Static water level and dynamic water level are two of the most important measurements used when selecting a submersible well pump.
Static water level shows where the groundwater rests when the pump is not operating. Dynamic water level shows where the water level falls while the pump is running at a specific flow rate.
The difference may appear simple, but using the wrong value can lead to an incorrect head calculation, insufficient pump submergence, excessive drawdown, or dry-running problems. A reliable pump supplier should therefore ask for both measurements before recommending a model.
static vs dynamic water level
What Is Static Water Level?
Static water level is the distance from the ground or wellhead reference point to the water surface when the well is not being pumped.
The pump should remain stopped long enough for the well to recover before this measurement is taken. Depending on the aquifer and previous pumping conditions, recovery may take minutes, hours, or longer.
Static water level provides a useful reference for groundwater conditions, but it does not show how the well behaves during operation. It should not be used alone to calculate the required pump head.
What Is Dynamic Water Level?
Dynamic water level, also called pumping water level, is measured while the pump is operating at a known flow rate.
When pumping begins, the water level normally falls below the static level. The amount of decline depends on the pumping rate, aquifer conditions, well construction, screen condition, and pumping duration.
A useful dynamic water-level record should include:
① Measured water level
② Pumping flow rate
③ Time since pumping started
④ Whether the water level had stabilized
For example, the statement “dynamic water level: 65 m at 40 m³/h after six hours of pumping” is much more useful than simply stating “dynamic water level: 65 m.”
What Is Well Drawdown?
Drawdown is the difference between the static water level and the dynamic water level.
The basic calculation is:
Drawdown = Dynamic Water Level − Static Water Level
If the static water level is 25 m below ground and the dynamic water level is 60 m below ground:
60 − 25 = 35 m drawdown
Drawdown shows how strongly the well responds to pumping. A large drawdown may indicate a high pumping rate, limited aquifer recharge, restricted well screens, or deterioration inside the well.
Drawdown alone does not prove that a well is defective, but it should always be reviewed together with pumping flow and test duration.
A Simple Water-Level Example
Consider a well with the following conditions:
① Total well depth: 150 m
② Static water level: 30 m
③ Dynamic water level: 68 m at 45 m³/h
④ Pump installation depth: 100 m
The drawdown is:
68 − 30 = 38 m
During operation, the pump is approximately 32 m below the dynamic water level:
100 − 68 = 32 m submergence
This information helps determine whether the pump has enough submergence, whether the motor can be cooled properly, and whether the pump is installed far enough above the well bottom.
It also provides the correct starting point for calculating Total Dynamic Head.
Why Dynamic Water Level Matters for Pump Head
A pump normally lifts water from the dynamic water level, not from the bottom of the well.
If a well is 150 m deep but the dynamic water level is 68 m, the initial vertical lift begins at approximately 68 m. Discharge elevation, outlet pressure, pipe friction, and equipment losses must then be added.
Using total well depth as the required head may result in too many pump stages, an oversized motor, excessive pressure, and unnecessary energy consumption.
Before calculating pump head, the project flow should also be confirmed. Our guide on how to calculate submersible well pump flow rate explains how daily water demand and available pumping hours affect the duty point.
Dynamic Water Level Changes with Pump Flow
A well does not have one universal dynamic water level. The level changes when the pumping rate changes.
For example:
① At 30 m³/h, the dynamic water level may be 50 m.
② At 45 m³/h, it may fall to 68 m.
③ At 60 m³/h, it may fall to 90 m.
This is why a supplier should ask which flow was used during the water-level test. Selecting a pump using the dynamic level measured at 30 m³/h is risky if the proposed pump will deliver 60 m³/h.
The proposed flow should remain compatible with the sustainable well yield. A larger pump cannot create more groundwater; it may only cause faster drawdown.
Dynamic Water Level May Continue Falling
Water level is often measured too soon after the pump starts.
A well may show a dynamic level of 55 m after ten minutes, then continue falling to 70 m after several hours. If the pump is selected from the first reading, the required head may be underestimated.
A pumping test should record water level at regular intervals until the level stabilizes or the planned test period ends. The test should also record flow because changes in valve position or pump performance can affect the result.
For continuous-duty projects, a stabilized long-term reading is more valuable than a short test result.
Seasonal Water-Level Changes
Groundwater levels may change between wet and dry seasons.
A pump selected using wet-season data may lose submergence during the dry season. The lower water level also increases the required pump head and may reduce delivered flow.
Where seasonal changes are significant, confirm:
① Highest expected water level
② Lowest expected dynamic water level
③ Minimum motor submergence
④ Safe pump installation depth
⑤ Dry-run protection requirements
The pump should remain below the lowest expected operating water level while still being installed far enough above the well bottom to reduce sediment intake.
How Water Level Affects Pump Installation Depth
Pump installation depth should not be selected only by lowering the pump as far as possible.
The pump should normally be positioned:
① Below the lowest expected dynamic water level
② With sufficient submergence for stable operation
③ Where the motor receives adequate cooling
④ Above the well bottom and sediment zone
⑤ Away from damaged or restricted casing sections
Installing the pump too shallow may increase dry-running risk. Installing it unnecessarily deep increases pipe length, cable length, lifting weight, installation cost, and maintenance difficulty.
The correct depth depends on the dynamic water level, seasonal variation, motor cooling requirements, well construction, and sediment conditions.
For a wider review of these factors, see our submersible well pump selection guide.
Water Level and Dry-Running Risk
If the dynamic water level falls below the pump intake, the pump may begin drawing air or stop receiving water completely.
Dry running can cause:
① Loss of flow
② Motor overheating
③ Bearing damage
④ Seal damage
⑤ Unstable current
⑥ Permanent pump failure
Low-yield wells and wells with strong seasonal variation should use suitable protection. Common options include water-level electrodes, current-based dry-run relays, pressure monitoring, flow switches, and intelligent control panels.
Dry-run protection should support correct pump selection, not replace it. A pump that continuously exceeds the well yield will still operate poorly even if protection stops it before complete failure.
How to Measure Well Water Level
Water levels can be measured using several methods, including electric water-level meters, pressure sensors, air-line systems, and permanently installed level transmitters.
For a reliable measurement:
① Use the same reference point each time.
② Record whether the pump is stopped or running.
③ Record the pump flow.
④ Record the measurement time.
⑤ Allow sufficient recovery before measuring static level.
⑥ Avoid measuring while another nearby well changes the aquifer condition.
For important municipal, industrial, or mining projects, continuous level monitoring provides better data than occasional manual readings.
What a Reliable Pump Supplier Should Ask
A reliable submersible well pump supplier should not ask only for well depth and horsepower.
Before recommending a pump, the supplier should confirm:
① Total well depth
② Static water level
③ Dynamic water level
④ Pumping-test flow
⑤ Well yield
⑥ Well casing diameter
⑦ Proposed pump installation depth
⑧ Required flow and Total Dynamic Head
⑨ Water quality and sand content
⑩ Voltage and frequency
The supplier should then mark the proposed duty point on the pump performance curve and confirm that the pump will remain adequately submerged under the expected operating conditions.
How to Compare Pump Recommendations
Two suppliers may recommend different pump models because they have used different water-level assumptions.
One supplier may calculate head from the static level, while another uses the dynamic level. One may account for dry-season decline, while another assumes the current water level will remain constant.
When comparing quotations, check that each supplier uses:
① The same required flow
② The same dynamic water level
③ The same discharge elevation
④ The same pipe dimensions
⑤ The same pressure requirement
⑥ The same seasonal assumptions
A lower-priced pump is not a better choice if its selection is based on incomplete water-level data.
Buyers can compare the final duty point with available SLAPK submersible well pump models, but the final model should be confirmed from complete project information.
Information to Send for Pump Selection
Before requesting a quotation, prepare:
① Total well depth
② Static water level
③ Dynamic water level
④ Flow during the pumping test
⑤ Pumping-test duration
⑥ Well recovery rate
⑦ Lowest seasonal water level
⑧ Well casing diameter
⑨ Required project flow
⑩ Pipeline and pressure information
⑪ Water quality and sand content
⑫ Electrical supply
Complete data helps the manufacturer select the correct pump stages, motor power, installation depth, cable, controls, and protection equipment.
Request a Pump Selection from SLAPK
Static water level shows the resting groundwater level. Dynamic water level shows the actual water level while the pump is operating.
For submersible well pump selection, the dynamic water level is usually the more important value because it affects vertical lift, pump submergence, motor cooling, and dry-running risk.
Send SLAPK your well-test data, required flow, pipeline information, outlet pressure, water quality, and electrical supply. Our engineering team can review the water-level conditions and recommend a pump supported by a performance curve and technical data.
For a broader overview of pump construction, operation, sizing, installation, and maintenance, read our complete guide to submersible well pumps.
