4.1.3. Modeling

Prior to 1990, efforts to develop a comprehensive modeling framework—following a recommendation from the 1982 expert panel report [35]—was limited to testing available software from USEPA, including a pesticide model (EXAMS) and two water quality transport models (QUAL2E and WASP3) [37]. Absent a transport model, a simple water balance approach was utilized to estimate Delta drainage contributions to THM formation potential in channel waters during the leaching and irrigation periods of water year 1988 [39]. Beginning in 1990, the MWQI program collaborated with the CDWR Delta Modeling Section to develop a framework for modeling THM precursor fate and transport in the Delta. Early model development was documented in a CDWR Division of Planning report [65], the CDWR Delta Modeling Section's "Methodology for Flow and Salinity Estimates in the Sacramento–San Joaquin Delta and Suisun Marsh" series [66–71], and other publications [72–76]. Aspects of this early model development that focused on organic precursor fate and transport provided a foundation for today's MWQI forecasting work.
