Cost-effectiveness analysis of different watershed management scenarios developed by simulation–optimization model

Abstract

The effort to control sediment yield at watershed scale is an ongoing challenge that needs to take into account trade-offs between two conflicting objective functions, i.e. economic and hydrologic criteria. Therefore, researchers have coupled hydrologic and multi-objective optimization models to find Pareto-optimal solutions. However, very limited studies have been conducted to analyse the cost-effectiveness (C/E) of scenarios obtained in the Pareto-front optimal. This could provide new information leading to effective watershed management. Therefore, in the present study, the Soil and Water Assessment Tool (SWAT) was used to simulate sediment yield under different combinations of best management practices (BMPs) and was coupled with the Non-dominated Sorting Genetic Algorithm (NSGA-II). The model attends to providing the Pareto-optimal solutions by minimizing the costs of BMPs and maximizing sediment reduction. The results of the application of the cost-effective optimization model in Mehran watershed, Iran, showed that the solutions in the Pareto-optimal front reduce sediment yield between 2% and 40.5% from baseline at costs of between $6,500 and $72,100, respectively. Finally, comparison of four sediment reduction solutions (i.e. 10%, 20%, 30%, and 40%) showed that the total cost and C/E ratio of solutions increased as the sediment reduction criteria increased.

Evaluation of best management practices for sediment and nutrient loss control using SWAT model

“…Site-specific conditions and dimensions of agricultural BMPs as well as the tillage practices can be incorporated in the SWAT model which is often beyond the capacity of most other watershed models (Xie et al, 2015). The effectiveness of BMPs using the SWAT model has been explored by researchers worldwide (McGregor et al, 1999;Pandey et al, 2005Pandey et al, , 2009b; Betrie et al, 2011;Zhang and Zhang, 2011;Bossa et al, 2012;Strauch et al, 2013;Rocha et al, 2015;Pare et al, 2015;Lampurlanes et al, 2016;Maharjan et al, 2016;Strehmel et al, 2016;Her et al, 2017;Noor et al, 2017;Merriman et al, 2018;Ni and Parajuli, 2018;Qiu et al, 2018;Wang et al, 2018). These studies revealed that the SWAT model has the ability to evaluate BMPs to reduce NPS pollution (sediment and nutrient load) depending on watershed characteristics, and the type and combinations of applied BMPs.…”

Modeling and Prioritizing Interventions Using Pollution Hotspots for Reducing Nutrients, Atrazine and E. coli Concentrations in a Watershed

“…Although few recent studies have shown that the cost-effectiveness of BMPs in mitigating pollution is greatly boosted by using BMP selection and placement tool at watershedscale [32,33], studies which incorporate hotspots and fund limitations, not only for sediment and nutrient load reduction, but also for Atrazine and E. coli, are rare. Thus, based on the financial constraint of $500,000 annually for three years of the NWQI, and the detailed preliminary assessment conducted by the NDEE, the objectives of this study are to: (i) simulate BMPs proposed by the NDEE within target sub-watersheds to determine reductions in pollutant loads and (ii) determine if water-quality standards are met at the watershed outlet.…”