Parsimonious hydrological modeling of urban sewer and river catchments

TLDR: In this paper, a parsimonious model of flow capable of simulating flow in natural/engineered catchments and at WWTP (Wastewater Treatment Plant) inlets was developed.

About: This article is published in Journal of Hydrology.The article was published on 2012-09-25 and is currently open access. It has received 36 citations till now. The article focuses on the topics: Impervious surface & Combined sewer.

Figures

Fig. 6. Sample hydrograph for the calibration period (a) and full validation period (b) for flow modeled at river outlet. Gray dashes are field measurements, solid lines are model predictions and precipitation rate is on the right abscissa of (b).

Fig. 7. Results of the sensitivity analysis. The model is sensitive to ksub; ksup and c to a lesser extent. The NS criterion is in black and NB in gray. All model parameters are scaled between 0 and 100.

Fig. 1. Schema of the WWTP catchment conceptualization. The pipe and channel netw reservoir. The other part of the rain jAp enters the pervious zone (Su), where it can ev framework applies for river basin modeling. In the case where the model is used to sim network, thereby modeling the drainage effect of the sewer system, which is in addition WWTP is replaced by the river. Symbols are explained in the text.

Fig. 8. Dominant pathways considered. Endpoints of the system are the river and the WWTP.

Table 1 Mathematical expressions of adopted fitting criteria functions e.g.,(Nash and Sutcliffe, 1970; Hingray et al., 2009; Schaefli and Gupta, 2007; Fenicia et al., 2007; Reusser et al., 2008). Zsim and Zobs are the modeled and observed values and n is the number of observations.

Table 2 Calibration parameters and the range of values considered. For the Monte-Carlo parameter optimization procedure, a uniform distribution was considered.

Frequently asked questions

Q1. What are the main physical processes driving the discharge at the two basin end-points in this?

The dominant physical processes driving water discharge at the two basin end-points in this study are Hortonian runoff, evapotranspiration, and gravity-driven percolation to groundwater. 

Q2. What are the two important assumptions that can be used to simplify sewer hydrologic/hydraulic?

Two important modeling assumptions are: (i) the pipe network is replaced by an underground impervious area and thus overland flow and pipe discharge can be together modeled as a fast discharge linear reservoir, and (ii) the water diverted out of the sewer system through the different CSOs can be combined together through the hydraulic discharge function of a representative CSO. 

Q3. What is the common urban hydrological model used in research and engineering?

Most popular urban hydrological models used in research and engineering (e.g., MOUSE (Hernebring et al., 2002), SWMM3) are spatially distributed with link-node drainage networks. 

Q4. What is the purpose of the study?

In this study, a hierarchical physically based storage and transmission model was designed as an alternative means for simulating continuous flow dynamics in complex engineered urban basins. 

Q5. What is the purpose of the model?

In addition, the hydrological model integrates functions that aim to reproduce characteristic daily variations of dry weather flow to the WWTP. 

Q6. Why is detailed modeling of drainage systems often deemed necessary?

Detailed modeling of drainage systems is often deemed necessary because of the complexity of flow paths in urban catchments (Cantone and Schmid, 2011; Gironás et al., 2009). 

Q7. What is the type of precipitation determined by the model?

The type of precipitation is determined based on a temperature threshold (DeWalle and Rango, 2008; Schaefli et al., 2005): when T is above the threshold Tcr , precipitation occurs as rain, otherwise precipitation is frozen. 

Q8. What is the closest CSO to the WWTP?

This CSO, the closest CSO to the WWTP, is responsible for more than a third of all CSO discharge, and is typically the first to become operational in storms (e-dric.ch, 2008). 

Q9. What is the model’s function for determining discharges at the WWTP inlet?

During dry weather, discharges arriving at the WWTP inlet are determined mainly by two phenomena: (i) infiltration of groundwater into the pipe network (see Section 2.2 and Dupont et al. (2006); Göbel et al. (2004)) and, (ii) water use and consequent wastewater production. 

Q10. What is the definition of a typical urban catchment?

It is a typical urban catchment, where much water comes from toilets, washing, industry and other uses, rather than directly from natural sources. 

Q11. What is the effect of the infiltration excess on the model?

Saturation excess was not implemented in their modeling scheme as the authors considered an unlimited reservoir height – i.e., the reservoir is never full – and this could lead to underestimation of surface runoff (Buda et al., 2009; MartínezMena et al., 1998; Nachabe et al., 1997).