Why this domain matters
Pools are the most visible discretionary water demand on a Mallorcan finca, they are being built at a rate that is now a live political issue, and every major Balearic aquifer appears to be over its own regulatory exploitation limit. Our highest-salience client pain and the island’s binding physical constraint meet here.
Key questions
- KQ3 — What is total pool water demand at island scale? Answered at archipelago level for 2015; see K1–K4.
- [~] KQ1 — Annual loss for a typical pool, split by pathway? Backwash quantified at sector level (K5); evaporation modelled not measured; splash-out and leakage unknown.
- KQ2 — What does a cover actually save under Mallorcan conditions, and what is the payback?
- [~] KQ4 — What is legally permitted on rustic land? See C5.
- KQ5 — How do natural/biological pools compare on water, energy, chemicals, maintenance and cost?
- KQ6 — Is evaporation increasing? Yes, per K4 — though modelled.
What we know
Sources verified against publisher metadata (Crossref, Semantic Scholar). Full texts not yet read — figures are as stated in the published abstracts.
| # | Claim | Value | Conditions | Tier | Source |
|---|---|---|---|---|---|
| K1 | Pool count, Balearic Islands | 62,599 pools | Archipelago-wide, 2015 | B | Hof et al. 2018 |
| K2 | Total evaporative loss | ~5 hm³ (5 billion L) | All Balearic pools, 2015 | B | Hof et al. 2018 |
| K3 | Share of urban water use | 4.9% of total urban water consumption; 9.6 L added per guest-night per person | Balearics | B | Hof et al. 2018 |
| K4 | Growth | +32% in pool water use by 2015 | Balearics, diachronic inventory | B | Hof et al. 2018 |
| K5 | Backwash loss is large and mismanaged | 5.5 million m³/yr, costing €13.96 million/yr | Public pools, Balearics | B | Domènech-Sánchez et al. 2021 |
| K6 | Backwash protocols are usually wrong | “inappropriate in most cases” — and correcting them would increase the water required | Public pools, Balearics | B | Domènech-Sánchez et al. 2021 |
| K7 | Best parameters for monitoring backwash need | Combined chlorine, ammonium, turbidity, COD | — | B | Domènech-Sánchez et al. 2021 |
| K8 | Local evaporation intensity | >4 million L per km² per year | Densely urbanised Balearic areas | B | Hof et al. 2018 |
Critical qualifier on K1–K4, K8. Hof et al. estimated evaporation using an empirical equation designed for open-water surfaces, applied to a pool inventory and standard meteorological data. These are modelled values, not measurements. That is the correct method at archipelago scale, but it means that even our best Tier B source does not tell us what one specific pool actually loses — which is precisely the gap Site Zero fills.
Critical qualifier on K5–K7. The backwash study covers public pools. The sector-level volume does not transfer to private fincas, but the finding that protocols are wrong in most cases plausibly does, and it is cheap to test.
What we assume
| # | Assumption | Reported value | Tier | Verify by |
|---|---|---|---|---|
| A1 | Annual pool water requirement ≈ 1.2× pool volume | The abstract states the water to refill all 62,599 pools and counteract evaporation “is equivalent to 1.2 pools per year” — phrasing ambiguous | B? | Read the full text. If it means annual demand ≈1.2× volume, it is an extremely useful rule of thumb. Do not use until confirmed. |
| A2 | Covers substantially reduce evaporation | Vendor claims of 50–97% reduction, ~30% energy saving | D | Still Tier D. Cumberland & Wilby (2025) recommend mandatory covers as policy, which supports direction but supplies no Mallorcan figure. |
| A3 | Pool counts for Mallorca alone | ~49,000 and ~59,000 reported; 10,680 built 2015–2024 | C/D | See conflict X1 below |
| A4 | Every major Balearic aquifer exceeds its exploitation limit | >80% exploitation across all major groundwater bodies; good-condition share fell 49.6% → 41% | D | Read the Hydrological Plan directly |
What we don’t know
| # | Open question | Why it matters | Routed to |
|---|---|---|---|
| U1 | What a private, uncovered, rural pool actually loses, measured | Both papers are archipelago-scale or public-pool; neither describes our client | measurement backlog — Site Zero |
| U2 | Leak rate in typical private installations | Invisible, unmeasured, possibly dominant | measurement backlog — Site Zero |
| U3 | Energy split: circulation vs heating vs cleaning | Determines the first intervention | measurement backlog — Site Zero |
| U4 | Backwash practice on private pools | K6 says practice is wrong on public pools; if it is wrong on private ones this is a cheap, behavioural, high-value fix | Site Zero + client sites |
| U5 | Real cover performance in Mallorcan wind and irradiance | A2 is Tier D and load-bearing | measurement + literature |
| U6 | Natural/biological pool performance vs conventional | KQ5 entirely open | next sprint — IOB, GIABN |
| U7 | Splash-out and cleaning losses | The unquantified remainder of the water balance | measurement |
Contradictions
| # | Conflict | Status |
|---|---|---|
| X1 | Mallorca pool count: ~49,000 vs ~59,000 vs Hof’s 62,599 | Partly resolved. Hof’s 62,599 is archipelago-wide, 2015. The other two are Mallorca-only and later. They are not necessarily inconsistent — but no figure should be quoted without its geography and date. |
| X2 | Policy direction: the draft Hydrological Plan reportedly emphasises desalination; GOB and Terraferida argue the binding problem is demand | Unresolved, and genuinely contested. Shapes which interventions have a future. |
Candidate interventions
- Backwash protocol optimisation — the first solution card, and a strong candidate for first intervention: cheap, behavioural, and with a published basis for believing current practice is wrong.
- To write: pool cover; variable-speed pump and schedule optimisation; leak detection and water balance; natural pool conversion.
Metrics
To define: pool water balance (m³/yr by pathway); backwash volume per event and per year; pool circulation energy (kWh/yr); evaporation rate (mm/day, normalised for temperature, humidity, wind).
Note that K7 hands us a ready-made instrumentation list for backwash monitoring — combined chlorine, ammonium, turbidity, COD.
Sources
- Hof, A., Morán-Tejeda, E., Lorenzo-Lacruz, J., & Blázquez-Salom, M. (2018). “Swimming Pool Evaporative Water Loss and Water Use in the Balearic Islands (Spain).” Water 10(12), 1883. DOI 10.3390/w10121883. Open access (CC BY). Tier B.
- Domènech-Sánchez, A., Laso, E., Berrocal, C. I., et al. (2021). “Water loss in swimming pool filter backwashing processes in the Balearic Islands (Spain).” Water Policy 23(5), 1314–1328. DOI 10.2166/wp.2021.217. Tier B.
- Cumberland, A. I., & Wilby, R. (2025). “Evaporation losses from residential swimming pools and water features under climate variability and change.” The Geographical Journal. DOI 10.1111/geoj.70008. Open access. Dubai, not Mediterranean — use as a method reference (Linacre 1977 equation, residential scale) and for its policy framing, not for figures.
Change log
| Date | Change | By |
|---|---|---|
| 2026-09-14 | Created; seeded from Wave 0 round 1 | Nico & Laure |
| 2026-09-14 | Round 2: two Balearic papers verified at abstract level; K1–K8 established; backwash surfaced as the leading intervention candidate | Nico & Laure |