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Where does one put a pump when doing test pumping of water well?

Depth 100m, SWL 22.6m, water Strike 44, Blow yield 37 m3/hr, screen at 45-85m

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Dear Gape,

Many congratulations on constructing what appears to be a highly productive borehole!

It is difficult to give specific advice without learning more about your borehole (geological log, construction log, aquifer type). For example I am presuming that the water strike at 44mbgl was not your main productive unit as this appears to have been cased off!

However as a general rule you do not want to lower the water level within the borehole below your main productive units. Therefore I would position your pump above these during the test (so probably a couple of meters above the well screen).

Best wishes,

Geraint

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Thanks alot Geraint.

Your advice helped a lot.I have been test pumping 4 boreholes so far and in all the boreholes after 1000min in a CRT they start recharging during the day. The aquifer is sandstone (Karoo) and is confined.

What are the causes of this. See attachment

semolo BH10862 CRT.xlsx

Gape Anderson gravatar imageGape Anderson ( 2016-02-08 13:18:13 -0600 )edit

Hello Gape, great to see this data. The fact that all four boreholes are recovering slightly during the day is odd. Before investigating other options it would be worthwhile checking your discharge rates - how are you measuring discharge? It may be that your pumping rate is slightly less during the day than the night. If you could email the data to help@hydrogeologistswithoutborders.or... along with the borehole logs and any discharge data you collected during the test then we could get a team of hydrogeologists to take a look at the information and get back to you with a potential answer to this question. Best wishes, Geraint

Geraint gravatar imageGeraint ( 2016-02-25 02:44:14 -0600 )edit
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Hello. Did your pumping test gives you also the drawdown of the pumping curves ? You should look at that before deciding the exact depth. The data you provides are only the characteristics of the well but not the result of the pumping test. I cannot really tell from these information only. Also please check if there are other borehole close by, in that case you should do the pumping test while other well are operating as it may influence on your aquifer. Check this drawing it explains what you need to know https://www.google.fr/search?q=pumpin.... This website may help you as well http://www.aqtesolv.com/pumping-tests...

This is also useful http://www.hydrogeologistswithoutbord...

Please do not hesitate if you need more info. Sorry I could not really answer yet. Graziella

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Hi there,

There is a great resource from ICRC about the way to conduct pumping tests;

https://www.icrc.org/eng/assets/files...

The pump should be set within the solid casing to protect it in case of collapse of the well. The screen is not as strong as the solid casing so is more at risk. Make sure the well is developed before testing to reduce the risk of collapse.

Have fun and good luck!

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I would place the pump a few metres above the top of the screen. One should ideally never place an electric submersible in a screened section, but rather in the cased interval. This is to ensure that the motor is properly cooled by high velocity water flowing over its surface. In a pumping test, I would place the pump as deep as possible as you don't (yet) know how much drawdown to expect - although in this case it looks like there won't be much drawdown.

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