Balinese Subak Irrigation Sharing Calculator

Why Subak communities benefit from a transparent calculator

For more than a millennium, Balinese farmers have coordinated irrigation through Subak associations linked to water temples. Priests synchronize planting calendars with ritual offerings so the entire watershed manages pests, water, and harvest festivals collectively. Tourism and urbanization now pressure canals, while climate change shifts rainfall. Younger members who work in hospitality or creative industries return home only on certain days and rely on clear schedules to maintain their terraces. This calculator translates traditional allocation principles—area-based shares, temple holy days, and rotation cycles—into a modern plan. By quantifying flow volumes, seepage losses, and member weights, Subak leaders can review decisions in temple meetings, share schedules via WhatsApp groups, and document fairness when negotiating with government irrigation projects.

Modern demands make clarity essential. Some members sell rice to resorts or organic cooperatives that require consistent water supply. Others steward UNESCO-protected terraces visited by tourists. Conflicts arise when upstream diversions shorten downstream flows or when new villas tap into canals. A transparent calculator helps Subak heads explain rotations, justify occasional priority for temple caretakers, and identify when infrastructure upgrades are necessary. It supports community resilience by blending customary law (awig-awig) with evidence-based water budgeting.

Understanding the input fields

Flow rate represents the average canal discharge measured in liters per second. Members can estimate it by timing how long the canal fills a bucket or referencing irrigation department data. Daily water window captures hours when gates remain open; many Subak irrigate during night hours to reduce evaporation, so the calculator accepts partial hours. Temple holy days reflect monthly pauses when water is held for rituals at the water temple, ensuring offerings proceed without muddy fields. Seepage and evaporation loss accounts for percolation through terrace bunds and sunny-day evaporation. Rotation cycle length sets how many days before the schedule repeats—often seven or ten days depending on planting stage.

Member entries include name, terrace area, and weight. Area is recorded in are, the Balinese unit (1 are = 100 square meters). Weight lets you honor elders or temple caretakers with a small bonus share while still keeping allocations proportional. If no special priority exists, leave the weight at 1.0. Because Subak decisions are communal, review entries during a temple assembly to verify accuracy and maintain trust.

How water volumes and rotation times are calculated

The calculator multiplies flow rate by daily water hours to determine base volume, adjusts for holy days, and subtracts seepage. Total available water per cycle equals $$V=Q\cdot h\cdot 3600\cdot (1-L)\cdot (1-\frac{D}{30})\cdot t$$ where $Q$ is flow in liters per second, $h$ is daily hours, $L$ is loss fraction, $D$ is holy days per month, and $t$ is rotation days. Each member’s share weight multiplies terrace area. The tool normalizes weights so the sum equals 1, then allocates water volume and converts to hours by dividing by flow. This respects the Subak practice of proportional sharing while honoring temple duties.

Members receive results in cubic meters (m³) to align with irrigation department records. Rotation hours indicate how long each member should open their tali (field gate) during the cycle. Notes flag if a member’s share is minimal (suggesting terracing maintenance) or if they receive a priority adjustment.

Worked example: Subak in Tegallalang

Imagine a Subak near Tegallalang with five members: Made (35 are), Wayan (28 are), Komang (22 are), Nyoman (18 are), and Ketut (15 are) who tends the water temple. The canal delivers about 40 liters/second and runs 14 hours per day, except for two holy days each month. Seepage losses average 8%. The rotation cycle spans seven days. The Subak grants Ketut a 20% weight bonus for temple duties, so his weight is 1.2 while others remain 1.0. Plugging these numbers into the calculator yields total cycle water around 13,000 m³. Made receives roughly 3,300 m³ and 6.5 hours per cycle, Wayan 2,640 m³ and 5.2 hours, Komang 2,070 m³ and 4.1 hours, Nyoman 1,695 m³ and 3.4 hours, and Ketut 1,940 m³ and 3.8 hours thanks to the weight adjustment. The schedule prints clearly so members can coordinate gate openings and rice transplanting.

If drought reduces flow to 30 liters/second, the calculator immediately shows shorter rotation times and highlights the need for staggered planting or supplemental groundwater. Subak leaders can share the CSV with the district irrigation office to request canal lining funds that reduce seepage, or to justify rotating night irrigation shifts to minimize evaporation. The tool also helps tour operators understand when fields will be flooded, aiding photography schedules and visitor safety.

Sample comparisons for Subak planning

These scenarios show how flow, holy days, and canal maintenance affect rotation hours. Communities can run similar comparisons to decide whether to line canals, request upstream releases, or adjust planting windows. Documenting these choices reinforces Subak autonomy while engaging tourism and government stakeholders.

Strengthening Subak governance with data

Use the calculator before temple meetings to prepare printed schedules and charts. Encourage each member to verify their terrace area and weight, updating records when land is leased or sold. Pair the results with rainfall forecasts so Subak heads can propose contingency plans—such as alternating wet and dry terraces to control pests. The CSV export supports grant applications for canal lining, sluice gate repairs, or water-saving pilot projects. Youth members studying abroad can review the spreadsheet to understand family responsibilities and remit funds for maintenance, complementing tools like the diaspora remittance fee comparison calculator.

Documenting water allocations also helps mediate disputes with tourism developers. When a villa taps the canal, Subak leaders can show how reduced flow shortens rotation hours, threatening UNESCO rice terraces. Combining calculator outputs with drone photos or IoT flow sensors builds evidence-based advocacy. The tool can also inform educational workshops hosted by water temples to teach visitors about Subak philosophy and sustainable agriculture.

Limitations and cultural respect

The calculator simplifies complex hydrology. Actual flows fluctuate hourly depending on upstream rainfall, volcanic springs, and upstream diversions. Holy day counts vary by temple calendar; always confirm with priests before finalizing schedules. Seepage losses may change when terraces are newly planted versus nearing harvest. Treat results as guidance, not as rigid directives. Moreover, Subak decisions emerge through consensus; numerical outputs must respect awig-awig traditions and priestly guidance. Do not override elders solely because a spreadsheet suggests efficiency.

Additionally, the model assumes area-based sharing remains appropriate. Some Subak allocate extra water to communal fields or to members maintaining canal structures. Adjust weights to reflect these duties and record agreements during temple ceremonies. Consider integrating this tool with rainfall harvesting or upstream spring protection plans to build holistic watershed stewardship. Above all, approach Subak culture with humility; numbers support the living heritage that UNESCO recognizes.