Table 3-6: Water Quality Objectives for Agricultural Supplya (in mg/l)

Parameter Threshold Limit Limit for Livestock Watering
Physical:
pH 5.5-8.3 4.5-9.0
TDS 10,000.0
EC (mmhos/cm) 0.2-3.0
Inorganic Parameters:
Aluminum 5.0 20.0 5.0
Arsenic 0.1 2.0 0.2
Beryllium 0.1 0.5
Boron 0.5 2.0 5.0
Chloride 142.0 355.0
Cadmium 0.01 0.5 0.05
Chromium 0.1 1.0 1.0
Cobalt 0.05 5.0 1.0
Copper 0.2 5.0 0.5
Flouride 1.0 15.0 2.0
Iron 5.0 20.0
Lead 5.0 10.0 0.1
Lithium 2.5b
Manganese 0.2 10.0
Molybdenum 0.01 0.05 0.5
Nickel 0.2 2.0
NO3+NO2 (as N) 5.0 30c 100.0
Selenium 0.02 0.05
Sodium adsorption
ratio (adjusted)d
3.0 9.0
Vanadium 0.1 1.0 0.1
Zinc 2.0 10.0 25

Notes:

a. For an extensive discussion of water quality for agricultural purposes, see "A Compilation of Water Quality Goals," Central Valley Regional Water Quality Control Board, May 1993.

b. For citrus irrigation, maximum 0.075 mg/l.

c. For sensitive crops. Values are actually for NO3-N + NH4-N.

d. Adjusted SAR = { Na /[(Ca + Mg)+2]0.5 }{1 + [8.4 – pHc]}, where pHc is a calculated value based on total cations, Ca + Mg, and CO3 + HCO3, in me/l. Exact calculations of pHc can be found in “Guidelines for Interpretation of Water Quality for Agriculture” prepared by the Univ. of California Cooperative Extension.