https://twitter.com/allixender/status/1330801820764151810
The establishment of the meteorological observatory of the University of Tartu laid the foundation for the hydrological observation network of Estonian inland waters. The observatory first measured the water level of the Emajõgi River in 1866, but more regular measurements began in the spring of 1867. Daily water level and regular flow measurements began on the Emajõgi River in 1922. In the 1920s, regular flow measurements were started on many other Estonian rivers.
From here it is possible to download the daily flow rates or drainage of the operating hydrometry stations. Information about operating stations can be found by clicking on the following link: https://www.ilmateenistus.ee/ilmateenistus/ Vaatlusvork/#hydro
The name of the station is followed by a homogeneous reference period. Long-term average and historical maximum / minimum flow rates have been calculated from the beginning of the uniform observation series for each station until 2015.
https://www.ilmateenistus.ee/siseveed/ajaloolised-vaatlusandmed/vooluhulgad/
Testing Mann-Kendall python package to calculate trend for flow timeseries
https://joss.theoj.org/papers/10.21105/joss.01556
https://pypi.org/project/pymannkendall/
The Jupyter notebook (view here) is provided in my GitHub repo.