QUESTION |
ANSWER |
| Q.1 Are residents and businesses in western Loudoun at imminent risk of having their wells go dry? | We don’t know. Approximately 19,000 wells are currently operating in western Loudoun; most are producing enough water to meet owners’ needs. A growing number have had to be replaced after going dry or providing inadequate supply. Drillers have been able to find new sources, though they have generally had to drill deeper to find them. |
| Q.2 Is the map that shows localized pockets of 10 to 40-foot declines in water tables the primary source of concern? | No, it simply illustrates that western Loudoun faces a serious, widespread groundwater problem. There are multiple lines of evidence that the groundwater supply in western Loudoun cannot keep pace with the increasing rates of groundwater withdrawal and drought conditions. |
| Q.3 Loudoun has experienced a noticeable proliferation of wells since 2000. Would this have a noticeable impact on groundwater levels? | Yes. Since 2000, more than 9,000 new wells have been drilled in western Loudoun. Not only are there many more wells withdrawing groundwater, but they have been drilled closer and closer together. Approximately 90% of western Loudoun’s wells are now within 550 feet of another well. And growth has brought other problems. |
| Q.4 The owners of a neighboring property are planning to drill a new well. How do I know if this will affect my own well? | Currently there is no way to know. Property owners aren’t required to inform neighbors or the County about how a new well may affect other wells. This is especially concerning when developers plan to drill many new wells in a small area to supply a clustered subdivision. It is advisable to take steps to know what your current conditions are.
LCPCC and participating organizations recommend that Loudoun County adopt changes to its Facilities Standards Manual to help to minimize impacts and require prior notification to neighboring properties. |
| Q.5 Are we getting less rain and snow than we used to and how could that affect our water tables and wells? | Records show a recent decline in precipitation and more frequent droughts in our area. Between 2021-2025, for example, Purcellville received 21-23 inches less rainfall than normal (about 12%) based on rain gauges operated by the USGS. The decline in precipitation varies based on location (see table below). In early 2026, Purcellville imposed mandatory water restrictions. Other rural towns and villages have had to call for water restrictions in recent years. |
| Q.6 How many County and USGS monitoring wells are in Loudoun and is the historical and real-time data from those wells publicly available? | The County currently maintains 14 wells and reports data twice a year. Data summary reports are presented annually. The USGS maintains 3 wells in or close to Loudoun and provides real-time data and interactive charts via websites. |
| Q.7 Have the Loudoun or USGS water level monitoring wells shown changes over time? | Some wells have shown changes over time due to either nearby pumping at other wells, nearby development and regional earthquake (at one well). Overall there does not appear to be a pattern of widespread nonreversible “water bankruptcy.” |
| Q.8 The private well drillers’ “static water level” data has been questioned as often inaccurate. Does this undermine the findings and conclusions of the Groundwater Assessment Study?
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No, LCPCC’s Groundwater Assessment Study report remains valid.
“Static Water Level” refers to the amount of water normally in a well when not in use, and best determined long after the well is drilled and after several hours after pumping. |
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The LCPCC Groundwater Study references private well drillers’ data called “static water level” which are based on individually drilled wells and hydrostudy reports which are based on subdivision development requirements that reference “safe yield.” (Q9 and Q10 provide an explanation of each term).
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| Q.9 Loudoun County requires a hydrostudy when permitting any subdivision larger than 9 lots. A hydrostudy aims to answer the question of whether there’s enough groundwater to serve the development based on “Safe Yield.” What does the term “Safe Yield” mean?
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The term “Safe Yield” refers to the maximum long‑term rate at which groundwater can be withdrawn without causing a persistent decline in water levels or damaging the aquifer system. It’s essentially the “sustainable pumping limit” for a well, aquifer, or water supply system. |
| Q:10 Explain the difference between drawdown and the water table? | The water table is the elevation of the top of the saturated zone in Loudoun’s unconfined aquifer. It represents the natural groundwater level in the surrounding geologic formation.
Drawdown is the amount the water level drops in response to pumping. |
Groundwater Study – FAQs (Frequently Asked Questions)
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