In the previous chapter, we introduced ourselves to the importance of satellite remote sensing for water management and why the technique is going to take greater importance in years to come as challenges mount from climate change, competing needs and lack of ground data. In this chapter, we will overview the basics of remote sensing, define key concepts and terms. Using these concepts and terms, we will develop an understanding of the fundamental principle required for the success of remote sensing.

Chapter 7 introduces the basic concepts and fundamental limitations (i.e., residues) of phase unwrapping. It presents three common unwrapping methods: the global Fourier transform method, the path-following branch-cut method, and the minimum cost flow method. Additionally, it covers methods for correcting integer ambiguities using phase closure within stacks of interferograms.

Three potential climate futures — 1.5 °C, 2 °C, and 3.6 °C — are predicted by the UNFCCC’s ‘climate action pathways’, each with major and escalating implications for adaptation and mitigation. Marina Romanello, Co-Lead Health Editor for The Monitor, highlights the dangers of anything above a 1.5 °C scenario, emphasizing increased health risks and economic damages. The chapter outlines the CVF Monitor’s projections for each of the three scenarios and discusses the significant differences in outcomes depending on global warming levels. Stressing the importance of adhering to international agreements like the Paris Agreement, immediate and substantial emissions reductions are crucial to avoid catastrophic impacts. The chapter underscores the need for global cooperation in achieving these goals.

This chapter focuses on the importance of circular business models and the synergies they create within circular economy liveable cities. Circular business models emphasise reducing waste, reusing resources, and recycling materials, promoting sustainable economic growth while addressing environmental challenges. By fostering innovation, resource efficiency, and collaboration across various sectors, these models help cities transition to a circular economy. The chapter highlights the role of leadership, imagination, and curiosity in driving this transformation. Leaders are key to setting ambitious goals and mobilising resources, while imaginative thinking and curiosity foster the development of innovative solutions to urban challenges. Examples from companies like Interface, Patagonia, and Philips Lighting demonstrate how visionary leadership and creative business models contribute to sustainability and circularity. The chapter explores the synergies between circular business models and urban systems, with case studies from cities like Amsterdam and Paris. These cities have adopted circular strategies that integrate sustainable waste management, renewable energy, and resource-efficient practices, showcasing the transformative potential of circular economies. Ultimately, the chapter argues that circular business models are essential for creating resilient, sustainable cities. By leveraging leadership, innovation, and cross-sector collaboration, cities can foster circular economies that promote environmental sustainability, economic growth, and improved quality of life.

Climate change impacts are, however, coming to us all — developing and developed countries alike. For instance, Hurricane Maria’s devastation in the Caribbean and extreme heatwaves in Europe exemplify how no region is immune. The chapter discusses how even developed nations face significant challenges, such as wildfires in Australia and California, and flooding in Germany. Comprehensive policy responses are essential to address these widespread impacts. Insights from experts such as Ken Ofori-Atta, Ghana’s Minister for Finance, highlight the extensive effects of climate change, including infrastructure damage, economic costs, health effects, and migration. The chapter calls for a unified global effort to mitigate climate risks, improve infrastructure resilience, and implement robust economic and health strategies to protect all populations from the escalating consequences of climate change.

This chapter focuses on dynamic water resource management for regenerative cities, emphasising the need for a more sustainable, circular approach to urban water management. As cities face increasing water scarcity, compounded by rapid urbanisation and climate change, traditional methods of water supply are no longer sufficient. The chapter advocates for a transition from linear water management systems towards more integrated and regenerative models. It introduces key concepts such as cities acting as water supply catchments, where urban areas manage and recycle their own water through innovative technologies like rainwater harvesting, greywater reuse, and advanced wastewater treatment. The chapter highlights global best practices, including Tokyo’s water-saving initiatives, Singapore’s closed water loop system, and China’s Sponge City programme, illustrating how cities can adopt diverse, multifunctional water strategies to secure their long-term water supply. Additionally, the chapter underscores the importance of blue–green infrastructure, which integrates natural and built systems to provide ecosystem services, mitigate flooding, and enhance urban resilience. By integrating dynamic water resource management with urban planning, cities can reduce their environmental footprint and foster sustainable development, making water security a central component of regenerative city planning.

This chapter delves into circular urban agriculture, examining strategies for sustainable food production in rapidly growing cities. As urbanisation accelerates, cities face the challenge of feeding an estimated nine billion people while minimising the environmental impact of agriculture. Traditional agricultural practices contribute to resource depletion and pollution, making a circular approach essential for sustainable urban development. Circular urban agriculture integrates resource efficiency by using waste streams, conserving water, and minimising inputs like soil and fertilisers. The chapter discusses various urban farming methods, including rooftop gardens, vertical farming, hydroponics, and community gardens. These practices can increase local food production while reducing the environmental footprint of cities. Water conservation and recycling are emphasised as critical components of circular urban agriculture. Strategies such as drip irrigation, greywater reuse, and rainwater harvesting help reduce reliance on municipal water supplies, lower operational costs, and promote sustainability. The chapter also highlights resource recovery, particularly through nutrient recycling and the use of biosolids, to enhance soil quality and increase agricultural productivity. By adopting circular practices, cities can support local food production, improve resource efficiency, and contribute to urban resilience, all while fostering community relationships and reducing the environmental impact of traditional agricultural systems.

This chapter outlines the best practices and strategies for cities to transition towards becoming circular and liveable. It emphasises the importance of adopting circular economy principles across various urban sectors, including waste management, energy efficiency, transportation, and urban agriculture. By applying the 5R approach – reduce, reuse, recycle, restore, and recover – cities can decouple economic growth from environmental degradation and create more sustainable urban environments. The chapter presents actionable strategies, such as implementing energy-efficient financing for building retrofits, promoting water reuse through grant programmes, and creating comprehensive electronic waste collection and disposal systems. It also emphasises the role of public participation and stakeholder collaboration in driving circular initiatives, highlighting the Quadruple Helix model, which involves academia, industry, government, and civil society working together to foster innovation. Additionally, the chapter explores the integration of nature-based solutions, sustainable infrastructure, and urban resilience practices. Case studies from cities like Amsterdam, Paris, and Copenhagen showcase successful examples of circular business models and governance frameworks that contribute to sustainability. Finally, the chapter presents a roadmap for moving forward, focusing on education, policy innovation, and community engagement as critical components for building resilient, circular cities that prioritise both environmental sustainability and social equity.

Earlier in Chapter 2, we had formalized our approach to remote sensing in the form of ‘target’, background and foreground. Now the first thing we need to focus on is the electromagnetic behavior of the target. This is best captured by the term ‘Black Body’. From here on, we will try to think of the target in water management relative to a black body and understand how much a black body it is under certain circumstances.