The Primeval Power of Water Methods of Measuring the Speed Flow of the River Drava

RUNNING WATER

STAGNANT WATER

About Drava spring – maximum water level zima – minimum water level running water 725 km (springs in South Tirol) Danube Varaždin, Legrad, Belišće, Osijek length: 719 km the size of the drainage basin: 40087 km2 depth: 4-7 m spring – maximum water level zima – minimum water level the bottom substratum either muddy or sandy the shore – strewn with rocks a river which is fast and strong

The History of Drava as an Important Water Resource in the 19th century many hydro-regulatory measures have been taken (before that, a lot of surrounding villages nearby Drava were often flodded – Bukevlje, Levača, Repaš…) water-mills hydro-electric power plants (Donja Dubrava)

The purpose of water-mills grinding of grains and making flour sawing of boards processing of textile manufacture of cast iron, etc.

What can we measure on a river?

pH pH is a measure of the acidity or basicity of an aqueous solution

TEMPERATURE a physical value by which we express the thermal state of something

RIVER WIDTH l

RIVER DEPTH h

CROSS SECTION

DETERMINING THE CROSS SECTION OF THE RIVER DRAVA

1ST PROBLEM OF THE COMENIUS TEAM utenslis: a ferry, 15 m long cord, grapples, 200 m long cord, measuring tape, an iron object the problem: 1. find an equation with the help of which we can determine the surface of the cross section of the river Drava 2. draw a curve which describes how the depth of the river Drava changes with its width

INSTRUCTIONS Secure the iron object on a 15 m cord. First measure the width of the river: secure the longer cord on the right bank of the river, and transfer onto the left bank. While returning towards the right bank, measure the depth with the shorter cord.

FLOW SPEED the volume of water which passes through the observed point in a certain time interval

Ways of Measuring the Flow Speed Q = V/t (m3/s)

Ultrasonic Flow Meter based on high-frequent sound waves which are generated by introducing a certain alternative voltage onto the piezoelectric crystal

Electromagnetic Flow Meter the fluid itself works as a voltage conductor, and there are two electrodes on the inner walls of the tube (which are isolated from the tube itself)

The Bucket Method measure the volume of the bucket find a location along the stream that has a waterfall (or using a weir) with a stopwatch, time how long it takes the waterfall to fill the bucket with water repeat steps two and three about six or seven times and take the average  

v = s/t (m/s) THE STREAMING SPEED the speed by which the fluid passes through the observed cross section v = s/t (m/s)

MEASURING THE STREAMING SPEED OF THE RIVER DRAVA

2ND PROBLEM OF THE COMENIUS TEAM utensils: a ferry, stopwatch, measuring tape, bits of paper the problem: 1. determine the streaming speed of the river Drava at Brodić 2. determine the maximum absolute and the maximum relative errors

INSTRUCTIONS climb onto the ferry measure the width of the ferry after the width of the ferry has been measured, throw bits of paper into the water from one end of the ferry measure the time needed for one bit of paper to get to the other end of the ferry

The Primeval and Unpredictable Power of Water  FLOODS November 2013, Karlovac (Kupa) February 2014, Sisak surroundings (Sava)

We often forget that the circle of water is the same thing as the circle of life. Jacques Yves Cousteau

The noblest of the elements is water. (Pindar) Who does not care for the water, does not care for a better tomorrow. (Old Irish saying) To a good man, one drop of water is the ocean; to an evil man, the ocean is but one drop of water. (Indian saying)

The Primeval Power of Water Methods of Measuring the Speed Flow of the River Drava