How to Read a California Irrigation Water Test (SAR, EC, Bicarbonate)
A water analysis lands on your desk as a column of numbers and units — pH, EC, HCO3-, Ca, Mg, Na, SAR, Cl, B — and the lab almost never tells you which lines matter for the operation in front of you. This guide does. It walks a typical California irrigation water report parameter by parameter, gives you the specific numbers PCAs and growers actually act on, and shows you how each line translates into a real problem: emitter clogging, lost infiltration, salinity stress, or a crop-specific toxicity. By the end you should be able to read your own report the way a seasoned PCA would and know which lever the water is asking for.
It is written for growers and the PCAs, CCAs, and agronomists who advise them. It is vendor-neutral on chemistry and method. Where a threshold cannot be tied to a published source it is stated qualitatively and flagged for confirmation against your extension reference rather than asserted as fact, because the wrong number confidently stated is worse than an honest "confirm this against your extension reference."
First, three things the report is actually telling you
Before you read any single line, understand that an irrigation water test is answering three separate questions, and they do not interact the way people assume:
- Will this water plug my system? — the clogging/scale question, driven mostly by bicarbonate, pH, and hardness.
- Will this water cut my infiltration? — the sodium/infiltration question, driven by SAR read against EC.
- Will this water stress or burn my crop? — the salinity and toxicity question, driven by EC, chloride, sodium, and boron, against crop-specific tolerances.
A water can fail one of these and pass the others. High-bicarbonate water can plug emitters while posing no salinity problem at all. High-SAR, low-EC water can destroy infiltration while reading "low salt." This is why you never judge water on a single headline number — you read the parameters in groups, against the question each group answers.
California context sets the baseline. Central Valley and Central Coast groundwater is commonly hard, alkaline, high in bicarbonate (HCO3-), and saline (general agronomic and extension literature; UC ANR). That is the chemistry most of this audience is starting from, and it is why bicarbonate, SAR, and EC are the three lines this guide spends the most time on.
pH — the dial, not the disease
What it measures. pH is the intensity of acidity or alkalinity right now, on a 0–14 scale. It tells you where the water sits at this instant. It does not tell you how hard the water will fight to stay there — that is alkalinity (below).
Thresholds to act on. A common acidification target growers design toward is pH ~6.5 (UMass Amherst Greenhouse & Floriculture, "Water Quality: pH and Alkalinity"). Water pH above ~7.5 is your flag to treat bicarbonate as a live concern, especially in combination with elevated HCO3- (UC ANR, "Maintenance of Microirrigation Systems: Chemical Precipitation," ucanr.edu/site/maintenance-microirrigation-systems/chemical-precipitation).
What it means for the operation. High pH itself rarely damages the crop directly; its damage is indirect. Elevated pH reduces the plant-availability of iron, manganese, zinc, and phosphorus, which shows up as high-pH iron chlorosis — interveinal yellowing on the newest leaves while the veins stay green (USU Extension; UMass Amherst Greenhouse & Floriculture, "Water Quality: pH and Alkalinity"). The single most important thing to understand about the pH line: it is the symptom and the dial you watch, not the load you are correcting. If alkalinity is high, you can chase pH all day and it will keep climbing back, because the bicarbonate reserve keeps pulling it up.
Alkalinity and bicarbonate (HCO3-) — the buffering load
What they measure. Alkalinity is the water's capacity to neutralize acid — its buffering reserve. In most California irrigation water that reserve is carried almost entirely by bicarbonate (HCO3-). Alkalinity is usually reported as ppm of calcium carbonate (CaCO3); bicarbonate is usually reported in milliequivalents per liter (meq/L) or ppm. They are related but not identical units, so check which one your lab used before comparing to a threshold.
Thresholds to act on. The combined field rule most PCAs carry: HCO3- above 2 meq/L (120 mg/L) combined with pH above ~7.5 is your clogging-risk flag (UC ANR, "Maintenance of Microirrigation Systems: Chemical Precipitation," ucanr.edu/site/maintenance-microirrigation-systems/chemical-precipitation). Expressed as alkalinity (ppm CaCO3), roughly 30–60 ppm is often cited as optimal for many crops, with corrective action commonly considered once alkalinity or bicarbonate climbs above ~150 ppm (UMass Amherst Greenhouse & Floriculture, "Water Quality: pH and Alkalinity").
What it means for the operation. This is the most fixable problem on most California water tests, and the one most often misread. When bicarbonate-rich water sits, warms, or loses CO2 at an emitter orifice or the end of a lateral, bicarbonate converts to carbonate and precipitates as calcium-carbonate (lime) scale. That scale plugs drip and micro-sprinkler emitters, reduces infiltration and root-zone oxygenation, and contributes to nutrient lockup (UC ANR, "Maintenance of Microirrigation Systems: Chemical Precipitation," ucanr.edu/site/maintenance-microirrigation-systems/chemical-precipitation). Bicarbonate is also the engine behind that high-pH iron chlorosis. Because neutralization is consumed as water moves through the system, clogging tends to show up "at the end of the line" first, where CO2 has had the most time to off-gas. For a deeper treatment of this single parameter, see our guide at /articles/high-bicarbonate-alkaline-irrigation-water-guide.
EC and TDS — the salinity load
What they measure. Electrical conductivity (EC) measures the total dissolved-salt content of the water by how well it conducts current; it is reported in deciSiemens per meter (dS/m). Total dissolved solids (TDS) is the same salinity story expressed as ppm or mg/L. They move together; EC is the field standard (UC ANR water-quality guidance).
Thresholds to act on. Salinity tolerance is crop-specific, so there is no universal "too salty" line — you read EC against your crop's threshold. The decision point is approaching or exceeding the crop tolerance, at which point yield begins to decline. Confirm your crop's salinity threshold against a current UC ANR or extension table.
What it means for the operation. Above the crop threshold, salinity drives osmotic stress — the plant spends energy pulling water against the dissolved-salt gradient, and yield falls. EC also sets the context for reading SAR (next section): the same SAR is far more damaging to infiltration at low EC than at high EC. So EC is doing double duty on the report — it is both a direct salinity hazard and the denominator you read sodium hazard against.
Calcium, magnesium, and sodium (Ca, Mg, Na) — the cations behind SAR
What they measure. These three cations, usually reported in meq/L, are the inputs to the sodium hazard calculation. Calcium and magnesium are the "good" cations for soil structure; sodium is the problem one.
What they mean on their own. You rarely act on Ca, Mg, or Na in isolation — their importance is in the ratio between sodium and the calcium-plus-magnesium pair, which is exactly what SAR captures. Note them, then read SAR. (Sodium and chloride also carry their own crop-toxicity story, covered under chloride below.)
SAR and adjusted SAR — the sodium/infiltration hazard
What it measures. The sodium adsorption ratio (SAR) measures sodium hazard relative to calcium and magnesium — it is the ratio of Na to the Ca/Mg pair (UC ANR water-quality guidance). Adjusted SAR refines that calculation to account for how bicarbonate and the precipitation of calcium carbonate change the effective calcium available to the soil, which matters precisely in the high-bicarbonate California waters this guide is about (UC ANR water-quality guidance).
Thresholds to act on. The hazard is crop- and soil-dependent and — critically — must be read against EC. High SAR combined with low EC is the dangerous combination: that is when sodium disperses soil aggregates and infiltration collapses. Confirm the SAR/EC infiltration-hazard bands against a UC ANR or other current extension reference for your soil.
What it means for the operation. High SAR disperses the soil surface, seals it, and cuts infiltration — water ponds, advances slowly, and wets shallowly (UC ANR water-quality guidance). The classic trap: a grower reads a low EC and concludes the water is "clean," not realizing that low EC is exactly what makes a high-SAR water destructive to infiltration. You must read SAR and EC together, on the same report, every time. For the infiltration side of the problem in depth, see our guide at /articles/lower-irrigation-water-ph-without-sulfuric-acid for how bicarbonate and sodium corrections interact.
Chloride (Cl) and sodium toxicity — the leaf-burn risk
What it measures. Chloride is reported in meq/L or ppm. Along with sodium, it is the parameter behind specific-ion toxicity, which is a different problem from general salinity.
Thresholds to act on. Chloride and sodium toxicity thresholds are crop-specific and are especially relevant for sensitive perennials and for sprinkler-applied water, where foliar uptake adds a second exposure route on top of root uptake. Confirm your crop's chloride and sodium tolerance against a UC ANR or extension table.
What it means for the operation. Specific-ion toxicity shows up as marginal leaf burn — scorching that begins at leaf tips and edges — distinct from the general stunting of osmotic salinity stress. Tree and vine crops, and anything irrigated overhead, are where this line earns close reading. A water can be acceptable on total EC yet still carry enough chloride or sodium to burn a sensitive crop, particularly under sprinklers.
Boron (B) — the narrow-window micronutrient
What it measures. Boron, reported in ppm, is a micronutrient with an unusually narrow band between deficiency and toxicity.
Thresholds to act on. Boron tolerance is strongly crop-specific and the deficient-to-toxic window is narrow, so this is a parameter where a generic threshold is genuinely misleading — confirm against a crop-specific UC ANR / extension boron-tolerance table.
What it means for the operation. Boron toxicity also presents as marginal leaf burn and is hard to remove from water by conventional acidification or by gypsum — it largely is not addressed by the bicarbonate and sodium corrections that handle the other lines on the report. On California waters where boron runs high, the practical levers are blending/dilution or selecting more boron-tolerant crops or varieties, not a chemistry correction. Flag it, confirm the crop threshold, and treat it as its own problem.
The parameter reference table
Carry this as a field decision aid, not a regulatory limit sheet. Your crop, soil, emitter type, and source water all shift the exact trigger, and each number below should be confirmed against a current UC ANR or extension reference before you build a program around it.
| Parameter | Typical units | Optimal / target | Watch | Act | What it governs |
|---|---|---|---|---|---|
| pH | (0–14) | ~6.5 target | 7.0–7.5 | > 7.5 with high HCO3- | Dial for bicarbonate; high-pH chlorosis (UMass Amherst; USU Extension) |
| Bicarbonate (HCO3-) | meq/L (or ppm) | < ~1.5 meq/L | ~1.5–2 meq/L | > |
Lime-scale clogging; nutrient lockup (UC ANR Microirrigation) |
| Alkalinity (as CaCO3) | ppm | ~30–60 ppm | ~60–150 ppm | > ~150 ppm | Buffering capacity; acid demand (UMass Amherst) |
| EC | dS/m | crop-specific | approaching crop threshold | above crop threshold | Salinity/osmotic stress; sets SAR context (UC ANR) |
| TDS | ppm / mg/L | crop-specific | approaching crop threshold | above crop threshold | Same salinity story as EC (UC ANR) |
| SAR / adjusted SAR | (ratio) | crop/soil dependent | rising vs. Ca/Mg | high SAR with low EC | Sodium dispersion; infiltration loss (UC ANR) |
| Ca / Mg / Na | meq/L | — | — | — | Cation inputs to SAR; Na also a toxicity ion |
| Chloride (Cl) | meq/L (or ppm) | crop-specific | approaching crop threshold | above crop threshold | Specific-ion toxicity; leaf burn (UC ANR) |
| Boron (B) | ppm | crop-specific (narrow) | near crop tolerance | above crop tolerance | Toxicity; narrow window (UC ANR) |
A decision framework: when to act, and which lever
Reading the numbers is half the job; the other half is turning them into a decision. Work the report in this order, because the order separates problems that have different fixes.
- Group the parameters by question. Sort the report into the three buckets above — clogging/scale (pH, HCO3-, alkalinity, hardness), infiltration (SAR read against EC), and salinity/toxicity (EC, Cl, Na, B against crop). A line only matters in the context of the question its group answers.
- Find which question is actually failing. Apply the thresholds. Is HCO3- over ~2 meq/L with pH over 7.5 (clogging)? Is SAR high while EC is low (infiltration)? Is EC over the crop threshold, or are chloride or boron near a crop toxicity line (salinity/toxicity)?
- Match the lever to the failing question — they are not interchangeable. Bicarbonate/scale responds to acidification or a biological water conditioner. Sodium/infiltration responds to a calcium source such as gypsum. Salinity (EC) is only truly reduced by reverse osmosis or blending. Boron is largely a blending-or-crop-selection problem. Using the wrong lever — gypsum for bicarbonate, acid for boron — wastes money and fixes nothing.
- Account for combined waters. California groundwater rarely fails just one question. High bicarbonate frequently travels with high SAR and high salinity, and the correction for one can shift another, so combined waters usually need a layered program rather than a single product.
- Re-test to confirm it holds. Groundwater chemistry drifts across a season and across years as aquifer levels change, so any single test is a snapshot. Re-test after any source change and after starting a correction program, to verify pH, bicarbonate, and SAR are holding where you designed them to.
| If this is the failing question | Read these lines | First-line levers to evaluate |
|---|---|---|
| Clogging / scale | pH, HCO3-, alkalinity, hardness | Acid injection or a biological water conditioner; design toward ~pH 6.5 |
| Infiltration loss | SAR read against EC | Gypsum (calcium source); pair with bicarbonate correction if pH/HCO3- also high |
| Salinity (osmotic) | EC / TDS vs. crop | Reverse osmosis or blending/dilution |
| Specific-ion toxicity | Chloride, sodium vs. crop | Blending/dilution; crop/variety selection; watch sprinkler vs. drip |
| Boron toxicity | Boron vs. crop | Blending/dilution; boron-tolerant crops/varieties |
Where a water-chemistry correction fits
For the clogging/scale question specifically, one of the levers worth evaluating is a biological water conditioner. AguapHlo is a biological water conditioner that corrects hardness, alkalinity, high bicarbonate, and salinity, sequesters and removes inanimate scale and bicarbonate, and improves infiltration and irrigation-system performance. For operations running an organic program or moving off continuous mineral-acid handling, it belongs alongside acidification and gypsum as an option to weigh on its water-chemistry and agronomic merits and to validate against your own water test. Correct the water. Correct the system.
A note on scope: AguapHlo is a water-chemistry and agronomic product. This guide and that option address bicarbonate, alkalinity, hardness, salinity, scale, and infiltration only — not biofouling, sanitation, or pest management, which are separate problems with separate (and separately regulated) tools.
Get a water-chemistry diagnosis
The fastest way to act on the report in front of you is to have each line read back against these thresholds and turned into a correction plan matched to your crop, soil, and irrigation system — a water-chemistry diagnosis rather than a generic recommendation. If you would like a parameter-by-parameter read of your own lab report, you can request a water-chemistry diagnosis through HydroOS.
Contact details for that request are a placeholder pending publication — no phone or email is published here yet.
Frequently asked questions
What numbers on an irrigation water test matter most in California?
For most California growers the three lines that drive the most decisions are bicarbonate (HCO3-) for emitter clogging and scale, SAR read against EC for infiltration, and EC/TDS for salinity — with chloride and boron checked against your specific crop for toxicity (UC ANR water-quality guidance). The reason is the regional baseline: Central Valley and Central Coast groundwater commonly runs hard, alkaline, high in bicarbonate, and saline (general agronomic and extension literature; UC ANR). Read those groups against the question each one answers — clogging, infiltration, or salinity/toxicity — rather than judging the water on any single headline number.
How do you read SAR and EC together?
You read them as a pair because the same SAR is far more damaging at low EC than at high EC. SAR measures sodium hazard relative to calcium and magnesium; high SAR disperses soil and cuts infiltration (UC ANR water-quality guidance). But that dispersion is worst when EC is low — low-salt water with high sodium is the combination that seals a soil surface. The common mistake is reading a low EC as "clean water" without checking SAR. Always look at both lines on the same report, and use the SAR/EC infiltration-hazard bands from a UC ANR or other current extension reference for your soil.
What is a high bicarbonate level on a water test?
A widely used field flag is bicarbonate above 2 meq/L (120 mg/L) combined with water pH above ~7.5, which signals rising lime-scale clogging risk in drip and micro systems (UC ANR, "Maintenance of Microirrigation Systems: Chemical Precipitation"). Expressed as alkalinity (ppm CaCO3), roughly 30–60 ppm is often cited as optimal for many crops, with corrective action commonly considered above ~150 ppm (UMass Amherst Greenhouse & Floriculture, "Water Quality: pH and Alkalinity"). Treat these as decision points to confirm against a UC ANR or extension source for your crop and system, not as fixed regulatory limits.
My EC is low — does that mean my water is fine?
Not necessarily. Low EC means low total salinity, but it tells you nothing about sodium hazard, bicarbonate, chloride, or boron. In fact, low EC combined with high SAR is the most damaging infiltration scenario, because there is not enough calcium and magnesium in solution to hold the soil structure against the sodium (UC ANR water-quality guidance). Read the whole report: a low-EC water can still plug your system on bicarbonate and seal your soil on SAR.
How often should I test my irrigation water?
Treat any single test as a snapshot, because California groundwater chemistry drifts within a season and across years as aquifer levels change. Re-test at meaningful intervals, after any change in source or blend, and — critically — after starting a correction program, to verify that pH, bicarbonate, and SAR are actually holding where you designed them to. The report only earns its keep when you act on it and then confirm the action worked.
Sources
- UC Agriculture and Natural Resources (UC ANR), "Maintenance of Microirrigation Systems: Chemical Precipitation" — bicarbonate above
2 meq/L (120 mg/L) with pH above ~7.5 drives calcium-carbonate (lime) scale and emitter clogging. ucanr.edu/site/maintenance-microirrigation-systems/chemical-precipitation - UMass Amherst Greenhouse & Floriculture, "Water Quality: pH and Alkalinity" — pH ~6.5 target; alkalinity 30–60 ppm CaCO3 optimal for most plants; >150 ppm problematic (iron chlorosis). ag.umass.edu/greenhouse-floriculture
- Utah State University (USU) Extension — high/alkaline-pH iron chlorosis as a visible symptom of elevated pH. extension.usu.edu
- UC ANR — additional water-quality interpretation: EC/salinity crop thresholds, SAR and infiltration hazard, chloride/boron crop tolerances. ucanr.edu
- General agronomic and extension literature — sodium adsorption ratio (SAR) and SAR/EC infiltration concepts, calcium-carbonate scale chemistry, adjusted-SAR method, specific-ion (chloride/sodium/boron) toxicity, regional California groundwater character.
This article addresses irrigation-water chemistry, scale, salinity, infiltration, and agronomic performance only. It is informational and does not constitute a recommendation for any specific product, rate, or program; design and verify all correction programs against current laboratory results and qualified agronomic advice.