Expert knowledge and local knowledge are not the same thing, and the gap between them is not closed by goodwill or proximity. But the translation problem in water management is not only vertical — between the technical expert and the community that needs to act on their findings. It is also horizontal — between technical domains that have developed their own conceptual vocabularies and cannot straightforwardly read each other's outputs. See The Mirror That Reflects the Expert for interventions that answer the expert's questions rather than the community's. See The Last Hundred Meters for the expert's willingness to cross the distance. This pattern is about the structural absence of anyone whose job it is to bridge it.

Experts assume that knowledge, once produced, is self-evidently communicable. That assumption is almost always wrong and almost never examined. The translation layer between technical knowledge and local understanding — and between technical domains themselves — is missing not because individuals lack willingness, but because no institution owns the gap.

The model output arrives. The risk map is printed. The technical report is delivered. The expert has done the work. What happens next is treated as obvious — the community will understand and act. But the map was drawn in a conceptual language the community was never taught. The risk is expressed in return periods and probability distributions that mean nothing to a farmer deciding whether to move his family before the monsoon. The communication task was never begun because it was never recognised as a task.

The same gap appears between expert domains. The urban planner receiving a hydraulic model output is not less intelligent than the engineer who produced it. They lack the conceptual framework to interrogate what the model assumes, where its uncertainties lie, and what its outputs imply for the land use decision they must make. The hydraulic engineer, symmetrically, may not understand what the planner actually needs. Both are experts. Neither speaks the other's language fluently. The missing middle is as absent at the interdisciplinary boundary as at the expert-layman boundary — and less often noticed, because two experts failing to understand each other looks like a coordination problem rather than a translation one.

The pattern repeats wherever domain boundaries exist: between water management and public health, between flood risk and insurance, between climate science and policy. Each domain has developed its own standards of evidence and its own implicit assumptions about what other domains will do with its outputs. These boundaries are not bridged automatically by joint meetings or interdisciplinary project structures. They require deliberate translation investment — and receive it least reliably precisely where it is most needed.

The middle remains missing because nobody is accountable for filling it. Technical communities regard communication as peripheral to the real work. Project budgets fund data collection, modelling, and reporting — and treat communication as something that happens naturally at the end, if there is time. There is never time.

Treat translation as a technical requirement, not a communications afterthought — at both the vertical boundary between expert and community and the horizontal boundaries between domains. Budget for the missing middle explicitly. Recruit for genuine bilingualism: fluency in the technical domain and fluency in the receiving context, with standing on both sides of the divide. In interdisciplinary projects, name the translation gaps as explicitly as the technical tasks and assign responsibility for bridging them. The map delivered is not the map understood.

Linked patterns: The Mirror That Reflects the Expert — the intervention that answers the expert's questions rather than the community's is partly a consequence of the missing middle. The Last Hundred Meters — willingness to cross the distance is necessary but not sufficient without translation capacity. The Exported Social Contract — invisible assumptions that don't travel are made visible only when someone owns the translation task. Water Is Not the Centre of the Universe — the failure to translate across domain boundaries is one reason water management consistently edits out everything the model cannot process.