ABSTRACT Estimating areal precipitation and quantifying the associated uncertainties are importan... more ABSTRACT Estimating areal precipitation and quantifying the associated uncertainties are important for both hydrological research and water resource management. However, many, if not all, precipitation products provide only the precipitation at reasonable spatial scales without uncertainty attached. In this paper, we promote a double smoothing technique to derive the precipitation amounts at small grid size based on gauge observations and then propose a bootstrap method to quantify the rainfall model estimation uncertainty (the uncertainty of rainfall estimation by a given model; here our model is double smoothing) by the traditional bootstrap for parameter uncertainty and the rainfall product uncertainty in term of prediction. As the residuals by the direct use of smoothing approach are heterogeneous, making the direct use of bootstrapping method invalid, we use an empirical transformation to stabilise the residuals. Furthermore, by using bootstrapping method, we can easily upscale the precipitation and the associate uncertainty to any required scales. The product is easy to use in research and practice. We demonstrate our methods by applying it to Murray Darling Basin in the eastern Australia. Crown Copyright
... Authors: Tits, Mia Van Overtveld, Koen Van De Vreken, Philippe Vandervelpen, Davy Peeters, Lu... more ... Authors: Tits, Mia Van Overtveld, Koen Van De Vreken, Philippe Vandervelpen, Davy Peeters, Luk Batelaan, Okke Van Orshoven, Jos Vanderborght, Jan Elsen, Annemie Bries, JanVandendriessche, Hilde Kuhr, Petra Wendland, Frank Diels, Jan. Issue Date: Feb-2010. ...
ABSTRACT Surface-groundwater (SW-GW) interactions constitute a critical proportion of the surface... more ABSTRACT Surface-groundwater (SW-GW) interactions constitute a critical proportion of the surface and groundwater balance especially during dry conditions. Conjunctive management of surface and groundwater requires an explicit account of the exchange flux between surface and groundwater when modelling the two systems. This paper presents a case study in the predominantly gaining Boggabri-Narrabri reach of the Namoi River located in eastern Australia. The first component of the study uses the Upper Namoi numerical groundwater model to demonstrate the importance of incorporating SW-GW interactions into river management models. The second component demonstrates the advantages of incorporating groundwater processes in the Namoi River model. Results of the numerical groundwater modelling component highlighted the contrasting groundwater dynamics close to, and away from the Namoi River where lower declines were noted in a near-field well due to water replenishment sourced from river depletion. The contribution of pumping activities to river depletion was highlighted in the results of the uncertainty analysis, which showed that the SW-GW exchange flux is the most sensitive to pumping rate during dry conditions. The uncertainty analysis also showed that after a drought period, the 95% prediction interval becomes larger than the simulated flux, which implies an increasing probability of losing river conditions. The future prospect of a gaining Boggabri-Narrabri reach turning into losing was confirmed with a hypothetical extended drought scenario during which persistent expansion of groundwater pumping was assumed. The river modelling component showed that accounting for SW-GW interactions improved the predictions of low flows, and resulted in a more realistic calibration of the Namoi River model. Incorporating SW-GW interactions into river models allows explicit representation of groundwater processes that provides a mechanism to account for the impacts of additional aquifer stresses that may be introduced beyond the calibration period of the river model. Conventional river models that neglect the effects of such future stresses suffer from the phenomenon of non-stationarity and hence have inferior low flow predictions past the calibration period of the river model. The collective knowledge acquired from the two modelling exercises conducted in this study leads to a better understanding of SW-GW interactions in the Namoi River thus leading to improved water management especially during low flow conditions.
ABSTRACT Estimating areal precipitation and quantifying the associated uncertainties are importan... more ABSTRACT Estimating areal precipitation and quantifying the associated uncertainties are important for both hydrological research and water resource management. However, many, if not all, precipitation products provide only the precipitation at reasonable spatial scales without uncertainty attached. In this paper, we promote a double smoothing technique to derive the precipitation amounts at small grid size based on gauge observations and then propose a bootstrap method to quantify the rainfall model estimation uncertainty (the uncertainty of rainfall estimation by a given model; here our model is double smoothing) by the traditional bootstrap for parameter uncertainty and the rainfall product uncertainty in term of prediction. As the residuals by the direct use of smoothing approach are heterogeneous, making the direct use of bootstrapping method invalid, we use an empirical transformation to stabilise the residuals. Furthermore, by using bootstrapping method, we can easily upscale the precipitation and the associate uncertainty to any required scales. The product is easy to use in research and practice. We demonstrate our methods by applying it to Murray Darling Basin in the eastern Australia. Crown Copyright
... Authors: Tits, Mia Van Overtveld, Koen Van De Vreken, Philippe Vandervelpen, Davy Peeters, Lu... more ... Authors: Tits, Mia Van Overtveld, Koen Van De Vreken, Philippe Vandervelpen, Davy Peeters, Luk Batelaan, Okke Van Orshoven, Jos Vanderborght, Jan Elsen, Annemie Bries, JanVandendriessche, Hilde Kuhr, Petra Wendland, Frank Diels, Jan. Issue Date: Feb-2010. ...
ABSTRACT Surface-groundwater (SW-GW) interactions constitute a critical proportion of the surface... more ABSTRACT Surface-groundwater (SW-GW) interactions constitute a critical proportion of the surface and groundwater balance especially during dry conditions. Conjunctive management of surface and groundwater requires an explicit account of the exchange flux between surface and groundwater when modelling the two systems. This paper presents a case study in the predominantly gaining Boggabri-Narrabri reach of the Namoi River located in eastern Australia. The first component of the study uses the Upper Namoi numerical groundwater model to demonstrate the importance of incorporating SW-GW interactions into river management models. The second component demonstrates the advantages of incorporating groundwater processes in the Namoi River model. Results of the numerical groundwater modelling component highlighted the contrasting groundwater dynamics close to, and away from the Namoi River where lower declines were noted in a near-field well due to water replenishment sourced from river depletion. The contribution of pumping activities to river depletion was highlighted in the results of the uncertainty analysis, which showed that the SW-GW exchange flux is the most sensitive to pumping rate during dry conditions. The uncertainty analysis also showed that after a drought period, the 95% prediction interval becomes larger than the simulated flux, which implies an increasing probability of losing river conditions. The future prospect of a gaining Boggabri-Narrabri reach turning into losing was confirmed with a hypothetical extended drought scenario during which persistent expansion of groundwater pumping was assumed. The river modelling component showed that accounting for SW-GW interactions improved the predictions of low flows, and resulted in a more realistic calibration of the Namoi River model. Incorporating SW-GW interactions into river models allows explicit representation of groundwater processes that provides a mechanism to account for the impacts of additional aquifer stresses that may be introduced beyond the calibration period of the river model. Conventional river models that neglect the effects of such future stresses suffer from the phenomenon of non-stationarity and hence have inferior low flow predictions past the calibration period of the river model. The collective knowledge acquired from the two modelling exercises conducted in this study leads to a better understanding of SW-GW interactions in the Namoi River thus leading to improved water management especially during low flow conditions.
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