Recommended abstraction rate for a borehole after test pumping?
After completing all the tests for borehole test pumping ,  i.e calibration test, step drawdown test, constant rate test,recovery test i got Transmissivity and storativity from the analysis graphs, last thing now is getting abstraction rate that will last for 10 yrs.
My inquiry is: How do you calculate the abstraction rate from T or S or from the available drawdown of the borehole and the rates that have been used. eg for this particular borehole, the following rates have been used; 20, 30, 40, 50 and 60m3/hr in the Step drawdown test and constant rate Q of 45m3/hr. Available drawdown is 16.07m. Transmissivity is 29m2/day and storativity of 0.06378. The aquifer is leaky confined. This is a production borehole.
Thankyou for your query. I have contacted the previous experts who responded to your initial query, and unfortunately they have confirmed that there is still insufficient information to respond fully to your query.
There are a number of queries :
1) to determine an optimum pumping rate, one would need to see and interpret the data collected from the step test and the constant rate and recovery test, rather than rely on a T and S value provided.
2) One would need the borehole location and geological log in order to properly interpret the pumping test data
3) It is unclear whether the available drawdown of 16.07m is the drawdown that was recorded when the well was pumped at 45m3/h, or whether this is the available drawdown that is available to set the pumping rate.
4) The design output from this well will be dependent on how much water is required - this is not stated
5) Other factors such as rainfall, recharge, other abstractions, potential environmental impacts of the pumping would also need to be taken into account.
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