Dm. Cooper et al., Catchment-scale simulation of stream water chemistry by spatial mixing: theory and application, J HYDROL, 233(1-4), 2000, pp. 121-137
A modelling framework is presented which gives catchment-wide estimates of
long-term stream water chemistry using complete spatial coverage of catchme
nt characteristics combined with measurements of stream water chemistry at
a limited number of sites. It has been developed for application to catchme
nts having acid headwaters which are diluted downstream by less acid runoff
, usually from improved agricultural land. The catchment is subdivided into
landscape types based on land use, soils and other characteristics defined
by existing national databases. Each landscape type is assumed to generate
stream water having a characteristic annual mean concentration of chemical
constituents. This concentration is estimated by regression analysis using
measured stream water chemistry data from a number of subcatchments, knowi
ng the proportion of each landscape type in each subcatchment. Catchment-wi
de stream water chemistry is estimated for conservative ions by mixing cont
ributing area estimated loads. Concentrations of non-conservative ions are
estimated using hydrochemical equilibrium equations constrained to give the
acid neutralising capacity estimated from the conservative ions. The model
is applied to the river Tywi, Wales and its performance investigated. Crow
n Copyright (C) 2000 Published by Elsevier Science B.V. All rights reserved
.