Estonie, terre de lacs

Environ 4,8 % du territoire de l’Estonie est recouvert de plans d’eau : plus de 110 000 objets au total. Les lacs naturels représentent le plus petit groupe (1 562), derrière les étangs (51 780) et les tourbières (45 309) en ordre de grandeur. Parallèlement, seulement 51 des plans d’eau excèdent les 1 000 000 m² (100 ha), la plupart d’entre eux sont des lacs naturels et seulement sept sont artificiels. La répartition dans l’espace des plans d’eau n’est pas égale - normalement, les terres hautes possèdent plus de lacs et d’étangs, dans la partie basse du pays les tourbières sont plus nombreuses. En Estonie, les lacs naturels se sont formés pendant le retrait de la glace continentale, ils sont principalement d’origine thermokarstique et constituent un matériau précieux pour les reconstructions paléolimnologiques. Au cours de l’Holocène, les lacs ont traversé des stades très différents de développement et de niveau d’eau (caractéristiques du bassin, dynamique sédimentaire et propriétés de l’écosystème variables) et de ce fait, ces stades pourraient être considérés et comparés en tant que plans d’eau complètement distincts. Pour comprendre l’état actuel du plan d’eau, nous devons connaître la trame de son développement. Dans le paysage, les petits plans d’eau forment un réseau, qui joue un rôle important dans le bien-être de l’Homme et qui fournit des services écosystémiques. Globalement, la majorité de l’interface terrestre et aquatique se situe dans des petits plans d’eau stagnante. Cette zone est considérée comme l’un des habitats les plus productifs. De nombreux auteurs ont démontré que les petits plans d’eau combinés accueillent plus d’espèces d’eau douce que les rivières ou les grands lacs. Le lac Peïpous est le quatrième plus grand d’Europe, mais puisque que la longueur de son littoral n’est que de 800 km, 23 000 des plus petits plans d’eau d’Estonie sont seulement nécessaires pour dépasser ce linéaire. Cela montre qu’il est essentiel de commencer à considérer les petits plans d’eau

The sedimentary sequence from the Lake Ķūži outcrop, central Latvia: implications for late glacial stratigraphy

Sediment samples from an outcrop in the near-shore area of Lake Ķūži (Vidzeme Heights, Central Latvia) were investigated using palaeobotanical (pollen and macrofossil analysis) and lithological (grain-size analysis) methods and accelerator mass spectrometry 14C dating. A dark, organic-rich sediment layer was found below 1.7 m of sandy layers approximately 30 cm above the present lake level. Radiocarbon dating of a wood sample from the lowermost layer (11 050 ± 60 14C BP, 13 107–12 721 cal BP) shows that the layer is of late glacial age. The composition of the pollen spectra is characterized by Betula nana, Cyperaceae pollen and spores of Equisetum, confirming that the lowermost sediments were formed during the late glacial. Fossils of obligate aquatic organisms in the upper layer, which include oospores of Characeae and seeds of Potamogeton, indicate an open water environment. Pollen of Myriophyllum and Potamogeton and non-pollen palynomorphs, such as algal Botryococcus and Pediastrum cf. boryanum, confirm this conclusion. The pollen assemblage from the greyish loam layer following this lacustrine phase shows a pattern characteristic of the Younger Dryas vegetation before the start of the real expansion of birch forests at the beginning of the Holocene

Estonia, the land of lakes

Around 4.8% of the territory of Estonia is covered with standing water bodies - in total over 110 000 objects. Natural lakes are one of the smallest group (1 562), exceed by ponds (51 780) and bog pools (45 309) by order of magnitudes. Same time only 51 on of standing water bodies are bigger than 1 000 000 m2 (100 ha), most of those are natural lakes, and only seven are man-made. Distribution of standing water bodies are not spatial even – normally uplands have more lakes and ponds, in the lower part of the country bog pools are more abundant. In Estonian natural lakes are formed during the retreat of the continental ice, are mostly of thermokarstic origin and offering valuable material for paleolimnological reconstructions. During the Holocene, lakes have gone through very different water-level and development stages (varying characteristics of the basin, sedimentation dynamics and ecosystem properties) and as a result, those stages could be considered and compared as of entirely different water bodies. For understanding the current status of the standing water body, we must know the development scenario. In landscape, small water bodies are forming a network, that plays an important role in the human well-being and providing ecosystem services. Collectively, most of the terrestrial-aquatic interface is in small standing water bodies. This zone is considered as one of the most productive habitats. Numerous authors have been demonstrated, that small standing water bodies combined support more freshwater species than rivers or big lakes. Lake Peipsi is 4th largest in Europe, but as its shoreline length is only 800 km, it takes around 23 000 smallest Estonian standing water bodies to exceed this number. That means that it is essential to start valuing small water bodies

Treshold-controlled three-stage hydraulic behaviour of a mantled shallow carbonate aquifer (Tuhala karst area, North Estonia)

As karst aquifers are often characterised by non-linear behaviour, ascertaining the turning points in their hydraulic regime may provide essential information on the functioning of the aquifer. These characteristics also apply to the Silurian-Ordovician aquifer system, composed of diverse carbonate rocks, in Estonia. The aquifer system is an important source of drinking water in northern Estonia. It also comprises the Nabala- Rakvere aquifer, a locally important groundwater resource that underlies the Tuhala karst area famous for an intermittently overflowing karst spring known as the Witch's Well. The water rich in humic substances of the Tuhala River recharges the Tuhala karst system, which is drained by two spring groups. In order to develop measures for the sustainable management of the aquifer in the future, the aim of this study was to enhance understanding of the hydraulic behaviour and hydrodynamic properties of the Tuhala karst system. From October 2014 to December 2016 an extensive field campaign was carried out comprising the observation of 22 surface- and groundwater monitoring points for water level and physico-chemical parameters and the performance of four quantitative tracer tests. The data obtained were evaluated in accordance with the input– output water level relation curves and a conceptual model of the system was set up. The results show that a strong hydraulic link exists, primarily through well-developed conduits between the recharge and discharge area of the karst system. Depending on the hydrological conditions, groundwater flow direc tions vary and maximum linear flow velocities range between ~225 and 800 m/h. A threshold-controlled throughput capacity and interaction with the adjacent aquifer cause imbalances between the input and output discharges of the karst system. Tracer tests coupled with surface and groundwater level relation curve analysis allowed the specification of flow threshold conditions for the Witch's Well spring group and the overflow threshold for the Witch's Well, among other key hydrological events. The hydraulic regime of the karst system was divided into three stages, each with differing threshold controls and hydrodynamic characteristics.Key words: karst system, shallow carbonate aquifer, monitoring, tracer test, water level relation curve, threshold, overflow. Določanje mejnih vrednosti tristopenjskega hidravljičnega obnašanja pokritega plitvega karbonatnega vodonosnika (Tuhalski kras, severna Estonija)Kraški vodonosniki se pogosto obnašajo nelinearno, zato lahko z ugotavljanjem mejnih vrednosti v hidravličnem režimu zagotovimo bistvene informacije o delovanju vodonosnika. To velja tudi za silurijsko-ordovicijski vodonosni sistem v Estoniji, ki ga sestavljajo različne karbonatne kamnine in je pomemben vir pitne vode na severu države. Vključuje tudi vodonosnik Nabala- Rakvere, ki je lokalno pomemben vodni vir. Na tem območju se nahaja Tuhalski kras, ki je znan po občasno bruhajočem kraškem izviru Witch's Well (Čarovničin vodnjak). Tuhalski vodonosnik napaja reka Tuhala, bogata z huminskimi snovmi, prazni pa se skozi dve skupini izvirov. Da bi v prihodnje razvili ukrepe za trajnostno upravljanje vodonosnika, je bil namen te raziskave izboljšati razumevanje hidravličnega obnašanja in hidrodinamičnih lastnosti kraškega sistema. Od oktobra 2014 do decembra 2016 smo opravili obsežno terensko delo, ki je obsegalo spremljanje vodostajev in fizikalno-kemijskih parametrov v 23 površinskih in podzemnih točkah ter izvedbo štirih kvantitativnih sledilnih poskusov. Pridobljene podatke smo ovrednotili na podlagi krivulje odvisnosti vhodnih in izhodnih vodnih nivojev. Vzpostavili smo konceptualni model sistema. Rezultati kažejo na obstoj močne hidravlične povezave predvsem z dobro razvitimi kanali med območji napajanja in praznjenja kraškega sistema. Odvisno od hidroloških razmer se spreminjajo smeri in hitrosti toka podzemne vode, ki znašajo od ~225 do 800 m/h. Kapaciteta prepustnosti, ki jo uravnavajo določene mejne vrednosti, in posledične in terakcije s sosednjimi vodonosniki povzročajo neravnovesja med vhodnimi in izhodnimi pretočnimi vrednostmi kraškega sistema. Združevanje rezultatov sledilnih poskusov z analizo krivulje odvisnosti površinskih in podzemnih vodostajev nam je omogočilo, da smo določili mejne pretočne vrednosti izvira Witch's Well in druge ključne hidrološke dogodke. Hidravlični režim kraškega sistema smo razdelili na tri faze, od katerih ima vsaka določene mejne vrednosti in hidrodinamične lastnosti. Ključne besede: kraški sistem, plitvi karbonatni vodonosnik, monitoring, sledilni poskus, krivulja odvisnosti vodnih nivojev, prag, preliv.

Kurtna Lake District: a natural pearl suffering from anthropogenic pressures

The Kurtna Lake District, situated in the northeastern part of Estonia, contains the largest number of lakes per km2 in the country – 38 natural lakes in a 30 km2 area. The unique area fell under severe anthropogenic influence in the middle of the 20th century and the influence has continued until the present day. Oil-shale, sand and peat mining, groundwater and surface water abstraction – all have been affecting the lakes in the district. Lake water levels have dropped, lake chemistries and consequently lake ecosystems have changed. For some lakes the effects have been larger, but some lakes have remained mostly unchanged. In 1987 a landscape protection area was formed, but that has not solved the problems. The lake district used to contain five rare clear water lakes with low nutrient and mineral content (L. Valgejärv, L. Liivjärv, L. Ahnejärv, L. Martiska, L. Kuradijärv). Nowadays, most of them have become significantly more eutrophic, because of water level decrease, but L. Valgejärv, with its preserved unique plant communities, is still considered to be one of the ecologically most valuable lakes in Estonia. The lake district also contains the only siderotrophic (iron rich) lake in Estonia – Lake Räätsma. Lakes Nõmmejärv and Konsu have had their water regime changed considerably. Lake Nõmmejärv accepts the inflow of sulphate-rich mine water and Lake Konsu has been turned into a surface water reservoir for an oil-shale processing factory. Lake Kihljärv on the other hand has effectively dried out in the recent years. At the same time, the picturesque Lake Saarejärv has remained largely unaffected. Therefore, the Kurtna Lake District is an area of great contrasts, partly it still resembles the pristine nature it used to be, and partly it is a sad monument for an overly eager consumption of natural resources

La région des lacs de Kurtna : un joyau naturel sujet aux pressions anthropiques

La région des lacs de Kurtna, située dans le nord-est de l’Estonie, compte le plus grand nombre de lacs par km2 du pays : 38 lacs naturels sur une superficie de 30 km2. Cette zone unique a subi une forte influence anthropique au milieu du 20e siècle et cette influence est encore d’actualité. L’extraction de schiste bitumineux, de sable et de tourbe, le captage d’eau souterraine et d’eau de surface : tout cela a affecté les lacs de la région. Les niveaux d’eau des lacs ont baissé, la chimie des lacs et, par conséquent, les écosystèmes lacustres, se sont transformés. Pour certains lacs, les effets ont été plus importants, tandis que pour d’autres, presque aucun changement ne s’est fait ressentir. En 1987, une zone de protection du paysage a été créée, mais cela n’a pas résolu les problèmes. La région des lacs comptait auparavant cinq lacs d’eau claire rares à faible teneur en nutriments et en minéraux (L. Valgejärv, L. Liivjärv, L. Ahnejärv, L. Martiska, L. Kuradijärv). Aujourd’hui, la plupart d’entre eux ont subi un processus d’eutrophisation, dû à la baisse du niveau de l’eau, mais le lac Valgejärv, avec ses communautés végétales uniques préservées, est toujours considéré comme l’un des lacs les plus précieux sur le plan écologique en Estonie. La région des lacs compte également le seul lac sidérotrophe (riche en fer) d’Estonie, le lac Räätsma. Les lacs Nõmmejärv et Konsu ont vu leur régime hydrique changer de façon considérable. Le lac Nõmmejärv reçoit l’afflux d’eau minière riche en sulfates, et le lac Konsu a été transformé en réservoir d’eau de surface pour une usine de traitement du schiste bitumineux. Le lac Kihljärv, en revanche, s’est effectivement asséché au cours des dernières années. Dans le même temps, le pittoresque lac Saarejärv n’a, quant à lui, pas subi de transformation majeure. Par conséquent, la région des lacs de Kurtna est une zone de forts contrastes : elle a conservé une partie de son état originel, soit une nature vierge, et il s’agit en partie d’un triste exemple de consommation excessivement avide des ressources naturelles

European perspectives on regional estimates of standing water bodies and the relevance of man-made ponds

International audienceThe majority of terrestrial standing water bodies (SWB) are small in size, however, their abundance and distribution is not fully known and they are under-represented in legislation. Also, the models for global inventories of SWB are so far not sufficiently designed for estimating the relative abundance of small SWB (below 0.2 ha) and provide differing estimates. In this pilot study, we suggest a bottom-up approach for estimating the number of SWB at EU-level that combines the ground-validated data on water bodies from state inventories and data from peer-generated map databases; we assess the inventories and relative importance of small terrestrial water bodies of two different countries, Estonia and France

Students and teachers’ need for sustainable education: lessons from the pandemic

The COVID-19 pandemic challenged the sustainability of higher education as millions of students were forced out of school, shifting to online learning instead of in-class education. In the Erasmus+ project, Virtual Presence in Higher Education Hybrid Learning Delivery (VIE), we were concerned with the level of readiness and the ability of higher-education students and teachers to face this changing situation. This paper reports the results of a survey which assessed the experiences that students and teachers had during the pandemic and, in particular, the development of soft skills through active learning methodologies. The project results show that there are still some unmet needs, but existing digital technologies, tools, and platforms already provide valuable solutions both for students and teachers that ensure a continuation of high-quality learning experiences.Erasmus+ program | Ref. KA226-A280C01

Kliimamuutuste ABC: põhjused, mõjud, lahendused. Teaduspõhine õppematerjal kliimamuutustest

Kliimamuutused kujutavad endast ökosüsteemidele ja inimestele suurt ohtu. Teadus on selge: me peame tegutsema, et inimtekkelistest kliimamuutustest tingitud riske vähendada. Siin astub vahele aga kliimamuutustealase kirjaoskuse laialdane puudumine Eestis. Kliima kirjaoskus lihtsalt seletatuna, sisaldab endas mõistmist, kuidas kliima mõjutab mind ja kogu ühiskonda, aga ka seda, kuidas mina ja meie mõjutame kliimat. Selles sisaldub ka arusaam kuidas vähendada kliimamõju (ehk kliimamuutusi leevendada) ja suurendada vastupanuvõimet kliimamuutustele (ehk kliimamuutustega kohaneda). Eesti inimeste suur kliimaskeptilisus püstitab väga suured tõkked kliimamuutustega kohanemiseks ja nende leevendamiseks. Tegutsemiseks ei piisa üksnes teadmistest, vaid tarvis on ka teadmistele tuginevaid väärtusi, hoiakuid ning oskusi. Siit tulebki vajadus selge riikliku poliitika järele, kuidas inimesi kliimamuutuste vallas harida. Euroopa majanduspiirkonna rahastatavas projektis „KLIIMATEADLIK - Kliimateadlikkus koolist ühiskonda: laste, noorte ja õpetajate võimestamine kliimamuutuste mõjude vähendamiseks“ keskendume kliimahariduse edendamisele Eestis. Teeme seda nii formaalses kui ka mitteformaalses hariduses, et suurendada kliimamuutuste leevendamiseks ja nendega kohanemiseks vajalikke pädevusi. Meie eesmärk on luua Eestis kliimamuutuste haridusprogramm, mis hõlmab kõiki haridustasandeid. Selleks arendame haridusstrateegiaid, loome õppematerjale ja toetame õpetajaid. Esiteks selgitasime välja praeguse kliimahariduse olukorra. Vaatasime läbi riikliku õppekava ning ainekavad. Selgus, et kliimamuutusi käsitletakse iseseisva teemana ainult mõningates loodusainetes. Kuid siingi tutvustatakse kliimat ekslikult kui pelgalt üht osa kohalikest keskkonnatingimustest. Puudub globaalse kliimasüsteemi terviklik käsitlus, mistõttu on kliimamuutuste teemade teistesse ainetesse lõimimine keeruline. Järgmine samm oli õpetamise olukorra väljaselgitamine. Analüüsisime Eestis kasutatavaid õpikuid ja korraldasime õpetajate küsitluse. Selgus, et kahjuks ei sisalda kooliõpikud tänapäevast teaduslikku arusaama kliimamuutustest. Õppematerjalides puuduvad selgitused kliimamuutuste põhjuste ja mõjude kohta. Pealegi ei käsitleta üldse kliimamuutuste leevendamist ja kohanemist. Õpetajate küsitlus andis ühelt poolt väga positiivse vastukaja, sest valdav osa õpetajatest pidas kliimamuutusi oluliseks teemaks ning oli ka nõus end neil teemadel harima. Teiselt poolt kurdavad õpetajad, et puudu on tänapäevased eestikeelsed õppevahendid kliimamuutuste käsitlemiseks. Eriti just mitteloodusainete õpetajad nendivad, et neil puuduvad teadmised, kuidas kliimaprobleeme õppesse lõimida. Projekti KLIIMATEADLIK esimene õppevahend „Kliimamuutuste ABC“ püüab neid tühikuid täita. Siin on kokku võetud tänapäevased teaduspõhised arusaamad kliimamuutustest. Õppematerjal tugineb Valitsustevahelise kliimamuutuste paneeli (IPCC) ja teiste organisatsioonide kliimaraportitele, kus on sünteesitud eelretsenseeritud kliimateadust. Õppematerjal hõlmab kliimamuutuste põhjuseid ja mõjusid koos kliimamuutuste leevendamise ja kohanemisega. Õppevahendi lõid projektipartnerid ühistöös ning seda katsetati 2023. aasta märtsis neljal koolitusel Tartus, Pärnus, Narvas ja Tallinnas, samuti Moodle’i e-õppekeskkonnas. „Kliimamuutuste ABC“ on kättesaadav kõigile huvilistele projekti KLIIMATEADLIK õppevahendite lehel kliimatarkused.ut.ee. See on mõeldud kogu Eesti rahvale. Õppevahend sisaldab mõtlemapanevaid ülesandeid, videoid ning kokkuvõtlikku teksti, milles on rohkelt viiteid. Teksti saab ka soovi korral välja printida. Suur tänu kõigile, kes on selle õppevahendi valmimisel kaasa löönud. Rõõmsat õppimist! Kliimateadlik muudab ühiskonda, mitte kliimat. Piia Post ja Velle Toll. September 2023Trükis valmis projekti “Kliimateadlikkus koolist ühiskonda: laste, noorte ja õpetajate võimestamine kliimamuutuste mõjude vähendamiseks” raames.Projekti rahastatakse Euroopa Majanduspiirkonna Finantsmehhanismi 2014−2021 programmi „Kliimamuutuste leevendamine ja nendega kohanemine“ avatud taotlusvoorust „Kliimateadlikkuse suurendamine

Lake basin development in the Holocene and its impact on the sedimentation dynamics in a small lake (southern Estonia)

Small lakes and their sediments are widely used for palaeolimnological reconstructions. Often only one core from the deepest part of the lake is used for reconstructing the lake catchment development, water-level changes and climate. To interpret palaeoinformation correctly, it is necessary to understand the spatio-temporal dynamics and the essence of lake basin evolution (topography, sedimentation zones, etc.) during the selected time period. The current study focuses on reconstructing the development of Lake Väike Juusa (southern Estonia) during the Holocene with the help of 3D digital elevation models compiled for the palaeolake stages at 9000 BP, 8000 BP, 4000 BP, 2000 BP and the present. The results suggest that we have to consider lake stages as completely different lakes with different sedimentation patterns – the hypsocraphic curve of Lake Väike Juusa was convex at the beginning of the Holocene and is concave nowadays. The proportion of the accumulation areas varied from 6% to 60% at the beginning of the Holocene and is around 30% nowadays. In order to understand lake basin development and water-level changes, the sampling sites should be selected close to the transitional zone and more than one core from a lake is needed. Commonly the sites located spatially rather close to each other have significantly different sedimentation patterns. Three-dimensional digital elevation models of palaeolake basins are useful tools for visualizing data and for hypothesizing about possible effects of lake-level fluctuations on the lake and its sedimentation regime