Water Wells During Drought
Livestock producers know that a reliable water supply is an essential part of a successful farm operation. In times of drought when the surface water dries up, groundwater supplies become even more important. But if you can't see what is going on, how can you be sure that all is well with your well?
Know the History of Your Well
Well construction records are a good place to start. Provincial regulations require well drillers to provide owners with a well completion report when a new well is drilled. The report should cover the basics - who, what, where, and when it was drilled. It may also describe the construction materials, the formation, the producing (screened) zone, the water quality, the yield, and the static (non-pumping) water level at the time it was drilled. If you don't have this record, you may be able to get more information from the provincial data base, or Prairie Farm Rehabilitation Administration(PFRA).
Understand Your Water Demand
Most farmers have a good idea how much water they use in average years, but patterns of use may change in dry times. It may be that livestock use the well mostly in winter, but if it will be used as a water supply for feeding over summer, be prepared for considerably more water use. In drought, there will also be increased water demand for gardens, trees and in the home.
Over-Pumping and Depletion - What Is It?
Over-pumping occurs when the water removal rate exceeds the well production rate. This may be the case if the pump is running longer, or a bigger pump is installed to keep up with increased demand during drought. If the pumping water level is drawn down into the screen area, it will introduce oxygen into the aquifer causing a build-up of biological slimes or mineral scales. Eventually, this can plug the well intake area and reduce well yield. To compensate, the well has to be pumped longer, making the problem worse.
Depletion refers to the situation where water is removed from the aquifer faster than it is being replaced or recharged causing regional water levels (water table) to decline. While this condition is common during drought, the onset can be slow and hard to identify. If you have recently had to lower your intake, depletion may be a problem.
What About the Iron?
Iron bacteria is not a health concern, however it can stain laundry and fixtures. Its growth is promoted when the pumping level reaches the screen, causing it to plug. While it is best to ensure the water level stays above the screen zone, if you already have iron bacteria, a shock chlorination routine should help prolong the life of the well.
Changes in water quality can signal other problems. Silty, dirty water may indicate the casing is rusted out or the seal is gone. Unpleasant odour may indicate a sulfate bacteria problem. Scale build-up on waterers and fixtures may suggest the screen could be prone to a similar problem.
When your well is first developed, the driller will record the static water level and recommend a pumping rate. From there, it is up to you to monitor and determine if the well is performing properly. This is done by measuring and recording water levels on a monthly or quarterly basis. Measure water levels with the pump on and off. Readings with the pump on will alert you to problems with well efficiency (for example, plugged screen). Readings with the pump off will indicate possible depletion problems.
What Does It Mean?
Water level information will provide some guidelines to help you decide if your well is operating properly. If the static water levels are fairly consistent and not dropping, chances are that aquifer depletion is not a problem. However, if the static water levels are fairly steady and the pumping water level has decreased, you probably have a well plugging problem. If not dealt with quickly, this could result in reduced yield or a progressive decline in the pumping level.
What To Do?
The single most effective water well management practice is to avoid pumping the water level below the top of the screen. To ensure this, you may have to restrict the pumping rate to stabilize the drawdown. This will protect the screen, the formation and the water quality. At that point, if you find you are short of water, you may have to install a cistern to handle peak flows. It can be a good investment, as it will likely extend the life of the well, and provide 1000-2000 gallons on demand. You will need a second pump for the cistern, but you may be able to use a smaller pump in the well.
If it appears that the well intake area is plugged, you will need to determine if it is due to biological, mineral or sediment plugging. A recent pump test and water quality analysis compared to the original well data will identify what changes have occurred. A driller familiar with well plugging problems and rehabilitation techniques should be consulted to perform this work.
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