The ability to predict the amount and character of natural organic matter (NOM) in a
drinking water supply can allow operators to anticipate coagulant or disinfectant demand. In
systems consisting of two reservoirs of differing water quality in series, the ability to predict
water quality can impact decisions of transfer from an upstream reservoir to a downstream
reservoir. CE QUAL W2 version 2 is a two dimensional laterally averaged hydrodynamic
and water quality modeling program that is capable of modeling reservoir storage, and
vertical and longitudinal gradients of temperature and 21 water quality constituents. With
minor modifications, this program can be used to model NOM surrogates including total
organic carbon (TOC), dissolved organic carbon (DOC) and the absorbance of ultraviolet
light at a wavelength of 254 nm (UV 254). UV 254 can be an effective predictor of
disinfection byproduct formation potential (DBPFP). Together, UV 254 and DOC can be
used to calculate specific UV absorbance (SUVA) which is an effective predictor of NOM
removal by coagulation. Wachusett Reservoir is part of an unfiltered supply for a large
metropolitan area. This reservoir receives significant transfer from another reservoir with
lower NOM levels. CE QUAL W2 effectively predicted TOC, DOC, UV 254, and SUVA at
the withdrawal from Wachusett Reservoir by including temperature dependent and light
induced decay of organic matter and organic matter formation by algal growth with an
intensive hydrodynamic model. It may be possible to implement simpler model and include
the same mechanisms to predict concentrations of NOM surrogates, which could aid in
making operational decisions. Includes 15 references, table, figures.