Development of a model-agnostic isotope tracer simulator

Abstract

The simulation of stable isotope compositions of modelled water storages and flows has demonstrated value in hydrological model verification, benchmarking, and calibration. However, to realize these benefits, an isotope tracer model must be linked to the hydrological model. An open-source model-agnostic isotope tracer simulator (MAITsim) has been developed which can be linked to different hydrological models, removing the need to write specific tracer simulators. This numerically stable simulator for both δ18O and δ2H is compatible with unidirectional flux-state hydrological models, without predetermined spatial divisions or process representation. MAITsim is compared to a published embedded isotope tracer model, verifying the equivalence of the simulated isotope compositions and is tested on conceptual models of variable structure. This post-processor model reduces the barriers to entry into isotope tracer simulation, allowing more models to benefit from the added information that isotope tracers can provide on hydrological processes and flow sources.