Planning for robust water supply system investments under global change

Climate change, population growth, institutional changes and the uncertainties inherent in these pose a major challenge to planning and management of water supply systems. Using historical river flow records to predict the behaviour of water resource systems into the future is no longer sufficient since the hydrologic record can no longer be assumed to represent future conditions. Planning under uncertainty approaches must allow considering future uncertainties in the water supply as well as demand and the institutions that manage water and its uses. Furthermore, water systems are complex and must meet multiple demands of a range of stakeholders whose objectives often conflict. Understanding these conflicts requires exploring many alternative plans to identify balanced solutions in light of important system trade-offs. The thesis focuses on improving the water resource planning process in the UK and to reflect trends in current water planning policy developments in the UK and worldwide. The challenge of longterm human-natural resource system planning is to identify high value portfolios of human interventions whilst considering the two main challenges: future deep uncertainty and multiple concurrent societal goals. This identification process is severely complicated by the exponentially large number of alternative combinations of schemes available to manage future resources. This research project demonstrates how simulating systems under multiple plausible realizations of the future coupled with ‘many-objective’ optimization can provide decision makers with robust solutions. Visual analytics is used to interact with results and demonstrate the benefits of this approach compared to traditional planning practices. Results presented here aim to aid water resources planners to orient investment strategies to meet key requirements and aspirations. These include but are not limited to maintaining the supply-demand balance and customer satisfaction in future, promoting sustainable use of resources, protecting the natural environmental, etc. The thesis aims to communicate to planners the increase in understanding of how such aspirations can be balanced taking into account uncertainties of future conditions using the proposed approaches

Screening robust water infrastructure investments and their trade-offs under global change: A London Example

AbstractWe propose an approach for screening future infrastructure and demand management investments for large water supply systems subject to uncertain future conditions. The approach is demonstrated using the London water supply system. Promising portfolios of interventions (e.g., new supplies, water conservation schemes, etc.) that meet London’s estimated water supply demands in 2035 are shown to face significant trade-offs between financial, engineering and environmental measures of performance. Robust portfolios are identified by contrasting the multi-objective results attained for (1) historically observed baseline conditions versus (2) future global change scenarios. An ensemble of global change scenarios is computed using climate change impacted hydrological flows, plausible water demands, environmentally motivated abstraction reductions, and future energy prices. The proposed multi-scenario trade-off analysis screens for robust investments that provide benefits over a wide range of futures, including those with little change. Our results suggest that 60 percent of intervention portfolios identified as Pareto optimal under historical conditions would fail under future scenarios considered relevant by stakeholders. Those that are able to maintain good performance under historical conditions can no longer be considered to perform optimally under future scenarios. The individual investment options differ significantly in their ability to cope with varying conditions. Visualizing the individual infrastructure and demand management interventions implemented in the Pareto optimal portfolios in multi-dimensional space aids the exploration of how the interventions affect the robustness and performance of the system

Tracking trade transactions in water resource systems: A node- arc optimization formulation

[1] We formulate and apply a multicommodity network flow node-arc optimization model capable of tracking trade transactions in complex water resource systems. The model uses a simple node to node network connectivity matrix and does not require preprocessing of all possible flow paths in the network. We compare the proposed node-arc formulation with an existing arc-path (flow path) formulation and explain the advantages and difficulties of both approaches. We verify the proposed formulation model on a hypothetical water distribution network. Results indicate the arc-path model solves the problem with fewer constraints, but the proposed formulation allows using a simple network connectivity matrix which simplifies modeling large or complex networks. The proposed algorithm allows converting existing node-arc hydroeconomic models that broadly represent water trading to ones that also track individual supplier-receiver relationships (trade transactions)

Sikringstiltak i Stokkbekken – effekter på vannkvalitet, bunndyr og fisk

Prosjektleder: Asle ØkelsrudNorges vassdrags- og energidirektorat (NVE) utførte sikringstiltak mot erosjon i ravinedaler med bekkeløp i kvikkleiresoner på Rødde i 2021 og 2022. Sikringsarbeidet inkluderte erosjonssikring av to bekker, Stokkbekken og Hørsdalsbekken. Sprengsteinen ble hentet fra et lokalt pukkverk på Sjøla, og besto i all hovedsak av lokal grønnstein. NIVA utførte, i 2022, en undersøkelse med formål om å kvantifisere mengden partikler, beskrive partikkelmorfologi, utlekking av nitrogen (nitrat/ammonium) og metaller, samt undersøke endringer i bunndyrsamfunnet og mulige fysiologiske skader på fisk. Resultatet indikerer at innslaget av sprengsteinpartikler utgjør en liten andel av den totale partikkelmengden på stasjon nedstrøms sikringsarbeid. Resultater både fra bekken og et forsøk på utlekking av nitrogen og metaller fra sprengstein, viser at konsentrasjonene avtar raskt nedstrøms, og utgjør liten risiko for toksiske effekter på fisk og bunndyr. Det var ingen tydelige effekter på fisk målt som hemoglobinverdier (proxy for oksygenopptak), avsetning av partikler på gjeller eller histopatologiske endringer på gjeller (mekaniske skader) på stasjon nedstrøms sikringsarbeid. Arbeidene med erosjonssikring i vassdragene vil trolig ha en forbigående effekt på bunndyrsamfunnene, hvor tidligere sikrede deler av bekken raskt koloniseres fra oppstrøms upåvirkede bekkestrekninger. Med bakgrunn i de innsamlede data, framstår effektene på bunndyr og fisk som følge av erosjonssikringen av Stokkbekken/Hørsdalsbekken som marginale og forbigående.Norges vassdrags- og energidirektorat (NVE)publishedVersio

Using many-objective trade-off analysis to help dams promote economic development, protect the poor and enhance ecological health

AbstractAllocating water to different uses implies trading off the benefits perceived by different sectors. This paper demonstrates how visualising the trade-offs implied by the best performing water management options helps balance water use benefits and find sustainable solutions. The approach consists of linking a water resources model that can simulate many management policies and track diverse measures of system performance, to a many-objective evolutionary optimisation algorithm. This generates the set of Pareto-optimal management alternatives for several simultaneous objectives. The relative performance of these efficient management alternatives is then visualised as trade-off curves or surfaces using visual analytic plots. Visually assessing trade-offs between benefits helps select policies that achieve a decision-maker-selected balance between different metrics of system performance. We apply this approach to a multi-reservoir water resource system in Brazil's semi-arid Jaguaribe basin where current water allocation procedures favour sectors with greater political power and technical knowledge. The case study identifies promising reservoir operating policies by exploring trade-offs between economic, ecological and livelihood benefits as well as traditional hydropower generation, irrigation and water supply. Results show optimised policies can increase allocations to downstream uses while increasing median land availability for the poorest farmers by 25%

Trade-off informed adaptive and robust real options water resources planning

Planning water resource systems is challenged primarily by two realities. First, uncertainty is inherent in the predictions of future supplies and demands due for example to hydrological variability and climate change. To build societal resilience water planners should seek to enhance the adaptability and robustness of water resource system interventions. Second, water resource developments typically involve competing interests which implies considering the trade-offs and synergies implied by the highest performing combinations of development options is useful. This work describes a real options based planning framework that generates adaptive and robust water system design alternatives able to consider and trade-off different goals. The framework can address different types of uncertainties and suggests the highest performing designs across multiple evaluation criteria, such as financial costs and water supply service performance metrics. Using a global city's water resource and supply system as a demonstration of the approach, we explore the trade-offs between a long-term water management plan's infrastructure services (service resilience, reliability, vulnerability) and its financial costs under supply and demand uncertainty. The set of trade-off solutions consist of different investment plans which are adaptive and robust to future changing conditions. Results show that the highest performing plans lower net present value (NPV) of needed investments by up to 18%, while maintaining similar performance across the other objectives. The real option value of delaying investments as much as possible approaches up to 14% of total NPV

Pulmonary Vasculature Responsiveness to Phosphodiesterase-5A Inhibition in Heart Failure With Reduced Ejection Fraction: Possible Role of Plasma Potassium

Introduction: Phosphodiesterase-5a inhibition (PDE5i) leads to favorable changes in pulmonary hemodynamic and cardiac output (CO) in patients with advanced heart failure (HF) and reduced ejection fraction (HFrEF). The hemodynamic response to PDE5i could be heterogeneous and the clinical variables associated with these changes are scarcely investigated. Materials and methods: Of 260 patients with advanced HFrEF referred for advanced therapies [cardiac transplant/left ventricular assist device (LVAD)], 55 had pulmonary hypertension (PH) and fulfilled the criteria for the PDE5i vasoreactivity test. Right heart catheterization (RHC) was performed as a part of clinical evaluation before and after 20-mg intravenous sildenafil. Absolute and relative changes in pulmonary vascular resistance (PVR) were evaluated to assess hemodynamic response to PDE5i. Clinical, biochemical, and hemodynamic factors associated with PVR changes were identified. Results: Sildenafil administration reduced PVR (- 45.3%) and transpulmonary gradient (TPG; - 34.8%) and increased CO (+ 13.6%). Relative change analysis showed a negative moderate association between baseline plasma potassium and changes in PVR (r = - 0.48; p = 0.001) and TPG (r = - 0.43; p = 0.005) after PDE5i. Aldosterone concentration shows a direct moderate association with PVR changes after PDE5i. A significant moderate association was also demonstrated between CO improvement and the severity of mitral (r = 0.42; p = 0.002) and tricuspid (r = 0.39; p = 0.004) regurgitation. Conclusion: We identified plasma potassium, plasma aldosterone level, and atrioventricular valve regurgitations as potential cofounders of hemodynamic response to acute administration of PDE5i. Whether modulation of potassium levels could enhance pulmonary vasoreactivity in advanced HFrEF deserves further research