Water Resources Research | 2019
How Important Are Model Structural and Contextual Uncertainties when Estimating the Optimized Performance of Water Resource Systems
Abstract
18 Uncertainty in simulating water resource systems (WRSs) makes it difficult to assess how 19 effective different water management decisions will be. Uncertainty in simulation models can 20 undermine the credibility of simulation and optimization studies and the uptake of their 21 results. We identify different sources of uncertainty in WRS models and find that structural 22 uncertainty (i.e. around definition of interrelationships within the system) and contextual 23 uncertainty (i.e. around definition of the system boundaries) are rarely considered when 24 simulating and optimizing WRSs. We propose a methodology to quantify the effects of 25 structural and contextual uncertainties on the estimated performance of optimized water 26 management decisions and demonstrate that they have a significant impact on a real-world 27 case study of a pumped-storage system in the UK. To the best of the authors’ knowledge this 28 is the first study to consider the impact of these types of uncertainty on optimized operating 29 policies and their simulated performances. Our main finding is that, of all the considered 30 uncertainties, the assumptions made about context – specifically around the level of 31 cooperation between neighbouring water companies – had the greatest impact on 32 performance estimates. This is important because few WRSs exist in isolation, yet discussion 33 of the effects that a given definition of the system boundaries have on the 34 simulation/optimization results is uncommon. We also highlight the significance of 35 adequately considering aleatory uncertainty when evaluating performance estimates – 36 something that few studies do – and present a simple technique to justify the sample size used 37 for the evaluation of optimization results. 38