katrinteubner

what do lakes and natural swimming ponds have in common?

Natural swimming ponds, Ried in Innkreis, Austria, 2006:
Connected swimming ponds of varios size and depths invite people for bathing in summer. Creating a pond can be fascinating for many of us! Some want to enjoy a small pond in the immediate living environment, located right next to the terrace, on the lawn or in the more secluded garden wildlife area. Life in a pond changes a lot with seasons! Visiting a nearby pond throughout the year puts us in touch with nature and gives us the opportunity to experience the four seasons in our daily life even if we live in urban surroundings. Others may decide to construct a pond as an attraction for visitors or tourists.

Ponds are artificial stagnant water basins. Ponds have for long been popular, even if the reasons for creating them, and the methods of construction, have changed over time. In the past ponds were mainly created for agriculture, to extract peat, clay and gravel or to protect against floods. Such ponds are known as village pond, mill pond, horse pond, duck pond, reservoir for flood control (see page about Biotop Auersthal S), groundwater-seepage pond, fishpond, peat pond (see page about Bergknappweiher S) and loam pit pond of a brickyard. These ponds were created as part of the tradition and cultural life-style of local people. Some of these ponds still even exist today, even if they don't serve their original purpose any longer. They can be valuable habitats for nature, the ecologically inferior to the natural small water bodies such as peat-bog lakes, kettle holes or other small lakes. In these ponds the basin is mainly build from naturally occurring local material, such as a waterproofing layer made of clay or natural stones, peat or sand. These ponds-for-life compare well with lakes that are defined as natural stagnant waters.

Natural swimming ponds, Ried in Innkreis, Austria, 2006:
The bottom of this large pond basin looks natural. This pond and other ponds operating as a swimming pond cluster attract many hundreds of people for swimming and bathing in summer. In this section of the lakeriver-Website, however, we deal with artificial water basins, which are less close to nature as the water is retained by pond liner or concrete. In some cases a container is used to create the water basin. These ponds are constructed by landscape planning to be a valuable place for recreation, for bathing or swimming or simply to attract wildlife in our parks, gardens or woods. In this situation these designed ponds are again used for different purposes. In the literature such artificial water retention basins are commonly described as ‘natural swimming ponds’ and ‘wildlife ponds’. These descriptions can be somehow misleading as we learned from the former paragraph that these designed ponds are not that close to nature as the traditional ponds created decades before. The name ‘natural’ might just refer to the fact that it is commonly agreed that no chemicals are used to clean up the pond water, quite different from the water in a pool. In swimming ponds and wildlife ponds, biological processes mainly achieve the ‘cleaning’ of the water. The influence of biology can easily be seen in some designed ponds as these elements are also used for decoration, as e.g. the green leaves of life plants or gravel pit on the basin ground. In other ‘natural’ designed ponds, ‘biology’ is still part of the system even it cannot be seen at first glance as the ‘biological module’ is hidden by a sophisticated concept and well executed design.

Natural swimming ponds, Ried in Innkreis, Austria, 2006:
A closer look into a retention basin used for phytoremediation to retain nutrients in a complex swimming pond system with circulating water. Nutrients are retained here by the uptake by filamentous green algae and diatoms. The latter can only be seen under a microscope and are living attached to the surface of the filamentous algae and on the bottom layer of the basin. The gas bubbles seen in the foreground of the photo indicate oxygen produced by these algae. These basins are most effective to remove phosphate even if the phosphorus concentration is not yet detectable by standards of chemical analysis (detection limit < 40 nanomol L^-1). The biomass of these filamentous algae needs to be harvested from time to time during bathing season to remove nutrients from the pond system. Shallow wildlife pond on the city area of the University of Vienna, 2013:
The concrete water basin became a valuable water habitat for many plants and animals within the city for many years. This pond is reminiscent of a reed belt in the shallow littoral zone of a clear-water lake (high water transparency), a close-to-nature assembled regeneration area of a designed natural pond, or a separate phytoremediation basin area connected by circulating water with swimming ponds. In this situation the plants that are mainly responsible for removing nutrients from the water body and hence avoiding the massive growth of floating photosynthetic microorganims (phytoplankton) are reed (mainly Phragmites australis) and charophyte underwater vegetation (e.g. Chara spec., see arrows).

Depending on the purpose and size of these designed artificial water bodies, they are just a single pond basin without or with a small regeneration zone or a cluster of few ponds arranged together with integrated regeneration zones or even with separate regeneration basins  (see for example Teubner et al. 2007 R, R). Some ponds are thus further connected to basins used for phytoremediation retaining nutrients outside the main basin. In these advanced and more complex artificial pond systems, the water of the main basin is circulating through the regeneration zones and phytoremediation basins (constructed wetland with reed; shallow water regeneration basins with filamentous green algae, on this page see gallery fotos 11-14 and the foto above on leftside) before re-entering again the main basin. The efficiency of retaining nutrients can be also improved when 'effectice microorganisms' ('EM') are applied to the pond water or pond sediment as a single treatment or when applied in addition to nutrient bounding by reed plants or filamentous green algae. A first aim of the three suggested treatments in the regeneration and phytoremidiation zones is to mobilize the nutrients (mainly achieved by 'EM', see for example Teubner et al. 2007 R, R; Teubner 2012 R). Furthermore artificial ponds might be designed in in a way, that the mobilized growth-available macro-nutrients are preferentially incorporated by filamentous algae or higher plants, which can be easily yielded by removing biomass and thus aim to eliminate nutrients from the water body of the pond system (biomass harvesting of filamentous algae in the retention basins throughout the growing season, Teubner et al. 2007 R, R; alternatively, cutting the reed stands in the shallow regeneration zone of the main basin or constructed wetland in late autumn or winter). Such treatment is key to balance the nutrient concentrations in artificial ponds as these modified systems are much simpler in terms of nutrient cycling than what is known from natural stagnant ecosystems. Surprisingly, in small swimming pond systems with circulating water, the retention time of water in the main basin is commonly adjusted by pumps to be just one day. In natural stagnant water ecosystems such a very short retention time, however, is not found. As described on the website of flushed riverine lakes, the theoretical water retention time is between 3 and 30 days (Grosser Mueggelsee S). In many other lakes, the time needed for water renewal of the whole water basin is even much longer and can exceed a period from months to years (see water retention time for lake examples on the pages about Ammersee S, Attersee S, Hallstaetter See S, Mondsee S, Taihu S, Traunsee S and Old Danube S). In large natural swimming ponds and also in shallow wildlife garden ponds the water retention time is longer than one day (about one month to a year), and they are hence more comparable to lakes than those discussed previously.

Shallow wildlife pond in the wood 'Familienwald' in Strasshof, Austria, 2013:
Every little helps! Even small, this pond liner filled up with water creates a habitat for many wild plants and animals throughout the seasons and could thus be a hotspot of enhanced species diversity in the wood. Shallow wildlife pond in the wood 'Familienwald' in Strasshof, Austria, 2013:
The frog is enjoying the sun in early summer!
Such shallow ponds are easy to manage and are very effective: lots of joy for you and a welcome place for wildlife in the wood, park or garden.

While many swimming ponds, at least those with a sand-gravel-filter, look ‘promising’ the first three to five years later their water body turns becoming turbid due to floating micro-algae. In order to sustain naturally designed ponds, much effort is commonly spent year by year maintain the pond in its initial state. This includes emptying, cleaning, re-filling and re-planting of the water basin at least once a year, frequently changing filters or permanently utilizing additional cleaning devices. Less technical support is needed in the situation where a cascade of biological processes achieves most of the purification process. This website aims at understanding how to maintain a natural pond in condition, while minimizing the cleaning treatments mentioned previously. Ecological principles maintaining a good water quality observed in lakes and watersheds ensure that a water body can have high water transparency for years. High water transparency points in two directions: indicating the ecological soundness in an ecosystem on the one side, and being a marker for high quality of ecosystem services on the other. In this view, water transparency today is understood as socio-ecological indicator, which goes far beyond how we have seen water clarity in limnology (Teubner et al. 2020 R, Teubner et al. 2021 R, pptx). Many lakes are well studied, and some of them are the size of a large swimming pond. Understanding natural aquatic ecosystems contributes to the understanding of the main factors required for effective pond management. The focus of this website is thus to discuss pond management relation to what we have learned from lakes and ponds in our landscape. The functionality and the rules for creating and maintaining a designed pond are the purpose of this work, not its architecture or specific instructions how to build a pond.

One question, however, couldn’t be answered here: Which kind of pond is best suited to you? It is up to you, just to buy an entrance ticket to enjoy bathing at a public place or to visit a lake for swimming in summer. Some prefer to build a swimming POOL. An alternative would be to create your own lovely natural pond. What matters most constructing and maintaining such a pond? And what lakes and swimming ponds have in common? How can the knowledge about lakes be applied to ponds? What organisms besides plants can be used to support the purification of water in designed swimming ponds and natural ponds? These questions will be to be answered soon in a greater detail on this website! This site about designed ponds is still in preparation!