Sediment change under climate changes and human activities in the Yuanjiang-Red River Basin

Abstract

Both the climate change and human activities are the major influence factors to the sediment change in mountainous rivers. Based on the over 40 years' record, suspended sediment loads (SSL) change at the Manhao gauging station in the lower reaches of Yuanjiang River (upper Red River). In this paper, the variation of the sediment and its drivers were analyzed through different methods such as synchronous data comparison, traditional correlation, linear regression, and Granger causality. The results show that (1) the general trend of the annual average sediment concentration (SSC) and SSL at Manhao station is increasing from the 1960s to the 1990s, and there is a quick change period after 1984; (2) the SSL and SSC at Manhao station, during different periods of the 1960s, 1970s, 1980s and 1990s, are 1.87, 2.49, 3.12, 3.63 kg/m 3 , and 28.7×10 6 , 40.3×10 6 , 44.1×10 6 , 60.3×10 6 t/a, respectively; (3) the correlation analysis and the Granger causality test proved that the climate changes in the catchment were the main driving factors to the sediment variation in the period of 1960s and 1990s, but the influence by the mountainous human actions on the sediment change is stronger than that by the local climate changes in the 1970s and 1980s; (4) the correlation between the sediment changes and the forest coverage change is negative, which further proves that the sediment changes are strongly affected by the human activities in the basin. sediment change, Granger causality test, Yuanjiang River, the Longitudinal Range-Gorge Region

When land, water and green‐grabbing cumulate: Hydropower expansion, livelihood resource reallocation and legitimisation in southwest China

“…comm., March 2015). Minimum downstream flow values were set at 26.1 m 3 /s for the Nansha dam and 30.2 m 3 /s for the Madushan dam, in line with the lowest recorded historical water discharge of 28.7 m 3 /s in Manhao, just downstream from the Madushan dam (He et al ., ; CDM, ; CDM, ). Yet the above Vietnamese informant reckoned that there was no way to ensure that China genuinely implemented environmental flow guidelines and raised doubts about their enforcement (pers.…”

“…Enforcing water releases that better replicate the natural variations of the Red River could be an efficient approach to sustaining the river's livelihood and ecosystem functions. This would involve ensuring much higher water releases during the flood season, when historical water discharge peaked at 4620 m 3 /s in Manhao (He et al, 2007). Likewise, maximum discharge values would be required for the dry season.…”

Spatial distribution and environmental factors of catchment-scale soil heavy metal contamination in the dry-hot valley of Upper Red River in southwestern China

“…According to the national survey of soil elements, in this region, the background values of Pb are 1.58-fold and of Cu are 1.44-fold higher than the national average. Severe soil erosion caused by high sand content in the soils and steep slopes in the DHV (Yang et al, 2003) may contribute to heavy metal pollution in the river system (Cenci and Martin, 2004;Fu et al, 2012) because of increased sediment loads (He et al, 2007;Le et al, 2007;Miao et al, 2010). Furthermore, hydropower exploitation via the proposed cascade reservoir system in the Upper Red River (Zhai et al, 2007) may submerge parts of the DHV, making this region a potential source of heavy metal pollution in downstream agricultural products, fisheries, and river ecosystems (Phan et al, 2013;Steininger, 2003).…”

A Modeling Approach to Diagnose the Impacts of Global Changes on Discharge and Suspended Sediment Concentration within the Red River Basin

“…The upstream part in China is dominated by tectonically active montane areas with steep slopes, usually above 25 • [47]. Intensive rainfall and prominent contradiction between human and land make this area vulnerable to high erosion with steep slopes [38,48,49]. The main soil types are Acrisols, such as latosol, red earth, yellow brown soil and fluvisol [48,50].…”

“…The Red River is a typical Asian river system, combining different land uses, affected by human activities such as intensive dam implementations and agriculture [36,37]. Recent studies of hydrology and suspended sediment in this basin mainly used data from gauge stations or sampling to do statistical analysis [38][39][40][41], or use modeling to perform simulations at a local scale [42] or in the delta part [43] at a monthly scale; few studies analyzed fluxes at daily scale, but only on a short period [37], in the delta [44] or only for discharge or suspended sediment [45]. Both Q and SSC can vary greatly from day to day; therefore, it would be more favourable to calculate flux at a daily scale.…”