Infrastructure for heat provision in the built environment needs to change remarkably to support lowering carbon emissions and achieving climate mitigation targets before 2050. We propose a computational approach for finding a mix of heat options per neighbourhood that minimises cumulative carbon emissions between 2030 and 2050, referred to as committed emissions, while at the same time adhering to technological constraints at both the household and neighbourhood scales. To establish this approach, we integrated bottom-up heat demand modelling at neighbourhood scale with a mixed-integer non-linear optimisation problem. Nine scenarios with different pathways for the insulation of buildings and the decarbonisation in electricity generation were considered and applied to three neighbourhoods in the city of Amsterdam, the Netherlands. The results show that (i) the committed emissions are ten times lower between 2030 and 2050 in scenarios in which ambitious measures are taken for the insulation of buildings and the decarbonisation in electricity generation, (ii) only in these ‘ambitious scenarios’ low temperature heat systems, such as heat pumps and low temperature heat networks, are optimal solutions for minimising committed emissions, (iii) if less ambitious insulation and decarbonisation measures are taken, high temperature heat options can be part of the heat mix with lowest committed emissions, and (iv) the minimum heat density for low temperature heat networks is not always achieved, creating risks for carbon lock-ins when applying these heat networks. Our results clearly indicate that pathways for the retrofitting of buildings and the decarbonisation in electricity generation need to be taken into account jointly when designing renewable and low-carbon heat systems to optimally reduce carbon emissions towards 2050 and reduce future carbon lock-ins.@en

Integrating the planning of a multi-reservoir system in nexus with agricultural and electricity infrastructure could alleviate security concerns for these resources in regions where demand is growing while water and land scarcity are exacerbated by climate change and anthropogenic pressures. This study focuses on the benefits of resource integration and cooperation in the Eastern Nile basin. To overcome common limitations of equilibrium and soft-linked partial equilibrium models (e.g. high levels of spatial aggregation, non-insightful cooperation scenarios and a lack of heterogeneity), we propose a regional hard-linked WEF-nexus model that explicitly represents resource connectivity networks for water and electricity, and describes heterogeneity in resource availability, production potentials and physical constraints. Using a non-linear operational process, we optimise reservoir operations, water allocations, cropping patterns, electricity mixes and trade quantities on a monthly time-step over multiple years in a receding horizon fashion to maximize economic benefits for each country and regionally. This iterative implementation allows the modelling of operational changes as feedback against exogenous climate disturbances and enables information exchange between upstream-downstream countries. Thus, we describe four different levels of transboundary cooperation with their corresponding constraints and policy objectives. Compared to the reference scenario of unilateral planning, our results indicate an increase in regional economic returns for scenarios in which river flow information is shared between countries (+9%), river flow and trade information are shared (+10%) and WEF resources are coordinated regionally (+15%). These increased returns successively come from an increase in the effectiveness of agricultural water consumption, especially in Sudan, a change in trade patterns for agricultural products and a shift in cropping patterns. These findings underscore the importance of adequate representations of spatial and temporal heterogeneity of resources and their connectivity, as well as the need for a more diverse set of collaboration scenarios to facilitate planning in transboundary river systems.@en

Integrating the operational planning of river, land and power infrastructure could safeguard the water, energy and food security in regions where these resources are under pressure by increasing demands and decreasing availabilities and production potentials. Our work focuses on the benefits of integration and cooperation in the operational planning of these resources and infrastructures between riparian states in transboundary river basins. Therefore we introduce a regional hard-linked WEF-nexus model that explicitly represents resource connectivity networks, gridded agro-hydrological potentials and constraints, national socio-economic demands and non-linear operational processes to optimise reservoir operations, water allocations, cropping patterns, electricity mixes and trade quantities on a monthly time-step over multiple years in a receding horizon fashion. This iterative process facilitates the modelling of changes as feedback against exogenous disturbances and, through the exchange of information between countries, different levels of cooperation. We optimize the total economic returns of resource allocation for four different transboundary cooperation scenarios over an historic planning period in the Eastern Nile basin, for each country and regionally, for multiple foresight settings and policy objectives. Compared to the reference scenario of unilateral planning, our results indicate an increase in regional economic returns for scenarios in which flow information is shared between countries (+8%), flow and trade information is shared (+9%) and resources are coordinated regionally (+13%), without this being accompanied by a significant decline in returns for any country. These increased returns successively come from an increase in the effectiveness of agricultural water consumption, especially in Sudan, a change in trade patterns for agricultural products and a shift in cropping patterns. These findings illustrate the importance of adequate representations of spatial and temporal heterogeneity and resource connectivity, and the need for a more diverse set of collaboration scenarios to quantify the costs and benefits of specific interventions and policies to facilitate comprehensively planning in transboundary river systems.@en