Water situation snapshots
kuukausikeskiarvokahden kuukauden kuluttua
Drought situation 24.5.2023
Soil moisture decreases and groundwater levels have started to fall
Soil moisture has begun to decrease, and groundwater levels have started or are starting to decline in most parts of the country. On the southwest coast, the soil is already low in water in some places. The impact of the melting snow and frost is still visible especially in the northern part of the country, where the soil is wet, and the groundwater levels are at their highest.
In the southern and central parts of the country, the water levels of small groundwater deposits are mainly close to the averages for the period or approximately 10–25 cm below the normal level in May. In places, the levels are higher than the May average. In the north, the levels of small deposits are mostly close to the average or 10–40 cm above it. In Kainuu and Northern Lapland, water from the melting snow and frost has raised the water levels even higher in places.
The water levels of large and medium-sized groundwater bodies in the southern part of the country vary by about 25 cm on both sides of the average for the period. In the central part of the country, the water levels are in many places at a normal level or 10–35 cm higher, in some places even higher. In Northern Finland, the water levels of large and medium bodies are mostly close to or 10–40 cm above the averages for the period.
Soil moisture decreases and groundwater levels usually fall throughout the summer. Warm weather and plants increase evaporation, allowing less water to be absorbed through the soil layers and become groundwater. Typically, soil moisture increases, and groundwater reserves begin to fill only in the autumn, but heavy rainfall may also increase groundwater levels in the summer.
How should I prepare for droughts?
A period of drought may reduce the volume and impair the quality of well waters and also hamper farming and horticulture. Droughts can and should be prepared for.
Monitor and plan ahead
A drought does not develop overnight, so do not let it catch you by surprise! Watch for the symptoms of draught in your environment and listen to weather forecasts. Observe the groundwater and soil moisture situation in your area and monitor the water level in your well. Find out where you can obtain water if your well runs dry. If you use tap water, keep an eye on any notifications issued by the water utility.
Be observant and store water
When the water level drops in your well, the quality of water may deteriorate. Observe the quality of your well water and if you suspect a quality defect, stop using the water in the kitchen and have it tested. Where possible, you can also store water for future use in a tank or irrigation basin, however remembering that the quality of stagnant water deteriorates quickly.
Start irrigation in time
You should start irrigating your crops early rather than late. If the ground surface is already dry, it is less absorbent and the water runs away. In lands prone to drought, draught risks should be taken into account when selecting crops for cultivation. The harms caused by drought can additionally be mitigated by selecting suitable tillage methods and other cultivation techniques.
Fun facts about droughts
Drought does not develop overnight
It takes a long time for the soil to dry. The soil surface dries out first, after which deeper soil layers are affected. Before long the groundwater level starts dropping, and the water level in you well will also go down or the well may dry out. This typically happens in late summer or early autumn when the water table is naturally at its lowest. Long periods of rains are needed before the groundwater level starts rising again, and recovery often takes as long as the drought took to develop.
Droughts have always been part of life
Weather statistics contain data on droughts in years gone by. There was a significant period of drought in Finland in 1939–1942, which hampered farming and hydropower production in a country fighting a war. Old records indicate that several dry and hot summers were experienced in Southwest Finland around the mid-17th century; apparently, it did not rain once in Turku during the growing season of 1652. More recently the country has been hit by droughts especially in 2002–2003 and 2018–2019.
A world tormented by drought
Many farming regions in the world are afflicted by droughts. More than one tenth of arable fields, and an even larger share of pastures, dependent on rainwater suffer from recurring periods of drought. While irrigating crops accounts for approx. 70% of the global water consumption, water shortages affect more than one half of irrigated arable lands. Over three billion people live in farming regions that suffer from scarcity of water, and almost one half of them face severe shortages of water.
Soil moisture index indicates drought
Soil moisture index describes the level of moisture in the soil. The value is usually determined for a layer of surface soil 60 centimetres in thickness. The reference value is a situation with a high level of soil moisture, such as in spring right after snowmelt. Precipitation, relative air humidity, wind speed and solar radiation are factored in to calculate the index value, and information on net radiation and geothermal heat flow is additionally needed to calculate evaporation from the ground.
Plants need water in early summer
Crops are particularly sensitive to drought at the beginning of the growing season as their developing root systems can reach no further than the surface soil. Nearer to harvest time, heavy rains are harmful as they may flatten cereal crops and cause the grains to germinate. According to an old saying, all rain before midsummer increases the crop yield, and all rain after midsummer reduces it.
Landrace varieties can tolerate drought
The old landrace varieties of cereal crops tolerated drought in early summer better than the today’s improved varieties with a higher yield. May and June are often excessively dry in Finland from the farmer’s point of view. In the times of subsistence farming, a seed that could not survive this dry spell in spring did not produce a crop, and its grains were consequently not used for sowing the field the following year. This was a natural way of improving the cereal varieties to tolerate a dry spring.
Soil is still moist but plants are wilting
There usually is plenty of water in the ground between soil particles, which plants absorb through their root hairs. When drought strikes, the water volume in the ground is reduced, and finally water is only present as a thin film around soil particles. The forces of physics hold this film tightly in place against the particle surfaces, and plant roots are unable to access the water. This may make plants wilt even before all water in the soil has evaporated.
Soil organisms need water
An enormous quantity of small organisms that maintain the soil ecosystem live underground. They need water for their vital functions, and some of them actually swim around in water. When the soil starts drying out, life becomes difficult for everyone. Some organisms die, some resort to dormancy, while others burrow deeper down into layers that still retain some moisture. For this reason there usually is less life in the soil in the middle of the summer than in other seasons, but these organisms recover quickly when moisture returns.
Drought causes stress in aquatic habitats
A long dry period reduces the flow rates in rivers and lakes and lowers water levels, changing the living conditions in them dramatically. In shallow rivers and lakes the water temperature may rise to higher values than normal. Water escapes from the shoreline, leaving sections of the bottom high and dry, and small rivers and drains may dry out completely. These changes put aquatic organisms under stress and may impair or change ecosystem functions. The composition of species may change, and reed beds may take over shores.
Drought triggers dormancy
When drought becomes a problem, the grey worm enters a dormant state. It empties its gut, builds a chamber inside a clod of soil and lines it with mucous that hardens to a glass-like consistency. The worm then curls up into a tight knot inside the chamber and waits for better times. Minute roundworms and tardigrades fall into an even deeper dormancy in which they are completely passive and which allows them to survive not only drought but also severe cold and other extreme conditions.