Extension of the QUASAR River‐Water Quality Model to Unsteady Flow Conditions

Abstract

A modification of the well-known water-quality model 'quality simulation along river systems' (QUASAR) is presented in order to extend its ability, so that it may be considered applicable under unsteady-flow conditions. An aggregated dead-zone travel-time parameter, based on (a) the kinematic wave velocity (celerity) of the flow wave and (b) the behaviour of the solute within so-called 'dead zones', has been incorporated into the existing model formulation. This extends the current continuouslystirred tank reactor-based model process to account for the behaviour of solute under unsteady-flow conditions. The enhanced water-quality model has been validated by application to the Colorado River.

Metabolism Modeling in Rivers With Unsteady Flow Conditions and Transient Storage Zones

“…A full dynamic flood wave routing, based on Saint‐Venant's equations and commonly used in one‐dimensional hydrological models, is suitable in unsteady flow conditions. The MUFT model uses a simpler flow routing model (Sincock & Lees, 2002) than a dynamic wave routing model (see Payn et al., 2017). The long reaches and time‐steps ( T s , t − α , t − τ s ) in the MUFT model create a physical anomaly that is, the advection delays ( α for ADV, τ s for ADZ) increase when discharge drops and thus the time‐step terms t − α and t − τ s at time t “look” further back in time as time progresses (see Figure S7 in Supporting Information ).…”

“… Conceptualization of river reaches in the (a) unsteady flow model adapted from Sincock and Lees (2002) and (b) ADV and ADZ models adapted from Lees et al. (2000) for conservative solute C. Q i , Input flow, Q , output flow, τ fl , advection fraction of flood wave travel time, T fladz , dispersion fraction of flood wave travel time, n c , number of continuous stirred‐tank reactors, C i , input dissolved oxygen concentration, C , output dissolved oxygen concentration, α and τ s , advection delay in ADV and ADZ models, T sadv , total solute travel time in the ADV model, T adz , dead zone residence time in the ADZ model, T sadz , total solute travel time in the ADZ model.…”

“…In the MUFT model, these formulations 10.1029/2022JG007245 3 of 20 (ADV or ADZ) are coupled with the unsteady flow routing and the two-station stream metabolism models. Previously, studies have proposed modifications in the QUASAR flow routing model to simulate unsteady flows (Sincock & Lees, 2002) as well as proposed coupling of ADZ and original QUASAR (steady flow) models to simulate non-conservative solutes (Lees et al, 1998). The MUFT model combines these efforts by coupling the unsteady QUASAR model and the ADZ model to simulate non-conservative solutes.…”

Overview of water quality modeling

“…Numerous commercial and open-source models have been applied to simulate complex water quality processes in diverse environmental conditions. Some of these models including MIKE21 (Chapman, 1996), HEC-RAS RAS (US Army Corps of Engineers, 2014, 1998), QUAL2K (Fang et al, 2008), WASP 6 (Artioli et al, 2005), QUASAR (Lees & Sincock, 2002;Whitehead et al, 1997), and SWAT (Grizzetti et al, 2003). Because of data, the existence of captures the core of the problem, the simplest reliable model is always chosen over complex models.…”

A Review of Surface Water Quality Models

“…With the exception of the typical models such as QUAL 2K model [52], WASP 6 model [24], QUASAR model [25, 53], SWAT model [21], and MIKE 21 [26] and MIKE 31 models [27] (Table 1), other water quality models have also been developed to simulate complicated water environmental conditions. For example, Whitehead et al [54] developed a semidistributed integrated nitrogen model (INCA) based on the effects of atmospheric and soil N inputs, land uses, and hydrology.…”