E-Flows in the Nam Songkhram River Basin
by David JH Blake with Ubolrattana Sunthornratana, Buapun Promphakping, Sukhavit Buaphuan, Juha Sarkkula, Matti Kummu, Mongkhon Ta-oun, Pattaraporn Waleetorncheepsawat, Sansonthi Boonyothayan, Rebecca Tharme, Maria Osbeck, Suparerk Janprasart (2011)
The study undertaken in the Nam Songkhram basin in northeast Thailand is based on the concept of E-Flows. The approach considers not only the importance of river flows from a physical or ecological perspective, but also relates to the socio-political side of the equation. The key to understanding E-Flows is the role that people play both as beneficiaries and at the same time, modifiers of the wider riverine ecosystem. As an “ecological water demand”, E-Flows should be regarded as a legitimate water use sector similar to the industrial or agricultural water use sectors.
The Nam Songkhram River Basin covers a total area of 13,126 km2 in northeast Thailand. Over its lower 300 km, the river crosses across some of the most significant wetland habitats in northeast Thailand before entering the Mekong River in Nakhon Phanom province, opposite Lao PDR. The Nam Songkhram River is an open riverine system intimately linked to the Mekong River mainstream in terms of ecology and hydrology. When the Mekong River’s level is high in some years, there will be a reverse flow of the Mekong River into the Nam Songkhram River for many kilometers. The Nam Songkhram Basin is noted for its abundant and biodiverse capture fishery and associated living aquatic resources.
The study emerged from a growing concern amongst many actors that river basins in Thailand are not being well managed and the core ecosystem services and functions they provide are gradually being degraded and diminished. The study was part of ongoing multi‐stakeholder efforts to develop and strengthen integrated planning processes in the Mekong Region in general, and the Lower Nam Songkhram specifically.
Key findings and conclusions
- The lower reaches of the Nam Songkhram River is still a functional floodplain system, as indicated by the wide diversity of aquatic fauna still present and a broad range of habitats, both aquatic and terrestrial. This type of floodplain river system dependent on prolonged annual flooding and inter‐connectedness with the mainstream Mekong is unique in Thailand and thus has high conservation value, presently poorly recognised by key actors.
- The study confirmed and strengthened the understanding of the close relationship between the mainstream Mekong river and the lower Nam Songkhram River Basin (LSRB), in terms of both ecology and hydrology, in particular the role of extensive seasonal flooding arising from a notable backwater and occasional backflow effect on to the LSRB floodplain. Comparisons with the Tonle Sap and Great Lake hydrology are valid and worthy of further research, as both systems are representative examples of tropical “flood pulse” river systems, a phenomenon that underpins the high biodiversity and productivity of both sub-systems within the same larger river basin.
- Because of the primary influence of the Mekong mainstream on LSRB flood timing, duration and extent (as highlighted in hydrological models produced for the lower Nam Songkhram Basin), any attempt to control flooding by building flow control infrastructure on the Lower Nam Songkhram River or main tributaries like the Nam Oon, is likely to be futile and counterproductive, creating negative environmental impacts, which so far have not been taken into account in project proposals.
- The LSRB floodplain is in the latter stages of an ecological transformation from being dominated by natural vegetation and diverse wetland habitats, to a more simplified ecosystem with fewer habitats, less biodiversity and enhanced anthropogenic disturbance. This is principally as a result of wholesale removal of natural forests and conversion to agricultural land, in particular paddy fields and latterly, monocrop industrial tree farms such as eucalyptus and rubber. The ecological impacts of this transformation are not well studied, but anecdotal evidence from local resource users and some empirical evidence collected during the study, suggests that they have far‐reaching implications in terms of biodiversity loss and reduced aquatic productivity. The loss of ecosystem functions and services appear to be having serious negative impacts on fishery productivity and local livelihoods through food and income security declines.