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Arias M.E.,University of Canterbury | Arias M.E.,Harvard University | Piman T.,Mekong River Commission | Lauri H.,EIA Finland Ltd | And 2 more authors.
Hydrology and Earth System Sciences | Year: 2014

River tributaries have a key role in the biophysical functioning of the Mekong Basin. Of particular interest are the Sesan, Srepok, and Sekong (3S) rivers, which contribute nearly a quarter of the total Mekong discharge. Forty two dams are proposed in the 3S, and once completed they will exceed the active storage of China's large dam cascade in the Upper Mekong. Given their proximity to the Lower Mekong floodplains, the 3S dams could alter the flood-pulse hydrology driving the productivity of downstream ecosystems. Therefore, the main objective of this study was to quantify how hydropower development in the 3S, together with definite future (DF) plans for infrastructure development through the basin, would alter the hydrology of the Tonle Sap's Floodplain, the largest wetland in the Mekong and home to one of the most productive inland fisheries in the world. We coupled results from four numerical models representing the basin's surface hydrology, water resources development, and floodplain hydrodynamics. The scale of alterations caused by hydropower in the 3S was compared with the basin's DF scenario driven by the Upper Mekong dam cascade. The DF or the 3S development scenarios could independently increase Tonle Sap's 30-day minimum water levels by 30 ± 5 cm and decrease annual water level fall rates by 0.30 ± 0.05 cm day-1. When analyzed together (DF + 3S), these scenarios are likely to eliminate all baseline conditions (1986-2000) of extreme low water levels, a particularly important component of Tonle Sap's environmental flows. Given the ongoing trends and large economic incentives in the hydropower business in the region, there is a high possibility that most of the 3S hydropower potential will be exploited and that dams will be built even in locations where there is a high risk of ecological disruption. Hence, retrofitting current designs and operations to promote sustainable hydropower practices that optimize multiple river services - rather than just maximize hydropower generation - appear to be the most feasible alternative to mitigate hydropower-related disruptions in the Mekong. © Author(s) 2014.

Liu J.,Innovation International | Paul S.,Innovation International | Manguerra H.,Mekong River Commission
Proceedings of the Watershed Management Symposium | Year: 2015

In 2012, the Halstead Fire of Salmon-Challis National Forest affected approximately 174,000 acres of forest. The post-fire logging operation to recover marketable timber calls for an extensive investigation on the environmental impacts of logging activity towards forestry recovery and sediment/water yields. This study analyzed these issues and compared seasonal differences between winter and summer logging using ArcSWAT. The 95,275-ac watershed was divided into three sub-watersheds for analyses. Corresponding to fire damage levels, land types of barren, grass, and shrub were assigned to areas with high, medium, and low severities, respectively. Four post-fire scenarios were simulated: No Recovery (NR)-the land type distribution remains unaltered after the fire and no logging activities; No Action (NA)-natural forestry recovery without logging operation; Summer Logging (SL)-forest recovery with logging activities in summer; Winter Logging (WL)-forest recovery with logging activities in winter. These scenarios were modeled using ArcSWAT from 2012 to 2019, with the proposed logging operation from 2015 till 2019. The outputs indicate that NR and SL can generate higher sediment/water yields; while NA and WL have similar yields as 95% of NR or SL. For the entire watershed, SL can generate 0.64 Mg/ha or 7,798 Mg/yr sediment more than WL, as well as 6,573 kg nitrogen and 1,827 kg phosphorus more than WL annually. The logging activities in winter after wildfires may be an optimal solution to recover marketable timber in terms of minimal environmental impacts towards the forestry ecosystem. © 2015 ASCE.

Ng H.H.,National University of Singapore | Vidthayanon C.,Mekong River Commission
Zootaxa | Year: 2011

Pseudeutropius indigens, a new species of schilbeid catfish from peninsular Thailand, is described here. It can be distinguished from congeners in having the following combination of characters: head length 23.1-24.3% SL, head width 10.5-11.0% SL, length of anal-fin base 45.6-50.4% SL, 37-41 anal-fin rays, isognathous jaws in which the premaxillary teeth are not visible when the mouth is closed, and long nasal, maxillary and mandibular barbels that reach to at least the analfin origin. Copyright © 2011 Magnolia Press.

Ng H.H.,Lee Kong Chian Natural History Museum | Vidthayanon C.,Mekong River Commission
Zootaxa | Year: 2014

We review members of the sisorid catfish genus Exostoma known from Thailand. Three species are recognized, of which two from the headwaters of the Chao Phraya River drainage in northwestern Thailand, are described here as new: E. effrenum and E. peregrinator. In addition to the two new species, E. berdmorei (which is here redescribed) is also known from the Salween River drainage in western Thailand. The three species can be distinguished from each other and other congeners by the morphologies of the adipose and caudal fins, as well as morphometric data for the eye diameter, head width, dorsal-to-adipose distance, body depth at anus, caudal-peduncle length, caudal-peduncle depth, and numbers of branched pectoral-fin rays and preanal vertebrae. Copyright © 2014 Magnolia Press.

Kranz N.,Ecologic Institute Berlin | Menniken T.,Mekong River Commission | Hinkel J.,Potsdam Institute for Climate Impact Research
Environmental Science and Policy | Year: 2010

The challenge of governing transboundary water resources is expected to increase with climate change and the resulting need to adapt to its impacts such as temperature increase, more precipitation in the wet season and less in the dry season. In a number of transboundary basins, international regimes, and in particular river basin commissions, are emerging to account for this and other challenges. Some basins are, however, rather advanced in terms of developing climate change adaptation strategies, while others are in a more nascent stage. For the two case studies of the Orange-Senqu and Mekong river basins, this paper attempts to explain the different degrees of progress towards climate change adaptation by applying regime effectiveness analysis. First, we analyze, using the Activity Diagram (AD) of the Management and Transition Framework (MTF), at which stage in the climate change adaptation policy formation process each of the two basins is. Then we attempt to explain the different degrees of progress towards adaptation by means of regime effectiveness theory. Variables indicating regime effectiveness are taken from the literature and further developed to suit the context of climate change adaptation. We find that the different degrees of progress can partially be explained by some variables of regime effectiveness such as the characteristics of rules and procedures, organizational structure, the role of riparian countries as well as international context. At the same time, the analysis points to the need for an analysis of additional factors that potentially shape decision-making and policy processes for climate change adaptation in international river basins such as (a) the hydrological, political and socio-economic setting, (b) underlying principles of regional cooperation (or conflict), (c) interests and values of the various actors in the negotiation process and (d) the possible linkages and trade-offs with other policy fields. © 2010 Elsevier Ltd.

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