Groundwater wells – the unsung heroes of irrigation in Canterbury
The overall success of your water supply relies on the pump, the well and the aquifer into which the well is screened. The performance of your supply may change over time – sometimes the well gets better, but more commonly it can degrade. Where would you be if your well ceased performing as needed? Periodic testing (with specialist interpretation) can provide forewarning of an avoidable catastrophe. It can help you identify issues early on (such as reductions in well performance or equipment ageing) which can save you time and money in the long run by providing valuable data that informs irrigation decisions and improves overall efficiencies. You can then ensure that you are maximising the value of your water resource while minimising energy use and environmental impacts.
The key purpose of testing is to gather data on the performance of a well (and the groundwater system into which the well is screened). This information can help you determine the maximum rate at which your well can be pumped long-term, assess the effects on neighbouring wells and/or streams, help you improve the efficiency of your irrigation practices, and plan pump and well maintenance out of season (when the well isn’t in use). Different tests are available to provide answers to different questions:
Step tests are designed to measure the performance of your pump and well. Periodic testing lets you monitor the rate of change so you can plan remedial works (such as well redevelopment or pump reconditioning) before it is too late. Step tests are small-scale tests and can be completed at any time.
Constant discharge tests involve pumping your well at a constant rate for an extended duration (such as 3-7 days) and monitoring the response in neighbouring wells. It is important to isolate the response in a neighbouring well to pumping your well from the effects of pumping other nearby wells. Therefore, it is usually best that constant discharge tests are undertaken outside of the irrigation season (when most other abstractions have ceased). These tests provide information about the aquifer system into which your well is screened.
Water chemistry and quality sampling enables us to ascertain the likely source of your water, such as young water from a nearby stream or older groundwater from deep groundwater storage. This can then help you manage health and environmental risks.
There are additional specialist tests that can be completed to resolve other specific hydrogeological questions. Also, if your groundwater take consent is up for renewal, it is likely that Environment Canterbury will require you to test your well to demonstrate sustainable yields and effects on surface water and nearby wells.
No two wells are identical, nor are the water requirements and irrigation systems between any two farms. It is important that the right tests are applied to match your needs. Proper testing requires a specialist combination of fieldwork that is carefully planned, carried out, analysed and interpreted. Specialist field hydrogeologists and irrigation engineers can complete well testing for you and walk with you through whatever process or decision you are facing to ensure your well remains the hero of your irrigation system.