As water's significance as a geopolitical resource is poised to surpass that of oil, this book explores the adaptation of Water, Sanitation, and Hygiene (WASH) services in the Middle East to climate change challenges, leveraging the Humanitarian-Development-Peace nexus for a sustainable transition and resilient solutions. Delving into the humanitarian and development sectors across the region, the authors advocate for a transformative approach towards more innovative, integrated, and localized programming. It draws a parallel between the increasing global shift in humanitarian needs, as starkly revealed by the COVID-19 pandemic, and the ongoing devastation wrought by climate change, particularly through water-related crises such as flooding, drought, famine, and conflict. The authors stress the urgent need for adaptive and sustainable strategies that can swiftly respond to evolving climate challenges. This book argues that there is currently a window of opportunity for WASH practitioners to develop broader, multi-sectoral experiences to meet these challenges. Drawing on discussions with humanitarian and development practitioners and new contemporary case studies, this book analyzes the financial, institutional, environmental, technical, and socio-cultural considerations for creating sustainable WASH services in transition. The narrative emphasizes the urgent need for a Humanitarian-Development-Peace nexus approach, advocating for multisectoral collaboration and localization as vital to addressing protracted crises and climate change's escalating threats. It calls for a strategic shift towards organizations that merge immediate humanitarian aid with sustainable development, enhancing local capacities for effective, enduring solutions. The authors conclude by outlining practical actions for humanitarian and development organizations at the local, national, regional, and global levels to support effective integrated and transitional WASH programming in the future.