Water Resources Management最新文献

In this paper, we present a new control model for optimizing pressure and water quality operations in water distribution networks. Our formulation imposes a set of time-coupling constraints to manage temporal pressure variations, which are exacerbated by the transition between pressure and water quality controls. The resulting optimization problem is a nonconvex, nonlinear program with nonseparable structure across time steps. This problem proves challenging for state-of-the-art nonlinear solvers, often precluding their direct use for near real-time control in large-scale networks. To overcome this computational burden, we investigate a distributed optimization approach based on the alternating direction method of multipliers (ADMM). In particular, we implement and evaluate two algorithms: a standard ADMM scheme and a two-level variant that provides theoretical convergence guarantees for our nonconvex problem. We use a benchmarking water network and a large-scale operational network in the UK for our numerical experiments. The results demonstrate good convergence behavior across all problem instances for the two-level algorithm, whereas the standard ADMM approach struggles to converge in some instances. With an appropriately tuned penalty parameter, however, both distributed algorithms yield good quality solutions and computational times compatible with near real-time (e.g. hourly) control requirements for large-scale water networks.

A modelling framework was developed to characterise groundwater drought at a catchment scale in the absence of adequate observational records. The framework was used to characterise historical groundwater drought events for a Chalk aquifer in southern England over the period 1971-2004 during which three major drought events occurred. A numerical groundwater model was used to simulate the groundwater level fluctuations driven by historical time-variable and spatially non-uniform recharge inputs. The standardised groundwater level index (SGI) was applied to the simulated groundwater levels to evaluate the spatial pattern of groundwater drought and of their severity and duration. A dimensionality reduction method, namely principal component analysis (PCA), was applied to the SGI dataset and to the standardised precipitation index (SPI) to further explore the spatio-temporal drought characteristics. The analysis showed inconsistency in the spatial distribution of the duration and severity among the three studied events. PCA indicated that the SPI was not a good predictor of groundwater drought during the extreme European heatwave of 2003 whereas the proposed modelling framework correctly identified the resilience of the groundwater system to that event and in line with observations. Furthermore, significant differences were observed between the spatial patterns obtained from SPI and SGI datasets highlighting the important role that hydrological and hydrogeological features of a catchment have in groundwater drought development.

Water resources planning in England has undergone a significant transformation from a fragmented, piecemeal approach to a more strategic, multi-scale framework. This shift is a response to the pressing need for increased resilience in the face of climate change, population growth, and environmental pressures. Recognising the limitations of existing planning frameworks established during privatisation, new national, regional, company, and sub-regional frameworks have emerged to address gaps and enhance strategic planning efforts. Understanding the critical pathway dependencies, opportunities, and constraints allows reforms to be designed and implemented with a better chance of success. Several key features characterise water resources planning in England. Firstly, the systems are inherently complex and fragmented, requiring tailored approaches rather than one-size-fits-all solutions. Secondly, planning operates within a neoliberal framework emphasising economic efficiency. Thirdly, subjective concepts like risk, uncertainty, and value are managed through technical quantitative methods which can pose challenges for transparency. Fourthly, while legislation often operates in silos, there is a growing demand for more integrated planning approaches. Funding and regulatory powers play crucial roles in water resources planning. Access to capital is influenced by the institutional environment and broader economic and political factors, with government and regulators ultimately holding power over the framework. Companies, driven by the profit motive, are responsible for detailed planning and delivery, regulated by standards and reputational incentives. Public participation is framed as consumer engagement. Aligning incentives for public good with financial rewards and ensuring effective regulation are vital for the framework's success.

Objectives: In the Philippines, patients on chronic hemodialysis with COVID-19 remain admitted in hospitals despite clinical recovery because most free-standing dialysis units require proof of negative conversion via Reverse Transcriptase - Polymerase Chain Reaction (RT-PCR). This study aims to determine the time to negative conversion of COVID-19 RT-PCR testing among adult patients on chronic hemodialysis with COVID-19 admitted at the Philippine General Hospital (PGH) and bring insight in using the symptom or time-based procedure as recommended by local guideline, and ultimately, to ensure delivery of adequate hemodialysis despite being infected with COVID-19, shorten isolation period, and conserve resources especially in resource-limited settings.

Methods: This is a retrospective cohort study on all adult patients on chronic hemodialysis who were admitted in PGH after the diagnosis of COVID-19 by RT-PCR between March 2020 and February 2021. Descriptive statistics was used in summarizing the data.

Results: A total of 90 patients on chronic hemodialysis who tested positive for COVID-19 via RT-PCR admitted at PGH were included in the study. Most of these patients had moderate COVID-19 at 53.3%. The median number of days from onset of symptoms to clinical recovery was 14.5 days. The median time to first negative conversion was 18 days. Most of these patients had negative conversion at the second week. The correlation coefficient between time to clinical recovery and negative conversion was 0.214.

Conclusion: Among adult patients on chronic hemodialysis who were admitted in PGH after the diagnosis of COVID-19, the time to negative conversion was longer compared to the time to clinical recovery with a very weak correlation between the two.