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.
Burden inputs corrected on 24 September 2026 against UN IGME 2024 and World Bank 2025 data: the under-five death rate and the under-five population share replace the values v1 carried as judgment. The crediting basis moved to the yield in use in the portfolio model, 0.163 credits per person-year.
Solar boreholes, piped taps, and chlorination for 3.99 million people by 2033, with the under-five mortality pathway the school model deliberately excluded.
This is the portfolio's largest projected credit line and its most complete health case: a community water supply reaching whole households, including under-fives, where the randomized evidence on chlorinated water and child survival applies. Unlike the Rwanda school model, the cost basis here carries every dollar of system construction, so this worksheet shows what the numbers look like when nothing is left out of the denominator.
Read against the Rwanda school worksheet: Burundi reaches under-fives in whole households, where diarrheal disease kills, and it carries full construction capex. On the corrected inputs its strict chain reads $6,514 per DALY against the Rwanda school worksheet's $6,021, while on the all-cause basis Burundi is the lower of the two. That is the general shape of the portfolio thesis: the community and household programs are where the health economics concentrate.
| Series | 2025 | 2026 | 2027 | 2028 | 2029 | 2030 | 2031 | 2032 | 2033 | Total | |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Systems operating (EOY) | 44 | 99 | 157 | 224 | 297 | 374 | 460 | 548 | 639 | — | |
| New systems installed | 44 | 55 | 58 | 67 | 73 | 77 | 86 | 88 | 91 | 639 | |
| People served | 274,695 | 618,057 | 980,163 | 1,398,432 | 1,854,193 | 2,334,909 | 2,871,814 | 3,421,204 | 3,989,325 | 17,742,792 ben-yrs | |
| Net credits (tCO₂e) | 0 | 0 | 98,000 | 227,287 | 301,362 | 379,493 | 466,756 | 556,048 | 648,385 | 2,677,331 | 2,677,331 |
| Carbon revenue at $15 floor ($) | 0 | 0 | 1,470,000 | 3,409,305 | 4,520,430 | 5,692,395 | 7,001,340 | 8,340,720 | 9,725,775 | 40,159,965 | 40,159,965 |
| System capex ($, 3%/yr inflation) | 2,992,000 | 3,852,200 | 4,184,190 | 4,978,464 | 5,587,026 | 6,069,959 | 6,982,818 | 7,359,565 | 7,838,773 | 49,844,995 | |
| Chlorine ($80/mo/system) | 42,240 | 95,040 | 150,720 | 215,040 | 285,120 | 359,040 | 441,600 | 526,080 | 613,440 | 2,728,320 | |
| Monitoring ($80/mo, first 18 mo) | 31,680 | 71,280 | 81,360 | 90,000 | 100,800 | 108,000 | 117,360 | 125,280 | 128,880 | 854,640 |
All rows trace to the proforma inputs of the base scenario and the program's contract terms: $68,000 full-recovery cost per new system, ~6,000 people per system, credits beginning two years after installation per the crediting methodology, and the contracted $15 per credit floor price. Credit yield basis 0.163 credits per person-year, the yield in use in the portfolio model, not yet reconstructed to the 2026 methodology revision (see section 04). The 2025–2033 credit and revenue totals are the portfolio model's figures at that yield; the year-by-year cells are the v1 vintage split and are restated at v2.
| TOTAL_PROGRAMME_COST, 2025–2033 | $53,427,955 | Formula capex + chlorine + monitoring, all years |
| Beneficiary-years served | 17,742,792 | Formula sum of the people row |
| Cost per beneficiary-year | $3.01 | Formula cost ÷ beneficiary-years |
Every figure on this page divides by this one cost; the build fails programmatically otherwise. Donor revenue in the program plan ($4M per year) is deliberately NOT netted out: donor money is the philanthropy whose cost per DALY this page measures. Excluded from the cost: operations beyond chlorine and monitoring (an optimistic omission, flagged in the critique), and all post-2033 years, including the projected carbon-self-sufficient era from 2035 (a conservative omission for donor economics).
| Input | Value | Provenance | Basis |
|---|---|---|---|
| Under-five share of population | 15.3% | Evidence-anchored | World Bank 2025 population structure. |
| Under-five annual death rate | 0.00965 /child-yr | Evidence-anchored | UN IGME 2024, Burundi: U5MR 47.1 per 1,000, annualized. Tested ±30% in S4–S5. |
| Diarrheal share of under-five deaths | 9% | Judgment · flagged | GBD-order estimate. |
| Under-five mortality reduction | 12% | Evidence-anchored | GiveWell's conservative in-line chlorination figure. The Kremer et al. 2023 meta-analytic 25% runs as scenario S1. |
| Years of life lost per under-five death | 33 | Judgment · flagged | Discounting convention pending. |
| Diarrheal incidence, under-five / over-five | 0.8 / 0.3 episodes/yr | Judgment · flagged | GBD lookups pending. |
| Diarrhea reduction, chlorination | 25% | Evidence-anchored | Wolf et al. 2022 (Lancet), point-of-use chlorination risk ratio ~0.75. |
| Delivery effectiveness (safe at the tap) | 90% | Sensor-measured | Portfolio monitoring record: 90.3% of samples safe under monitored delivery (n=1,685). |
| Household usage share | 70% | Judgment · flagged | Share of drinking water actually drawn from the tap; no survey yet. Tested 50–90% in S2–S3. |
| Effective coverage | 63% | Formula | 90% × 70%. The same number the credit quantification uses. |
| YLD per episode | 0.002215 DALY | Formula | Disability weight 0.188 × 4.3 days ÷ 365. |
| Step | Value | Computation |
|---|---|---|
| Under-five child-years | 2,714,657 | 17,742,792 beneficiary-years × 15.3% |
| Under-five diarrheal deaths averted | 177.9 | U5 child-years × 0.00965 × 9% × 12% × 63% effective coverage |
| DALYs from mortality (YLL) | 5,872 | deaths × 33 years of life lost. 72% of total health value. |
| Diarrheal episodes, all ages | 6,680,167 | U5 child-years × 0.8 + over-five person-years × 0.3 |
| DALYs from morbidity (YLD) | 2,330 | episodes × 25% × 63% × 0.002215. 28% of total. |
| DALYs averted, total raw | 8,202 | — |
| $ / DALY averted, raw | $6,514 | $53,427,955 ÷ 8,202 |
| $ / DALY averted, evidence-adjusted | $17,008 | ÷ composite 0.383 → 3,141 adjusted DALYs |
| xCash (GiveWell / egalitarian / wellbeing / weighted) | 0.105× / 0.046× / 0.165× / 0.108× | DALY moral weights 2.3 / 1.0 / 3.6; GiveDirectly benchmark 0.00335 units per dollar. Ranking stable. |
| Factor | Score | Basis |
|---|---|---|
| Internal validity | 0.75 | Strong reduction anchors. The population share and the under-five death rate now carry World Bank and UN IGME sources; diarrheal share, incidence and years of life lost remain judgment. |
| External validity | 0.75 | In-line chlorination and point-of-use evidence transferred to piped community supply in Burundi. |
| Publication bias | 0.80 | Systematic reviews without an independent funnel-plot confirmation in this model. |
| Implementation quality | 0.85 | Sensor-instrumented delivery plan, but no issuance track record yet: Gold Standard registration expected Q1 2027. |
| Composite | 0.383 | Formula product of the four; reported alongside the raw figure, never silently multiplied in. |
| Residual baseline-practice factor | 0.70 | Judgment · flagged The crediting basis (0.163 credits per person-year, the yield in use) has NOT yet been reconstructed to the 2026 methodology revision, so the residual over-crediting risk is priced larger than Rwanda's 0.78. A measured baseline survey replaces this. |
| Delivery effectiveness | 0.90 | Sensor-measured The same cell the health chain uses. |
| Leakage / rebound | 1.00 | Negligible for water treatment. |
| Credit integrity ratio | 0.63 | Formula 0.70 × 0.90 × 1.00 |
| Cookstove-overlap exposure | ~7% | The AERA cookstove program (GS11140) overlaps this service area; forecast baseline haircut of roughly 7% where households hold both interventions. Quantified in the overlap analysis; folded into the baseline factor at v2. |
| $ / tonne, credited basis | $19.96 | $53,427,955 ÷ 2,677,331 t · 9.3× below the $185 social cost of carbon |
| $ / tonne, integrity-adjusted | $31.68 | ÷ (2,677,331 × 0.63) · 5.8× below the SCC |
| Revenue coverage of full cost | 75.2% | $40,159,965 ÷ $53,427,955 at the $15 floor → net philanthropic cost $13,267,990 |
| Net donor $ / DALY averted | $1,618 | the fund's primary metric for a program that is not yet self-financing in-window |
The additionality picture differs from Rwanda's: with no issuances yet, no host-country authorization yet, and construction gated on blended donor and carbon finance, the case that the carbon contract causes the program is currently strong. The corresponding risk moved elsewhere: crediting volume (see S7).
| Scenario | Varied input | DALYs | $ / DALY raw | xCash GW | Net donor $ / DALY | Reading |
|---|---|---|---|---|---|---|
| Base case | — | 8,202 | $6,514 | 0.105× | $1,618 | as above |
| S1 · Kremer mortality effect | 25% | 14,563 | $3,669 | 0.187× | $911 | the meta-analytic all-cause anchor roughly doubles mortality DALYs |
| S2 · household usage low | 50% | 5,859 | $9,120 | 0.075× | $2,265 | — |
| S3 · household usage high | 90% | 10,545 | $5,066 | 0.136× | $1,258 | — |
| S4 · under-five death rate −30% | 0.006755 | 6,440 | $8,296 | 0.083× | $2,060 | — |
| S5 · under-five death rate +30% | 0.012545 | 9,964 | $5,362 | 0.128× | $1,332 | — |
| S6 · floor price $10 | $10/t | 8,202 | $6,514 | coverage 50.1% · net $3,250/DALY | price risk is real but bounded | |
| S7 · contracted credits only | 210,000 t | 8,202 | $6,514 | coverage 5.9% · net $6,130/DALY | the load-bearing carbon risk: crediting volume, not price | |
Recomputed robustness statement: raw $/DALY spans $3,669 to $9,120 across the single-input health scenarios, and the net donor figure spans $911 to $2,265. No scenario brings the health frame near the cash-transfer bar on full cost, and none lifts the climate cost above the SCC. The fragile claim is the carbon ramp itself: if only the currently contracted 210,000 credits materialize, coverage collapses to 6% and the program is donor-funded construction with a carbon topper. Gold Standard registration and the issuance ramp, not the floor price, carry the carbon case.
| Dimension | Rating | Assessment |
|---|---|---|
| Effect-size quality | The reduction anchors are strong (GiveWell's conservative chlorination figure, Wolf 2022), and the population share and under-five death rate now come from World Bank 2025 and UN IGME 2024. The diarrheal share of deaths, the incidence rates and years of life lost are still judgment pending GBD lookups, and household usage has no survey. Preliminary status is correct. | |
| Counterfactual robustness | Few alternative funders operate at this scale in Burundi; funging is low to moderate and unmodeled in v1. Carbon additionality is currently stronger than Rwanda's: no issuances, no authorization yet, construction gated on the blended finance. | |
| Moral-weight transparency | All frameworks reported; the mortality-dominant pathway keeps the ranking stable. Net donor cost per DALY (~$1,618 raw) is the decision-relevant number. | |
| Attribution and integrity | Amazi Water delivers; Virridy develops the carbon and monitoring layer. The model charges full system capex and claims full health benefit, which is internally consistent, but a funder-specific split (carbon investment against donor capex) belongs in v2. The integrity ratio's weak link, the 0.70 baseline residual on an unreconstructed crediting basis, is flagged, not hidden. | |
| Excluded factors | Excluded: time savings from proximate taps (likely large, conservative), water-quantity and hygiene benefits (conservative), operations beyond chlorine and monitoring (optimistic), and all post-2033 years including the projected self-financing era (conservative for donor economics). The two-year crediting delay also leaves in-window credits understating steady-state yield. | |
| Ranking stability | Health and climate frames are stable across S1–S7. The sensitive claim is crediting volume: registration and ramp risk, priced in S7, dominates price risk. |