Assessing uncertainties in surface water security: An empirical multimodel approach

Abstract

Various uncertainties are involved in the representation of processes that characterize interactions among societal needs, ecosystem functioning, and hydrological conditions. Here we develop an empirical uncertainty assessment of water security indicators that characterize scarcity and vulnerability, based on a multimodel and resampling framework. We consider several uncertainty sources including those related to (i) observed streamflow data; (ii) hydrological model structure; (iii) residual analysis; (iv) the method for defining Environmental Flow Requirement; (v) the definition of critical conditions for water provision; and (vi) the critical demand imposed by human activities. We estimate the overall hydrological model uncertainty by means of a residual bootstrap resampling approach, and by uncertainty propagation through different methodological arrangements applied to a 291 km2 agricultural basin within the Cantareira water supply system in Brazil. Together, the two‐component hydrograph residual analysis and the block bootstrap resampling approach result in a more accurate and precise estimate of the uncertainty (95% confidence intervals) in the simulated time series. We then compare the uncertainty estimates associated with water security indicators using a multimodel framework and the uncertainty estimates provided by each model uncertainty estimation approach. The range of values obtained for the water security indicators suggests that the models/methods are robust and performs well in a range of plausible situations. The method is general and can be easily extended, thereby forming the basis for meaningful support to end‐users facing water resource challenges by enabling them to incorporate a viable uncertainty analysis into a robust decision‐making process.

Probabilistic Projections of Hydrological Droughts Through Convection‐Permitting Climate Simulations and Multimodel Hydrological Predictions

“…The SWAT model (Gassman et al, 2007) is a physically based and continuous watershed simulation model, which is capable of simulating a high level of spatial details, and thus, it has been widely used for hydrological assessment. The SWAT model uses a basin discretization that divides the study area into several subbasins and Hydrological Response Units (HRUs), and subbasins have unique land use, soil, and slope categories (Neitsch et al, 2011; Rodrigues et al, 2015). Each HRU conducts a simulation of hydrological processes, and the output water fluxes are routed to the watershed to generate the total discharge values.…”

“…The calibration period was selected from 1981 to 1990, and the validation period was from 1991 to 1995. The HYMOD and SWAT models were combined into a general framework using a weighted‐average aggregation method (Rodrigues et al, 2015; Wilby & Harris , 2006). The weights were calculated in proportion to model performance based on the adjusted correlation coefficients (CORs), which were computed for the calibration period (1981–1990), and then the weights were applied for the validation period (1991–1995) and the forecast period (2085–2099) by where R adj is the adjusted COR, r is the linear COR, and n is the sample element.…”

Assessing water security in the São Paulo metropolitan region under projected climate change

“…1), the climate is humid subtropical, according to the Köppen climate classification, characterized by hot and wet summers (October to March) and dry winters (June to September) (Alvares et al, 2013). The average annual rainfall and temperature are 1592 mm and 25 • C, respectively (Rodríguez-Lado et al, 2007). Pasture used for livestock production (70 %) is predominant, and the remaining natural vegetation accounts for 12 % and 8 % of the respective eucalyptus and pine of forest wood crops.…”

“…Due to its ability to successfully represent the major processes driving catchment dynamics, and owing to its relative simplicity, HYMOD has been widely used in studies related to the assessment of methods for model calibration, uncertainty and sensitive analysis, climate change impacts, water security, and several others (Bastola and Misra, 2014;Chen et al, 2013;Gong et al, 2013;Parra et al, 2018;Rodrigues et al, 2015). The relative simplicity of its structure facilitates computationally fast data processing, and it imposes minimal requirements for input data, while maintaining a suit- able level of hydrological process representation (Gong et al, 2013).…”

Assessing Water Security in the Sao Paulo Metropolitan Region Under Projected Climate Change

“…Due to its ability to successfully represent the major processes driving catchment dynamics, and due to its relative simplicity, HYMOD has been widely used in studies related to assessment of methods for model calibration, uncertainty and sensitive analysis, climate change impacts, water security, and several others (Bastola and Misra, 2014;Chen et al, 2013;Gong et al, 2013;Parra et al, 2018;Rodrigues et al, 2015). The relative simplicity of its structure facilitates computationally fast data processing, and it imposes minimal requirements for input data, while maintain a suitable level of hydrological process representation (Gong et al, 2013).…”