Salting your plants
I have 392 mg/liter sodium in my well water. Which plants can take this and which cannot? With overhead watering, I've seen the leaves turning brown on the lilacs and the blueberries....but when they are watered from the root, they seem fine. The tomatoes, sunflowers, daylilies and irises don't care one whit. Neither do the peas.
While the 392 mg/liter sounds like a high number it does not tell the complete story. The sodium hazard is calculated in terms of the sodium adsorption ratio or SAR. The SAR is calculated from the ratio of sodium to calcium and magnesium. The Ca and Mg ions tend to counter the effects of sodium. If, like most of us in Douglas County you are planting in clay soil you may need to amend your soil with additional Ca and Mg. Have you soil tested first to see what your current levels are.
That said, blueberries In particular need an adequate supply of water from blossom until the fall rains arrive. Since they have a shallow root system a drip or under canopy irrigation is the best approach. For your lilacs, if they are established cut back on your water. Neil Bell, OSU Extension Agent for Marion County, has done considerable research on lilacs and has found them to be extremely drought tolerant. Neil says, "Watering is the single worst thing you can do for these plants." At this point you may want to worry more about how your plants are being watered rather than the sodium content. Cut back on the water to your lilacs and use a drip irrigation on your remaining garden.
If you have further questions on this subject contact your local Master Gardeners. They are located in the Douglas County Courthouse Annex at 1134 SE Douglas Ave. Roseburg OR 97470. They can also be reached by phone at 541-672-4461 and their summer hours are Monday through Friday 1 to 4 p.m. The Master Gardeners will also be able to give you information on soil testing in the area.