Tehiskärestiku ökohüdrauliline modellerimine Laeva kalapääsu näitel
Laen...
Kuupäev
2025
Kättesaadavus
09.09.2025
Autorid
Ajakirja pealkiri
Ajakirja ISSN
Köite pealkiri
Kirjastaja
Eesti Maaülikool
Abstrakt
Käesolev magistritöö käsitleb kalade rändetingimuste hindamist tehiskärestiku tüüpi kalapääsus muutuvate hüdroloogiliste olude juures. Probleemi aktuaalsust suurendab kliimamuutustest tingitud voolurežiimi muutus Eesti jõgedes, mis mõjutab rände tingimusi kevadisel perioodil, mil toimub paljude kalade kudemisperiood.
Voolurežiimi muutuste analüüsimisel kasutati sisendina 1960–2020. aasta ööpäevaseid äravoolumooduleid kümnel Ida-Eesti vesikonna jõel. Lisaks analüüsiti eraldi uuritava Laeva jõe arvutuslike vooluhulkasid aastatel 1960–2024. Töös esimeses osas analüüsiti trende 30 päeva keskmistes minimaalsetes äravooludes ja leiti, et talvisel perioodil on minimaalsed vooluhulgad oluliselt kasvanud, samas kui mai kuu minimaalsed vooluhulgad on vähenenud.
Laeva jõe tehiskärestiku toimivust hinnati ökohüdraulilise modelleerimisega, kus särg (Rutilus rutilus) oli uuritavaks kalaliigiks. Hüdraulilise modelleerimise sisendina kasutati ööpäevaseid arvutuslike vooluhulkasid aastal 2019, mida võib pidada vaeevaseks aastaks. Metoodikas kombibeeriti HEC-RAS tarkvaras koostatud 2D hüdrauliline mudel elupaiga sobivusindeksiga (HSI). HIS koondindeks põhines iga võrgusilma voolukiiruse ja veesügavuse osaindeksist.
Tulemused näitasid, et rajatud Laeva tehiskärestik tagab särjele sobivad rändetingimused. Kärestiku ülesvoolu osas võimaldavad madalveesäng ja seda ümbritsev madalam ala kalade läbipääsu erinevate vooluhulkade korral. Kärestiku allavoolu osas, kus madalveesäng puudub, jääb väga väikeste vooluhulkade puhul veekiht kalade liikumiseks liiga madalaks.
Antud tööd kinnitab, et ökohüdrauliline modelleerimine on kauslik tööriist, mis sobib kalapääsude hindamiseks nii hüdraulilisest kui bioloogilisest aspektist juba projekteerimise etapis. Meetodi laiem rakendamine Eestis suurendaks kalapääsude tõhusust ning parendaks veekeskkonna taastamiseks kasutatavate vahendite kasutamise efektiivsust.
This master's thesis analyses fish migration conditions in an artificial rapid under changing hydrological conditions. The relevance of the topic is increased by climate change-induced alterations in the flow regime of Estonian rivers, particularly affecting the spring period that coincides with the spawning season of many fish species. To analyse changes in the flow regime, daily specific discharge data from 1960 to 2020 were used from ten rivers in the eastern Estonian basin. Additionally, theoretically calculated discharge rates for the Laeva River from 1960 to 2024 were analysed separately. The first part of the study investigated trends in the 30-day moving average of minimum discharge values and found that minimum discharge has significantly increased in winter, while the values in the month of May show a decreasing trend. The Laeva River artificial rapid fish passage effectiveness was assessed using ecohydraulic modelling, with the roach (Rutilus rutilus) as a model species. Hydraulic modelling was based on daily discharge data from the low-flow year 2019. The methodology combined a 2D hydraulic model built with HEC-RAS software with a habitat suitability index (HSI) analysis to assess the fish passage effectiveness. HSI composite index was based on sub-indices from flow velocity and water depth from each grid point. The results showed that the constructed Laeva rapid provides suitable conditions for roach migration. The upstream section with a low-flow channel and the surrounding shallower area ensure fish passage under various flow conditions. In contrast to the downstream section, where the low-flow channel is not constructed, the fish passage effectiveness is low under low flow conditions due to low water depth. The study confirms that ecohydraulic modelling is a useful tool for evaluating fish passage effectiveness already at the design stage. Wider adoption of this method in Estonia would enhance the effectiveness of fish passages and also improve the efficiency of resource management in aquatic habitat restoration.
This master's thesis analyses fish migration conditions in an artificial rapid under changing hydrological conditions. The relevance of the topic is increased by climate change-induced alterations in the flow regime of Estonian rivers, particularly affecting the spring period that coincides with the spawning season of many fish species. To analyse changes in the flow regime, daily specific discharge data from 1960 to 2020 were used from ten rivers in the eastern Estonian basin. Additionally, theoretically calculated discharge rates for the Laeva River from 1960 to 2024 were analysed separately. The first part of the study investigated trends in the 30-day moving average of minimum discharge values and found that minimum discharge has significantly increased in winter, while the values in the month of May show a decreasing trend. The Laeva River artificial rapid fish passage effectiveness was assessed using ecohydraulic modelling, with the roach (Rutilus rutilus) as a model species. Hydraulic modelling was based on daily discharge data from the low-flow year 2019. The methodology combined a 2D hydraulic model built with HEC-RAS software with a habitat suitability index (HSI) analysis to assess the fish passage effectiveness. HSI composite index was based on sub-indices from flow velocity and water depth from each grid point. The results showed that the constructed Laeva rapid provides suitable conditions for roach migration. The upstream section with a low-flow channel and the surrounding shallower area ensure fish passage under various flow conditions. In contrast to the downstream section, where the low-flow channel is not constructed, the fish passage effectiveness is low under low flow conditions due to low water depth. The study confirms that ecohydraulic modelling is a useful tool for evaluating fish passage effectiveness already at the design stage. Wider adoption of this method in Estonia would enhance the effectiveness of fish passages and also improve the efficiency of resource management in aquatic habitat restoration.
Kirjeldus
Magistritöö
Vesiehituse ja veekaitse õppekaval
Märksõnad
magistritööd, HEC-RAS, kalapääsu tõhusus, elupaiga sobivusindeks, jõe trendianalüüs, Roheline Ülikool (töö toetab EMÜ Rohelise Üikooli põhimõtteid), loodusvarad, veevarud, loodusvarade kaitse, jätkusuutlikkus, säästev areng