Using structural equation model to estimate nitrate pollution in the Melen Watershed of the Turkey

Abstract

In this study, Bayesian technique was applied in order to
estimate export coefficients for the Melen Watershed.
Furthermore, instead of calculating the contributions of
subwatersheds individually, the whole watershed was considered
for the estimation of the total load at the outlet of the Melen
Watershed using the calculated nitrate export coefficient. The
Bayesian approach has the goal of combining prior knowledge
with data to optimally use both sources of information. Success of
the Bayesian approach is directly proportional to sufficiency of
data for acquiring the prior information about estimands.
Bayesian analysis was conducted through Structural Equation
Model (SEM) using AMOS software and posterior information
about land use based export coefficients was obtained through
Markov Chain Monte Carlo (MCMC) method. Estimated land use
based nitrate export coefficients are in kg/km2/day unit. In
addition, monthly river retention value of nitrogen in all
subwatersheds of the Melen Watershed were estimated. This
information was used in order to predict nitrate export
coefficients appropriately. This study is aimed to be an important
precedent for other basins that are determined as in priority in
terms of pollution by The Ministry of Forest and Water Works of
Turkey.