Hydrological alterations from water infrastructure development in the Mekong floodplains

Abstract

The Mekong floodplains, which encompasses the region from Kratie Township in Central Cambodia to the Vietnamese East Sea, is a region of globally renown agricultural productivity and biodiversity. The construction of 135 dams across the Mekong basin and the development of delta‐based flood prevention systems have caused public concern given possible threats on the stability of agricultural and ecological systems in the floodplains. Mekong dams store water upstream and regulate flow seasonality, while in situ flood prevention systems re‐distribute water retention capacity in the floodplains. The main aim of this paper is to evaluate possible impacts of the recent development of both hydropower dams and flood prevention systems on hydrological regimes in the Mekong floodplains. An analysis of measured daily and hourly water level data for key stations in the Mekong floodplains from Kratie to the river mouth in Vietnam was conducted. Hydropower dam information was obtained from the hydropower database managed by the Mekong River Commission, and the MODIS satellite imagery was used to detect changes in flooding extent related to the operation of flood prevention systems in the Vietnam Mekong Delta. Results indicate that the upper part of the floodplains, the Cambodian floodplains, may buffer upstream dam impacts to the Vietnam Mekong Delta. Flood prevention up to date has had the greatest effect on the natural hydrological regime of the Mekong floodplains, evidenced by a significant increase of water level rise and fall rates in the upper delta and causing water levels in the middle delta to increase. The development of flood prevention systems has also effected spatial distribution of flooding as indicated via a time series analysis of satellite imagery. While this development leads to increase localized agricultural productivity, our historical data analysis indicates that development of one region detrimentally affects other regions within the delta, which could increase the risk of future conflicts among regions, economic sectors and the ecological value of these important floodplains. Copyright © 2016 John Wiley & Sons, Ltd.

Has dyke development in the Vietnamese Mekong Delta shifted flood hazard downstream?

“…Recently, Fujihara et al (2016) and Dang et al (2016) attempted to quantify the impacts of the high-dyke development on downstream water levels. Both studies derived high-dyke areas from Moderate Resolution Imaging Spectroradiometer (MODIS) satellite images and analysed historical records to detect trends in water levels and to attribute these trends to the dyke development.…”

Changes in the Lake Area of Tonle Sap: Possible Linkage to Runoff Alterations in the Lancang River?

“…Siev et al [31] used MODIS data to analyze seasonal variations in and water quantity of the flooding area (excluding the water area of Tonle Sap Lake) between Tonle Sap Lake and the Mekong River during the years of 2003 to 2005. To explore the relationship between the construction of water conservancy facilities in the lower reaches of the Mekong River and hydrological variations, Dang et al [32] used a method similar to the method proposed by Arias et al [8]; considering typical water levels during the dry season and flood season from 2000 to 2013, this method was used to select the appropriate MODIS product (namely, MOD09A1) of the corresponding period and extract the flooding zones. Tangdamrongsub et al used several satellite data products (included GRACE, MODIS, and TRMM) to estimate terrestrial water storage and quantify flood events over the Tonle Sap basin between 2002 and 2014 [33].…”

Large-scale impacts of hydropower development on the Mompós Depression wetlands, Colombia

“…There are numerous examples worldwide of how changes in flow, sediment, and temperature regimes; loss of river connectivity; and other impacts associated with reservoirs and dams cumulatively affect physical and ecological processes that determine the integrity of major river systems, and in particular, of riverine lowland floodplains and wetlands (Arias, Piman, Lauri, Cochrane, & 10 Kummu, 2014;Dang, Cochrane, Arias, Van, & de Vries, 2016;Grill et al, 2015;J. J. Opperman, Luster, McKenney, Roberts, & Meadows, 2010;Tockner & Stanford, 2002).…”

“…Due to their central role in processes operating at the basin scale, and to the economic value of the numerous services they provide, hydrologically and ecologically functional riverine floodplains should be considered in sustainable water management infrastructure development. Such considerations should go beyond project-scale environmental impact assessments to consider the cumulative effect of all interventions located upstream (Dang et al, 2016;20 Fitzhugh & Vogel, 2011;Yang & Lu, 2014).…”

“…Like habitat fragmentation, changes in the magnitude, frequency, duration, and temporality of river flows also exhibit nonlinear cumulative behavior (Townsend and Hildrew, 1994;Stanford et al, 1996;Poff et al, 1997;Dang et al, 2016). While the artificial regulation effect of individual dams on hydrologic alteration depends both on reservoir storage capacity in 5 comparison to the natural river discharge and on the operational rules (Williams and Wolman, 1984), at the basin level, dam placement determines both the spatial extent and the degree of alteration; certain relative dam locations can enable (or preclude) attenuation of streamflow from tributary rivers, and multiple dams located in the same river branch or sub-basin can amplify the artificial regulation-resulting in hydrologic alteration greater than the sum of the individual effects of single reservoirs-propagating impacts hundreds or thousands of kilometers downstream (Angarita, Delgado, Escobar-Arias, 10 & Walschburger, 2013;Fitzhugh & Vogel, 2011;Piman, Cochrane, & Arias, 2016;Richter & Baumgartner, 1998).…”