Migrating sands: Refocusing transboundary flows from water to sediment

Abstract

Over 55,000 km of the world’s interior political border is formed along river channels. Yet it is more than just water that is conveyed downstream and across these borders by river systems, with sediment, pollutants, nutrients also transported, impacting downstream ecosystem service provision and livelihoods. Fundamentally, water and sediment operate in two distinct cycles, the behaviours of which have major implications for their management. The water cycle is inherently circular, with water being replenished by climatic processes across the basin. The sediment system, however, is linear, where once sediment is hindered or removed from the system, it cannot be reintroduced without anthropogenic action. In this paper, the balance between discourses of water and sediment are redressed by viewing the dialogues around transboundary management practices from these two cycles. Using the Mekong River, Southeast Asia as a focus, it is concluded that despite a political discourse that may predominantly focus on water, the management of waterways that traverse or cross international political borders must recognise that flows of water and sediment are intrinsically linked. The flow of rivers across political borders presents both challenges (potentially hindering data generation and sharing) and opportunities for international cooperation on environmental issues. It is argued that the framework for international cooperation on water is a good place to start when trying to address sediment issues, but a recognition of the differing behaviours of water and sediment systems is necessary to ensure appropriate and sustainable management of the sediment resource.