Well Rehabilitation

The specific capacity of a well is the ratio of the flow rate (usually in gallons per minute) and the resulting drawdown (usually in feet).  If you see the drawdown increasing at a constant flow rate, it is either because of well interference (another nearby well is also pumping) or, more likely, that the well screen or borehole is becoming plugged.  Unfortunately, a well that becomes plugged will rarely be returned to the original efficiency, therefore, it is important to keep track of the specific capacity on an ongoing basis.  Some water managers rely on the advice of their drilling or service contractors to determine when a well needs to be redeveloped, while other managers put the wells on a routine redevelopment schedule.  Both of these approaches may result in wells being redeveloped when they really don’t need to.  Moreover, the costs associated with pulling pumps and mechanically or chemically treating the screen are a significant hit to any water delivery budget.

Wells become plugged in part because of the precipitation of minerals in the water on the well screen or borehole.  The precipitation can occur because of the significant pressure drop that happens when water leaves the aquifer and enters the well.  In a screened well, you can calculate the entrance velocity of water into the well.  Many water managers pump the well to the maximum capacity and pay no attention to entrance velocities.  However, pumping the well at the optimal flow rate can greatly increase the life of the well and increase the time between rehabilitation.

Aqua TrueVue technology enables you to track specific capacity on an ongoing basis, to develop acceptable ranges for each well, and to determine optimal flow rates for each screened well on an ongoing basis.  In addition, a color coded a graph (e.g. green for safe, yellow for caution, and red for “redevelop now!”) can be customized so your operators know when it is time to address rehabilitation issues.