Field parameters with a stabilisation test, major-ion chemistry with a charge balance check, a Piper diagram, water-type naming, groundwater flow direction from three wells, and the ochre-colour pH estimate for drainage from disturbed ground.
| # | pH | EC | T | DO | Eh |
|---|
A sample taken before the parameters stabilise is a sample of the casing, not the aquifer. Three consecutive readings within pH ±0.1, EC ±3% and temperature ±0.5 °C is the usual criterion.
Head is the water-table elevation: casing elevation minus depth to water.
Water flows down the head gradient. Add hydraulic conductivity and porosity and this becomes a seepage velocity — which is what tells you when a plume arrives.
Iron precipitates in drainage from disturbed ground are pH-controlled minerals. The stain on the streambed estimates the chemistry before a probe leaves the bag.
Concentrations are not activities. In fresh water a doubly charged ion behaves as though only about two-thirds of it were there, and ignoring that puts the saturation index out by a whole unit. The Davies equation is used, which holds to roughly I = 0.5 molal.
Stiff gives every water a shape you recognise across a whole catchment at a glance. Schoeller puts several analyses on one logarithmic scale so that waters of very different strength can still be compared line for line.
A high SAR replaces calcium with sodium on the clay, which collapses the soil structure and stops it draining. The water can look perfectly clean and still ruin the ground it is put on.