Reconciled 2026-08-13 against the portfolio financial model’s re-base: this worksheet’s program series, contracted floors, and cost rows are unchanged by it. The re-base adjusted SPV sell-through pricing and financing mechanics, which this worksheet does not use.
Gravity-fed and solar-pumped chlorinated water in Diana, Menabe, and Amoron'i Mania, targeting 350,000 people by 2030.
This is the earliest-stage model in the portfolio: the program launched in 2025, no credits have been issued yet, and it is the first project on an Article 6 pathway in a country with no prior host-country authorization. The model says so, scores itself accordingly, and publishes every input anyway.
Helvetas and its donors build the water systems; the carbon channel finances verification and service. This model prices only the carbon channel, and says so on every figure.
Virridy's carbon-side outlay only: the $210,000 guaranteed first purchase (the first 7,000 credits at $30) plus every later credit purchased on delivery at the contracted buy price, $2.75M in total over 2025–2033. This is the money the carbon market puts into the program.
Partner construction capex and donor funding for the RANO WASH delivery model sit outside the portfolio financial model, so a full-delivery-cost $/DALY cannot be computed yet. Until it can, the dollars-per-DALY figures here describe what the carbon financing buys, never what the program costs, and must not be quoted against GiveWell benchmarks.
Partner-published context, not a model input: Helvetas reports 51% of children under five in its program regions affected by diarrheal disease. The under-five death rate and the under-five population share now come from published country data; incidence, enrollment and usage remain flagged judgment values, which is the main reason this is a preliminary.
Correction, 24 September 2026: the burden inputs were checked against UN IGME 2024 and World Bank 2025 data and both moved. The under-five death rate rose from 9 to 12.9 per 1,000 child-years, which raises deaths averted and improves every mortality figure on this page. The under-five share of the served population fell from 17% to 14.4%, which shrinks the exposed child population and lowers baseline episodes. The crediting basis also moved from the 0.21 yield the program was booked at to the 0.141 yield in use in the portfolio model, which roughly doubles the cost per credited tonne.
Same protocol, same transparency as the flagship worksheet: every input with its provenance, every calculation in order.
| Series | 2025 | 2026 | 2027 | 2028 | 2029 | 2030 | 2031 | 2032 | 2033 | Total |
|---|---|---|---|---|---|---|---|---|---|---|
| Projected credits (tCO₂e) | 0 | 0 | 0 | 11,277 | 18,325 | 25,373 | 25,373 | 25,373 | 25,373 | 131,094 |
| Buy price to partner ($/cr) | 9.20 | 9.20 | 9.30 | 9.50 | 9.60 | 9.70 | 9.80 | 9.90 | 9.90 | — |
| Population served (derived) | 0 | 0 | 55,957 | 85,957 | 135,957 | 185,957 | 235,957 | 285,957 | 285,957 | 1,271,700 person-yrs |
| Virridy carbon outlay ($) | 0 | 0 | 254,184 | 171,485 | 274,090 | 378,795 | 485,600 | 594,505 | 594,505 | 2,753,163 |
Credits and buy prices are proforma inputs (contracted offtake: 51,000 credits on the voluntary market, 2028–2030; first issuance 2027, already rolled forward one year). Population is a formula, credits ÷ yield, and is flagged twice: the annual cells were derived at the 0.21 yield the program was booked at, and the derived 2030 population (186K) sits below the program's 350K target because crediting lags service by roughly two years. The 2027 outlay row includes the $210,000 guaranteed first purchase (first 7,000 credits at $30). The credit total is the 131,094 credits the portfolio model now carries for 2025–2033 at the 0.141 yield in use; the annual credit cells above are the per-year path from the portfolio model on that yield. The annual restatement lands in v2.
| TOTAL CARBON-FINANCING COST, 2025–2033 | $2,753,163 | Formula first batch + on-delivery purchases; no advances for this program |
| Person-years of service financed | 1,271,700 | Formula sum of the derived population row |
| Financing per person-year | $2.16 | Formula cost ÷ person-years |
Every figure on this page divides by this one cost, and the build fails programmatically if any figure uses a different denominator. What this basis is not: it contains no partner construction capex and no donor funding, so it is not the program's cost-effectiveness. When partner cost data is available, a v2 adds the full-delivery-cost frame alongside this one.
| Input | Value | Provenance | Basis |
|---|---|---|---|
| Under-five share of served population | 14.4% | Evidence-anchored | World Bank 2025 population structure. |
| Diarrheal incidence, under-five | 1.0 episodes/child-yr | Judgment · flagged | GBD lookup pending; high-burden setting. |
| Diarrheal incidence, over-five | 0.35 episodes/person-yr | Judgment · flagged | GBD lookup pending. |
| Diarrhea reduction, piped treated supply | 30% | Evidence-anchored | Wolf et al. 2022 (Lancet), piped water of higher quality. |
| Enrollment (share of population connected) | 85% | Judgment · flagged | No enrollment data; program launched 2025. |
| Usage (share of drinking water from system) | 70% | Judgment · flagged | No usage survey; continuous monitoring not yet deployed at scale here, so unlike the flagship this cell is not sensor-measured. |
| YLD per episode | 0.002215 DALY | Formula | 0.188 disability weight × 4.3 days ÷ 365. |
| Under-five death rate | 12.9 / 1,000 child-yrs | Evidence-anchored | UN IGME 2024, Madagascar: U5MR 62.4 per 1,000, annualized. |
| Diarrheal share of under-five deaths | 9% | Judgment · flagged | Cross-check input only; not multiplied into the central estimate (see D). |
| All-cause under-five mortality reduction | 12% | Evidence-anchored | GiveWell-style conservative estimate for water treatment; the Kremer et al. 2023 meta-analytic ~25% runs as scenario S4, not the central case. |
| YLL per under-five death averted | 33 | Evidence-anchored | Standard life-table basis. |
| Step | Value | Computation |
|---|---|---|
| Under-five person-years | 183,124 | 1,271,700 × 14.4% |
| Diarrheal episodes at baseline | 564,126 | 183,124 × 1.0 + 1,088,576 × 0.35 |
| Episodes averted | 100,696 | 564,126 × 30% × (85% × 70% effective coverage) |
| YLD DALYs averted | 223 | 100,696 × 0.002215 |
| Baseline under-five deaths in served population | 2,362 | 183,124 × 12.9/1,000 |
| Deaths averted (central, conservative) | 168.6 | 2,362 × 12% all-cause × 59.5% effective coverage |
| Cross-check: diarrhea-attributable pathway alone | 38.0 | 2,362 × 9% share × 30% × 59.5%. The all-cause estimate implies ~4.4× the diarrhea-only prediction, the pattern the Kremer meta-analysis documents. Stated, not hidden. |
| YLL DALYs averted | 5,564 | 168.6 × 33 |
| TOTAL DALYs averted (raw) | 5,787 | YLD + YLL; 96% mortality-driven |
| $ / DALY, financing basis, raw | $476 | $2,753,163 ÷ 5,787 |
| Evidence adjustment (E) | × 0.274 | 5,787 → 1,586 DALYs adjusted |
| $ / DALY, financing basis, adjusted | $1,736 | $2,753,163 ÷ 1,586 |
| xCash, GiveWell / egalitarian / wellbeing weights | 2.19× / 1.61× / 2.28× | mortality weight 117 / 87 / 120 per death, morbidity 2.3 / 1.0 / 3.6 per DALY; financing basis, so not comparable to full-cost models |
| xCash, moral-uncertainty weighted | 2.07× | 0.45 / 0.25 / 0.30 prior |
| Factor | Score | Basis |
|---|---|---|
| Internal validity | 0.70 | Meta-anchored effect sizes, but every exposure input is judgment. |
| External validity | 0.70 | Trial contexts transferred to rural Madagascar piped schemes. |
| Publication bias | 0.80 | Systematic-review anchors. |
| Implementation quality | 0.70 | Launched 2025, no issuance record, first Article 6 pathway with no prior host-country authorization. |
| Composite | 0.274 | Formula the lowest composite in the portfolio, as it should be for the earliest-stage program. |
| Residual baseline-practice factor | 0.60 | Judgment · hard flag The 0.141 yield in use replaces the 0.21 the program was booked at, following the 2026 methodology reconstruction that cut comparable reconstructed yields by ~45%; this is the portfolio's most exposed baseline. A measured baseline survey and the reconstruction replace it. |
| Delivery effectiveness | 0.85 | Judgment · flagged Assumed pending sensor deployment; unlike the flagship, not yet sensor-measured. |
| Leakage / rebound | 1.00 | Negligible for water treatment. |
| Credit integrity ratio | 0.51 | Formula 0.60 × 0.85 × 1.00, the portfolio's lowest. |
| $ / tonne, credited basis | $21.00 | $2,753,163 ÷ 131,094 t · 8.8× below the $185 SCC |
| $ / tonne, integrity-adjusted | $41.18 | $21.00 ÷ 0.51 · 4.5× below the SCC. Fails the SCC test only below integrity 0.114, implausible even under full reconstruction. |
| Scenario | Varied input | Cost | DALYs | $ / DALY | xCash GW | Reading |
|---|---|---|---|---|---|---|
| Base case | — | $2,753,163 | 5,787 | $476 | 2.19× | central, conservative mortality |
| S1 · first issuance slips to 2028 | ramp −1 yr | $2,158,658 | 3,710 | $582 | 1.79× | the already-realized risk repeats; economics barely move, the window truncates |
| S2 · contracted offtake only | 51,000 cr | $636,510 | 920 | $692 | 1.50× | downside book; $12.39 per credited tonne |
| S3a · integrity 0.40 | 0.40 | $2,753,163 | 5,787 | $476 | 2.19× | $52.50 per real tonne, 3.5× below SCC |
| S3b · integrity 0.80 | 0.80 | $2,753,163 | 5,787 | $476 | 2.19× | $26.25 per real tonne, 7.0× below SCC |
| S4 · Kremer 25% all-cause mortality | 0.25 | $2,753,163 | 9,782 | $281 | 3.66× | meta-analytic upper anchor, scenario only |
S1, S2 and S4 still carry the pre-correction burden inputs (17% under-five share, 9 per 1,000 death rate) and are restated in v2; the base case and the two integrity scenarios are on the corrected inputs. Recomputed robustness statement: the climate finding holds across the whole integrity band, and no scenario moves financing-basis health figures by more than ~2.4×. The binding risk for this program is not economics but issuance: registration is pending, the country pathway is new, and the ramp has already slipped once. That is a timing risk the fund's first-loss capital is designed to carry.
| Dimension | Rating | Assessment |
|---|---|---|
| Effect-size quality | The under-five death rate and age structure now come from UN IGME and World Bank data; incidence, enrollment and usage stay flagged judgments, and nothing program-specific has been measured yet. The 0.274 composite is the portfolio's lowest, deliberately. | |
| Counterfactual robustness | Unmodeled in v1. Other WASH funders are active in Madagascar; a named-funder funging pass is required for v2. Carbon-side additionality is an assumption about the future until first issuance. | |
| Moral-weight transparency | All frameworks reported. Mortality carries 96% of the DALYs, so under-five weighting drives everything. | |
| Attribution and integrity | The cost basis is Virridy's financing only, so the $/DALY is not program cost-effectiveness and is labeled as such everywhere it appears. Integrity 0.51 is the portfolio's lowest, and the crediting basis now uses the 0.141 yield. | |
| Excluded factors | Partner capex (excluded by construction and labeled), time savings from piped proximity (likely material, conservative omission), water-quantity and hygiene effects, post-2033 operation. | |
| Ranking stability | Climate case stable, 3.5–7.0× below SCC across the integrity band. Health figures span ~2.4× across scenarios. The decision-relevant risk is issuance timing, not cost-effectiveness. |