How Soon Might Your Well Go Dry?
by Bill Papian
Residential water-well pumps used in these parts fall into two basic classes: shallow-well or suction pumps and submersible pumps. Shallow-well pumps, which work on the basis of suction, are recognizable by the fact that the pump is almost always located above ground, often in the residence itself.
Wells installed over 20 or 30 years ago used mostly suction pumps; almost all new installations use submersible ones.
If you care about such facts, you likely live in one of Anne Arundel County’s some 37,000 households, mostly in the southern part of the county, that draw their water from private wells. The other 139,000 households have public water service, with water coming from reservoirs or lakes.
Anne Arundel well water comes largely from the first aquifer down, the Aquia. The next one down is the Magothy aquifer; it requires deeper wells plus water softening apparatus to reduce its high iron content.
The top of the Aquia aquifer varies with the topography, but it is about 100 feet above sea level — not ground-surface level — in the ‘highlands’ northwest of here and about 100 feet below sea level where it approaches the shore of the Bay. The Aquia’s water is under pressure and its crucial level is, of course, that to which its water will rise if we drill into it with a well.
Wells with suction pumps may extend into the aquifer for many feet, but the length of the water column to be sucked up is determined by the vertical distance from the potentiometric level up to the pump. The depth from which a column of water can be sucked is theoretically limited to somewhere under 30 feet. Over that limit, the water in the piping from the suction well starts to cavitate — that is to develop sections of partial vacuum and air — and the pump no longer functions. With no water flowing through the pump, it soon overheats and shuts off or burns out. So, if the water source is deeper than 20 to 30 feet, you’re in trouble.
Fortunately, that crucial “potentiometric” level has been close enough to the surface for shallow-well pumps to satisfy the needs of many of us, at least until recent years.
The second kind, a submersible pump, located as it is at the bottom of the well, has a different job. It has to support a column of water, not suck it, and that it can do with no significant limit, as much as hundreds of feet depending on its horsepower. A properly installed submersible pump is going to work as long as there’s aquifer water for it to pump.
The bad news for well-owners of both sorts is that the level of the Aquia aquifer has been going down for many years at an increasing rate. In other words, it is being mined. We are taking out more water than the natural recharge by rain is replacing. And that disparity is increasing with increasing population and commercial demand. Could the level go down to a dangerous degree for all of us, regardless of well-pump type? Theoretically certainly. Pragmatically and politically, yes — unless something changes the trend.
Who is monitoring this problem?
The state, with primary responsibility, has recently issued an executive order, “Water Resource Management Advisory Committee,” on this very subject, which indicates that the state is worried about the problem. However, our state administration is about to change and this order has yet to be implemented. None of the committee’s members has yet been appointed. Del. Dick D’Amato, who jockeyed this order through the administration and the legislature, is also about to be replaced.
The county is also involved; its health department worries about water potability, performs inspections on wells and issues new well permits. Because the rate of mining the Aquia aquifer increases with increased development, the county’s Planning and Zoning people should be concerned about growing population and particularly about any development in the northwest areas where rain helps recharge the aquifer.
The Chesapeake Environmental Protection Association is the citizens’ watchdog, monitoring reports from test wells and reporting the results.
If you’re concerned about how soon your well might go dry, write to the governor, the governor-elect, your delegation in the legislature and the county executive.
Bill Papian is on the Board of Trustees of Chesapeake Environmental Protection Association.
