Abstract:
This paper presents a hybrid approach for stormwater runoff modelling and pollutant load estimation in
a hilly catchment. The stormwater runoff hydrograph was simulated by developing a conceptual hybrid
model (HM) using transfer function. Model parameters were estimated by non-linear optimization. The
simulated runoff hydrographs showed an excellent match with the observed data. Next, a relationship
was developed between runoff and pollutant load and the developed relationship was used for estimation
of pollutant load. A novelty of this hybrid approach is that it could bring out a generic HM. By using
the derived model, the pollutant load was successfully predicted from simulated runoff (R2 > 0.75) by
considering rainfall as the only input. In addition, assessment, characterization and analysis of the first
flush of urban runoff also form part of the study. The HM was tested and validated by applying it to 25
storm events monitored during two monsoon seasons in the Nainital Lake catchment (approx. 1900 m
a.m.s.l.), India.
