Plan a Balinese Subak water rotation by terrace area and agreed share weights
This Subak irrigation calculator turns canal flow, daily gate-opening hours, expected conveyance losses, ceremonial pauses, and a rotation length into a water budget that members can inspect together. Enter the shared canal conditions and each member's rice-terrace area to produce daily volume allocations and gate-time slots for the selected cycle.
What the Subak water-sharing results show
- Estimate distributable canal water each day after entered seepage, evaporation, and holy-day adjustments.
- Divide the available water transparently according to terrace area multiplied by any agreed priority weight.
- Express each allocation as a gate-opening time so the cycle can be arranged as practical rotation slots.
- Download the Subak schedule as CSV for a WhatsApp group, temple meeting, printed notice, or irrigation-office communication.
Subak water-budget inputs and planning assumptions
This Subak calculation treats canal discharge as a single flow rate available during a stated daily water window. It reduces the resulting daily volume by: (1) a loss percentage for seepage and evaporation, and (2) a holy-day fraction calculated from the number of irrigation-pause days entered for a 30-day month. It then applies the rotation cycle length to find the water budget for the full cycle.
Each member's allocation is based on effective area: (terrace area in are) × (share weight). A weight of 1.0 represents an ordinary area-based share. Use a modest bonus, such as 1.1 or 1.2, only where the Subak has agreed that a caretaker or duty-holder should receive a somewhat larger allocation.
Formulas for Subak canal volume and rotation hours
The Subak water-allocation calculation follows these steps (with units shown):
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Daily distributable volume (m³/day):
Vday = Q × h × 3600 ÷ 1000 × (1 − L) × (1 − D/30)
where Q is flow (L/s), h is the daily water window (hours), L is loss fraction (for example, 8% → 0.08), and D is holy days per month. - Cycle volume (m³/cycle): Vcycle = Vday × rotationDays
- Member share (dimensionless): share = (area × weight) / Σ(area × weight)
- Rotation time per cycle (hours): hours = (memberCycleVolume × 1000) / (Q × 3600)
Worked Subak irrigation example with canal losses and holy-day pauses
For a Subak canal flowing at 40 L/s with a 14-hour daily water window, 2 holy-day pause days/month, 8% losses, and a 7-day rotation, the unadjusted daily flow is: 40 × 14 × 3600 ÷ 1000 ≈ 2016 m³/day. Applying the loss and holy-day factors gives 2016 × (1 − 0.08) × (1 − 2/30) ≈ 1728 m³/day. The seven-day cycle therefore has about 12,096 m³ available after those adjustments.
A member with 20% of the total effective terrace area receives about 0.20 × 1728 ≈ 346 m³/day. Their cycle slot is about 0.20 × 7 days × 14 hours/day ≈ 19.6 hours; the calculator obtains that time from the allocated cycle volume and canal flow. This check can help a Subak identify an implausible flow, loss, pause, or area entry before agreeing on the schedule.
Tips for reliable Subak irrigation entries
- Flow rate: when measuring with a bucket, repeat the observation several times and plan from an average, since canal discharge can change during the day.
- Loss %: lined channels may be nearer 0–5%, while earthen channels and hot or windy conditions can justify a higher planning allowance.
- Holy days: check the temple calendar; when water is paused for only part of one day, a fractional entry such as 0.5 can represent that pause.
- Areas: enter every member's terrace area in are (1 are = 100 m²). Convert hectares by multiplying by 100.
- Weights: keep adjustments limited and record why any weight differs from 1.0 in the meeting notes.
Introduction: transparent Subak irrigation rotations for shared terraces
Subak communities coordinate terrace irrigation through collective rules, water-temple calendars, and shared maintenance of channels and fields. A visible water-sharing schedule lets members see why a rotation has a particular order or duration, can reduce disagreement during scarce periods, and supports coordination of labor. It can also help communicate planning assumptions to district irrigation offices when repairs, canal lining, or upstream releases are under discussion.
This Subak planning page does not replace customary law (awig-awig) or temple guidance. It supplies a consistent calculation from agreed flow, loss, holy-day, area, and weight entries, allowing discussion to focus on those choices rather than on repeated volume and time arithmetic.
Understanding Subak canal and terrace input fields
For this Subak rotation plan, flow rate is the average canal discharge in liters per second. If measurements are occasional, choose a conservative average for planning. Daily water window is the number of hours per day that the irrigation gate is open. Holy days are days per month when irrigation pauses for ceremonies or coordinated temple activities. Loss percentage represents seepage through canal banks and bunds plus evaporation. Rotation cycle length states how many days pass before the proposed schedule repeats.
Subak member rows contain a name, cultivated terrace area in are, and an optional share weight. Where no priority arrangement exists, leave the weight at 1.0. When a different weight is entered, the schedule labels that row “Includes priority weight” so the adjustment remains visible.
Limitations and respectful use of Subak allocation estimates
This Subak irrigation estimate simplifies changing field and canal conditions. Actual discharge may vary by hour with rainfall, upstream diversions, and maintenance work. Temple-calendar timing and conveyance losses also vary with season and field condition. Use the figures as a basis for planning, then confirm the important assumptions together before putting a rotation into practice.
When communal fields, maintenance obligations, or other special agreements need representation, use the weight field and record the reason for it. A sound Subak schedule makes its inputs, allocation method, and resulting rotation hours understandable to every member.
How to use the Balinese Subak irrigation sharing calculator
- Enter the measured or agreed Canal flow rate (liters/second) for the shared irrigation channel.
- Enter the Daily water window (hours) during which the canal gate supplies irrigation water.
- Enter Temple holy days without irrigation (days/month) from the relevant ceremony and water-use calendar.
- Plan the water rotation, then review the terrace shares and gate times against a second agreed set of Subak conditions before adopting the schedule.
Arcade Mini-Game: Balinese Subak Irrigation Sharing Calculator Calibration Run
Use this quick arcade run to practice separating useful scenario inputs from common planning mistakes before you rely on the calculator output.
Start the game, then use your pointer or arrow keys to catch useful inputs and avoid bad assumptions.
Subak Water Allocation and Gate-Rotation Schedule
| Member | Area (are) | Share weight | Daily volume (m³) | Rotation time per cycle (hours) | Notes |
|---|
Practical workflow for a Subak water-allocation meeting
- Measure or agree on a planning flow rate (L/s) and daily water window (hours).
- Confirm holy-day pauses for the month and choose a rotation cycle length (often 7–10 days).
- Read out member areas and confirm any weights (keep them modest and documented).
- Generate the schedule, then export the CSV for sharing and record-keeping.
- If conditions change (drought, repairs, upstream changes), rerun the calculator and compare the new schedule.
For Subak maintenance planning that involves relatives outside the village, the diaspora remittance fee comparison calculator may help compare transfer costs for contributed funds.