the summer will be hot and dry. Especially July and September

Hydrological drought. What does it mean and how is it different from “regular” drought?

When it does not rain for a long time, the plants wither and the earth dries up, we usually speak of meteorological drought. It is specific to a particular region. The level is determined by specifying the number of days with no rain or with less than the threshold for a particular area.

On the other hand, we are talking about hydrological drought, taking into account the effects of a lack of precipitation on the amount of surface and underground water and its impact on the hydrological system: soil moisture, flow of watercourses, the level of reservoirs, lakes and rivers, as well as groundwater.

This is the type of drought that affects the environment the most, such as agriculture (we are talking about agricultural drought), people and economy (socio-economic drought) and wildlife habitats.

How does a hydrological drought arise? Less water in rivers, less soil moisture

The Institute of Meteorology and Water Management reports that the risk of drought has increased due to insufficient rainfall, high sun exposure and strong winds.

He also pointed out that the number of rivers in Poland with the so-called low water, and this already indicates a risk of hydrological drought.

Low water levels, especially in the Warta basin, were caused by:

  • no effective rainfall (these are those that provide more than 20mm of water per day. They can accumulate on the surface or run off and feed the reservoirs). Effective rainfall is usually not heavy, but rather moderate and prolonged),
  • higher day and night temperatures that increase evaporation.

These two factors are also the reason for the reduction of soil moisture in the above-ground layer (from 0 to 7 cm) and in deeper layers.

The decline in bottom water resources is especially visible in western and central Poland, but the problem is also noticeable in Pomerania and the eastern part of the country. The mountain and submontane regions are richer in water – informs the Institute of Meteorology and Water Management

The Institute of Meteorology forecast, released in May 2022, indicates that we can expect an increase in the risk of drought.

IMiGW Warnings: The worst could be in July and September when the highest temperatures are expected. Storms and heavy rainfall are also forecast for this summer.

The hydrological situation of the country is deteriorating.

Since 2015, water shortages in rivers and soils in Poland have been increasing. We are dealing with a drought, the course and surface of which is periodic and often of a local nature, but the drought has kept us busy for years. We cannot forget her. In addition, drought is associated with a high fire risk, which increases in the summer months. We must be responsible and contribute with our behavior to save as much water as possible – said Grzegorz Walijewski, deputy director of the Hydrological Center of the National Protection Center and press spokesman for the Institute of Meteorology and Water Management-National Research Institute.

Why don’t thunderstorms and heavy rainfall improve the situation and reduce drought?

Despite the fact that there are local storms and even heavy rainfall, the general condition of soil moisture and water content in water reservoirs is still insufficient. Some of the precipitation is convective precipitation, which does not improve the hydrological condition of the country.

They appear when a moist air mass from the ground heats up and rises rapidly, condensing the water vapor it contains, forming cumulonimbus clouds. Usually these are showers of a small range

Effective rainfall is the kind that improves soil moisture, as well as water infiltration into water reservoirs. Even intense rainfall can have different impacts on the hydrological situation of the area depending on many factors, eg

  • soil permeability,
  • the level of humidity before the onset of rainfall (if it was very low, even heavy rain will not improve the situation. Dry soil is like an armor, on which water flows in watercourses without penetrating into the depths),
  • vegetative period (which affects the water demand of a particular area).

This means that even severe storms are not a cure for hydrological drought. In order to improve the hydrological situation after a period of drought, the rain must be prolonged and provide the area with effective water.

The cure for this deteriorating condition is to build retention reservoirs that hold the water locally. It is also important to install stormwater tanks at homes to store rainwater and not to increase water intake for watering the already scarce natural resources.

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