Why water and wetlands


Lost water

Water has been a hot topic lately. And no wonder. Extreme rainfalls and flash flooding severely hit our society across the board just a few years ago; some areas continue to suffer from frequent torrential rain and local floods. The devastating drought of 2015 and the overall water deficit have sparked a strong reaction among not only the general population but also politicians. Water shortages have been talked about fairly openly, and strategies are being developed for if and when it becomes a real threat. Forecasts for the future are not very optimistic, predicting an increase in the average annual temperature, an increase in the number of hot and dry days during the summer, and higher frequency of extreme torrential rain.

Narovnaný a zahloubený potok rychle odvádí vodu z krajiny

Straight and deep stream lost its natural floodplain.

Obviously, these problems are partially due to climate change. The amount of precipitation has not changed essentially within our territory, but its character and extent over time has. Simply put, the rain has changed: it rains in spurts, locally, on smaller areas. The amount of snowfall has decreased, while short-term droughts in the spring are more frequent. Water from short-term, heavy rain infiltrates poorly, quickly flowing away as run-off. Groundwater is not being replenished in sufficient amounts, and bodies of surface water are also beginning to suffer from the water deficit.

This is caused, to an enormous extent, by changes in the land and environment we ourselves have created and live in. It is a sad reality that those parts of the landscape that directly shape and affect the hydrological regime and the water cycle are now substantially disturbed. The majority of natural hydrological structures such as meandring watercourses, flood plains, springs, and wetlands have been damaged or even totally destroyed in the territory of the Czech Republic. The surrounding areas have also been changed by humans, often severely limiting even the entry of water into the soil. This is how the landscape loses its ability to capture and naturally retain water. And water, once standing in the way of human development, is now in short supply.

If we look at the landscape and its parts vital for the water regime, the numbers are alarming. Of the original 1.3 million hectares of wetlands evidenced in the 1950s, a mere 350 thousand hectares have remained to date (Just et al. 2003). This means that two thirds of our wetlands have disappeared. This was largely caused by the intensification of agricultural production in the 1970s and 1980s, when large-scale draining of wetlands and straightening of smaller streams was conducted. Of the total area of 4.3 million hectares of agricultural land, one million hectares (i.e. almost 1/4) was drained by tubular drainage. In addition, vast wetlands were drained by a system of surface channels. Approximately 7 thousand kilometres of open water ditches are reported on agricultural land alone. Tubular drainage amounts to a further 4 thousand kilometres. Fifteen percent of accelerated water drainage from the land is caused by agricultural drainage systems (Vopravil et al. 2010). The area of surface drained forest swamps, enormous in quantity, must be added to this, although a summary for the whole country is not available in this case.

Povrchové odvodňovací rýhy

Open drainage ditches

The total length of watercourses has drastically shortened, reduced by a third from the original 76 thousand kilometres due to river regulation interventions (Simon et al. 2008). Save for a few rare exceptions, all larger water courses were straightened and altered. Regulation also affected a large number of small watercourses (over 14 thousand kilometres), which have been transformed into straight, deep channels, especially on agricultural land, becoming part of the drainage system. The extent of such interventions to the landscape is so high that most people perceive the current condition as totally normal, and they cannot encounter – let alone imagine – a naturally undulating stream in their neighbourhood. The loss of natural watercourses is multiplied by the eradication of their alluvial plains which were regularly flooded by water, later absorbed by the soil to a large extent. The total area of alluvial plains in the Czech Republic is 3,791 km2 (5% of the territory, Demek et al. 2011); however, a large portion of them have been isolated from the main course, drained and extensively exploited, even built up in many cases.

95 % of original peatlands were destroyed in Germany. Often arduous cultivation of peatbogs begun already in 18th and 19th century, partly due to extensive donation programmes, for aquisition of agricultural land and human settlements. This resulted in a massive intervention in water balance of the landscape and enormous loss of habitats and biodiversity. More about wetlands in Bavaria on BUND Naturschutz website.


The significance of wetlands in the landscape

The significance of wetlands on the water regime and the proper functioning of the landscape has been ignored for a long time. Only now has their actual value arisen as well as their role in the possible mitigation of consequences of climatic change. Wetlands are areas that impound and accumulate water on a long-term basis, favourably functioning especially in dry periods. Thanks to their intensive evaporation, they affect local climatic conditions, lowering the air temperature and increasing its relative humidity. Wetlands therefore effectively cool down the landscape – in hot summer days, the temperature differences can be even several dozen degrees Celsius in comparison with built-up urban areas and dry open surfaces. In this way, wetlands facilitate the short water cycle and evaporation precipitation similar to forests. In addition, they provide water needed by the vegetation and fauna alike, a fact of utmost importance in dry periods.

By contrast, the role of wetlands in retaining extreme precipitation is smaller, as their soil quickly saturates with water which then flows off on the surface. Nevertheless, this overland flow is decelerated by the rough environment, especially vegetation and micro-relief. Wetlands are much more efficient in retaining water from medium-intensive precipitation. The exceptions are wetlands in valleys and river floodplains that capture large volumes of inundated water from watercourses even in high precipitation amounts.

Why is it beneficial to return mires and wetlands to the landscape?

The gradual restoration of mires in the landscape and the improvement of their condition is to a significant measure to retain water in the long term, something that can considerably alleviate the effects of frequent dry periods induced by the climatic change. This is nicely described by the old folk saying: “Rain does not fall on dry land”. Moreover, the restoration of natural watercourses, and their flood zones in particular, is an important flood control measure that allows capturing high volumes of water from torrential rain and supports its absorption into the soil. Wetlands restoration thus addresses the essence of the problem, i.e. renewal of the functioning water regime that preserves water in the landscape as well as the water cycle, so that water does not gradually peter out together with its sources. This is vital, because even expensive technical solutions like artificial reservoirs would be pointless without natural sources of water.

Sources:

Jaromír Demek a kolektiv (2011): Změny ekosystémových služeb poříčních a údolních niv v České republice jako výsledek vývoje využívání země v posledních 250 letech VÚKOZ, Praha

Tomáš Just a kolektiv (2003): Revitalizace vodního prostředí – AOPK ČR, Praha

Jan Vopravil a kolektiv (2010): Půda a její hodnocení v ČR Výzkumný ústav meliorací a ochrany půdy, Praha

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