Water well glossary

Acidization Adjudicated basin Affinity laws Annular seal Baseline Best efficiency point (BEP) Biofouling Bowl assembly Brake horsepower (bhp) California Well Standards Casing Cavitation Change in storage Cone of depression Constant-rate test Critical speed De minimis extractor Division of Drinking Water (DDW) Drawdown Driller’s log / well completion report Electronic annual report (eAR) Energy intensity (kWh/AF) Gravel pack / filter pack Groundwater elevation Groundwater sustainability agency (GSA) Groundwater sustainability plan (GSP) Historian Ingestion Lifecycle model Mineral scale / encrustation Monitoring network Net positive suction head (NPSH) Perforated interval / screened interval Preferred operating region (POR) Pump curve Pump efficiency test Pumping water level Recoverable cost Recovery Redevelopment Sanding SGMA SGMA annual report Specific capacity Static water level Step-drawdown test Submersible pump Sustainable yield System of record Telemetry Title 22 Total dynamic head (TDH) Transmissivity Variable-frequency drive (VFD) Vertical turbine pump Video survey Water horsepower (WHP) Water loss audit Water year Watermaster Well destruction Well development Well interference Well IQ score Well loss Well rehabilitation Well screen Wire-to-water efficiency

Hydraulics

Static water level

The depth to water in a well that has not been pumped for long enough to recover — the resting level of the aquifer at that point. Measured from a fixed reference (usually the top of the casing) with a sounder or transducer. Its trend over years describes the aquifer; its difference from the pumping level describes the well.

Pumping water level

The depth to water while the well is being pumped, after the level has stabilized at the test rate. Read too early and it overstates the well’s performance; read at a different rate than last time and the comparison means little.

Drawdown

Pumping water level minus static water level: how far the water is pulled down to produce the flow. Part of it is aquifer loss (linear with rate), part is well loss through the screen and pack (grows with the square of the rate).

Specific capacity

Pumping rate divided by drawdown, in gallons per minute per foot (gpm/ft). The single best indicator of a well’s own condition, independent of the pump. A falling specific capacity at a steady static level means the well is plugging; many districts act at a 15–25 % decline from baseline.

Well loss

The extra drawdown caused by turbulent flow through the screen, gravel pack and damaged formation near the borehole — the CQ² term in a step-drawdown analysis (s = BQ + CQ²). Rehabilitation reduces C; nothing reduces B.

Step-drawdown test

A test in which the well is pumped at three or more increasing rates, each held until the level stabilizes, so the aquifer-loss and well-loss coefficients can be separated. The cleanest baseline a new or rehabilitated well can be given.

Constant-rate test

A test at one rate held for hours or days while drawdown is logged, used to estimate transmissivity and storage and to confirm the sustainable yield. Usually run after the step test on a new well.

Transmissivity

How readily an aquifer transmits water horizontally through its full saturated thickness (hydraulic conductivity × thickness), typically in ft²/day or gpd/ft. Estimated from pumping-test data; it belongs to the aquifer, not the well.

Cone of depression

The funnel-shaped lowering of the water table or piezometric surface around a pumping well. Its radius grows with time and rate; where cones from neighboring wells overlap, each well’s drawdown increases.

Well interference

Additional drawdown in one well caused by pumping in another whose cone of depression reaches it. Common in tightly spaced municipal well fields; a reason to compare specific capacity under the same neighboring conditions.

Recovery

The rise of the water level after pumping stops. Recovery data are as useful as drawdown data for aquifer analysis and less affected by pump fluctuations; a well that recovers slowly relative to its history is usually plugging.

Sustainable yield

The rate a well (or basin) can supply over the long term without unacceptable consequences — declining levels, subsidence, water-quality change. A basin-scale concept under SGMA; at the well it is the rate the aquifer and screen can sustain without mining.

Total dynamic head (TDH)

The total head a pump must produce: the lift from the pumping water level to the discharge, plus the discharge pressure converted to feet (psi × 2.31), plus friction losses in the column and piping. The head used with flow to compute water horsepower.

Pumps and energy

Water horsepower (WHP)

The useful hydraulic power delivered: WHP = flow (gpm) × TDH (ft) ÷ 3960. A well moving 900 gpm against 400 ft of head is doing 90.9 water horsepower of work regardless of how much electricity it consumes.

Brake horsepower (bhp)

The mechanical power delivered to the pump shaft. Read from the manufacturer’s curve at the operating point; bhp ÷ WHP is the inverse of pump efficiency.

Wire-to-water efficiency

Also overall plant efficiency (OPE): water horsepower divided by electrical input power, with kW converted to hp (kW × 1.341). Folds together motor, drive, shaft, bowls and column. New well pumps run 70 % and above; below 55–60 % a rebuild usually pays for itself.

Pump efficiency test

A field measurement of flow, pumping level, discharge pressure and input power on a running well pump, producing wire-to-water efficiency, energy intensity and recoverable cost. Historically funded by utility programs in California; the most under-used engineering study a district owns.

Energy intensity (kWh/AF)

Kilowatt-hours consumed per acre-foot pumped: kW ÷ (gpm × 60 ÷ 325,851). Rises with lift as well as with inefficiency, so a plugging well costs money before flow visibly drops.

Recoverable cost

The annual energy cost that would be saved if a plant ran at a target efficiency instead of its measured one, at the district’s rate and volume. The number that decides whether a rebuild is a maintenance line or an investment.

Pump curve

The manufacturer’s plot of head, efficiency and brake horsepower against flow for a pump at one speed. Multiply per-stage head by stage count for a vertical turbine; scale with the affinity laws for other speeds. Where the well’s operating point sits on it is the diagnosis.

Best efficiency point (BEP)

The flow at which a pump converts shaft power to hydraulic power most efficiently and runs with the least vibration and radial load. Selection aims to put the normal operating point near it.

Preferred operating region (POR)

Roughly 70–120 % of BEP flow (Hydraulic Institute guidance): the band in which a pump runs without accelerated wear. The allowable operating region (AOR) is the wider manufacturer-defined band outside which life shortens quickly.

Affinity laws

For a given pump, flow scales with speed, head with speed squared and power with speed cubed. They let one curve be redrawn at any VFD speed and explain why part-speed operation saves so much energy on friction-dominated systems — and so little on pure static lift.

Variable-frequency drive (VFD)

An electronic drive that varies motor speed by varying supply frequency (Hz). Speed is quoted as a percentage, in hertz (60 Hz = full speed) or in rpm; skip bands are programmed to avoid the column’s resonant speeds.

Critical speed

A shaft speed at which the lineshaft’s natural frequency is excited, shaking the column and eating bearings. VFD skip frequencies jump over it; the band belongs in the well record so no one sets a minimum speed inside it.

Vertical turbine pump

The standard large municipal well pump: a multistage bowl assembly at depth, driven through a lineshaft by a motor at the surface. Stage count sets the head; setting depth must stay below the pumping level with margin.

Submersible pump

A pump close-coupled to a sealed motor, both installed below the water level. Common for smaller wells and deep settings; efficiency losses sit in the motor and cable rather than a lineshaft.

Bowl assembly

The stacked impellers and diffusers of a vertical turbine — the part of the pump that actually generates head. Worn impellers and wear rings show up as an operating point below the curve.

Net positive suction head (NPSH)

The pressure margin above vapour pressure at the pump inlet. Submergence below the pumping level must exceed the manufacturer’s required NPSH or the pump cavitates — a particular risk when water levels fall.

Cavitation

Vapour bubbles forming and collapsing inside a pump when inlet pressure drops too low, eroding impellers and causing noise and vibration. In wells, usually the result of a pumping level falling toward the pump setting.

Construction and rehabilitation

Driller’s log / well completion report

The record filed with the California Department of Water Resources when a well is constructed, modified or destroyed: lithology, casing, screen intervals, seal, development and yield. The foundation document of a well’s record.

Casing

The pipe that lines the borehole, keeping it open and isolating it from the formation. Diameter fixes the largest pump the well can take; material and wall thickness fix its corrosion life.

Well screen

The perforated or slotted section of casing through which water enters. Louvered, bridge-slot and continuous-slot wire-wrapped screens are the common municipal types; slot size is chosen from the formation’s grain-size analysis.

Gravel pack / filter pack

Graded, rounded sand or gravel placed between the screen and the borehole wall to hold back formation fines while passing water. Sized against the formation’s sieve analysis; under-sized packs sand, over-sized packs plug early.

Annular seal

Cement or bentonite grout placed in the annulus between casing and borehole from the surface down, keeping surface water and shallow poor-quality water out. Minimum depths are set by the California Well Standards and local ordinance.

California Well Standards

DWR Bulletins 74-81 and 74-90, the state minimum standards for water well construction, modification and destruction, adopted and often exceeded by county ordinances.

Well development

Surging, airlifting, jetting or over-pumping a newly constructed well to remove drilling fluids and fines, settle the filter pack and open the formation. Skipped or shortened development leaves a well that never reaches its potential.

Perforated interval / screened interval

The depth range(s) over which the well is open to the aquifer. Needed for every later interpretation of water levels and water quality, and for a well to qualify in a GSA monitoring network.

Video survey

A downhole camera inspection of the casing and screen. Distinguishes mineral scale from biofilm from corrosion or collapse — the diagnosis that decides which rehabilitation method, if any, will work.

Mineral scale / encrustation

Calcium carbonate and iron or manganese oxides precipitating on the screen and in the pack as pressure and gas content change at the well face. The most common cause of falling specific capacity in hard, oxidizing groundwater.

Biofouling

Slimes built by iron- and sulfur-related bacteria that trap fines and plug screens. Often a sudden decline after years of stability; treated with biocides plus mechanical removal, and prone to regrowth if treated chemically alone.

Well rehabilitation

Restoring a plugged well’s specific capacity by chemical treatment (acids, biocides, dispersants), mechanical agitation (brushing, surging, jetting, pressure-pulse tools) and redevelopment. Earlier treatment recovers more; recovery after a 40 % decline is markedly poorer.

Acidization

Chemical rehabilitation with an inhibited acid to dissolve carbonate and iron scale, followed by agitation and development pumping. Effective on mineral scale; useless on biofouling or structural failure.

Redevelopment

Development applied to an existing well after rehabilitation or as maintenance: surging and pumping to remove loosened material and restore the pack. The step most often shortened, and the one that decides how long the treatment lasts.

Sanding

Production of formation sand with the water, caused by an over-sized slot or pack, poor development or over-pumping. Wears pumps and valves and fills the sump; a construction problem more than an operating one.

Well destruction

Permanent sealing of a well that is no longer used, under the Well Standards, so it cannot become a conduit for contamination. Reported to DWR on a completion report; a status change the GSA’s list needs to reflect.

Regulation and reporting

SGMA

The Sustainable Groundwater Management Act (2014): California’s framework requiring groundwater sustainability agencies to bring medium- and high-priority basins to sustainability, with plans, annual reports and, where needed, pumping controls.

Groundwater sustainability agency (GSA)

The local agency (or agencies) responsible for a basin under SGMA: adopting a sustainability plan, monitoring, reporting annually to DWR and, if required, regulating extraction. Member districts supply most of its well-level data.

Groundwater sustainability plan (GSP)

The GSA’s plan for reaching sustainability within 20 years: sustainable management criteria, monitoring networks, projects and management actions. The annual report tracks progress against it.

SGMA annual report

The report a GSA files each spring covering the prior water year: groundwater elevations, extraction by sector, surface-water supply, total water use and change in storage. Assembled largely from member districts’ metered well records and water-level readings.

Water year

The 12-month accounting period from 1 October to 30 September, used for groundwater and surface-water reporting in California.

De minimis extractor

Under SGMA, a person extracting two acre-feet or less per year for domestic purposes. Generally outside GSA extraction reporting, though some basins ask for registration.

Electronic annual report (eAR)

The annual report a public water system files with the State Water Resources Control Board’s Division of Drinking Water: sources, production, population, water quality and system data. Its production figures should reconcile with SGMA and metering records.

Division of Drinking Water (DDW)

The State Water Board division that permits and regulates public water systems in California, including source approval, monitoring schedules and the eAR.

Title 22

The California Code of Regulations title containing drinking-water standards and monitoring requirements that public water systems must meet for each source.

Adjudicated basin

A groundwater basin whose pumping rights have been determined by a court judgment and are administered by a watermaster, with its own reporting regime separate from (or alongside) SGMA.

Watermaster

The person or body appointed to administer a court judgment or agreement over water rights in a basin or stream — allocating, monitoring and reporting extraction.

Water loss audit

The AWWA-method audit California urban retail suppliers file to quantify apparent and real losses between production and billed consumption. Its production side comes from source meters — the same well records.

Groundwater elevation

The water level in a well expressed as an elevation above a datum rather than a depth below the casing, so readings from different wells can be compared on a map. Requires a surveyed reference-point elevation for each well.

Monitoring network

The set of wells a GSA uses to measure groundwater elevation and quality for its plan. A production well qualifies when its construction details and reference elevation are known and its water-level readings are taken consistently.

Change in storage

The volume of groundwater gained or lost in a basin over a period, computed by the GSA from elevation change and aquifer storage properties, and reported annually under SGMA.

Records and the platform

System of record

The single authoritative source for a category of data. Waterwell IQ™ is designed as the system of record for a district’s wells: construction, tests, events, telemetry and documents in one timeline, with the arithmetic recomputed from the record rather than typed in.

Baseline

The reference against which later tests are compared: the as-built or post-rehabilitation specific capacity and efficiency, at a stated rate. Without a baseline the question ‘has this well declined?’ has no answer.

Well IQ score

Waterwell IQ’s composite condition index for a well, computed by the engine from specific-capacity trend, efficiency, water-level trend, age and event history. A ranking tool for the fleet, not a substitute for the underlying numbers.

Lifecycle model

The Markov-chain model in Waterwell IQ that estimates the probability of each condition state over coming years for a well, from the district’s own transition history, and evaluates the cost of rehabilitating, re-pumping, replacing or waiting.

Telemetry

Automatically collected operating data — flow, level, pressure, power, run state — read from SCADA or a data logger. Waterwell IQ takes it one way, read-only, through an agent that never connects into the control network.

Historian

The time-series database behind a SCADA system (Ignition’s tag historian, AVEVA PI, FactoryTalk Historian, VTScada and others) that stores tag values over time; the source an agent reads to backfill a well’s telemetry.

Ingestion

Reading a document — pump test, driller’s log, rehabilitation report — into structured data. In Waterwell IQ the AI extracts, a person reviews and approves, and only then does the record change.

Terms are defined the way the engine uses them; where a regulation defines a term differently, the regulation governs. Suggest an addition at [email protected].