Is My Irrigation Water Safe? Testing for Lawns, Crops, Stock & Garden Use
Irrigation water quality problems rarely announce themselves immediately. A bore, dam, or surface water source that delivers adequate water in year one can be quietly degrading your soil, stressing your crops, blocking your drippers, and reducing your pasture yield — and the cause won't be obvious until the damage is visible and expensive to reverse.
The most common irrigation water problems in Australia — iron staining, salinity-related plant stress, sodium soil damage, and dripper blockage — all trace back to water chemistry that is invisible in the water itself. Saline water looks identical to fresh water. High-iron water runs clear from the tap and only stains once it contacts surfaces and oxidises. Knowing what is in your irrigation water before problems develop is significantly cheaper than treating the consequences after they do.
This guide covers the main irrigation water quality parameters, how they affect different uses — lawn and garden, food crops, pasture and dryland farming, stock water, and drip irrigation systems — and what testing is appropriate for each situation. It applies to any untreated irrigation water source: bores, dams, catchments, creeks, rivers, surface water, recycled water, and hydroponic source water.
Why irrigation water quality is different from drinking water quality
Irrigation water assessment uses a completely different framework from drinking water assessment. Where drinking water is benchmarked against the Australian Drinking Water Guidelines (ADWG), irrigation water is assessed against the ANZECC/ARMCANZ 2000 Water Quality Guidelines — a framework developed specifically for agricultural and irrigation applications.
The parameters that matter for irrigation are different from those that matter for drinking safety. Lead and arsenic — critical drinking water concerns — are largely irrelevant at typical irrigation water concentrations. Sodium, SAR, bicarbonate, and electrical conductivity — central to irrigation assessment — are only secondary concerns in a drinking water context.
A drinking water test result cannot tell you whether your irrigation water is suitable for your crops, your soil, or your livestock. An irrigation screen benchmarked against ANZECC guidelines is the appropriate tool.
The key irrigation water parameters and what they mean
Salinity — electrical conductivity and total dissolved solids
Electrical conductivity (EC) is the primary measure of overall salinity in irrigation water. It measures the concentration of all dissolved salts — chloride, sodium, sulphate, bicarbonate, calcium, magnesium, and others — in a single composite reading.
The ANZECC guideline threshold for irrigation water is 800 µS/cm for most crops and lawn grasses. Above this level, growth suppression becomes increasingly likely in salt-sensitive species. Above 3,000 µS/cm, only salt-tolerant species can be sustained under continued irrigation.
The cumulative nature of salinity is its most damaging characteristic. Every irrigation cycle deposits a small amount of salt in the soil profile. Without adequate rainfall to leach accumulated salts downward, salinity builds season after season — slowly degrading the productive capacity of irrigated land regardless of how the water looks or smells.
Coastal aquifers and shallow bores in low-lying areas are most prone to salinity. Dams fed by runoff from cleared agricultural land can also carry elevated salt loads, particularly after dry periods when accumulated surface salts wash off with the first rainfall.
Sodium and SAR — soil structure damage
Sodium is more damaging to soil than salinity alone. High sodium causes clay particles to disperse, collapsing soil pore structure and dramatically reducing infiltration and drainage. This condition — sodicity — is one of the most serious and difficult-to-reverse consequences of poor irrigation water quality.
The Sodium Adsorption Ratio (SAR) is the index used to assess sodium hazard in irrigation water. It is calculated from the measured concentrations of sodium, calcium, and magnesium, and expresses the relative proportion of sodium compared to the other major cations. The ANZECC guideline threshold for SAR is 6.0 for most soil types — above this level, soil structural degradation becomes increasingly likely under continued irrigation.
A bore or dam delivering water with elevated SAR can progressively reduce drainage and aeration in irrigated paddocks and gardens even where the EC is within acceptable limits. The effects appear slowly — reduced infiltration after rain, waterlogging in previously free-draining areas, declining pasture density — and are often attributed to compaction or climate rather than water quality.
Iron and manganese — staining and system damage
Iron and manganese are the most commonly reported irrigation water problems in Australia, particularly from shallow bores drawing on iron-rich geology in Western Australia, South Australia, and coastal Queensland.
In its dissolved ferrous form, iron is invisible in water. It oxidises to insoluble ferric iron when it contacts air — precipitating as the characteristic orange-brown stain on any surface contacted by irrigation spray. The ANZECC guideline for iron is 0.3 mg/L. Many Australian bores operate well above this threshold.
Manganese causes darker staining — black-brown deposits on hard surfaces and inside irrigation fittings. The ANZECC guideline for manganese is 0.2 mg/L. At elevated concentrations, manganese also accumulates inside drip emitters, contributing to progressive blockage.
Beyond staining, elevated iron and manganese affect plant health at higher concentrations through phytotoxicity — primarily relevant for sensitive horticultural crops.
Hardness and bicarbonate — dripper blockage and scale
Total hardness — the combined calcium and magnesium content — determines the scaling potential of irrigation water. High hardness combined with elevated bicarbonate causes carbonate precipitation inside drip emitters, soaker hose fittings, and micro-spray heads when water contacts air or changes temperature.
The ANZECC guideline for bicarbonate in irrigation water is 400 mg/L as HCO3. Above this level, carbonate scale accumulation becomes increasingly likely without acid injection or regular emitter maintenance. Blocked drippers create uneven coverage, dry patches, and compounding plant stress — and replacing blocked drip irrigation infrastructure is a significant cost on larger systems.
Severe calcium carbonate blockage is common in drip irrigation systems using hard, high-bicarbonate bore water. The relevant threshold for drip irrigation is a Langelier Saturation Index (LSI) calculation combining pH, calcium, alkalinity, and temperature. In practical terms, water with bicarbonate above approximately 500 mg/L and calcium above 100 mg/L in combination warrants assessment before use in a drip system.
Boron — crop-specific toxicity
Boron is phytotoxic — directly toxic to plants — at concentrations that are orders of magnitude lower than most other parameters of concern. The ANZECC guideline for sensitive species is 0.5 mg/L. Many fruit trees, grapes, and ornamentals show toxicity symptoms at concentrations between 0.5 and 2.0 mg/L.
Boron is naturally elevated in some Australian aquifer systems, particularly in parts of SA and inland NSW. It has no taste, colour, or odour in water. Boron toxicity in plants presents as characteristic marginal leaf scorch — brown, papery edges on older leaves — that is often misdiagnosed as drought stress or other nutrient deficiencies.
Nitrate and nutrients
Elevated nitrate in irrigation water is most relevant for stock water applications, where the ANZECC guideline for livestock is 100 mg/L as NO3. For crop irrigation, nitrate represents a nutrient input that needs to be accounted for in fertiliser management rather than a direct toxicity concern at typical concentrations.
For properties with grazing livestock relying on bore or dam water, nitrate should be included in any water quality assessment — elevated nitrate from agricultural runoff and septic leachate is documented in groundwater across many Australian farming regions.
pH
pH affects nutrient availability, soil microbiology, and the effectiveness of any water treatment or fertigation program. Very acidic irrigation water (below pH 6.0) can mobilise soil aluminium and manganese. Very alkaline water (above pH 8.5) reduces the availability of phosphorus, iron, zinc, and manganese in the soil. For drip irrigation, pH above 7.5 in combination with elevated calcium and bicarbonate accelerates emitter calcification.
How risk varies by water source
Bore water
Bore water chemistry is determined by the aquifer it draws from. Salinity varies enormously — coastal aquifers in WA and SA tend toward moderate salinity with elevated iron and manganese; inland aquifers can be highly saline and may carry elevated sodium, fluoride, or boron from geological sources. Agricultural aquifers may carry nitrate, pesticide residues, or PFAS from historical land use above.
The Swan Coastal Plain Superficial Aquifer underlying Perth's metropolitan area is the most widely tested irrigation bore aquifer in Australia — characterised by moderate salinity, low pH, elevated iron and manganese, and in some areas, PFAS from airport and defence facility contamination. For a full treatment of Perth's irrigation bore water profile, see our Perth bore water irrigation testing guide.
Dam and surface water
Dam and creek water quality reflects the catchment it drains. Agricultural catchments carry elevated salinity from fertiliser and irrigation return flows, potential herbicide and pesticide residues, elevated turbidity, and significant seasonal variation. Microbiology is a concern for food crop irrigation — E. coli from livestock access to waterways or upstream contamination represents a food safety risk when water contacts edible plant parts.
Dam water quality can change significantly between seasons and after significant rainfall events. A single annual test may not capture the full range of variation — testing after significant inflow events is relevant for properties relying on dam water for sensitive crops.
Recycled water
Recycled water supplied through Class A recycled water schemes is managed to specific quality standards in each state, but private recycled water from on-site greywater or treated effluent systems varies widely. Key parameters are salinity, sodicity, pathogens, and any industrial chemicals from household sources.
How risk varies by use case
Lawn and garden irrigation — salinity, SAR, iron, manganese, and pH are the primary concerns. Most established lawn species tolerate moderate salinity; sensitive ornamentals and food plants require lower EC.
Vegetable and food crop irrigation — microbiology becomes relevant alongside chemical parameters. E. coli in irrigation water applied to leaf vegetables is a direct food safety concern. Boron toxicity affects a wide range of food crops at concentrations that would be unremarkable in other contexts.
Drip irrigation systems — iron, manganese, calcium, and bicarbonate are the infrastructure concerns. A bore that tests acceptable for spray irrigation may be entirely unsuitable for drip without treatment.
Pasture and broadacre irrigation — salinity and SAR dominate. Soil structural integrity over multiple seasons is the primary long-term risk.
Stock water — salinity (total dissolved solids), nitrate, sulphate, blue-green algae (for dams), and pH are the key parameters. The ANZECC stock water guidelines specify thresholds by livestock type — cattle and sheep have different tolerances to horses and poultry.
How irrigation water quality varies by region
Western Australia — Iron and manganese are elevated across much of Perth's Superficial Aquifer. Salinity increases toward the coast. Bicarbonate-driven scale is a common problem in drip systems across the metropolitan area.
South Australia — Shallow aquifers in agricultural regions carry elevated bicarbonate and in some areas elevated boron. Murray system salinity affects properties irrigating from channels and drains. Some SA aquifer systems are naturally elevated in fluoride.
Queensland — Bore water across coastal QLD frequently carries elevated iron. Shallow aquifer salinity is common in low-lying areas. Dam and surface water in agricultural catchments may carry pesticide residues from cropping runoff.
New South Wales — Murray-Darling salinity affects irrigation water quality across the western agricultural zone. Groundwater nitrate elevation from intensive agriculture is documented across parts of the Liverpool Plains and other farming regions.
Victoria — Northern Victorian irrigation areas sourced from the Murray system carry seasonal salinity variation. Local bore water quality varies by aquifer.
What a complete irrigation water test covers
A meaningful irrigation water test appropriate for Australian conditions includes:
Full water chemistry — pH, EC, TDS, SAR, hardness, alkalinity, calcium, magnesium, sodium, potassium, chloride, sulphate, bicarbonate, carbonate
Iron and manganese — both total and dissolved where relevant
Nutrients — nitrate, nitrite, ammonia, phosphorus
Boron — particularly in SA, inland NSW, and properties with sensitive crops
Microbiology — E. coli and Thermotolerant Coliforms, particularly for food crop irrigation and stock water
PFAS — for properties near airports, defence facilities, or industrial sites
Pesticides and herbicides — for rural properties with agricultural land use in the catchment
Results should be compared against the ANZECC/ARMCANZ 2000 guidelines for irrigation and stock water — the relevant Australian framework for agricultural water quality assessment.
Safe Water Lab offers irrigation and farm water testing kits covering all of the above parameters, with results benchmarked against ANZECC/ARMCANZ 2000. View our farm and irrigation water testing kits →
When to test
For any bore, dam, or surface water supply used for irrigation:
Before first use — establish a baseline before applying the water to soil or crops
Annually — groundwater chemistry varies seasonally and with recharge events
After significant rainfall — dam water chemistry changes with inflow; bore recharge can introduce surface contamination
After nearby land use changes — new agricultural activity, development, or reported contamination in the catchment
When plant or livestock health problems are unexplained — poor growth, leaf scorch, soil structural problems, livestock production decline.
Also using your bore or dam for drinking?
An irrigation screen is not an assessment of drinking water safety. The parameters and benchmarks used for irrigation assessment are completely different from those relevant to drinking water safety. An irrigation screen does not test for the contaminants — including E. coli at full sensitivity, arsenic, lead, uranium, PFAS, and nitrate at health-relevant thresholds — that determine whether water is safe to drink.
If you use your water source for drinking or household purposes, see our bore water drinking safety guide and our bore water drinking kits, benchmarked against the Australian Drinking Water Guidelines.
Safe Water Lab provides mail-order irrigation and farm water testing across Australia using NATA-accredited laboratory analysis. All results are benchmarked against ANZECC/ARMCANZ 2000 irrigation and stock water guidelines with plain-language explanations.