What is yield test of Borewell?
Yield testing of borewell is pumping test conducted to determine optimum output from a borewell. A successful yield test operation can decide the HP and stages of Pump required for a constant output from borewell
A suitable pump will decrease electricity load , increase efficiency of borewell , avoid dry run state and maximize output from a borewell
Why Yield Test or borewell pumping test is conducted ?
Pumping test for borehole is carried out to achieve a balance output from borewell Yield test of borewell provides insight on the output flow rate of borewell and input replishment rate of borewell.
Under any circumstances if discharge from borewell is more than replishment rate it will lead to dry run state . A dry run state impacts Pump and Borewell life which ultimately leads to failure of borewell . Yield test can address the issue by determining optimum yield of borewell
What are different methods for Conducting Yield Test of borewell ?
Commonly used Constant yield test is considered an optimal method for conducting yield test of borewell. Other methods are Step drawdown test, Aquifer pumping test.
How to perform Constant yield test?
Constant yield test is conducted to determine safe yield of borewell. In constant yield test static level of ground water in borewell is measured . Hydrogeologist selects the pump to be lowered down for testing purpose on the basis of local geology and aquifer details by collecting information from site and through geophysical instruments
A suitable pump is lowered down and delivery pipe is connected to a flow meter . Output from Borewell is measured and draw down level is recorded . When a constant yield is achieved the output capacity of a borewell can be deduced and suitable pump can be recommended .
How to Perform Step Draw down test?
In step draw down test output capacity of pump is gradually increased in steps initially the discharge capacity of pump can be set to 1000 liters per hour and increased to determine maximum output a borewell can produce.
On the basis of maximum yield a balance between discharge and flow rate can be calculated. This type of test is particularly useful to determine the effectiveness of the borehole, but not useful in determining the long term sustainable yield of a borehole. In this regard the constant rate test is more useful.
When to Measure and Record Water Levels ?
When testing the well yield, the water level in the well must be measured and recorded as follows:
- Immediately before commencement of pumping
- At 10 minute intervals or more frequently during the first hour of pumping
- At 30 min interval during next hour of pumping.
- At one hour interval
- At the end of pumping test.
Devices to Use to Record Water Levels ?
A water level indicator can be used depending on size of borewell to measure ground water level The above does not apply if the design of the well does not allow for the water level in the well to be measured during the yield test. Tape tied with rock at the end can be used to determine water level in borewell.
Device used to record flow rate of water?
To find out abstraction rate or flow rate from borewell water flow meter can be installed at delivery pipe
Best practices to consider for yield testing of borewell
- Installation of a portable submersible pump for the purposes of conducting well yield tests.
- The pumping rate during the yield test should be similar to the intended pumping rate in order to replicate the well’s probable water levels and usage.
- A calibrated flow meter should be used so that no error occurs during the time of taking readings.
- Measure water levels with accurate meters such as an electrical water level indicator.
- Abstracted water form borewell can be transferred to tank or storage structure to aovid wastage of groundwater
- Pumping test should be carried out under guidance of hydrogeologist.
- In case of no electrcitiy a DG set should be deployed at site
Importance Of The Yield Test ?
The borewell yield test provides important information on:
The yield test information can be used to :
What to choose Bhoojal Survey for Yield Testing ?
Bhoojal Survey has experienced team of hydrogeologist working across India for yield testing workhydrogeologist working across India for yield testing work . Our team has sound knowledge and latest instrument calibrated for performing yield testing of borewell We have successfully worked on yield test projects for Tata projects , Indian Oil , coal India , Dmart , ACC and many more.
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