Yield • Test Pumping • Kenya

Borehole Yield Explained in Kenya: What It Means, How It’s Measured & How to Plan Your System

“Yield” is the word everyone hears after drilling—then confusion starts. Yield is not pressure. It’s not “how fast the tap feels.” Yield is about how much water the borehole can sustainably supply without failing in dry season or damaging the pump.

🗓️ ⏱️ 9–13 min read ✅ Simple examples + checklist
Yield Sustainable yield Test pumping Pump sizing Tank sizing Pressure vs flow
On this page
  1. Yield, flow, pressure: the difference
  2. Common yield units in Kenya (L/min, m³/hr)
  3. Sustainable yield (the only number that matters)
  4. How test pumping measures yield
  5. Why yield drops (and what’s not actually yield)
  6. How to size pump + tank using yield
  7. Simple examples (home, rentals, farm)
  8. Mistakes that cause “low water” complaints
  9. Mini yield-to-system tool
  10. FAQ

1) Yield, flow, pressure: the difference

These three get mixed up all the time: yield is what the borehole can supply, flow is how much water is moving through the pipe at that moment, and pressure is the force pushing water through your plumbing.

  • ✓
    Yield (borehole capacity)
    The supply limit of the borehole/aquifer system over time.
  • ✓
    Flow (instant delivery)
    How much water per minute/hour is coming out right now.
  • ✓
    Pressure (tap “strength”)
    A plumbing/pump design result—pipe sizes, elevation, booster system, valves.
Key insight: You can have a good-yield borehole but weak taps if pipes are undersized or pressure design is wrong.

2) Common yield units in Kenya (and quick conversions)

Yield is commonly quoted as L/min, L/hr, or m³/hr. What matters is that you convert everything into a daily plan (litres per day) for tank and schedule design.

Quick conversions:
• 1 m³ = 1,000 litres
• 1 m³/hr = 1,000 L/hr
• L/min × 60 = L/hr
• L/hr × pumping hours/day = litres/day

3) Sustainable yield (the only number that matters)

Sustainable yield is the pumping rate the borehole can maintain without the water level dropping too far or failing to recover. Some boreholes can produce a high burst for a short time, then collapse in performance. Sustainable yield is what protects you from dry-running pumps and “it worked in rainy season only” stories.

Think of it like this: A borehole is a battery + charger. You can “draw” water (battery), but recharge rate (aquifer recovery) controls what you can sustainably take.

4) How test pumping measures yield

After drilling and development, test pumping runs the borehole at a controlled rate while monitoring water level behavior. The goal is to see drawdown (how far the water level falls) and recovery (how fast it rises after pumping). That behavior is what allows professionals to recommend a safe operating rate.

  • 1
    Set a pumping rate
    Run a pump at a chosen flow and keep it steady.
  • 2
    Monitor water levels
    Track drawdown during pumping and recovery after stopping.
  • 3
    Interpret stability
    Stable behavior supports sustainable yield planning.
Don’t skip this: Buying a final pump before test pumping often leads to resizing (buying twice).

5) Why yield “drops” (and what’s not actually yield)

Some yield changes are real, others are system issues that look like yield problems. Dry season can reduce recharge, but many “low yield” complaints are caused by wrong pump sizing, leaks, blocked filters, or undersized pipes.

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    Real reasons
    Seasonal recharge drop, competing nearby abstraction, clogging/siltation, formation changes.
  • ✓
    System reasons that look like yield issues
    Pump too big, dry-run protection missing, controller mis-set, pipes too small, tank float problems, leaks.

6) How to size pump + tank using yield

The simplest reliable approach is storage-first: pump at a safe rate into tanks, then supply users from storage with stable pressure. This lets you match demand peaks without forcing the borehole to deliver peak flow instantly.

  • 1
    Pick a safe pumping rate
    Based on test pumping (sustainable yield).
  • 2
    Choose pumping hours/day
    Solar vs grid affects your feasible pumping window.
  • 3
    Plan litres/day
    Rate × hours = daily volume available.
  • 4
    Tank buffers peaks
    Tank size reduces “low pressure” and protects the borehole.
Simple sizing thought: If your borehole sustainably gives 2,000 L/hr and you pump 6 hours/day, that’s about 12,000 L/day available for storage and use.

7) Simple examples (home, rentals, farm)

Home: Often works best with steady pumping to a tank + a pressure booster for house taps.
Goal: stable supply + good pressure. Tank buffers morning/evening peaks.
Rentals: Peaks are bigger and complaints are louder.
Goal: bigger storage + pressure control. Direct pumping without storage often disappoints tenants.
Farm: Think in schedules and zones.
Goal: match irrigation zones to sustainable yield, use storage, and protect drippers/sprinklers with filtration.

8) Mistakes that cause “low water” complaints

Many projects blame the borehole when the real issue is system design. Fix these first before calling it “low yield.”

  • ✕
    Oversized pump
    Pulls faster than the borehole can recover → dry-running and failures.
  • ✕
    No storage buffer
    Peak demand hits borehole directly → pressure drops and downtime.
  • ✕
    Undersized pipes
    Creates huge friction losses → weak taps even with good supply.
  • ✕
    Missing protection/controls
    No dry-run protection or faulty float switches → pump damage and interruptions.

Want help reading your yield results?

Send your test pumping details (rate, duration, drawdown/recovery notes) and your intended use. We’ll advise a sensible pump + tank plan that protects the borehole and gives stable taps.

Request sizing support Back to blog

9) Mini yield-to-system tool (quick guidance)

Enter what you know to get a practical “next move” for sizing and stability.

10) FAQ

Is a higher yield always better?

Higher yield helps, but your system still needs correct pump sizing, storage, and plumbing. A high-yield borehole can still perform poorly if the system is designed badly.

Can I improve yield after drilling?

Sometimes performance improves with proper development, rehabilitation, or removing clogging/siltation. But if the aquifer is limited, the best “improvement” is usually storage and smarter demand scheduling.

What’s a “good” yield in Kenya?

“Good” depends on your demand. A home can be fine with modest yield if storage is planned well, while farms and institutions may need higher sustainable yield or larger storage to meet schedules.

Hydrodrill Solutions Hydrogeological surveys • Test pumping • Pump & tank sizing • Water system planning