HS5.2.3

Climate-warming greenhouse gas emissions can be reduced by replacing petroleum-driven vehicles with electric vehicles powered by rechargeable lithium batteries. By 2025, 45% of the world’s Lithium will be sourced from water-intensive mining operations adjacent to fragile eco-hydrological systems in the Atacama Desert, the world’s driest desert. In the remote Atacama salt flat basin, home to one of the world’s richest deposits of high-grade lithium, brines are being mined from aquifers, with potential impacts on the long-term environmental, ecological, economic, and social viability of the system. Stakeholders (scientists, communities, and decision-makers) are currently entrenched in adversarial relationships and top-down policy-making and implementation.

A socio-hydrology stance considering telecoupled systems of people and water is essential to address the paradox between the quest for global decarbonisation and unsustainable use of water resources in the Atacama region. The inclusion of social drivers (beliefs, biases, values, and heuristics), however, adds complexity to the analysis. To address this complexity, novel methodologies such as participatory modeling (PM) and agent-based modeling (ABM) can be implemented. The former can enrich the system with specialist and local knowledge, increase the perceived utility of models, their credibility through transparent communication of the limitations and uncertainties, and the adoption and acceptance of the model results, which ultimately guide public policy. The latter seeks to represent explicitly the complexity and heterogeneity in these telecoupled systems.

The socio-hydrological problem at the Atacama salt flat is conceptualized using the Fuzzy-Logic Cognitive Mapping methodology through participatory workshops, involving scientists, regulators, and government officials. An ABM is then coupled to an integrated and regional groundwater-surface water model to better understand the impacts of management scenarios and social interactions, and their feedbacks on the eco-hydrological system. Ultimately, the aim of this research is to take a socio-hydrology stance to analyze a wicked problem with social, environmental, and economic implications at the local and global scales, and in doing so, expand fundamental knowledge of socio-hydrology.

How to cite: Canales, M., Castilla-Rho, J., Vicuña, S., Ball, J., and Filatova, T.: Using a socio-hydrology stance to address the paradox between global decarbonisation, lithium fever, and sustainability in the Atacama Salt Deposit, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-385, https://doi.org/10.5194/egusphere-egu21-385, 2021.

In this study, decision-making models in uncertain conditions are developed to identify optimal strategies for reducing competition between agricultural and environmental water demand. The decision-making models are applied to the irrigated Miyandoab Plain, located upstream of endorheic Lake Urmia in Northwestern Iran. Decision-making models are conceptualized based on static and dynamic Bayesian Belief Networks (BBN). The static BBN evaluates the effects of management strategies and drought conditions on environmental flow and agricultural profit at the annual scale, while the dynamic BBN accounts for monthly dynamics of water demand and conjunctive use. The reliability and performance of BBNs depend on the quantity and quality of data used to train the BBN and create conditional probability tables (CPTs). In this study, simulated outputs from a multi-period simulation-optimization model (Dehganipour et al., 2020) are used to populate the CPTs in each BBN and reduce the BBN training error. Cross-validation tests and sensitivity analysis are used to evaluate the effectiveness of the resulting BBNs. Sensitivity analysis shows that drought conditions have the most significant impact on environmental flow compared to other variables. Cross-validation tests show that the BBNs are able to reproduce outputs of the complex simulation-optimization model used for training, and therefore provide a computationally fast alternative for decision-making under uncertainty.

Reference: Dehghanipour, A. H., Schoups, G., Zahabiyoun, B., & Babazadeh, H. (2020). Meeting agricultural and environmental water demand in endorheic irrigated river basins: A simulation-optimization approach applied to the Urmia Lake basin in Iran. Agricultural Water Management, 241, 106353.

How to cite: Dehghanipour, A., Schoups, G., Babazadeh, H., Ehtiat, M., and Zahabiyoun, B.: Bayesian Belief Networks for the metamodeling of simulation-optimization model to identify optimum water allocation scenario, Application in Miyandoab plain, Urmia Lake basin, Iran, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1691, https://doi.org/10.5194/egusphere-egu21-1691, 2021.

Due to climate change, the water cycle is changing which requires to adapt water management in many regions. The transdisciplinary project KlimaRhön aims at assessing water-related risks and developing adaptation measures in water management in the UNESCO Biosphere Reserve Rhön in Central Germany. One of the challenges is to inform local stakeholders about hydrological hazards in in the biosphere reserve, which has an area of only 2433 km² and for which no regional hydrological simulations are available. To overcome the lack of local simulations of the impact of climate change on water resources, existing simulations by a number of global hydrological models (GHMs) were evaluated for the study area. While the coarse model resolution of 0.5°x0.5° (55 km x 55 km at the equator) is certainly problematic for the small study area, the advantage is that both the uncertainty of climate simulations and hydrological models can be taken into account to provide a best estimate of future hazards and their (large) uncertainties. This is different from most local hydrological climate change impact assessments, where only one hydrological model is used, which leads to an underestimation of future uncertainty as different hydrological models translate climatic changes differently into hydrological changes and, for example, mostly do not take into account the effect of changing atmospheric CO₂ on evapotranspiration and thus runoff.   

The global climate change impact simulations were performed in a consistent manner by various international modeling groups following a protocol developed by ISIMIP (ISIMIP 2b, www.isimip.org); the simulation results are freely available for download. We processed, analyzed and visualized the results of the multi-model ensemble, which consists of eight GHMs driven by the bias-adjusted output of four general circulation models. The ensemble of potential changes of total runoff and groundwater recharge were calculated for two 30-year future periods relative to a reference period, analyzing annual and seasonal means as well as interannual variability. Moreover, the two representative concentration pathways RCP 2.6 and 8.5 were chosen to inform stakeholders about two possible courses of anthropogenic emissions.

To communicate the results to local stakeholders effectively, the way to present modeling results and their uncertainty is crucial. The visualization and textual/oral presentation should not be overwhelming but comprehensive, comprehensible and engaging. It should help the stakeholder to understand the likelihood of particular hazards that can be derived from multi-model ensemble projections. In this contribution, we present the communication approach we applied during a stakeholder workshop as well as its evaluation by the stakeholders.

How to cite: Müller, L. and Döll, P.: Communicating water-related climate change hazards to local stakeholders, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8368, https://doi.org/10.5194/egusphere-egu21-8368, 2021.

The storage-reliability-yield (SRY) relationship is a well-established tool for preliminary design of reservoirs fulfilling consumptive water uses, yet rarely employed within hydropower planning studies. Here, we discuss the theoretical basis for representing the trade-offs between reservoir size and expected revenues from hydropower production, under uncertain inflows, by taking advantage of the stochastic simulation-optimization approach. We also demonstrate that under some assumptions, the complex and site-specific problem, mainly induced by the nonlinearity of storage-head-energy conversion, can be significantly simplified and generalized as well. The methodology is tested across varying runoff regimes and under a wide range of potential reservoir geometries, expressed in terms of a generic shape parameter of the head-storage relationship. Based on the outcomes of these analyses we derive empirical expressions that link reliable energy with summary inflow statistics, reservoir capacity and geometry.

How to cite: Efstratiadis, A., Tsoukalas, I., and Koutsoyiannis, D.: Revisiting the storage-reliability-yield concept in hydroelectricity, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10528, https://doi.org/10.5194/egusphere-egu21-10528, 2021.

The Open Hydrosystem Information Network (OpenHi.net) is an information infrastructure for the collection, management and dissemination of hydrologic information related to inland waters in Greece. The OpenHi.net is under development in the context of HIMIOFoTS, a national infrastructure integrating both marine and inland waters. OpenHi.net is mainly oriented to collect and manage river and lake stage data. Geographic data are essential to link stage data with the upstream basin’s hydrologic characteristics. The OpenHiGis is the GIS component of the OpenHi.net platform. The geographic database design and implementation are based on the Hydrography Theme specified by the INSPIRE Directive. The main goal is to collect, query, analyze, and offer web services relevant to hydrologic - geographic information for hydrographic network, lakes and reservoirs, river basins, drainage basins and station basins at a national level. In this sense, data stored for (a) hydrographic network (geometry, length, segment’s slope, geographical name and stream order), (b) lakes and reservoirs (geometry, area, elevation and geographical name) , and (c) basins (geometry, area, elevation, slope, basin order, main watercourse length and slope, runoff Curve Number.

The European Digital Elevation Model (Copernicus, EU-DEM version 1.1) with spatial resolution of 25 m, is selected (after examining a few well-known elevation models) for extracting hypsometric information, which is basic for river basin’s response. Other main data sources found and used are the: (a) hydrographic network, lakes and reservoirs from the implementation of EU 2000/60/EC Directive, (b) hydrographic network from EU 2007/60/EC Directive and (c) OpenStreetMap publically available hydrographic network and river networks from various scanned maps at scales approximately 1:50 k.

The ArcGIS Model Builder environment is used as the main spatial analysis tool. Several models are created to run the geographic processes and perform calculations (create INSPIRE compliant geodatabase, data import from various sources, watercourse extraction from DEM and hydrographic network definition, river basins delineation and geomorphologic attributes calculation, watercourse naming, topology creation and validation). The extraction of a primary (before editing) watercourse line is achieved by using the EU-DEM, applying  an upslope contribution area threshold equal to 10 km², which is proposed by the EU 2000/60/EC Directive. Spatial relationships between features are defined using topological rules. All the modeling procedures and the output datasets are considered to be at a scale 1:50 k.

The QGIS software is used to perform the final editing by using OSM’s, ESRI’s, Google’s and Bing’s base-maps. Furthermore, QGIS is used to make a connection to the ArcGIS geodatabase and transfer the data to PostGIS (Postgres). Finally, the MapServer software is used for publishing the data to the web. Two services, the Web Map Service (WMS) and the Web Feature Service (WFS), are provided to the user to access, query or download the geographic data through the OpenHi.net platform.

How to cite: Papageorgaki, I., Koukouvinos, A., and Mamassis, N.: OpenHiGis: A national geographic database for inland waters of Greece based on the INSPIRE Directive Hydrology Theme, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13465, https://doi.org/10.5194/egusphere-egu21-13465, 2021.

In Colombia around 70% of the electricity generation is from hydropower. It is documented that their infrastructure and operation rules affect the natural regime of flows and sediments with several impacts on aquatic ecosystem functioning mainly on the Magdalena-Cauca river basin, where most of the projects are located. Also, social conflicts have been documented downstream hydropower projects due to water use incompatibilities. Considering that Colombia has a great potential to expand hydropower generation as well as there is a growing demand from other water users, it is necessary to attend the ecological requirements of aquatic ecosystems and to improve the water management in order to avoid irreversible environmental impacts and governance problems.

In 2018, the Colombian Ministry of Environmental and Sustainable Development (MADS) developed a methodology to consider environmental flows both in the water management decisions and in the environmental impact assessment of new projects with impacts on hydrologic regimen. The opportunity to carry out a validation of its premises aims to research its effectiveness in terms of reduction in hydrologic alterations when environmental flow allocation is decided. 

That is why we have developed a computer model (HeCCA 1.0) which contains the most important methods contemplated in the methodology proposed by MADS. Thus, using river discharge data of 15 different river systems located throughout the entire country, the methodology mentioned has been tested in basins with low anthropic alteration of the hydrological regime. In this test, we cover a range of drainage areas, from 180 to 73000 km², located between 25 and 2993 meters above sea level, and different climatic and geomorphological characteristics. 

The following results have been obtained using the HeCCA tool. For the 15 river systems, the statistical quartiles Q1, Q2 and Q3 for the percentage of use are monthly correspond to 24%, 47% and 100% respectively. The systems belong to different seasonal behaviors depending on the geographical location; nine of them count on a monomodal regimen, which average percentage of use is 61%±8, and the highest percentages of use (located in the Pacific basin) are not found during the wettest months, (77%±29); four of the watersheds are in the Orinoco basin, providing use of water between 61% and 67%. Six systems have bimodal regimen, whose average percentage of use is 49%±32, the two lowest percentages of use (14% and 19%) are found in the biggest bimodal watersheds, with sizes over 1700km², which also have the highest average yields. The highest percentage of use found during the wettest months of the year is 99%, corresponding to the system located at one of the lowest points of the Caribbean basin.  

Thus, the percentage of available water depends on the watershed size, if it is related to the runoff seasonality along the year in the different catchment areas of the country. This approach provides stakeholders a clear overview of the water availability and management through a useful tool which improves the integral water management for hydrological systems.

How to cite: Fernandez Berbeo, M. C., Cortes Torres, N., Ortega Tenjo, K., Perez Pedraza, M., Laverde Mesa, L., Cubillos Peña, C., and Salazar Galan, S.: Testing the environmental flow allocation requirements in Colombia through the HeCCA 1.0 tool, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13769, https://doi.org/10.5194/egusphere-egu21-13769, 2021.

Global warming and population growth increase the need for better management of freshwater resources, in particular in arid and semi-arid regions. Due to increased rainfall variability,  reservoirs became a vital management tool that stores the water during rainfall, thus decrease flood risks and supply water during drought periods. However, large amounts of water are lost by evaporation, which markedly affects reservoirs’ function of ensuring water availability. In Egypt, about 20.0% of the country's Nile share (12.1 to 15.4 billion m³) are lost annually by evaporation from Lake Nasser. The floating covers, i.e. spheres, shade the water surface and act as a physical barrier that decreases energy flux into the water, thus decrease evaporation. Studies that compare the evaporation suppression efficiency of the floating covers, over different climatic conditions, while considering its impact on the water ecology are limited.

A field experiment in an outdoor setting (class A-pan) was conducted for nine months (March to November) in two locations that vary in their climatic conditions, i.e. Aswan and Damanhur, representing northern and southern Egypt, respectively. The water surface was covered by white, black, or multicolor spheres, in addition to the control. Daily evaporation rate (ER), water temperature (WT), evaporation suppression efficiency (ESE), were determined. Moreover, the microalgae growth was measured as an indicator of water ecology.  

Obtained results revealed massive evaporation losses from the uncovered water surface (control) in Aswan location, in which the nine-month average was 2.25 times higher than in Damanhour location. The floating spheres reduced ER in both locations, in particular the white spheres. The ESE in Aswan was less than in Damanhour location. The ESE in Damanhour was 63.38, 58.13, and 54.8%, while in Aswan was 48., 42.5, and 41.6% for white, multicolor and black spheres, respectively. Floating spheres decreased WT in the morning and mid-day, while in the evening the control treatment was the coldest, indicating partial isolation of covered water surface. Irrespective of the spheres’ color, the spheres had no detrimental effect on microalgae growth, indicating enough light penetration and gas exchange through the gaps between spheres.

In conclusion, the floating spheres is an effective mean for evaporation suppression and its efficiency is dependent on the climate and spheres’ color. The ESE of spheres is lower in environments with lower relative humidity. The white spheres are recommended for evaporation suppression without negative impacts on microalgae growth which could be a viable indicator for the ecology of the water ecosystem. Further studies on larger water reservoirs are needed while considering several aquatic organisms.

How to cite: M. Shalaby, M., N. Nassar, I., and M. Abdallah, A.: The influence of floating spheres on evaporation suppression under different climatic conditions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7942, https://doi.org/10.5194/egusphere-egu21-7942, 2021.

The EU-funded program European Water Initiative Plus for Eastern Partnership Countries (EUWI+), which is the biggest commitment of the EU to the water sector in the EaP countries, helps Armenia, Azerbaijan, Belarus, Georgia, Moldova, and Ukraine to bring their legislation closer to EU policy in the field of water management, with a main focus on the management of transboundary river basins. It supports the development and implementation of pilot river basin management plans, building on the improved policy framework and ensuring a strong participation of local stakeholders.

In 2019, with the support of EUWI+, groundwater experts from Ukraine and the Republic of Belarus identified transboundary groundwater bodies (GWBs) in the Dnipro River Basin of Ukraine and the Republic of Belarus. In total eight (3 unconfined and 5 confined) transboundary GWBs in Ukraine were identified as transboundary linked with six GWBs in Belarus. As some of these GWBs are significantly large, follow-up studies in 2020 aimed at identifying those sub parts of the GWBs which are subject to transboundary groundwater interaction. Finally, on both sides of the border, transboundary corridors at a distance of 50 km from the state border were identified as sub-zones of the existing large GWBs. This distance was chosen to capture the recharge areas of the zone of active water exchange (watersheds) and the areas of groundwater discharge (river valleys).

The investigated transboundary territory is located in Polissia, a zone of excessive moisture, where the GWBs are mainly recharged by precipitation - the unconfined GWBs all over the whole territory, the confined GWBs at places where shallow water-bearing rocks occur. In the transboundary zone, the regional recharge area is located in the Ukrainian Shield; most of the aquifers are recharged on its slopes. The direction of groundwater flow is from the Ukrainian Shield towards the artesian basins in Belarus. 

The Ukrainian part of the territory, where the confined aquifers are recharged, is characterised by minor anthropogenic pressures - very low population density and no large industrial enterprises. Therefore, impacts from the Ukrainian side on the GWBs in Belarus are limited. In contrast, the border area in the Republic of Belarus is one of its most developed industrial regions.

The analysis showed that the groundwater monitoring network in the Ukrainian 50-km transboundary zone has practically been destroyed due to long-term underfunding and it requires substantial restoration. In Belarus, the monitoring network is quite representative and requires some improvements; in some GWBs  the monitoring network is unevenly distributed and in some GWBs, the number of monitoring wells is insufficient

Within this study a comprehensive set of analytical material on geological-hydrogeological, hydrogeochemical, hydrodynamic aspects of the study area was collected, a number of open issues were identified, which will substantially contribute to the development and harmonization of not only the groundwater monitoring system of the transboundary territory of the Pripyat and Dnieper river basins in Ukraine and the Republic of Belarus, but also the groundwater monitoring system of the countries as a whole.

How to cite: Lyuta, N., Sanina, I., Biarozka, O., Vasniova, O., Scheidleder, A., and Humer, F.: Transboundary subparts of groundwater bodies (GWB) and transboundary monitoring network of the Republic of Belarus and the Ukraine - developed under the European Water Initiative Plus for Eastern Partnership Countries (EUWI+), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4599, https://doi.org/10.5194/egusphere-egu21-4599, 2021.

Water resources systems face a wide range of uncertainty in future hydroclimatic and socio-economic conditions, justifying an adaptive planning approach. Recent advances in dynamic adaptation have designed policies in which infrastructure and management actions are triggered by thresholds of indicator variables monitored over time. Typically, one or more of these components are prespecified, constraining the flexibility of policy design and evaluation. The opportunity exists for methods to identify policies combining the most relevant indicators, actions, and thresholds for dynamic adaptation to climate change. Here we present a generalized framework based on multi-objective policy tree optimization, a heuristic policy search method in which adaptation policies are represented as binary trees. We demonstrate this approach using an illustrative water resources planning problem in California where infrastructure expansion, reservoir operations, conservation rules, and conjunctive use are adapted over time to balance flood risk, water supply, and environmental objectives. To capture the uncertainty in nonstationary forcing, indicator variables include long-term hydroclimatic statistics from downscaled GCM projections along with uncertain land use and economic conditions. Policy robustness is determined by validation against a held-out scenario ensemble. A key focus of the results is comparing the indicators and actions selected by robust versus non-robust policies to identify cases where policies adapt to a signal rather than noise. This framework is supported by open source software and is generalizable across water resources systems challenged with adaptive planning under climate uncertainty.

How to cite: Herman, J. and Cohen, J.: A policy tree optimization approach to dynamic adaptation under climate uncertainty, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-739, https://doi.org/10.5194/egusphere-egu21-739, 2021.

Proper consideration of uncertainty has become a cornerstone of model-informed planning of water resource systems. In the UK Government’s 2020 Water Resources Planning Guidelines, the word “uncertainty” appears 48 times in 82 pages. This emphasis on uncertainty aligns with the increasing adoption by UK water companies of a “risk-based” approach to their long-term decision-making, in order to handle uncertainties in supply-demand estimation, climate change, population growth, etc. The term “risk-based” covers a range of methods - such as “info-gap”, “robust decision-making” or “system sensitivity analysis” - that come under different names but largely share a common rationale, essentially based on the use of Monte Carlo simulation. This shift in thinking from previous (deterministic) “worst-case” approach to a “risk-based” one is important and has the potential to significantly improve water resources planning practice. However its implementation is diminished by a certain lack of clarity about the terminology in use and about the concrete differences (and similarities) among methods. On top of these difficulties, in the next planning-cycle (2021-2026) two further step changes are introduced: (1) water companies are requested to move from a cost-efficiency approach focused on achieving the supply-demand balance, towards a fully multi-criteria approach that more explicitly encompasses other objectives including environmental sustainability; (2) as a further way to handle long-term uncertainties, they are required to embrace an “adaptive planning” approach. These changes will introduce two new sets of uncertainties around the robust quantification of criteria, particularly environmental ones, and around the attribution of weights to different criteria. This urgently calls for establishing structured approaches to quantify not only the uncertainty in model outputs, but also the sensitivity of those outputs to different forms of uncertainty in the modelling chain that mostly control the variability of the final outcome – the “best value” plan. Without this understanding of critical uncertainties, the risk is that huge efforts are invested on characterising and/or reducing uncertainties that later turn out to have little impact on the final outcome; or that water managers fall back to using oversimplified representation of those uncertainties as a way to escape the huge modelling burden. In this work, we aim at starting to establish a common rationale to “risk-based” methods within the context of a fully multi-criteria approach. We use a proof-of-concept example of a reservoir system in the South-West of England to demonstrate the use of global (i.e. Monte Carlo based) sensitivity analysis to simultaneously quantify output uncertainty and sensitivity, and identify robust decisions. We also discuss the potential of this approach to inform the construction of a “decision tree” for adaptive planning.

How to cite: Pianosi, F., Penuela-Fernandez, A., and Hutton, C.: Disentangling uncertainties in risk-based planning of water resources in the UK, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10225, https://doi.org/10.5194/egusphere-egu21-10225, 2021.

The importance of considering equity in climate change adaptation planning is increasingly being acknowledged. A preferred adaptation strategy is one that not only yields robust outcomes under multiple futures, but also has a fair distribution of benefits and harms across affected actors. In this study we propose two complementary approaches for assessing the equity of impacts of adaptation strategies. First, in the explorative approach, we explore what different multi-actor inequality patterns might emerge under different policy and uncertainty scenarios. Put differently, we identify who benefits and who loses under which kind of circumstances. Second, in the normative approach, we attempt to rank alternative strategies based on their performance across uncertain futures. Identifying which strategy is more preferable requires us to define what kind of distribution is considered to be ‘good’. We thus employ six alternative distributive moral principles that each has its own maxim in justifying the moral righteousness of a distribution: utilitarianism, prioritarianism, sufficientarianism, envy measures, weighted utilitarianism, and the Rawlsian difference principle.

We apply both approaches to a case study on agricultural adaptation planning in An Giang and Dong Thap, two provinces in the upper Vietnam Mekong Delta. We develop an integrated assessment metamodel to assess the equity implications of six alternative adaptation strategies, including dikes (de)construction policies, fertilizer subsidy, and seeds upgrading. We evaluate the distributional impacts of the alternative strategies to 23 districts in the two provinces under a large number of strategic scenarios, i.e., combinations of policy scenarios and uncertain futures. From the explorative approach, we discover six distinctive inequality patterns and identify the strategic scenarios that give rise to each inequality pattern. We find a trade-off between districts located along the Mekong river and those located further away. In some strategic scenarios the former group of districts are substantially better-off than the latter, and vice versa.

From the normative approach, we find a mixed result of preferred strategies depending on what moral principle is being adopted. The dikes deconstruction policy in Dong Thap, which performs best from a utilitarian point of view, ranks fifth from a prioritarian perspective. Upgrading seed is the most preferred strategy from the prioritarian view, but it performs the worst when looked at from a sufficientarian point of view. We further find that the results from each principle are strongly affected by uncertainties. For example, the fertilizer subsidy policy ranks last in approximately 70% of the uncertain futures according to the sufficientarian principle, but it becomes the most preferable in the other 20% of the uncertain futures. Our findings further emphasize the simultaneous consideration of both uncertainties and alternative distributive principles in adaptation planning. By using multiple moral principles, we expand the information base upon which adaptation decisions are made, and thus minimizing potential surprises and unintended consequences from our choice.

How to cite: Jafino, B. A. and Kwakkel, J.: Equitable adaptation planning under deep uncertainty for the upper Vietnam Mekong Delta, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9445, https://doi.org/10.5194/egusphere-egu21-9445, 2021.

Increasingly frequent and severe droughts are jeopardizing urban water security in water stressed regions, but cities also struggle to justify the costs and energy consumption of some drought-resilient technologies. Previous literature in urban water modeling developed strategies to expand and diversify urban water supply portfolios to enhance water resilience cost effectively.  This literature has also demonstrated that high-resolution, household-level modeling is necessary to represent the real energy footprint of different water technologies and the integration of centralized and decentralized water solutions. This urban-focused modeling scale, however, does not support the characterization of water availability at extra-urban sources resulting from watershed-wide hydrological processes. Conversely, watershed-scale water resources planning characterizes water variability and stress, supports climate change analysis, but overlooks key distributional and technological aspects. 

This project develops a watershed-to-end-user decision support tool for cost-effective, adaptive water augmentation pathways to ensure robustness in many climate futures. The novelty of our work lies in a true multiscale modeling framework that captures the complex system dynamics that link climate impacts to household water security. A robust, multi-objective, evolutionary-based optimization framework (i.e., EMODPS) is used to derive the technology portfolio, deployment location, and construction timing that defines a city’s Pareto frontier of water resilience and cost. This work informs urban water resource planners, as well as guides technology innovation by explicitly valuing technology attributes that enable resilience to droughts of varying duration, severity, and intensity. We apply this model to the City of Santa Barbara, California, given the time relevance to city planning efforts, the diversified water supply mix, and the relative isolation of the community, enclosed between the ocean and a mountain range.

How to cite: Zaniolo, M., Fletcher, S., and Mauter, M.: Robust technology and policy pathways to urban water security, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6835, https://doi.org/10.5194/egusphere-egu21-6835, 2021.

Effective optimisation methods have emerged over the last few decades to deal with the management of multiple reservoirs serving multiple and often conflicting objectives. Despite the abundant literature on the subject, the practical use of these techniques in the field remains very limited because they are perceived as “black boxes” whose behaviour is difficult to understand for users and decision-makers (Pianosi et al. 2020).

Optimisation using one or more aggregated objectives can create stakeholder reluctance when they do not recognize their values and objectives in the optimization formulation, while also raising ethical concerns related to the inclusion of undesirable and/or hidden trade-offs. In contrast, an approach considering many non-aggregated objectives has the potential to bring out alternative courses of action that better reflect the diverging perspectives of stakeholders, and align better with ethical concerns (Kasprzyk et al. 2016).

To deal with this problem, we here follow the Wierzbicki's (1979) "reference objective" concept considering each single objective as a utopia point optimised separately by deterministic dynamic programming. The optimisation, taking into account given hydroclimatic conditions and a chosen set of constraints, provides yearly probabilistic upper or lower rule curves reflecting the risk of failing to achieve each of the objectives in the future (Bader 1992). In order to use these data, we have developed a graphical user interface based on an R Shiny application showing the risk probability of future failure of each objective depending on the calendar day and the current or forecasted storage state of each reservoir.

This framework is applied on the Seine catchment area in Paris, France, which includes a system of 4 large reservoirs to protect against floods and water shortages for multiple flow thresholds and multiple locations downstream from the reservoirs. Historical datasets as well as climate change projections are used to take into account the non-stationarity nature of hydroclimatic conditions. Among other applications, this example shows the utility of such a tool in order to justify the stakeholders decisions to discard minor objectives when they undermine the chances of success of major objectives in critical situations.

References

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Bader, J.-C., 1992. Consignes de gestion du barrage à vocation multiple de Manantali: détermination des cotes limites à respecter dans la retenue [Multiple use management of Manantali Dam: determination of limiting storage levels]. Hydrologie Continentale 7, 3–12.

Kasprzyk, J.R., Reed, P.M., Hadka, D.M., 2016. Battling Arrow’s Paradox to Discover Robust Water Management Alternatives. Journal of Water Resources Planning and Management 142, 04015053. https://doi.org/10.1061/(ASCE)WR.1943-5452.0000572

Pianosi, F., Dobson, B., Wagener, T., 2020. Use of Reservoir Operation Optimization Methods in Practice: Insights from a Survey of Water Resource Managers. Journal of Water Resources Planning and Management 146, 02520005. https://doi.org/10.1061/(ASCE)WR.1943-5452.0001301

Wierzbicki, A.P., 1979. The Use of Reference Objectives in Multiobjective Optimization - Theoretical Implications and Practical Experience (No. WP-79-66). International Institute for Applied Systems Analysis, Laxenburg, Austria.

How to cite: Dau, Q., Dorchies, D., and Bader, J.-C.: Many-objective risk assessment framework for guiding operational decisions on multiple reservoirs, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10676, https://doi.org/10.5194/egusphere-egu21-10676, 2021.