Editing Salinity (section)

===Lakes and rivers===

[[Limnologist]]s and chemists often define salinity in terms of mass of salt per unit volume, expressed in units of mg/L or g/L.<ref name=wetzel/> It is implied, although often not stated, that this value applies accurately only at some reference temperature because solution volume varies with temperature. Values presented in this way are typically accurate to the order of 1%. Limnologists also use [[electrical conductivity]], or "reference conductivity", as a proxy for salinity. This measurement may be corrected for temperature effects, and is usually expressed in units of [[Siemens (unit)|μS/cm]].

A river or lake water with a salinity of around 70&nbsp;mg/L will typically have a specific conductivity at 25 °C of between 80 and 130 μS/cm. The actual ratio depends on the ions present.<ref>{{cite journal|last1=van Niekerk|first1=Harold|last2=Silberbauer|first2=Michael|last3=Maluleke|first3=Mmaphefo|title=Geographical differences in the relationship between total dissolved solids and electrical conductivity in South African rivers|journal=Water SA|date=2014|volume=40|issue=1|pages=133|doi=10.4314/wsa.v40i1.16|doi-access=free|bibcode=2014WatSA..40..133V }}</ref> The actual conductivity usually changes by about 2% per degree Celsius, so the measured conductivity at 5 °C might only be in the range of 50–80 μS/cm.

Direct density measurements are also used to estimate salinities, particularly in highly [[saline lake]]s.<ref name="anati"/> Sometimes density at a specific temperature is used as a proxy for salinity. At other times an empirical salinity/density relationship developed for a particular body of water is used to estimate the salinity of samples from a measured density.
{| id="SalinityTable" style="margin-left:auto; margin-right:auto;"
|-
! style="background:#B8E0F6" colspan="4"|Water   salinity
|-style="background:#87CEFA"
![[Fresh water]]
![[Brackish water]]
![[Saline water]]
![[Brine]]
|-style="background:#00BFFF"
! < 0.05%
! 0.05 – 3%
! 3 – 5%
! > 5%
|-style="background:#00BFFF"
! < 0.5 ‰
! 0.5 – 30 ‰
! 30 – 50 ‰
! > 50 ‰
|}