Tile drainage systems of the San Joaquin Valley were monitored for nutrients (nitrogen and phosphorus). The objectives were to determine: (1) the average nutrient concentrations in tile drainage, (2) the magnitudes of annual, areal and seasonal variability of nutrients and discharges, (3) if a possible correlation exists between nutrients and agricultural practices, and (4) if existing soil conditions influence nutrient concentrations and flows. From this information it will be possible to determine the algal growth potential (AGP) of the waste, and the degree of treatment required for removal of AGP. (Modified author abstract)