Resource information
The ionic composition of water in the vadose zone of the Salt River Valley in south central Arizona was studied for three different water regimes: desert, irrigated, and flooded by urban runoff. The desert area exhibited high salinity in the top 10 m, probably due to concentration of salts over several years. Below 15 m, the salinity decreased with depth and approached the salinity of the native ground water. For the irrigated area, the chemical composition of the soil water was similar to that of the applied water but concentrations were higher. The irrigation efficiency calculated from the salinities of the irrigation and soil water was 78%.The average NO3-concentration from five of six sites was 100 mg/l, but was as high as 24,000 mg/l at another. Soil water from the urban runoff site had an electrical conductivity that was about three times less than that from the irrigated site, showing the effect of leaching with rain water. The observed salt distributions in the vadose zone were reasonably correlated to land use at the sites sampled.
