Technical Abstract: Increasing demands on fresh water supplies by municipal and industrial users means decreased fresh water availability for irrigated agriculture in semi arid and arid regions. There is potential for agricultural use of treated wastewaters and low quality waters for irrigation but this will require consideration of the impact of the water on the soil physical properties as well as on crop production. Current water quality criteria were developed as simple criteria designed to avoid problems under most conditions. Consideration of site specific conditions is necessary for better water utilization. Many waters considered unsuitable have value under specified climatic, soil and management conditions. Rather than classification of waters as suitable and unsuitable it is more useful to develop predictive relationships that describe how certain water quality parameters impact crop and soil responses. Incorporation of this information into models such as SWS, will allow evaluation of when and under what conditions low quality waters can be used for irrigation at specific sites. New guidelines are developed for SAR and EC criteria as well as use of high B containing waters.