Designing river flows to improve food security futures in the Lower Mekong Basin

Abstract

Rivers provide unrivaled opportunity for clean energy via hydropower, but little is known about the potential impact of dam-building on the food security these rivers provide. In tropical rivers, rainfall drives a periodic flood pulse fueling fish production and delivering nutrition to more than 150 million people worldwide. Hydropower will modulate this flood pulse, thereby threatening food security. We identified variance components of the Mekong River flood pulse that predict yield in one of the largest freshwater fisheries in the world. We used these variance components to design an algorithm for a managed hydrograph to explore future yields. This algorithm mimics attributes of discharge variance that drive fishery yield: prolonged low flows followed by a short flood pulse. Designed flows increased yield by a factor of 3.7 relative to historical hydrology. Managing desired components of discharge variance will lead to greater efficiency in the Lower Mekong Basin food system.

Spatial and temporal variation in fish community structure and diversity in the largest tropical flood‐pulse system of South‐East Asia

“…The interannual variation in the TSRL fish communities found in this study could be explained by many reasons; however, the variation in annual flows (such as peak water levels) has been described as a main factor affecting the TSRL fish communities (Baran et al, 2001;Halls, Conlan, et al, 2013;Halls, Paxton, et al, 2013;Sabo et al, 2017;van Zalinge et al, 2003). Our results highlighted that the changes in the TSRL fish community were significantly linked to hydrology.…”

“…Human activities, such as ongoing water development projects in the Mekong River Sabo et al, 2017), intensive fishing and farming with the use of pesticides and chemical fertilisers as well as the clearance of flooded forests in the TSRL, could also influence the interannual changes in the TSRL fish communities, and this topic needs further investigation. In addition, during the time of the survey, a fisheries policy reform, leading to the abolition of all 35-century-old industrial-scale fishing lots (see Figure 1), took effect in 2012.…”

“…Given that hydropower dams are still being built in the Mekong, good design flows (Sabo et al, 2017) that would help reduce dam effects and boost fisheries production, for example in the Tonle Sap, should be prioritised and applied as one of the mitigation measures on existing and planned dams in the Mekong. At last, maintaining the naturally predictable seasonal rising and falling flood pulses as well as the longitudinal and lateral connectivity of the main habitats of the Mekong and its tributary systems, including the Tonle Sap River, are likely the key drivers to maintaining seasonal fish migrations and, hence, the TSRL's seasonal assemblage diversity and productivity.…”

“…Despite being highly productive, the Mekong system, including the Tonle Sap, has received little ecological research on many aspects of its resources and ecology, including fish, reptiles, invertebrates and primary producers (Dudgeon, 2000(Dudgeon, , 2003Sabo et al, 2017).…”

A Review of the Integrated Effects of Changing Climate, Land Use, and Dams on Mekong River Hydrology

“…Findings from global studies also suggest that water scarcity areas tends to travel downstream in regions where flows are significantly regulated by dams [60]. A recent study has proposed ways to design reservoir management in the Mekong by carefully analyzing the characteristics of the flood pulses, which could help increase fishery yield and improve the food system efficiency in the Lower Mekong [61].…”