‘Is it normal what is happening to the weather before our eyes?’
‘Basically, yes, it’s normal. A drought, like, for example, a flood, is an extreme natural phenomenon. One must bear in mind that a drought develops gradually: from an atmospheric drought, through a deficit of water in the soil, which is called agricultural drought, to lowering of the groundwater and surface water table level. The last two phases are referred to as hydrological drought – whose consequences for us and all of nature are the most severe. Droughts have always occurred from time to time, except that in the past they were caused by natural factors, whereas recently they have been caused increasingly often by human activity. The frequency of water deficit periods has been increasing recently; also, they have been occurring at an unusual time, for example, in the spring. So, in this sense, it is an abnormal phenomenon. And what’s more, according to the forecasts prepared by the Intergovernmental Panel on Climate Change (IPCC), this phenomenon is going to intensify – as are floods. And yes, no such spring drought as we had this year has ever been recorded.’
‘Apparently, the total annual precipitation in our region hasn’t changed. So why do we have a drought, and in spring for that matter, when all plants are in the greatest need of water?
‘Yes, it’s true: the total annual average precipitation over a long-term period remains unchanged (613 mm), although both very wet (for example 940 mm in 2017) and extremely dry (280 mm in 1969 or 454 mm in 2014) years occur. We are still suffering from the consequences of the three years (2013-2015) of water deficit. Unfortunately, the groundwater plate, which should be restored in successive years, is decreasing. The precipitation distribution is to blame, but not only that. We have little snowfall in winter. Snow is the natural reservoir of water, which increases the groundwater resources while melting. Last winter there was practically no snow. Torrential rains have been an increasingly frequent phenomenon. Water from them runs off to ditches, storm sewerage systems and rivers before soaking into the ground. And, to make matters worse, they wash out the surface, fertile soil layer.’
‘Groundwater, why is it so important?’
‘Because it supplies water to our rivers, lakes and wetlands. If the water table decreases (and you can see that, for example, when you look into a well), the water table in our rivers and lakes also decreases. This is when symptoms of what is called a hydrological drought appear. Currently, the water table in rivers in Poland is very low; in most cases, it is at the level of so-called “profound drought”. Even the water table of the Łyna River at the IMGW stream gauge in ul. Tuwima is in the low-level zone, and the amount of water carried by the river is half of the average amount for the springtime (3.86 m3/s). We haven’t seen such a low level of water resources in our river in Olsztyn since 1970.’
‘Why is it important?’
‘It is because we have to be prepared for bans on drawing water for unreturnable purposes, for example for watering plants. We can’t take so much water away from nature that its level falls below the limit of inviolable resources. It creates a risk of a loss of the biological continuity in rivers and, in consequence, degradation of its resources.’
‘That means that we have drought because although the amount of rainfall is the same as before, it rains not when we want it, and rains are torrential.’
‘Yes, but paradoxically, even if the total rainfall in successive years is similar, droughts can develop! And this is what we are observing now. Why? An increase in the air temperature is to blame. The annual average temperature in our region has increased by 2 degrees Celsius during the 60 years since we started the temperature monitoring! It greatly affects the evaporation rate. Not only are groundwaters not supplied evenly with precipitation, but also the evaporation rate is increasing. And the higher the temperature, the higher the evaporation rate, which applies both to water in soil and in all water bodies. Now the situation is not so bad because of low water and air temperatures, but if the situation with rainfall does not improve, it will be bad in summer.
Drought not only inhibits, but it prevents plant vegetation. It is also responsible for wind erosion and degradation of soil. The wind blows out the finest particles from soil, which makes it even drier and more barren and the effects are obvious.’
‘So we have a series of adverse phenomena: a drought which inhibits plant vegetation and soil erosion caused by torrential rain and wind. Is there anything we can do about it? And if there is, what?’
‘There is, and in our region, we don’t have to resort to such sophisticated methods which are applied in desert countries, where, for example, water is recovered from dew. At home, above all, we should save water. We should also collect rainwater because a time may come when watering gardens with tap water will not be allowed. It is a paradox that in our region, where lakes abound, groundwaters are susceptible to deficits. However, we can easily increase their resources by small water retention. It involves gathering water in small ponds, forests and fields. The small water retention programme has been conducted by regional boards of the State Forests under the supervision of our University staff. Very good results have been achieved, for example, in the Maskulińskie Forest District, which has completed a small water retention programme prepared by a team led by Prof. Hołdyński of the Faculty of Biology and Biotechnology. Small water retention should also be done in agricultural areas. Here we can also offer effective solutions for retaining water in the soil. The staff of our department take pride in solutions that limit underground water runoff, owing to which water is available to plants later, during a water shortage.
Nature conservation areas are a different issue. The recent fire in the Biebrza National Park showed the possible consequences of hydrological drought. As could be seen, even peatland in a river valley can burn.’
‘Are there any solutions for towns?’
‘Yes. For example, blue-and-green infrastructure. These are urbanistic solutions, based on nature, thanks to which we can retain rainwater at the place of precipitation, which helps to increase the groundwater supply, regulate the air temperature and store and purify rainwater. These are also measures that generally lead to a reduction in concrete surfaces in favour of permeable areas. We know that the groundwater table underneath towns is dramatically low, which is caused by covering large areas by concrete and by rainwater being run off to rivers immediately by storm sewage systems. This is unproductive runoff and the water cannot be used by vegetation in towns. It is also noteworthy that rain also washes out all contaminants, which it carries off to rivers, posing a threat to the water quality. There are a number of solutions are being tested at our department for a doctoral dissertation by Ewelina Pochodyła, Master of Landscape Architecture. She is studying the effectiveness, for example, of green roofs, rain gardens, retention ponds, bioretentive basins using different substrates and, above all, suitable plant species. One must bear in mind that having vegetation and water in a city means creating a better microclimate and a natural biofilter. That is why, among other things, the renovation of Kortowo Park involved replacing the concrete pavements with gravel alleyways permeable to water.’
The interview by Lech Kryszałowicz