For professionals, students, regulators and researchers in the field of hydrology and hydrogeology, I am finalising a range of useful calculators. These will be released soon.

## Permeability Calculator

**Permeability calculator** estimates permeability from field tests using a constant head permeameter and circular holes in unsaturated materials. The calculator comes with a diagram of the *Cromer Constant Head Permeameter*, a field permeability nomogram, and detailed Notes.

## Stream Flow Calculator

**Stream flow calculator** allows you to estimate flow volume in streams, rivers, pipes, canals, square or rectangular channels and all other flowing water bodies of any cross sectional shapes and dimensions. Enter values for water depth and the velocity of water flow at up to ten locations on a cross section. From these entries, the calculator determines a volume rate of flow. Choose from over 40 different units of volume flow. The calculator comes with typical cross sectional diagrams of a stream, and detailed Notes.

## Stream Load Calculator

**Stream load calculator** allows you to estimate the weight of a constituent (suspended or dissolved) passing a fixed point in a stream, river, canal, pipe, etc. in a specified time, if its concentration and the volume rate of flow of the water are known. (Use the Stream Flow calculator to obtain volume rate of flow first.) Choose from almost 40 different units, from g/sec to lb/month to kt/year. The calculator comes with detailed Notes.

## Stream Mix Calculator

When two streams or rivers merge, or water is discharged from a pipe to a stream, **Stream Mix Calculator** estimates the concentrations of dissolved or suspended constituents after mixing, by assuming steady state conditions and instantaneous mixing. The approach can be applied to reactive materials as well, because the assumption of instantaneous mixing means there is no change due to reaction. Given constituent concentrations for Stream 1 and Stream 2, the calculator determines the Mixed values for most commonly measured field parameters, and any other constituents. (It also automatically converts dissolved oxygen in mg/L to % saturation by correcting for temperature, elevation and chloride content.) The calculator comes with detailed Notes.

## Catchment Flow Calculator

Catchment flow is the total volume of water passing a fixed cross-section of a stream or river, and derived only from a defined catchment area. If, as in the **Catchment Flow Calculator**, the volume is measured over weeks, months or annually, it tends to be average volume flow rather than peak flow arising from rain events. Choose a time period, rain and a runoff ratio, and the volume of water discharging from the catchment is calculated for each time period. (Then apply Stream load calculator and/or Stream Mix calculator). Choose from 12 volume units, such as cubic metres (m3, or kilolitres, kL), gallons (gal), cubic feet (ft3), and for larger volumes, acre feet (acre.ft), megalitres (ML), gigalitres (GL), teralitres (TL, or km3),and so on, over the defined time period. The calculator comes with detailed Notes.