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Reports from European Environment Agency indicate that over the past decades, Europe has been experiencing frequent and severe weather and climate-related natural hazards like droughts, forest fires, heatwaves, storms and heavy rain. Climate change will make these events even more intense and more frequent. The summer of 2024 was the hottest on record for Europe and globally. While up to recently the extreme events were not considered usual in Zemgale region, experience from few previous seasons raise precautions. In summer 2024, there were heaviest rains that Latvia has experienced since 1945.

The impact of various extreme weather events has been particularly pronounced in places with high population density, such as the city of Jelgava. The region’s flat topography and land surface elevation relative to sea level result in high groundwater levels, which place additional stress on the city’s drainage and storm water drainage systems.

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In Jelgava, the main challenges from rainfall include high risk of flooding and damage to infrastructure during prolonged rainfall. The Lielupe River and its tributary floodplains, as well as low topography and high-water tables, make drainage and stormwater drainage systems difficult to operate. The extreme rainfall of July 2024 confirms that the existing sewerage system is inadequate to cope with such situations. In the region’s rural areas, the threats affect both settlements and villages and fertile agricultural land, which plays an important role in the region’s economy.

Storms are the second most pronounced weather extreme in the region and, although on average winds are not expected to change significantly over the 21st century, by the end of the century (relative to the period 1971-2000) there will be a greater number of both windless days and stormy days per year. In recent years, the Zemgale region has been severely affected by thunderstorms and storms that have brought heavy rainfall in the form of both rain and hail, destroying agricultural crops and damaging infrastructure in many places. Severe storms in summer and early autumn, when trees and shrubs are still in leaves, have caused severe damage.

Climatologists believe that the current extreme values will become the norm in the future, while extreme weather events will cause even more damage. Climate models also predict an increase in total annual precipitation over the 21st century, with an average annual precipitation in Latvia of 775.7 [±60.0] mm for minor, 806.5 [±72.8] mm for moderate and 814.2 [±79.7] mm for major climate change. Predictions foresee substantial increase in duration of heatwaves from climatic norm of 8 days to 16 [±8] days for minor, 22 [±9] days for moderate and 33 [±12] days for major climate change.

Forecasting extreme weather events is quite complicated task, as these events are characterized by short-term nature, they and spatially limited, and thus short warning times are operational. Measures for adaptation to climate change thus become essential by preparedness for more days with extreme temperatures and for more extreme precipitation events. Decision-makers and local authorities need data and information to make the necessary preparations in advance by adapting to the different scenarios and possible consequences.

Within activities of IMPETUS project, the Adaptation Pathways are elaborated for Zemgale region with particular focus on flooding occurrences from river spring floods and heavy rain events:

Adaptation pathways are developed to support in better management of river flood risks and heavy rain floods (flash floods).
Aimed to implement a set of measures for reducing the frequency and extent of flooded areas in both rural (agricultural) land and urban settlements.
In exchange with the stakeholders, adaptation options are identified, assessed and included in the pathways to increase adaptive capacity in Zemgale region.
Structural measures, e.g., upgrading of existing drainage and stormwater drainage systems, and aligning them with nature-based solutions for water retention in rural and urban areas, and cleaning of riverbeds are considered.
Non-structural measures for improving flood risk early warning system (EWS), increasing awareness of inhabitants and improving the efficiency of actions of competent authorities in case of floor risks are addressed.

Flooding

Eutrophication

Zemgale is a very flat region, located in a lowland area with a high density of rivers. The Lielupe River is characterized by its slow course, due to Zemgale’s flat topography and the low gradient of the riverbed. The height of the Lielupe floodplain does not exceed 1 m above water level. Downstream of Jelgava, the Lielupe River drops only 5-10 cm/km. The riverbed is much lower than the average level of the Baltic Sea.

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Climate change in the Zemgale region by the end of the 21st century will have a major impact on the hydrological regime. One of the most significant changes will be increased precipitation: under a moderate climate change scenario, winter precipitation will increase by 24-38%, while under a significant climate change scenario, precipitation is expected to increase by as much as 35-51%. Maximum daily precipitation will increase by about 3-6 mm, in some places by as much as 10-12 mm. On a seasonal basis, the greatest increases in precipitation are expected during the winter and spring seasons, so that the risk of flash flooding increases significantly during the cool season, when evapotranspiration is not intense. Periods of high rainfall will alternate with prolonged droughts, which will have a particular impact on heavy rainfall events, increasing the frequency of flash floods. During heavy rainfall, short, localised flooding can be observed in both larger and smaller towns, as well as in flat rural areas.

One of the activities in Zemgale in the IMPETUS project is the improvement of the Flood Early Warning System using the HEC-RAS 2D model. This model simulates water flow in two dimensions, which is particularly useful for flood modelling and forecasting. The HEC-RAS 2D model uses two-dimensional Diffusion Wave Equations to calculate the water flow. The developed model performs 2D

Key Benefits of Using Such a Hydraulic Model

Accuracy and Detail: The HEC-RAS 2D model provides high accuracy and detail, which is essential for flood risk assessment and management.
Integration: The HEC-RAS 2D model can be integrated with other geographic information systems (GIS), facilitating data processing and visualization.
Early Warning Systems: The model is crucial for the development of early warning systems, as it allows for the prediction of flood spread and impact, thereby helping to timely warn residents and take necessary measures.
This solution automatically reads hydrological forecast data from the forecast system of the Latvian Environment, Geology and Meteorology Centre.

These model results are crucial for the operation of the Early Warning System, which uses this data to identify potential flood areas and prepare warnings at the property (cadastral unit) level.

Eutrophication

Extreme events

Due to its fertile soils, Zemgale region in Latvia is characterised by an intensive agriculture where large-scale farming dominates. Agricultural activities are well developed and focus on the cultivation of crops.

During the last decade, the area of croplands in the region has increased along with application of high amounts of mineral fertilisers. Excessive loading of nutrients (nitrogen and phosphorus) lead to eutrophication of water bodies e.g., causing overgrowing of rivers, and thus putting a pressure on biodiversity and natural habitats.

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Municipal wastewater effluent is another source of eutrophication in the region. Quite often performance of wastewater treatment facilities is not sufficiently effective to ensure complete purification of waste waters causing water pollution with nutrients. As the result the ecological water quality of the rivers in Zemgale region is mostly moderate or bad.

According to water quality monitoring data of 88 waterbodies located within the Lielupe River basin district, there are 53 waterbodies having significant disperse pollution load and 14 water bodies where point source pollution load prevails (Source: LEGMC, 2024).

Climate change related increase of temperature catalyses eutrophication processes in water bodies. Climate models predict continuation of the increase of temperature thus intensifying the symptoms of eutrophication in freshwaters. Therefore, along with reduction of use of fertilisers, improvement of municipal wastewater treatment facilities, application of additional measures to prevent nutrient runoffs from agricultural land and urban environment to water bodies is of pivotal importance.

Together with regional and local stakeholders in Zemgale region, IMPETUS project partners in Latvia are developing Zemgale regional climate change adaptation plan, that will highlight the possibilities and intention of implementation of nature base solutions, e.g., constructed wetlands in Zemgale region to reduce the nutrient leakages/runoffs, reduce eutrophication intensity and improve the quality of surface waters.

Extreme events

Flooding

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Information according to § 5 DDG (Digital Services Act Implementation in Germany)

Person responsible for content in accordance with § 18 (2) MStV (German State Media Treaty)

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Extreme events

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Flooding

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High temperatures

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Flood risk

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Energy and waste water

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Eutrophication

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