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Wednesday, November 9, 2011

Homemade rain gauge

The rain is here, and is causing a huge mess.

In Portugal the higher precipitation value registered was back in January of 1977, in a place called Penhas da Saúde.
When measuring precipitation scientists have a goal, a very simple one, to determinate the water quantity that falls in a given place during a given period of time.

The measure is done by collecting water with a rain gauge, and estimating the high that it would reach if there was no evaporation, no infiltrations, and no draining.
The quantity of precipitation is measured in mm or in, in a given time period in a given area, that means, for example 24in/ft2/24h.
Today we will see a easy way to do this measure... in your own backyard. In fact the procedure is very simple and doesn't require any special material, obviously we will not collect scientific precision data, but its good enough to have a good idea on the procedure.

First of all, this experiment can only be done in the rain season, and because we are not using scientific equipment, is convenient the temperature is low, otherwise the water will evaporate.

We are going to build our first tool on the homemade "meteorological station", the rain gauge

We will need:
  • paper,
  • pen,
  • ruler,
  • plastic bottle, with a flat bottom,
  • large can, can be a bucket or similar, the bottle has to fit in,
  • waterproof pen, an alternative is to arrange water resistant tape where you can write,
  • insulating tape,
  • shovel,
  • a corner in the backyard, that is not protected from rain.
How to:
  1. On a sheet of paper draw a graph, the X-axis and Y, on the X-axis mark the day, the days can be different from the day of the month you are in, the important is you know the number of days you experience has. Day1 can be the first day of the test, you can record the duration of the test in the title bar of the graph, for example, "Rain on granny’s backyard- from 10/11/2011 to 10/12/2011", the y-axis is the amount of rainfall in “in” (I advise to mark the bottle not in “in” but in 1/10in or millimeters);
  2. Wash the bottle, remove any glue or paper;
  3. The bottle is round on top and straight on the bottom, cut it in 2 pieces in the place it becomes straight, its about 1/3 from the top (the neck).
  4. Use the ruler and water resistant pen and mark in on the straight part, which now looks like a big water glass, I advise to mark the bottle not in “in” but in 1/10in or millimeters, the more small is the measure the more accurate is the reading;
  5. Place the top of the bottle (upside down, type funnel) at the bottom (glass);
  6. With duct tape firmly attach both parts;
  7. Dig a hole in the "corner of the backyard," this place has to be exposed to rain;
  8. Bury the bucket / bin;
  9. Place the bottle in;
  10. When you put the bottle the experience begin, record the time of the day;
  11. Every day, at the same time, and during the entire period of your experience, register on the chart the height of water on the bottle;
  12. After each reading, empty the bottle and put it back into place;

NOTE: As an alternative to plastic (PET) bottle can use a tall glass flask and a plastic funnel, the procedure is the same.


Et voila!


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