Case study · Viticulture · Occitanie
Optimising a 3,500 m² irrigation storage basin for a large vineyard in arid conditions
An AOC Languedoc estate in Hérault relied on a 3,500 m² winter storage basin to support supplemental irrigation across 42 ha. With summer pumping restrictions and a reference evaporation rate of 1,150 mm/year, the technical team quantified passive losses before deploying modular Hexprotect AQUA floating covers.
- 3,500 m²
- Storage basin surface area
- 1,150 mm/year
- Reference evaporation E_ref (DRIAS, Occitanie)
- 4,025 m³/year
- Gross loss V = (S × E_ref) / 1,000
- 3,542 m³/year
- Secured volume V × η (η = 0.88 conservative)
Estate context
42 ha AOC Languedoc operation, syrah and grenache on stony soils. The 3,500 m² basin, fed in winter by a borehole and network top-up, supports late-cycle drip irrigation and occasional tank cooling. In 2024–2025, prefectoral orders limited summer withdrawals: every stored cubic metre became strategic to protect the vintage without compromising aromatic profile.
Initial diagnosis
Pre-cover water balance: V = (3,500 × 1,150) / 1,000 = 4,025 m³/year evaporated from open water. At an estimated supplemental irrigation cost of €0.45/m³ (pumping energy, fees, labour), passive loss exceeded €1,800/year — excluding late-season quality risk. Surface algae increased cleaning operations and stored-water compliance concerns.
Solution deployed
Hexprotect AQUA PEHD hexagonal modules deployed by direct pour onto the basin, without structural supports or a permanent specialist crew. One operator covered the full surface in under a week while keeping the irrigation network operational. The cover limits direct solar radiation, breaks the vapour transfer boundary layer and reduces algal proliferation.
Measurable results
With the conservative η = 0.88 simulator coefficient, secured volume reaches 3,542 m³/year — 88% of gross loss intercepted passively, with zero energy use. In supplemental irrigation terms, that covers more than 14 ha at a typical 250 m³/ha in a dry year. Surface temperature stability also reduced thermal swings, valued during maturation.
Lessons for viticulture
For estates with exposed basins in Mediterranean zones, passive evaporation is often the first leak in the water balance — before network losses. An on-site audit refines E_ref (dominant wind, shading, geometry) and η (80–96% depending on configuration). This Occitanie profile applies to vineyard basins in Catalonia, Roussillon and western Sicily where E_ref frequently exceeds 1,100 mm/year.
Frequently asked questions about this case
Why use η = 0.88 instead of 0.96?
0.88 is Hydropreserve's conservative coefficient for Europe, where wind and basin geometry modulate performance (80–96% range). 0.96 reflects the maximum measured under extreme arid conditions (Nevada 2024, AWTT / Hexprotect AQUA reference).
Does this apply to smaller or larger basins?
Yes. Model V = (S × E_ref) / 1,000 scales linearly with surface. A 10,000 m² basin at 1,150 mm/year loses 11,500 m³/year gross; at η = 0.88, over 10,100 m³ are secured. Use the homepage simulator for your configuration.
What is the source for E_ref = 1,150 mm/year?
Consistent with DRIAS / Météo-France references for Occitanie viticulture and the 1,000–1,400 mm/year range on the viticulture culture page. An on-site audit refines the value for actual basin exposure.
Calculation: V = (S × E_ref) / 1,000. Secured volume = V × η with η = 0.88 (conservative coefficient). Representative profile based on a typical Occitanie vineyard estate — figures to be validated by on-site audit. See Methodology for the full protocol.