Rock-water interaction and consequent liberation of ions causes salinity of water.
The contamination of water after the use cycle is represented by further increase
in salinity. The present work discusses the application of microwave remote sensing
to detect salinity of waters. The emissivity values recorded at microwave frequencies
depend on the complex dielectric constant of the media, state of polarization and
angle of incidence of microwaves. At lower microwave frequencies (0.5 – 15.0 GHz),
the real part of the dielectric constant decreases, while the imaginary part increases
with increase in salinity. At higher microwave frequencies (> 15.0 GHz) the dielectric
constant becomes independent of salinity. The emissivity and brightness temperature
responses have higher values for vertical polarization, compared with the horizontal
polarization of electromagnetic waves. An increase in angle of incidence of microwaves
lowers the emissivity in horizontal polarization, while in the other polarization the trend is
reversed. The computed depth of penetration in river waters is about 20.0 cm while in
sea water maximum is 1.0 cm. Two layered models are discussed to demarcate water
logged and salt affected areas. A frequency range of 1.0 – 2.0 GHz is found to be best
suited for determination of salinity of natural waters and soils.