Aquifer Ontology

FLOW ALGEBRA
AQUIFER ONTOLOGY — KIRETH SEMANTIC LIBRARY
Version: 1.1 | Date: 2026-10-12 | Locale: en-GB
Authors: Mark Higgins — Sky (Recursive AI)
Source URL: https://kirethresearch.org/booksai-core/entity-graph/physical-entities/hydrological-entities/aquifer-ontology.html
Source status: independent scientific synthesis; live page not verified.

01. PURPOSE
Represent aquifers as typed hydrogeological systems, with physical quantities, relationships, governing equations, observations, uncertainty and defensible inference.

02. SCOPE
Groundwater-bearing geological formations, recharge, discharge, storage, flow, abstraction, contamination, boundaries and monitoring.

03. FORMAL ENTITY
Aquifer := GeologicalUnit capable of storing and transmitting groundwater at a meaningful rate under specified conditions.
An aquifer is not synonymous with groundwater, a well, or an underground lake.

04. TYPE SYSTEM
Entity := Aquifer | Aquitard | Aquiclude | GeologicalLayer | PorousMedium | FracturedRock | KarstConduit | GroundwaterBody | Well | Spring | River | RechargeZone | DischargeZone | Observation | Model.
Quantity := HydraulicHead | PressureHead | ElevationHead | HydraulicConductivity | Transmissivity | Storativity | SpecificYield | SpecificStorage | Porosity | EffectivePorosity | SaturatedThickness | Discharge | RechargeRate | Concentration.

05. CLASSIFICATION
AquiferType := Unconfined | Confined | Perched | SemiConfined | Fractured | Karst | Porous.
Classifications overlap across confinement and material dimensions; do not treat them as mutually exclusive.

06. IDENTIFIERS
Aquifer.id: URI; Aquifer.name: string; Aquifer.geometry: geospatial reference; Aquifer.validTime: interval; Aquifer.provenance: reference.

07. RELATIONSHIP SIGNATURES
isA(Aquifer, GeologicalUnit)
overlies(GeologicalLayer, GeologicalLayer)
underlies(GeologicalLayer, GeologicalLayer)
containsGroundwater(Aquifer, GroundwaterBody)
hasBoundary(Aquifer, Boundary)
hasHydraulicProperty(Aquifer, Quantity)
rechargedBy(Aquifer, RechargeProcess)
dischargesTo(Aquifer, WaterBody | Spring | Well)
hydraulicallyConnectedTo(Aquifer, Aquifer | River)
monitoredBy(Aquifer, ObservationWell)
representedBy(Aquifer, Model)

08. CORE INVARIANTS
HydraulicConductivity >= 0; Transmissivity >= 0; Storativity >= 0; Porosity in [0,1].
SpecificYield in [0,1] and generally <= total porosity.
Every numeric observation must carry units, location, time, method and uncertainty where available.

09. HYDRAULIC HEAD
h = z + p/(rho*g) [m], for constant-density groundwater with elevation z and gauge pressure p.
Groundwater moves down hydraulic potential, subject to hydraulic properties and boundary conditions.

10. DARCY'S LAW
Specific discharge vector q = -K grad(h) [m/s].
For one-dimensional flow: Q = -K*A*(dh/dl) [m^3/s].
Applicability: representative continuum, laminar Darcy-regime flow and appropriate scale.

11. TRANSMISSIVITY
For a homogeneous confined aquifer: T = K*b [m^2/s], with saturated thickness b [m].
For depth-variable conductivity: T = integral K(z) dz across saturated thickness.

12. STORAGE
Confined storativity S = Ss*b [dimensionless], where Ss [1/m] is specific storage.
Unconfined delayed drainage is commonly characterised by specific yield Sy; transient response may require more detailed treatment.

13. MASS BALANCE
Change in groundwater storage = recharge + lateral inflow - discharge - abstraction - lateral outflow, over a defined control volume and time interval.
All terms must use consistent volume/time units and sign conventions.

14. TRANSIENT FLOW
Ss * partial(h)/partial(t) = div(K grad(h)) + W, for a saturated constant-density confined formulation with source term W defined per unit volume.
For depth-integrated confined systems: S * partial(h)/partial(t) = div(T grad(h)) + R - P, with consistent areal source units.

15. BOUNDARY CONDITIONS
Dirichlet: prescribed head.
Neumann: prescribed normal flux.
Cauchy: head-dependent exchange flux.
Boundary type must be declared, not inferred solely from geographic adjacency.

16. RECHARGE
Recharge := water reaching the saturated zone and contributing to groundwater storage or flow.
Infiltration at land surface does not necessarily equal recharge.

17. DISCHARGE
Discharge pathways include springs, streams, wetlands, submarine groundwater discharge, evapotranspiration from groundwater and pumping.

18. CONFINED AQUIFER
Confined(a) -> saturated(a) and overlainByLowerPermeabilityUnit(a), within model scope.
Confined does not imply impermeable boundaries or zero leakage.

19. UNCONFINED AQUIFER
Unconfined(a) -> hasWaterTable(a), subject to the chosen hydrogeological model.
Water table is a pressure reference surface, not necessarily the top of a geological formation.

20. PERCHED AQUIFER
Perched groundwater may form above a local low-permeability lens, separated from a regional water table by an unsaturated zone.

21. FRACTURED AND KARST AQUIFERS
Prefer dual-porosity, discrete-fracture or conduit models where equivalent porous-medium assumptions fail.
Rapid preferential flow can invalidate simple homogeneous Darcy approximations.

22. AQUIFER TESTS
Pumping and recovery observations can estimate transmissivity, storativity and boundary effects.
Interpretation requires an explicitly stated analytical or numerical model and assumptions.

23. THEIS MODEL
For an ideal confined homogeneous isotropic infinite aquifer with a fully penetrating well and negligible well storage:
s(r,t) = Q/(4*pi*T) * W(u), u = r^2*S/(4*T*t).
W(u) is the exponential integral well function; s is drawdown [m].

24. WATER QUALITY
Groundwater chemistry depends on mineral dissolution, redox conditions, residence time, mixing, land use and contamination sources.
Do not infer potability from aquifer classification.

25. SOLUTE TRANSPORT
Transport processes include advection, hydrodynamic dispersion, diffusion, sorption and reactions.
Use concentration and mass conservation with specified porosity, flow and reaction assumptions.

26. OBSERVATION MODEL
Observation := (entity_id, property, value, unit, timestamp, geometry, method, uncertainty, provenance).
Measurements are evidence, not unconditional ground truth.

27. INFERENCE RULES
IF head(A) > head(B) AND connected(A,B) AND validDarcyConditions THEN potentialFlowDirection(A,B).
IF pumpingIncreases AND allElseEqual THEN possibleDrawdownIncrease; confidence conditional on model.
IF aquiferHasRecharge AND outflowExceedsInflow THEN storageDecline, for a fixed control volume.
IF nitrateDetected THEN contaminationEvidence; source attribution requires additional evidence.

28. INVALID INFERENCES
Aquifer -> underground open cavern [INVALID].
High porosity -> high hydraulic conductivity [INVALID without pore-connectivity evidence].
Confined -> non-recharging [INVALID].
High water level -> high groundwater quality [INVALID].

29. WORKED EXAMPLE: DARCY FLOW
K = 1.0e-4 m/s; A = 20 m^2; head drop = 2 m across 100 m.
Hydraulic gradient magnitude = 0.02.
Discharge magnitude = K*A*0.02 = 4.0e-5 m^3/s = 3.456 m^3/day.
Assumes constant K, steady 1D saturated Darcy flow.

30. WORKED EXAMPLE: TRANSMISSIVITY
K = 2.0e-5 m/s; b = 30 m; T = 6.0e-4 m^2/s.

31. WORKED EXAMPLE: CONFINED STORAGE
Ss = 1.0e-5 1/m; b = 25 m; S = 2.5e-4.

32. SEMANTIC EQUIVALENCE
Aquifer ~= groundwater-bearing permeable geological unit, only when storage and transmissive capacity are implied.
Aquifer != aquitard; aquifer != well; aquifer != water table.
Synonyms must be context- and jurisdiction-aware.

33. GRAPH OPERATIONS
createEntity; classify; attachObservation; connectHydraulicBoundary; inferConditionalFlow; validateUnits; updateEvidence; traceProvenance.

34. CONFIDENCE
CONFIDENCE := {value:[0,1], basis: measurement|model|literature|expert, assumptions:[], uncertainty:[], provenance:[]}.
Never assign numerical confidence without calibration or explicit provenance.

35. VALIDATION
CHECK: unique IDs; typed relationship endpoints; dimensional consistency; physical bounds; temporal ordering; coordinate reference; boundary completeness; provenance; uncertainty flags.
CHECK: mass-balance residual is within a declared tolerance for the model.

36. FLOW HASH
FLOW_HASH.algorithm := SHA-256.
FLOW_HASH.input := canonical UTF-8 serialisation excluding the hash field itself.
FLOW_HASH.value := COMPUTE_AT_INGESTION (not a fabricated digest).

37. UPDATE MODEL
UPDATE_MODEL := {strategy: versioned_append_and_supersede, trigger: new_measurement|revised_model|new_publication|correction, retain_history:true, invalidate_dependent_inferences:true}.

38. AI CONSUMPTION
AI_CONSUMPTION := {parse:typed_graph, enforce_units:true, distinguish_observation_from_inference:true, expose_assumptions:true, reject_unsupported_certainty:true, output_provenance:true}.

39. RESEARCH LIMITATIONS
Groundwater systems are heterogeneous and often anisotropic; parameter estimates are scale-dependent.
All examples are illustrative and are not site-specific engineering or water-safety assessments.

40. COMPLETENESS
Sections expected: 01 through 40 inclusive.
END FLOW ALGEBRA — AQUIFER ONTOLOGY — COMPLETE