Integrating natural and built infrastructure for water management-
Water is linked to many facets of human health and well-being, far beyond what we directly consume. It is essential for food production and many aspects of socio-economic development including activities related to energy, transport, industrial processes, and tourism. The ability to manage water-related uncertainties and mitigate the risks of water-related hazards such as floods and droughts is also essential for human welfare. Allowing for available water resources to support ecosystem health and functioning is also vital. Hence, sustainable water management must address a range of priorities with many complex and interconnected challenges.
Water resource management: Risks and opportunities
The dramatic surge in infrastructure development throughout Southeast Asia in recent years provides both opportunities and risks for water resource management in the region. For example, the countries in the Mekong basin are currently engaged in a rapid process of dam building. Some 48 dams have been built, or are under construction, with at least 70 more being planned for the near future. These dams will enable greater control of flow regimes, and if operated well, will provide significant opportunities for power and food production, as well as potential for flood and drought mitigation.
However, the dams are also accompanied with risks. It is estimated that 60 million people are dependent on the Mekong for some aspect of their livelihoods. Freshwater and marine fisheries of the Mekong and its tributaries produce more fish than any other river in the world. Approximately 2.6 million tonnes of freshwater fish, valued at some $2.5 billion, is produced each year. Because the dams will alter flow regimes and potentially block fish migration, it is anticipated that these fisheries will be placed in jeopardy.
Similarly, the trapping of sediment within the newly created reservoirs will significantly reduce the inflow of sediment to the Mekong delta and the nearshore marine environment. The loss of “nature’s fertiliser” for the Delta farmers (as the sediment is rich in nutrients), in conjunction with the increase in the sea level and erosion as a consequence of climate change, could devastate the lives of many of the 12 million residents.
In the present era, sustainable water resource development and management call for an increased consideration of the environment and the ecosystem services that are provided. The viability of water-related planning decisions should not just take into account engineering, financial, and social perspectives, but also the trade-offs and synergies with ecosystems. This is not a matter of simply supplying “water for nature”, but also an argument that makes good economic sense. It is essential to protect key ecosystem functions so that they can continue to deliver and sustain the essential ecosystem services, on which large numbers of people depend. For example, managing floods in the Mekong basin needs to factor in the damage they cause, which is mainly linked to the destruction of infrastructure and crops, as also the significant benefits that they provide for agriculture and fisheries.
Innovative perspectives and strategies
To do this is not easy and can greatly complicate decision-making. Water resource planning needs to incorporate new ways of thinking that are much more holistic in nature, integrated across all levels and scales, and built around the concept of multiple benefits across the various socio-economic groups in society. Far greater consideration needs to be given to the full range of possible infrastructure interventions, the likely consequences of each, and the cumulative impacts. Ecosystems themselves should be recognised as “natural water infrastructure” that provides benefits in much the same way as built infrastructure such as dams, canals, boreholes, and embankments. Innovative approaches need to be identified, trialled, refined, and upscaled.
In many countries, road infrastructure is used to collect run-off that then recharges aquifers. A twist on this idea is the concept of “underground taming of floods for irrigation” (UTFI). This is an example of the sort of innovative thinking that is required. The basic idea is to strategically recharge depleted aquifers in upstream regions of catchments with “excess” wet-season flows, thus preventing downstream urban flooding and simultaneously providing additional groundwater for irrigation during the dry season (Fig. 1). This concept that exists only on paper still needs to be further researched and tested, though a desk study has demonstrated the plausibility of the approach for the Chao Phraya river basin in Thailand. Further work on this approach is currently under way in South Asia.
Similarly, the notion of designing and managing human-made reservoirs, not only to produce energy, but also to replace lost food production and sustain ecosystem services, is another idea that builds on the concept of multiple uses. For example, operating rules might need to be designed to ensure that physical, chemical, and biological conditions within the reservoir are appropriate for fisheries and not undermined by releases for hydropower and/or irrigation.
Another idea is to increase the productivity of reservoir fisheries and support reservoir-based livelihoods by creating permanent wetlands within the drawdown zone of reservoirs to provide a habitat for fish when the water level of the reservoir is lowered (see Fig. 2). In Laos, the Theun Hinboun Power Company is considering the construction of such wetlands within the drawdown zone of the recently constructed Nam Gnouang reservoir on the Nam Theun river.
In Vietnam, trials of short-duration cassava have been conducted in the drawdown zone of the Yali reservoir in Sai Thay district, which have demonstrated the technical feasibility of growing dry-season crops on residual moisture. Research on the Nam Ngum basin in Laos has revealed how the construction of hydropower dams and associated dry-season releases have facilitated downstream irrigation in the Vientiane plains.
Consideration must also be given to the ways that dams are designed and operated to enable the transport of sediment downstream, as has been attempted in some places. Currently, researchers from the Natural Heritage Institute, in conjunction with sediment experts from the region, are investigating options of improving sediment transport in the Mekong river after the new dams are built.
Water strategy that protects ecosystems, livelihoods, and the future
Finally, sustainable water development will only be achieved if it is supported by an enabling environment that targets synergies across sectors. Water challenges need to be considered holistically. Water infrastructure investments, be they in hydropower dam construction on the Mekong or the Nam Thuen, or in flood-proofing the Chao Phraya basin, need to be properly planned and operated, with due consideration of the interests of all stakeholders including both existing and future generations. n
Matthew McCartney is a principal researcher specializing in water resources and wetland and hydro-ecological studies. His experience stems from participation in a wide range of research and applied projects often as part of a multi-disciplinary team. He was a steering committee member on the UNEP Dams Development Project and is currently a member of the Ramsar Science and Technical Review Panel.
Paul Pavelic specializes in groundwater and conjunctive use management in relation to issues such as floods & droughts, watershed development, small scale irrigation development and riverbank filtration. He has worked in sub-Saharan Africa, South Asia and South East Asia and is currently based in Vientiane, Laos.
