Simulating THM Formation Potential in the Sacramento Delta. Part II

Abstract

An existing numerical hydrodynamics and water‐quality model was employed to simulate trihalomethane (THM) precursors and salinity transport in California's Sacramento‐San Joaquin Delta. Using steady‐state assumptions and historically observed hydrologic and water‐quality boundary conditions, seven model scenarios were defined. These scenarios were defined to quantify the relative contribution of THM precursors from a variety of sources at eight delta monitoring locations. Empirical relationships developed in a companion paper, bromine incorporation factor and bromine distribution factors, were employed to estimate bromide effects at each monitoring location. Model results, reported as THM formation potential (THMFP) concentrations, compared favorably with historical observations. Deviations between predicted and observed values were greatest at monitoring stations heavily influenced by agricultural drains, emphasizing the need for further data in that region. The analysis presented in this paper illustrates the numerical model's ability to be used as a planning tool in evaluating source‐water management alternatives with respect to THMFP in the delta.