Borehole
A borehole is a cased well, usually deep, in which a submersible pump is installed. The water does not come from an “open source” but from an aquifer. When pumping, the water level drops around the well: this is called drawdown.
Important levels:
- Static level: water level at rest, without pumping.
- Dynamic level: water level during pumping at a given flow rate.
- Water level drop: decrease in level due to pumping.
How this affects the pump:
- The harder we pump, the lower the dynamic level drops → the pump must draw water from a lower elevation → the Total Head increases.
If the dynamic level drops too low, there is a risk of:
- sucking in air or sediment,
- exceeding the pump’s capacity,
- temporarily drying out the well area.
Common constraints / limits:
- Maximum sustainable flow rate: beyond this, the dynamic level drops rapidly and the well “runs dry.”
- Water quality: sand: silt, iron/manganese → can wear out the pump.
- Diameter and casing: limit pump size and flow rates.
- Installation depth: the pump is placed below the dynamic water level with a safety margin.
HMT
m
m
m·m³/h
m³/h
-
<span id="hmt-unit" class="unit">m</span>
</div>
</div>