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Chemical Quality
All groundwater contain salts carried in solution. The kinds and concentration of
salts depend upon the environment, movement, and source of ground water.
Ordinarily higher proportions of dissolved constituents are found in
groundwater than in Surface Waters because of the greater exposure to soluble
materials in geologic strata. Soluble salts found in groundwater percolating
through soils by soluble products of soil weathering, and of erosion by rainfall
and flowing water. Soluble fertilizers also add to groundwater.
Concentration of different chemical constituents are generally expressed in
parts per million (ppm) per litre. Total dissolved solids are measured by
electrical conductance (EC) of groundwater samples and are expressed in
milliomhos/cm.
Physical characteristics are expressed in colour, turbidity etc.
Bacteriological studies indicate presence of chloroform bacteria.
Quality Standards followed for irrigation, drinking water and industrial
purposes are shown separately.
The classification of water for irrigation use according to various criteria is given
below :- (Source : NABARD, 1989)
Table 6.7 : Classification of Irrigation water
Constituent
Water Classification
Class I
Class II
Class III
Total dissolved solids 0 - 700 ppm 700 - 2000 ppm Above 2000 ppm
Chloride
0- 150 ppm 150 - 500 ppm Above 500 ppm
Boon
0 - 0.5 ppm 0.5 - 2.5 ppm Above 2.5 ppm
Percentage Alkalies
Under 60% 60 - 75% Above 75%
Class I Water is regarded as entirely safe for irrigation under ordinary soil and
climate conditions, even for sensitive crops.
Class II Water is regarded as intermediate which may be safe for certain crops
but may be slightly harmful for other type of crops.
