Irrigation water quality problems are typically pH, nitrates, and salinity. Proper filtration and fertilizer injection/mixing into irrigation water (fertigation) is also important, yet sometimes overlooked. Helping growers of any size think about the implications of the long-term use of low quality irrigation water on soils and plants are also important for changing grower habits (for instance, the generally good practice of leaching soils as a method to reduce salt build up in the soil).
I hope this helps.
Dr. Jonathan Teichroew, PhD
Avocado and Pecan Tree Nursery Specialist