Colonialism continues to have an enduring impact on hydrological research, practice, and education. This paper examines the colonial legacy in hydrology and highlights the need for decolonisation to achieve justice, inclusivity, and sustainability in water management. Through tracing the development of hydrology research and examining stories from Canada, Indonesia, India, West Asia, and Africa, the paper uncovers the different ways colonial-era policies that have shaped contemporary water challenges. Findings indicate that colonial hydrological practices have led to significant ecological and social impacts, disrupted Indigenous knowledge systems, and intensified transboundary water conflicts. We advocate for considering, when desired by communities, place-based and Indigenous knowledge into the sciences, practices, and outputs of hydrology, revisiting ownership practices, and addressing neo-colonial influences through co-creation and inclusive learning. By reflecting on our colonial past, we propose pathways through reflective questions and a decision tree to guide future water knowledge generation and support local water management.