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Societies, economies and ecosystems depend on sustainable and resilient hydrological services provided by in-tact hydrological systems and processes. These services are defined by the inter-dependencies of various drivers of which land use and land cover changes (LULC) as well as climate change are increasingly dominating, often leading to degraded hydrological services and altered ecosystem dynamics with different levels of societal and economic impacts.Increasing and more frequent hydrological extremes (floods and droughts) and reduced water availability for various users and uses, often accompanied with increasing water demands, require effective operational water management. Therefore, in-depth knowledge of hydrological processes and their links to LULC, climate changes and other human interventions as well as tools are required to guide water management and policy decisions, such as, increasing water storage in grey and/or green infrastructure, caps on water consumption, or ecosystem restoration. This presentation reviews key processes and introduces the Hydrological Status and Outlook System (HydroSOS) and related assessment and reporting approaches to inform decision and policy-making. Therefore, a scale-specific approach is suggested in which LULC, water use and hydrological processes are embedded in a larger systems approach (including natural and human systems) to guide operational management and policies.

There are several factors increasing pressure on water resources such as demographic, economic, social, and climatic changes, in addition to the growing demand for energy, food, and water. Water-related hazards, such as floods and droughts, are affecting millions of people’s lives and will become more frequent, and the need for early warning systems is growing and is being addressed by UN Early Warnings for All initiative. Water is the 6th of the 17 Sustainable Development Goals (SDGs) and impacts on 15 other SDGs. There is a growing demand for water by different sectors.Responding to the above water challenges and related hazards demands hydrological data that is findable, accessible, interoperable, and reusable, sufficient, and useful. Unfortunately, in most countries and regions, management of water resources is mostly addressed without adequate consideration of the inter-sectoral and transboundary implications of planned developments or decisions on different sectors. This is due to lack or inadequate management and exchange of reliable data among various sectors. It is essential that the management and sharing of hydrological data are performed effectively to maximize the benefits of data collection and optimize data reuse, and thus get a return on investment.Data exchange is still a challenge in hydrology from both the technological and policy perspective. The technology challenges include sparse measuring networks and lack of automatic data transmission, inadequate data quality control systems, heterogeneous and incompatible standards and protocols for data and metadata storage and exchange, and the inability to openly publish and maintain data and metadata in a publicly interoperable way. The policy challenges are often related to restrictive national legislation and financial consideration on data sharing. The WMO Unified Data Policy adopted in 2021 and the Earth System approach will help to address some of the issues, while the relevant integrated and interoperable data management and access tools, will support the technical aspects.WMO programmes promote exchange of Earth System data. WHOS (WMO Hydrological Observing System) is the hydrological part of the WIS providing data sharing solutions. It is a system of systems supporting interoperable hydrological data exchange using open standards and web services, and harmonizing the data to meet specific user needs.The goal of WHOS is to make hydrological data accessible through the use of open standards and free open-source tools for the harmonization of data, metadata, protocols, and vocabularies. Due to the diversity in the use of hydrological data and heterogeneous data sources, their effective exchange requires the implementation of interoperability enablers and data exchange mechanisms such as WHOS Discovery and Access Broker (DAB) technology, and development of hydrological terminologiesand Metadata Data Profiles.The WHOS has been implemented in La Plata Basin, Arctic Region, Dominican Republic, UK, and SAVA River Basin. Those regions benefit from a platform that enables interoperable data sharing among different stakeholders and water resources management. With new countries connecting to WHOS each year, there will be a notable improvement in global, regional and national implementation of Early Warning systems and other projects.

Climate change and other anthropogenic stressors have led to long-term changes in the thermal structure, including surface temperatures, deepwater temperatures, and vertical thermal gradients, in many lakes around the world. Though many studies highlight warming of surface water temperatures in lakes worldwide, less is known about long-term trends in full vertical thermal structure and deepwater temperatures, which have been changing less consistently in both direction and magnitude. Here, we present a globally-expansive data set of summertime in-situ vertical temperature profiles from 153 lakes, with one time series beginning as early as 1894. We also compiled lake geographic, morphometric, and water quality variables that can influence vertical thermal structure through a variety of potential mechanisms in these lakes. These long-term time series of vertical temperature profiles and corresponding lake characteristics serve as valuable data to help understand changes and drivers of lake thermal structure in a time of rapid global and ecological change., Measurement(s) temperature of water • temperature profile Technology Type(s) digital curation Factor Type(s) lake location • temporal interval Sample Characteristic - Environment lake • reservoir Sample Characteristic - Location global Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.14619009

A total of 13 satellite missions have been launched since 1985, with different types of radar altimeters on board. This study intends to make a comprehensive evaluation of historic and currently operational satellite radar altimetry missions for lake water level retrieval over the same set of lakes and to develop a strategy for constructing consistent long-term water level records for inland lakes at global scale. The lake water level estimates produced by different retracking algorithms (retrackers) of the satellite missions were compared with the gauge measurements over 12 lakes in four countries. The performance of each retracker was assessed in terms of the data missing rate, the correlation coefficient r, the bias, and the root mean square error (RMSE) between the altimetry-derived lake water level estimates and the concurrent gauge measurements. The results show that the model-free retrackers (e.g., OCOG/Ice-1/Ice) outperform the model-based retrackers for most of the missions, particularly over small lakes. Among the satellite altimetry missions, Sentinel-3 gave the best results, followed by SARAL. ENVISAT has slightly better lake water level estimates than Jason-1 and Jason-2, but its data missing rate is higher. For small lakes, ERS-1 and ERS-2 missions provided more accurate lake water level estimates than the TOPEX/Poseidon mission. In contrast, for large lakes, TOPEX/Poseidon is a better option due to its lower data missing rate and shorter repeat cycle. GeoSat and GeoSat Follow-On (GFO) both have an extremely high data missing rate of lake water level estimates. Although several contemporary radar altimetry missions provide more accurate lake level estimates than GFO, GeoSat was the sole radar altimetry mission, between 1985 and 1990, that provided the lake water level estimates. With a full consideration of the performance and the operational duration, the best strategy for constructing long-term lake water level records should be a two-step bias correction and normalization procedure. In the first step, use Jason-2 as the initial reference to estimate the systematic biases with TOPEX/Poseidon, Jason-1, and Jason-3 and then normalize them to form a consistent TOPEX/Poseidon–Jason series. Then, use the TOPEX/Poseidon–Jason series as the reference to estimate and remove systematic biases with other radar altimetry missions to construct consistent long-term lake water level series for ungauged lakes.

© The Author(s) 2020. Published by Nature Research. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons. org/licenses/by/4.0/. Globally, lake surface water temperatures have warmed rapidly relative to air temperatures, but changes in deepwater temperatures and vertical thermal structure are still largely unknown. We have compiled the most comprehensive data set to date of long-term (1970–2009) summertime vertical temperature profiles in lakes across the world to examine trends and drivers of whole-lake vertical thermal structure. We found significant increases in surface water temperatures across lakes at an average rate of + 0.37 °C decade−1, comparable to changes reported previously for other lakes, and similarly consistent trends of increasing water column stability (+ 0.08 kg m−3 decade−1). In contrast, however, deepwater temperature trends showed little change on average (+ 0.06 °C decade−1), but had high variability across lakes, with trends in individual lakes ranging from − 0.68 °C decade−1 to + 0.65 °C decade−1. The variability in deepwater temperature trends was not explained by trends in either surface water temperatures or thermal stability within lakes, and only 8.4% was explained by lake thermal region or local lake characteristics in a random forest analysis. These findings suggest that external drivers beyond our tested lake characteristics are important in explaining long-term trends in thermal structure, such as local to regional climate patterns or additional external anthropogenic influences. Funding in support of this work came from the following sources: Belarus Republican Foundation for Fundamental Research; IGB Long-Term Research; the European Commission within the MANTEL project; the DFG within the LimnoScenES project (AD 91/22-1); OLA-IS, AnaEE-France, INRAE of Thonon-les-Bains, CIPEL, SILA, CISALB; Universidad del Valle de Guatemala; Archbold Biological Station; the Oklahoma Department of Wildlife Conservation, the Oklahoma Water Resources Board, the Grand River Dam Authority, the US Army Corps of Engineers, and the City of Tulsa; the Ministry of Business, Innovation, and Employment (UOW X1503); the Natural Environment Research Council of the UK; the IGB’s International Postdoctoral Fellowship; NSERC, Canada Foundation for Innovation, Canada Research Chairs, Province of Saskatchewan; University of Regina; Queen’s University Belfast; Natural Environment Research Council; US-NSF, California Air Resources Board, NASA, and US National Park Service; the Ministry of Higher Education and Research (projects № FZZE-2020-0026; № FZZE-2020-0023) and RSCF 20-64-46003; US National Science Foundation Long Term Research in Environmental Biology program (DEB-1242626); the Environmental Agency of Verona; US National Science Foundation, the Gordon and Betty Moore Foundation, the Mellon Foundation, and the University of Washington; KMFRI, LVEMP, University of Innsbruck, OeAD, IFS, and LVFO-EU; Waikato Regional Council and Bay of Plenty Regional Council; Swedish Environmental Protection Agency and the Swedish Infrastructure for Ecosystem Sciences; US National Science Foundation grants DEB-1754276 and DEB-1950170. Faculty yes

Satellite radar altimetry has been widely used in the monitoring of water levels of lakes, rivers and wetlands in the past decades. The conventional pulse-limited radar altimeters have a relatively large ground footprint, which limits their capability to retrieve surface elevation information over small and medium-sized water bodies. A new generation of satellite radar altimeter system, a dual-frequency SAR radar altimeter (SRAL) onboard the Copernicus Sentinel-3 satellite, has produced densely sampled elevation measurements with a smaller footprint for the Earth's surfaces since June 2016, owing to the Delay-Doppler processing technique. Four standard SRAL SAR altimetry waveform retracking algorithms (known as retrackers) have been designed to retrieve elevation measurements for different types of surfaces: Ice-Sheet retracker for polar ice sheets, SAMOSA-3 retracker for open ocean and coastal zones, OCOG retracker for sea-ice margins, and Sea-Ice retracker for sea ice. In this research, we evaluated the performances of the Sentinel-3 SRAL SAR altimetry retrackers over lakes, particularly over seasonally ice-covered lakes in one hydrological cycle. For 15 lakes and reservoirs with different sizes and at varying latitudes in the northern hemisphere, we compared the lake water levels estimated by each of standard SRAL SAR retrackers against in-situ water level measurements for different seasons (a full hydrologic cycle) during 2016–2017. Our evaluation shows that Sea-Ice retracker was unable to provide continuous estimates of lake water levels, as a result of the high rate of missing data. Although the precision and relative accuracy of lake water level estimates from these three standard SRAL SAR retrackers are similar, the SAMOSA-3 retracker has the least bias in comparison with ground-based gauge measurements. When the lakes in the mid- and high-latitude regions were covered by ice in the winter season, these three standard SAR retrackers generated erroneous lake water level measurements, significantly lower than the true lake water levels recorded by in-situ gauge stations. The measurement errors of these three standard retrackers increase with the growth of the lake ice thickness. To address the negative effect of the seasonal ice cover, we developed a new bimodal correction algorithm. We demonstrate that our bimodal correction algorithm can retrieve the ice thickness and reliably estimate water levels for the ice-covered lakes in winter, hence enabling the generation of temporally consistent lake water level measurements throughout all seasons for lake hydrological analysis.

The regional climate model REMO was coupled with the FLake lake model to include an interactive treatment of lakes. Using this new version, the Fenno-Scandinavian climate and lake characteristics were studied in a set of 35-year hindcast simulations. Additionally, sensitivity tests related to the parameterization of snow albedo were conducted. Our results show that overall the new model version improves the representation of the Fenno-Scandinavian climate in terms of 2m temperature and precipitation, but the downside is that an existing wintertime cold bias in the model is enhanced. The lake surface water temperature, ice depth and ice season length were analyzed in detail for 10 Finnish, 4 Swedish and 2 Russian lakes and 1 Estonian lake. The results show that the model can reproduce these characteristics with reasonably high accuracy. The cold bias during winter causes overestimation of ice layer thickness, for example, at several of the studied lakes, but overall the values from the model are realistic and represent the lake physics well in a longterm simulation. We also analyzed the snow depth on ice from 10 Finnish lakes and vertical temperature profiles from 5 Finnish lakes and the model results are realistic.

The regional climate model REMO was coupled with the FLake lake model to include an interactive treatment of lakes. Using this new version, the Fenno-Scandinavian climate and lake characteristics were studied in a set of 35-year hindcast simulations. Additionally, sensitivity tests related to the parameterization of snow albedo were conducted. Our results show that overall the new model version improves the representation of the Fenno-Scandinavian climate in terms of 2-m temperature and precipitation, but the downside is that an existing wintertime cold bias in the model is enhanced. The lake surface water temperature, ice depth and ice season length were analyzed in detail for ten Finnish, four Swedish, two Russian and one Estonian lakes. The results show that the model can reproduce these characteristic with reasonably high accuracy. The cold bias during winter causes e.g. overestimation of ice layer thickness at several of the studied lakes, but overall the values from the model are realistic and represent well the lake physics in a long-term simulation. We also analyzed the snow depth on ice from ten Finnish lakes and vertical temperature profiles from five Finnish lakes and the model results are in realistic.

International audience; Concern over the potential impact of anthropogenic climate change on flooding has led to a proliferation of studies examining past flood trends. Many studies have analysed annual-maximum flow trends but few have quantified changes in major (25–100 year return period) floods, i.e. those that have the greatest societal impacts. Existing major-flood studies used a limited number of very large catchments affected to varying degrees by alterations such as reservoirs and urbanisation. In the current study, trends in major-flood occurrence from 1961 to 2010 and from 1931 to 2010 were assessed using a very large dataset (>1200 gauges) of diverse catchments from North America and Europe; only minimally altered catchments were used, to focus on climate-driven changes rather than changes due to catchment alterations. Trend testing of major floods was based on counting the number of exceedances of a given flood threshold within a group of gauges. Evidence for significant trends varied between groups of gauges that were defined by catchment size, location, climate, flood threshold and period of record, indicating that generalizations about flood trends across large domains or a diversity of catchment types are ungrounded. Overall, the number of significant trends in major-flood occurrence across North America and Europe was approximately the number expected due to chance alone. Changes over time in the occurrence of major floods were dominated by multidecadal variability rather than by long-term trends. There were more than three times as many significant relationships between major-flood occurrence and the Atlantic Multidecadal Oscillation than significant long-term trends.

Cryophenological records (i.e. observational series of freeze and breakup dates of ice) are of great importance when assessing the environmental variations in cold regions. Here we employed the extraordinarily long observational records of river ice breakup dates and air temperatures in northern Fennoscandia to examine their interrelations since 1802. Historical observations, along with modern data, comprise the informational setting for this analysis carried out using t-test. Temperature history of April-May season was used as climatic counterpart for the breakup timings. Both records (temperature and breakup) showed seven sub-periods during which their local means were distinctly different relative to preceding and subsequent sub-periods. The starting and ending years of these sub-periods occurred in temporal agreement. The main findings of this study are summarized as follows: (1) the synchrony between the temperature and river ice breakup records ruled out the possibility that the changes would have occurred due to quality of the historical series (i.e. inhomogeneity problems often linked to historical time-series); (2) the studied records agreed to show lower spring temperatures and later river ice breakups during the 19th century, in comparison to the 20th century conditions, evidencing the prevalence of cooler spring temperatures in the study region, in agreement with the concept of the Little Ice Age (1570–1900) climate in North-West Europe; (3) the most recent sub-period demonstrate the highest spring temperatures with concomitantly earliest river ice breakups, showing the relative warmth of the current springtime climate in the study region in the context of the past two centuries; (4) the effects of anthropogenic changes in the river environment (e.g. construction and demolition of dams) during the 20th century should be considered for non-climatic variations in the breakup records; (5) this study emphasizes the importance of multi-centurial (i.e. historical) cryophenological information for highly interesting viewpoints of climate and environmental history.

In this study climate change impacts on water balance components were estimated from transient climate scenarios for 1951–2099 in Finland. The future changes in evapotranspiration and discharge in annual and seasonal scales as well as annual mean high and low flows were projected for four catchments in different parts of Finland. The assessment was carried out using temperature and precipitation series simulated by four regional climate models (RCMs) as input to a conceptual hydrological model. The daily data from RCMs was bias corrected with the quantile–quantile mapping method and statistical properties of the simulated discharges were analysed to detect trends over time. Without bias correction the simulated discharges in the control period did not match the observed discharges, but the fit was improved considerably after bias correction. The results showed that seasonal changes, most importantly increase in winter runoff, were clearly visible and consistent in different climate scenarios and catchments. Individual scenarios also produced changes in annual mean, high and low flows, but without consistency in scenarios. The use of bias corrected RCM data as input to the hydrological model enables transient simulations, but the simulation results aggregate considerable uncertainties from the climate modelling, bias correction and the hydrological model.

Often extreme events, more than changes in mean conditions, have the greatest impact on the environment and human well-being. Here we examine changes in the occurrence of extremes in the timing of the annual formation and disappearance of lake ice in the Northern Hemisphere. Both changes in the mean condition and in variability around the mean condition can alter the probability of extreme events. Using long-term ice phenology data covering two periods 1855–6 to 2004–5 and 1905–6 to 2004–5 for a total of 75 lakes, we examined patterns in long-term trends and variability in the context of understanding the occurrence of extreme events. We also examined patterns in trends for a 30-year subset (1975–6 to 2004–5) of the 100-year data set. Trends for ice variables in the recent 30-year period were steeper than those in the 100- and 150-year periods, and trends in the 150-year period were steeper than in the 100-year period. Ranges of rates of change (days per decade) among time periods based on linear regression were 0.3−1.6 later for freeze, 0.5−1.9 earlier for breakup, and 0.7−4.3 shorter for duration. Mostly, standard deviation did not change, or it decreased in the 150-year and 100-year periods. During the recent 50-year period, standard deviation calculated in 10-year windows increased for all ice measures. For the 150-year and 100-year periods changes in the mean ice dates rather than changes in variability most strongly influenced the significant increases in the frequency of extreme lake ice events associated with warmer conditions and decreases in the frequency of extreme events associated with cooler conditions.

This paper presents characteristics of the discharge regime, long-term trends and variability in Finland. A selection of long-term discharge records including both unregulated and regulated rivers and lake outlets were analysed up to the year 2004. In addition to individual time series, monthly and annual discharges from the territory of Finland were calculated for the period 1912–2004. The observed drought and flood periods are also discussed, as well as the connection between discharge regime and climate. Moreover, the periodicity of the time series is examined for a couple of sites. The Mann–Kendall trend test was applied to assess changes in annual, monthly and seasonal mean discharges, maximum and minimum flows and, in addition, the date of the annual peak flow. The trend analysis revealed no changes in mean annual flow in general, but the seasonal distribution of streamflow has changed. Winter and spring mean monthly discharges have increased at most of the observation sites. The spring peak has moved to an earlier date at over one-third of the sites. However, the magnitudes of spring high flow have not changed. Autumn flow did not show trends in general. Minimum flows have increased at about half of the unregulated sites.

Spring temperatures were reconstructed by multiproxy database for south-west Finland since 1750. Proxy records used here were ice break-up in the Aurajoki River, the Baltic Sea ice extent, the plant phenological index and the annual varve thickness in the Pyhajarvi Lake. Records were integrated into one palaeoclimate model using time-scale dependent calibration techniques. Reconstruction was verified with statistics showing a high degree of validation between the reconstructed and observed temperatures in Turku, south-west Finland. Reconstruction demonstrates that the springs have become warmer and reveals a warming trend since 1850s. Except for the period from 1750 to around 1850, the springs have been characterized as having a larger low-frequency variability, as well as by having a smaller range of annual temperature variations. Analyses of decadal variations revealed that the coldest springtimes occurred in the 1840s and 1850s and the first decade of the 19th century. Reconstruction was compared with the available meteorological series of central England, Stockholm, St. Petersburg, Uppsala and the spring-temperature reconstruction from western Norway. The effect of global solar, volcanic, greenhouse gases and aerosol forcings were examined together with the North Atlantic Oscillation (NAO) indices at local scale over the reconstructed period. Reconstructed spring-temperature changes have been related to changes in the atmospheric circulation, as indicated by the NAO (February–June).

This chapter compiles and assesses information on run-off and discharge from rivers within the Baltic Sea drainage basin. Some information is also available on ice duration on inland waterways. Although decadal and regional variability is large, no significant long-term change has been detected in total river run-off to the Baltic Sea over the past 500 years. A change in the timing of the spring flood has been observed due to changes in the timing of snowmelt . Change in temperature seems to explain change in run-off better than does precipitation. Later start dates for ice formation on waterways, and earlier ice break-up dates have resulted in shorter periods of ice cover.

Lake and river ice seasonality (dates of ice freeze and breakup) responds sensitively to climatic change and variability. We analyzed climate-related changes using direct human observations of ice freeze dates (1443–2014) for Lake Suwa, Japan, and of ice breakup dates (1693–2013) for Torne River, Finland. We found a rich array of changes in ice seasonality of two inland waters from geographically distant regions: namely a shift towards later ice formation for Suwa and earlier spring melt for Torne, increasing frequencies of years with warm extremes, changing inter-annual variability, waning of dominant inter-decadal quasi-periodic dynamics, and stronger correlations of ice seasonality with atmospheric CO2 concentration and air temperature after the start of the Industrial Revolution. Although local factors, including human population growth, land use change, and water management influence Suwa and Torne, the general patterns of ice seasonality are similar for both systems, suggesting that global processes including climate change and variability are driving the long-term changes in ice seasonality.

Both nettle (Urtica dioica) and cranberry (Vaccinium oxycoccus) are widely known to have good influence on health. The aim of this study was to investigate antimicrobial properties of nettle powder and cranberry powder against Escherichia coli (E. coli) and monitor the growth of the bacteria by a rapid flow cytometry (FCM) method. For FCM measurements samples were stained with fluorescent dyes. The inhibitory effects of plant material on growth of E. coli were estimated by comparing the results of control sample (E. coli) to E. coli samples with plant material. FCM offers both a brilliant tool to investigate the kinetics of the growth of bacterium, since subsamples can be taken from the same liquid medium during the growing period and with fluorescent dyes a rapid method to investigate viability of the bacterium.

Valtakunnallista aikuisopiskelijan viikkoa vietettiin syyskuun alussa. Viikon tämänkertaisena teemana oli Tietoyhteiskunta kaikille. Tietotekniikkaan paneutumista silmällä pitäen valittiin myös tämänkertainen Vuoden aikuisopiskelija. Hän on Raili Kilponen Kuhmon Lentiirasta.