It is essential to have the yield of a borehole tested for numerous reasons:

 

• To establish the safe yield at which the borehole can be pumped. 

• To determine the safe yield duty period that the borehole can be operated for indefinitely, without endangering the aquifer.

• To determine the quality of the groundwater in relation to its intended use, the performance characteristics of the borehole and the hydraulic parameters of the aquifer.

 

How long should the test-pumping take?

 

The length of the pumping test is directly proportioned to the duty period that the borehole is to be pumped.

For instance, a borehole supplying domestic water to a house will have a shorter duty period than an irrigation borehole. As a result, the type and length of the test pumping performed on a domestic borehole will be shorter than the test on an irrigation borehole.

 

Test Pumping:

 

During testing we will issue a certificate upon which the date, depth at which the test pump was installed, static water level, pumping rate at the end of the test and water color is recorded.

 

It is normal to undertake a six hour test and then install a pump with a capacity of around 40-50% of the flow at the end of the test. This 40-50% safety margin is sufficient in most cases, but not always.  We will consult with the end user to determine what their needs are what type of test will best suit these needs.

 

Boreholes that are to be used every day and must supply a dependable daily water supply, for instance bulk water supply for municipal, industrial or irrigation, require more sophisticated and longer water yield tests which will cost more. However the extra initial cost can save a great deal of money in the long run. Unless absolutely necessary, never pump the borehole at its full capacity.

 

 

 

Yield:

 

The water yield can vary depending on the time of the year, the number of new boreholes in the vicinity, the yearly changes in the annual rainfall and the local detrimental effects of increased transpiration as a result of the planting of large numbers of trees.

It is for these reasons that wide safety margins are allowed when installing the correct pumping system.

 

Important FACTS to Remember:

 

An estimate of the water yield by the driller is not sufficient and can be inaccurate.

If you are lucky enough to have a borehole that yields plenty of water, do not pump more than you need.

Groundwater is a very precious resource and should not be wasted.