**	Area that is bare clay after excavation. Seeded with meadow plants.
16.**	Sensitive trees planted north of Clean water pond beside rocks
17.	Sensitive low-growing trees on north side of Big Pond
18.*	Stone circle

Budget

What	Cost
excavation, small ponds (mainly rental cost)	2000 €
excavation, big pond , including gravel and pipes	6300 €
water analysis (“Pro JBL Aquatest” kit)	137 €
Bridges – oak logs – 2”x 8” timber	200 €
Deck – 2”x8” timber	1000 €
Bark mulch	100 €

Implementation Backlog

What	Q3/2021	Q4/2021	Q1/2022	Q2/2022	Q3/2022	Q4/2022	2023
Design	in the works	in the works	in the works
Build deck			to do	to do	In Progress		In Progress
Analyse incoming ditch water from S				to do			Done
Prepare bark mulch paths				to do	Done
Build bridges over ditches				to do	In Progress
Dig shallow ditch for overflow from Garden pond				to do	In Progress
Build small decks for small ponds							to do

Maintenance

“How to Build a Natural Swimming Pool” (p. 203…) states “The focus in maintaining natural pools is on supporting appropriate water quality, keeping swimming area clean, managing plants and filters and regularly servicing equipment. Measures also need to be taken to keep the water level stable.” Our ponds are not swimming pools but we do hope to be able to swim in the big pond.

Maintenance tasks that are mentioned are:

Task	Comment	ToDo
Removing coatings and sediments from constructed elements	So far there are no constructed elements in the ponds. A deck is planned.	–
Preventing leaf accumulation in autumn	This could be done by constructing a temporary net fence on the side of prevailing wind (W – SW) to prevent leaves from flying into the pond (NSP p. 205). There are willows in the ditch west to the big pond. The clean water pond and garden pond have trees to the north-east.	observe
Controlling the water level	Controlling water level would mean refilling water into the ponds. However we don’t have a water source for this so we just must accept the water levels going down during the summer. Only the garden pond is so small that we have considered refilling it (to save the tadpoles). In natural swimming pools the challenge of refilling is nutrient accumulation. In our case the nutrients are concentrated in a smaller amount of water.	observe
Maintaining water quality	In our situation this is not really a maintenance task because there is not much we can do about water quality except hope that the system will eventually function as planned. The main factor is that appr. 60% of the water surface is covered with water plants. Now in the early days it is nothing close to that and it takes time for the water plants to establish themselves.	observe

2023 is the second full summer after excavations of the ponds. So far they have not required any real maintanence and in the short term not much maintenance is foreseen.

• Incoming ditches: At some point – maybe after 10 years the ditches need to be cleaned. Now the main concern is that the main incoming ditch is bare soil. Vegetation is coming in slowly and will eventually tie the soil to its place and decrease erosion of solids into the pond. Cleaning the ditch will again increase erosion so it should be done as seldom as possible.
• The small sedimentation pond between ditch and big pond: This is where the most part of the solids stop so it might be topical to empty it with a small excavator every 4-5 years.
• For the moment the main worry is that there is not enough vegetation in the big pond. It is a natural succession which can not be much affected with planting. Eventually this will turn around and vegetation must be harvested from the pond as food, mulch and compost material.
• It should take decades before emptying the big pond from solids becomes necessary.

Evaluation

Evaluate the design and process

Pond excavations

In practise designing and implementing were somewhat overlapping regarding excavations in Q3/2021. Some points were not properly communicated to the excavator operators due to this:

1. What we meant with the shallow part of the pond was not clear. Now the shore is relatively steep going to appr. 1 metre depth quite fast while it would have been better to have a more gradual deepening of the shallow side of the pond to create more of pond zone 2 and 3.
2. Water should not have contact to the original topsoil of the field. So even if topsoil is not taken away it should be removed from the shore so that only pure clay is in contact with the water. Now topsoil was visible in some parts of the pond shore.
3. It would be good to have a higher edge where the shallow area borders the deeper area. This would prevent mud from flowing into the deeper pond area. This was not implemented at all.

Achieved pond volume over 1300 m3 compared to targeted 1000 m3.

Evaporation and leakage in the Big Pond

Originally I did not think much about evaporation of water from the water surface and leakage which now both seem relevant factors.

Evaporation could be calculated as gh = Θ A (xs – x) and depends on factors like water temperature, air temperature, wind, air moisture. Based on summer conditions (0,5 m/s wind, 20°C water temp, 25°C air temp) the evaporation rate from the big pond could be 170 kg/h or 4000 kg/24h or 28 m3 in a week so potentially we could be loosing 12 cm/month of water by evaporation. (This is a crude estimate but even with a big “mistake” it gives an idea of the scale.)

“How to Build a Natural Swimming Pool” mentions that a pool can loose more than 5 mm water per day through direct evaporation and transpiration from plants (NSP p.206) so that would be 15 cm cm/month so even more than I estimated above. NSP also mentions that without a lining dry soil around the pond will suck in water from the pond even without actual leakage (NSP p. 130).

In 2022 the water level in the big pond decreased 37 cm in 2 months between early July and early September despite there being some rain in July and August.

In 2023 the water level in the big pond has dropped much faster probably due to less rain. There hasn’t been practically any rain after 3.5.2023 until late June (21.6.2023). The incoming water flow from the ditch went dry in late May and the water level started to drop reaching -40 cm by mid June – in just 2 weeks. Even with no rain evaporation alone can not explain so fast water level drop. It looks like the big pond is leaking which is evident by the soil staying wet on the north side of the pond. This could be because of an old drainage pipe still functioning or the coarse glacial till (moren) found on the north side of the pond bottom when it was dug. In the later case it would be impossible to fix. The drainage pipe option was already considered in spring 2022 and the north side was dug open to break the drainage pipes but it did not seem to fix the problem. Now we will have to follow the situation this summer and see how low the water level goes.

The water level reached -50 cm by 3rd July but stabilised there. July was rainier with 48 mm of rain and the water level was -39 cm by 8th August. By 20th August it was again -49 cm. So far the water level has not gone below the -50 cm mark so there might be something preventing that, i.e. level of point of leakage or ground water level.

“The problem is the solution“. If it is not possible to fix the leakage maybe there is some benefit. At least the soil on the north side of the pond stays wet which could also be an opportunity in developing a different kind of biodiversity there.

Comparing the water level drop in 2022 and 2023:

Water quality in the Big Pond

In 2022 the water quality remained swimmable – however we did not do any water analysis. In mid June in 2023 increasing amounts of string algae started to appear indicating excessive nutrient content and maybe also elevated temperatures due to the hot spell. It did not seem appetising to swim. However this kind of development could be foreseen because the water vegetation has not developed to the degree it should.

The other Ponds

Also the “Garden Pond” is suffering from leakage. This is most probably because of the excavation work that was already done in the same area when the house’s water piping was dug into place. Probably the pond is in contact with soil that was dug then and leaks into it. There is a lot of tadpoles in the pond and very little string algae.

The “Clean Water Pond” is keeping its water level very well. It keeps wet above the pond long into early June and is replenished by ground water. It is in the same water system as our well. Until late June the water level has dropped only appr. 10 cm. There is very little string algae.

The “Eutrophic Pond” is drying quite fast comparable with the Big Pond. There is nothing feeding it with more water after surface water has dried after winter. The water from the sauna and hot tub are used for irrigation so it doesn’t benefit the pond. String algae development is strong.

Water analysis

My original plan was to use a commercial water analysis service but as I started looking at it more closely I realised that it would become very expensive to do repeated analysis from 4 different ponds. Reading again NSP, they recommend getting a water analysis test kit and one of the recommended kits is JBL that you can get from Aquarium shops. I bought the JBL “PRO Aquatest” and together with our wwoofers did all the tests for the Big Pond, Eutrophic pond, Clean pond and our tap water from the well.

Overall all the values are extremely low including nitrogen in any form. However P-level is mesotrophic and O2 level even going towards eutrophic (NSP p34). Nevertheless the question arises, how can string algae still grow? As NSP explains (p36) the main parameters to look at in the Carbon limitation strategy are pH and Hardness.

• In our case the pH is too high as it should be <7 in order to limit inorganic carbon availability which limits undesirable algae growth.
• High hardness is also undesirable as it results in higher HCO3 content which enhances growth or green algae. The dH should be <5.

The target should be to lower pH and Hardness. For both purposes a solution is to add bog peat (p36). We are already doing that with the TWL bog. However I will present that as a separate design. The other important factor is plant growth. For the moment we are nowhere close to 60% plant coverage of the pond. When plants grow they absorb carbon and release oxygen into the water thus suporting the carbon limitation strategy.

Reflecting on the Vision and needs

Vision / Need	Evaluation in 6/2023
– The system should provide us with sufficient water for cultivations.	Mainly the Big Pond and the Clean Water Pond are used for irrigation in the garden and forest garden and are a huge asset in getting over the early summer draughts that seem to get increasingly severe.
– The main pond should be large enough and water quality good enough that it is possible to swim (from sauna / for children)	This remains to be seen. In 2022 we swam in the Big pond the whole summer but in 2023 there is more string algae which makes the idea of swimming after mid June less appetising. However this was expected as it will take several years before water plants cover over 60% of the water surface and the water quality should stabilise.
– The system should enhance a beautiful landscape and provide recreation for us and visitors.	Certainly the ponds are more interesting than just field. Aesthetics will require more plants both in and around the ponds. A 50 cm drop in water level is also an aesthetic challenge and it will be challenging to find the right plants for conditions where the pond edge is under water from late autumn to May but goes dry in the summer.
The water system should rely on local resources in terms of water sources, energy and material.	Making the ponds required external resources in the form of excavation work. After that no external resources are needed apart from a few plants purchased outside. Mostly we rely on wild plants.
There should be no outputs from the system in terms of waste water or nutrient leaching (Biogeochemical cycles).	The ponds should cause a net reduction in nutrients and solids passing through our site compared to just having the ditches as before building the ponds. The pond system holds resources on the site.
The system should support wildlife and biodiversity on Iso-orvokkiniitty.	The ponds create different kinds of smalll ecosystems and microclimates that enhance biodiversity. On the level of larger animals we have already had several birds stay for shorter or longer periods in the ponds (Canadian Geese, Mallard, Golden Eye, Common Teal, Common Greenshank, an unidentified shorebird, Northern lapwing. Barn swallows are now much more numerous. Not to speak of all the insects and other critters in the ponds which we have not systematically surveyed.
The design and experience is shared with others for inspiration.	Here it is.

Using Permaculture Design Principles

In David Holmgren’s terms (3) this design is in the domains of “Land & Nature Stewardship” and “Built Environment” and broadly speaking a “Land Based” design. The Ethics of Permaculture (Earth care, People care, Fair share) have been taken into account in the Vision which was considered separately regarding ponds and plants.

DESIGN PRINCIPLE (Holmgren)	Evaluation
OBSERVE AND INTERACT.	The design is based on several years of observing our site and interacting with it since 2014. Observing how the ponds will develop over the years will be extremely interesting to see and observe. Observing will enable us to interact.
CATCH AND STORE ENERGY.	This is the main design principle in “Ponds at Iso-orvokkiniitty” as we are catching and storing water that moves through our site. When we are not moving water gravitationally we use the help of catching sun energy for running pumps.
OBTAIN A YIELD.	The ponds supply water for cultivation while creating recreational value and biodiversity. Some ediple plants can be harvested, f.ex. cattail Typha latifolia. Plant material and algae can be harvested for mulching or compost if it seems necessary to get nutrients out of the system. The main yield for us is however irrigation water.
APPLY SELF-REGULATION AND ACCEPT FEEDBACK.	The Water system is designed to be highly self-regulated and independent of external inputs after setup. Some technical helps are needed to obtain the yield. The design is not ready in one go – feedback is expected from the system and will be reacted to with tweaks as necessary.
USE AND VALUE RENEWABLE RESOURCES AND SERVICES.	Water and sun energy are renewable and in the core of this design.
PRODUCE NO WASTE.	The water system is designed to produce practically no waste. The system output is the clean water leaving the site through the overflow pipe to the road pipe.
DESIGN FROM PATTERNS TO DETAILS.	The pattern of water flowing gravitationally in the landscape through ditches and reservoirs (ponds in our case).
INTEGRATE RATHER THAN SEGREGATE.	Integration of water systems and plant systems (the different elements) to benefit each other and create several functions (clean water, catch and store water, irrigation, recreation, biodiversity, harvest plant material etc).
USE SMALL AND SLOW SOLUTIONS.	While the main part of the excavation was done in September and October 2021, after that the system will develop slowly with a natural succession (helped with planting and seeding) of the plants and water ecology and adding necessary tweaks.
USE AND VALUE DIVERSITY.	Each pond is in some way different from the others which increases diversity in and between them. Planted and seeded plants increase the diversity.
USE EDGES AND VALUE THE MARGINAL.	Where until now was grassland field is now ponds and ditches creating various kinds of edge effect between moving and standing water and soil and water bodies of different depths etc.
CREATIVELY USE AND RESPOND TO CHANGE.	The Water system combined with the plants will be in constant change through the seasons and succession over years. This change will build a permanent but evolving system.

Yeoman’s Scale of Permanence

1st evaluation (during design)	2nd evaluation (20 months after excavation: June-July 2023)
Climate: We will invest fossil fuels (carbon emissions) in the design mainly in the excavation works and some plastic pipes. Can we compensate that (or more) with carbon sequestration in vegetation in and around the ponds?	Fossil fuels for excavation works: – excavators for Big pond 58h x 20l = 1160 l – tractor for big pond 32h x 10l = 320 l SUM for Big Pond appr. 1500 l fuel meaning appr. 4000 kg CO2 emissions (2,63 kg CO2/kg diesel: wikipedia). That is roughly half of the average Finns’ annual CO2-equivalent emissions so not a small number! The question of compensating that is almost impossible to answer. The comparison should be between the situation earlier (permanent lay), emissions of CO2 during the earthworks (from the soil) and now (pond banks + the ponds). Does the pond itself sequester CO2 and how does that compare to the grass field? (Water bodies with excessive amounts of nutrients act as methane sources but our ponds are low in nutrients.) Maybe also take into account how much the forest garden around the pond benefits from irrigation (faster growth more carbon sequestration). Unfortunately I am not able to find sufficient data to do the calculation or to back the idea that we could compensate.
Landshape: Definitely we affect landshape with digging ponds and ditches and making some mounds. However it is hardly visible from a distance unless you are flying, f.ex. from Varkalahdentie road that passes our property.	The ponds are mainly visible for us on the site.
Water Supply: Water supply is the main focus of this design. We are catching water that runs through our site.	We can store 1300-1400 m3 of water in the ponds which earlier went through the site in the ditches.
Roads/Access: We need to prepare paths around the ponds and small bridges over the ditches.	A bark path was made around the big pond in 2022. One bridge is made, 2 more under construction.
Trees: Trees will be planted around the ponds.	Coniferous trees on the north side. There is a Japanese Maple planted on the island.
Soil: The banks around the ponds are the heavy clay from the excavation. Building a topsoil will partly be achieved with time and deep rooted plants and leguminous plants (clovers etc), partly with bringing new topsoil to the spots where we want to see faster results from planting plants.	Topsoil being built with clovers. Some topsoil brought in for planting. In 2023 white clover in June-July and red clover later are blooming massively despite the drought.
Structures: Bridges, the deck, the TWL, the Flowform	One bridge is made, 2 more under construction. TWL and Flowform under construction (separate design).
Subdivision Fences: Not planned for the moment.	Coniferous tree area was fenced in 2022 instead of protecting each tree separately.

Planetary boundaries

Earth-system process	What can we do?	Evaluation (20 months after excavation: June-July 2023)
1. Climate change	See no 1. in Yeoman’s.	Potentially negative.
2. Biodiversity loss	One of the main targets of the Water & Ponds design is enhancing biodiversity	The ponds have and will certainly increase biodiversity on our site and some results can be seen quite fast but mostly it will take more time. This will be interesting to observe. Looking at our area more broadly, small and medium size freshwater ponds are not typical in the landscape (we have lakes, woody wetlands and marsh). So the ponds might bring some elements of biodiversity which are not at the moment present in our landscape and which are difficult to predict.
3. Biogeochemical	Plants use N and P from the water flowing through the system thereby decreasing the amounts of nutrients that get in the watershed. We might have caused erosion during the excavation works.	Now that the ponds are made erosion should have decreased although it probably was not a big problem here anyway. Most solids moving with the inflowing water will sediment in the ponds. The water flows out of the big pond from the surface through an overflow pipe so most solids will stop in the pond. Nutrients will be bound into the pond vegetation once it has developed properly. Plant material can be harvested and used as mulch or composted.
4. Ocean acidification	C-limitation strategy in the ponds	This question has mostly to do with CO2 in the atmosphere, i.e. climate change. I’m not sure if our pond has any direct relevance to the topic.
5. Land use	We are transforming field into ponds and increasing diversity of land use.	Appr. 1300 m2 of grass field was transformed into ponds creating water bodies and edges. It can be argued that as land use the project had a positive impact, i.e. the opposite effect compared to building roads or buildings or doing monocropping on the field.
6. Freshwater	We are using fresh water for cultivation. Freshwater itself is not a critical limiting factor in our conditions.	We created new freshwater bodies.
7. Ozone depletion	no effect presumed
8. Atmospheric aerosols	no efect presumed
9. Chemical pollution	We avoid all chemical pollution.	Apart from machine work for digging (oil, hydraulic oil, diesel) no chemicals have been used.

What tools were used

• VOBREDIMET
• PMI
• Scale of Permanence
• Planetary Boundaries

I used VOBREDIMET in this design instead of just OBREDIM. Without a Vision one wouldn’t know what to design. The first stage of VOBRE (Vision – Observe – Borders – Resources – Evaluate) happens in reality in loops. Formulating a Vision requires that observation and evaluation has already been done to some extent and observation and evaluation depend partly what the vision is. External information (books, internet research) is included in Evaluate because external information enables you to evaluate the possibilities to realise the Vision in light of the observed situation. When the VOBRE-part has been done the Design comes pretty easy as the Vision, Observations and Evaluation largely dictate the Design. Even Implementation can in reality still feed back to the Design but Maintenance and Evaluation of what got done feeds into the Tweaks.

I used PMI in 2 occasions:

• to analyse possible sources of water
• to analyse properties of the different ponds

PMI works well in bringing to surface different aspects you wouldn’t necessarily think about otherwise.

Both the Scale of Permanence and Planetary Boundaries act as tools to look at the designs from the wider perspective. The Scale of Permanence analysis shows that we are in this design working on a relatively high level in the scale of permanence and that we therefore might even have a negative effect on the highest level; Climate. Planetary Boundaries in my view give a more balanced perspective to the different effects the design might have. It is not only about Climate but on the other hand we get into comparing apples with mushrooms. the effct on climate change is not clear but biodiversity is enhanced.

Tweaks

Tweaks in the sense that something needs to be changed don’t seem to be necessary in any bigger scale. The reflections about what went wrong in the excavations works cannot in my mind be corrected without doing more harm than benefits.

A main benefit of the design is to stop water on our property (i.e. store it) and to be able to use it for irrigation. From that perspective it could make sense to dig even more small ponds where the main water flows through the property are. That would mean

1. The ditch on the north side of the property could be enlarged into a pond. The water originates from the neighbours field on the north and from the forest. However it is difficult to fit the pond there due to trees that have already been planted. On the other hand it is possible to move trees with the excavator (most are not very big yet). The benefit would be water closer to the trees planted for the wind shield.
2. A pond could be fitted between the Clean water pond and the Big pond. However it would risk draining water from the Clean water pond and the well.
3. A pond could be fitted higher up (to the SE) on the main ditch. The benfit would be water closer to the forest garden.

So 1. and 3. are possible tweaks to consider but no need to act anytime soon on them.

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References:

(1) Lasse Järvenpää ja Mika Savolainen (toim.) Maankuivatuksen ja kastelun suunnittelu. (2. päivitetty painos). YMPÄRISTÖHALLINNON OHJEITA 4 | 2015

(2) Freshwater Habitats Trust: Help and Resources. https://freshwaterhabitats.org.uk/projects/million-ponds/help-and-resources/

(3) David Holmgren: Essence of Permaculture. 2013.

(4) Wolfram Kircher, Andreas Thon: How to Build a Natural Swimming Pool. The complete guide to healthy swimming at home. 2019. filbert press.