DECADAL CHANGES OF INFLOW TO THE SACRAMENTO-SAN-JOAQUIN DELTA, CALIFORNIA

The Sacramento-San Joaquin Delta is both an important environmental re source and a critical link in the water supply system for California. Concern for the adequacy of Delta water supplies increases with growin g population and environmental maintenance needs and with the hydrocli matic uncertainty of global warming. Reconstructed or unimpaired disch arges for Delta tributary areas are analyzed for trend and for changes in the seasonal regime of Delta inflows. Nonparametric tests indicate the absence of trend for annual inflows, but the low inflow months of September and October display increasing trends that are statisticall y significant. Additional changes in the Delta inflow regime are evide nt when inflow volumes are expressed relative to annual inflow. Decrea sing trends in the spring fraction of annual total inflows and in the monthly fractions for April and May are statistically significant. Mar ch displays a significant increasing trend in the monthly fraction of inflow. The emerging decadal changes in monthly inflows have practical ramifications for water managers in the Delta.